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  • 1. Adamopoulos, S
    et al.
    Karastergiou, S
    Foti, D
    Filippou, V
    Chips recovered from waste particleboards by hydro-mechanical methods2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It was studied the recovery of wood chips from waste particleboards by immersion in water at ambient temperature and by mechanical treatment (agitation and impact, waterblasting). Four different categories of waste particleboards were used, with and without coating, after their reduction in smaller pieces with dimensions of about 7 × 8 cm.  The investigated methods were: (I) immersion for 3 days-impregnation with vacuum and pressure-agitation and impact (II) immersion for 7 days-drying-rewetting for 12 hours-agitation and impact (III) immersion for 3 days-waterblasting. The maximum thickness swelling (about 90%) was achieved by immersing the particleboards in the water for 3 days, and therefore the vacuum and pressure impregnation step can be omitted in practice. Recovery of wood chips was significantly higher (51.54%) in the case of successive wetting and drying cycles compared to simple immersion in water (17.32%). Both these methods I and II, involving agitation and impact for recovering wood chips from waste particleboards, are easily applicable at the industry. Method III with waterblasting resulted in complete recovery of wood chips within a very short time, but its application requires more research

  • 2.
    Adamopoulos, Stegerios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Gellerich, A
    Georg-August-University Göttingen, Germany.
    Mantanis, G
    Technological Educational Institute of Larissa, Greece.
    Kalaitzi, T
    Aristotle University of Thessaloniki, Greece.
    Militz, H
    Georg-August-University Göttingen, Germany.
    Resistance of Pinus leucodermis heartwood and sapwood against the brown-rot fungus Coniophora puteana2012Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, Vol. 7, nr 4, 242-244 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study assessed the decay resistance of Pinus leucodermis wood to the brown-rot fungus Coniophora puteana. Based upon the median weight losses of 30.65% for heartwood and of 34.68% for sapwood obtained in the biological tests, both the heartwood and sapwood material examined was classified as not durable (durability class 5) according to the CEN/TS 15083-1 classification. Total extractives were low, 3.93% in heartwood and 1.00% in sapwood, while lignin content was 22.60% and 25.41% in heartwoodand sapwood, respectively. It is highly recommended to use protective treatments before using P.leucodermis wood in outdoor conditions.

  • 3.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    A laser drilling technique to improve impregnability of spruce and fir2016Inngår i: 3rd BASF Wolman Conference, 14 September 2016, Linnaeus University, Växjö, Sweden, 2016Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 4.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Flexural properties of black locust (Robinia pseudoacacia L.) small clear wood specimens in relation to the direction of load application2002Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, nr 5, 325-327 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Values of pure moduli of elasticity (PMOE), experimental modulus of elasticity (MOE) in static bending and moduli of rigidity (GLR, GLT) were calculated in juvenile and mature black locust defect-free small wood specimens after loading in static bending alternately on true radial and tangential surfaces. For both juvenile and mature specimens, no significant differences (t-test, 95% probability level) were found between the radial and tangential moduli of elasticity and rigidity. Values of PMOE were found to be 27–32% higher than the corresponding values of MOE at the 15:1 span-to-depth ratio.

  • 5.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Influence of hot-water extractives on radial and tangential shrinkage of black locust wood (Robinia pseudoacacia L.)2002Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, nr 5, 377-378 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    IntroductionRemoval of extractives increases the shrinkage and swelling of wood (Nearn 1955, Salamon and Kozak 1968, Cooper 1974, Taylor 1974). The effect of progressive extraction on the above properties has not been investigated much. In oak (Quercus conferta L.), a forest species rich in extractives, the shrinkage progressively increased with progressive extraction (Voulgaridis et al. 1980). In black locust (Robinia pseudoacacia L.), much of the main-stem volume is comprised of heartwood, characterized by the presence of dark yellow-brown extractives. While the extractives of black locust give the heartwood its distinctive color and decay resistance, they comprise only 6.2 to 8.3% of the dry weight of the main stem (Stringer 1992). Hot-water extractives range from 5.2 to 8.6% (Hart 1968, So et al. 1980). The present study was primarily undertaken to determine whether the progressive removal of hot-water extractives affects the radial and tangential shrinkage of black locust heartwood.

  • 6. Adamopoulos, Stergios
    Radial variation of fiber and vessel member dimensions as an indication of juvenile/mature wood transition in black locust2006Inngår i: Wood Structure and Properties ’06. / [ed] S. Kurjtatko, J. Kúdela and R. Lagaňa, 2006, 19-23 s.Konferansepaper (Fagfellevurdert)
  • 7.
    Adamopoulos, Stergios
    TEI Thessaly, Greece.
    Recovery and utilization of wood and rubber at the end of their lifespan to produce innovative products2014Inngår i: Development and Business Prospects in Thessaly by Symbiotic Utilization of Agricultural and Industrial Solid Waste to Produce Materials and Energy, November 24, Larissa, Greece, 2014Konferansepaper (Annet vitenskapelig)
  • 8. Adamopoulos, Stergios
    Silvicultural practices in relation to quality of timber produced in Greece1999Inngår i: 2nd Workshop of COST Action E10: Wood properties for Industrial Use, 13-15 June, Tapada de Mafra, Portugal, 1999, 50-53 s.Konferansepaper (Annet vitenskapelig)
  • 9.
    Adamopoulos, Stergios
    TEI of Thessaly, Greece.
    Utilisation of recovered wood and rubber for alternative composite Products (Woodrub)2013Inngår i: Tire Rubber Recycling Forum 2013, November 19-20, Brussels, Belgium, 2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Promoting sustainable raw material management and increasing the recycling of waste wood and waste rubber are two strategic thrusts that open large domains for new technologies and innovations.

    This project, in line with objectives of LIFE+ Environment Policy & Governance aims to increase resource efficiency through the utilization of these wood and rubber wastes through the manufacturing of new products based on innovative mixed composites (wood/rubber). This new products will constitute an alternative for the utilization of other traditional and less eco-efficient products in the residential and civil construction sector.

    Moreover, the project will provide a novel end of life route for wood waste managers and rubber waste managersʼ products and entities a new environmental friendly product to public and private construction sector.The use of these products will increase the carbon storage in buildings and replace other building materials which are less environmentally friendly towards carbon storage and emission, both in production processes and raw material use.

    The recovered wood category to be utilised will be waste wood from households (furniture, doors, windows, floors, etc.). This material is chemically contaminated by glues, lacquers, paints and coatings but not by preservatives. After collection, the waste wood material will be chipped and processed in the form of chips without any prior biological, thermal or chemical treatment. This is an innovative approach since the removal of all these chemicals is difficult and time/ cost consuming.

    Recovered rubber form tyres in the form of particles, free from other materials as wires, ropes, synthetic fibres, etc., will be utilised with recovered wood chips or sawn timber for the production of innovative composite products by thermal processes.

    This project is in line with latest research in wood – rubber applications (Yang et al. 2004, Zhao et al. 2008).

  • 10.
    Adamopoulos, Stergios
    et al.
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Bastani, Alireza
    Georg-August-University Göttingen, Germany.
    Gascón-Garrido, Patricia
    Georg-August-University Göttingen, Germany.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Adhesive bonding of beech wood modified with a phenol formaldehyde compound2012Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, nr 6, 897-901 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Untreated (controls) and phenol–formaldehyde (PF)-modified beech wood (10 and 25 % solid content) were glued with phenol resorcinol formaldehyde (PRF) and polyvinyl acetate (PVAc). Shear strength of PRF-bonded specimens was higher than that of PVAc-bonded ones under dry and wet conditions irrespective of the pre-treatment. Under dry conditions, only PVAc-bonded specimens exhibited reduction in shear strength due to PF-modification with 25 % PF concentration as compared to the controls. PF treated wood provided inferior bonding under wet conditions with the exception of 25 % PF concentration specimens glued with PRF adhesive. Modification with PF resulted in a decrease of adhesive penetration into the porous network of interconnected cells, especially at 25 % PF concentration.

  • 11.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Chavenetidou, Marina
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Span-to-depth ratio for shear free deformations in static bending of small wood specimens2011Inngår i: Wood research, ISSN 1336-4561, Vol. 56, nr 3, 429-434 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Disregarding shear effects is a principal defect in predicting the bending strengths of small clear specimens of timber according to standards. The present study proposes a method to determine spans of 2 x 2 cm wood specimens of black locust and chestnut for shear free deformations in static bending. It was found that for both ring-porous species, spans of at least 40 cm in a bending test would ensure a negligible influence of shear on modulus of elasticity.

  • 12.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Chavenetidou, Marina
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Effect of cambium age and ring width on density and fibre length of black locust and chestnut wood2010Inngår i: Wood research, ISSN 1336-4561, Vol. 55, nr 3, 25-36 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between wood density (WD) and fibre length (FL) with cambium age (CA) and ring width (RW) was studied in two ring-porous species, black locust and coppice-grown chestnut, collected in the Sithonia Peninsula, Chalkidiki, Greece. Using regression analysis methods, models of WD and FL in relation to CA and RW were obtained. It was found that the effect of CA and RW on WD and FL was similar for both species examined. WD of black locust and chestnut was predicted better through a model using CA and RW. A model for FL variations was also obtained with CA and RW and was more accurate than the simple models based on the two factors, CA and RW, separately. The multiple regression models suggested that the use of cambial age of growth rings together with their width might explain better their effects on WD and FL of black locust and chestnut.

  • 13.
    Adamopoulos, Stergios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Foti, Dafni
    Aristotle University of Thessaloniki, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Manufacturing and properties of gypsum-based products with recovered wood and rubber materials2015Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 3, 5573-5585 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The experimental production of gypsum-based products (cylindrical samples, solid bricks) using different fractions of wood chips and rubber particles was studied. Recovered rubber and wood materials were mixed with gypsum and water in various proportions to fabricate gypsum-wood and gypsum-rubber cylindrical samples and standard solid bricks with six holes using appropriate molds. It was shown that to manufacture gypsum-wood and gypsum-rubber products with good mechanical strength, coarse fractions of wood and rubber should be used, but the proportion of wood or rubber should not exceed 25%. No thermal conductivity differences were found between the wood-and rubber-type of gypsum products, and particle size and material proportion had no effect. Samples with fine wood and rubber particles present at a lower proportion (25%) exhibited similar sound absorption behavior. The solid bricks had slightly higher strength when loaded at the large surface of their lateral upper side than when loaded at the small surface. The bricks provided better thermal insulation than both the extruded and pressed house bricks but lower than that of insulating bricks. The emission of volatile organic compounds out of the bricks was at an acceptable level according to regulations for construction products.

  • 14.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Hosseinpourpia, Reza
    Georg-August-University Göttingen, Germany.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Tensile strength of handsheets prepared with macerated fibres from solid wood modified with cross-linking agents2015Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, nr 8, 959-966 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was conducted to explain the tensile strength loss of wood due to the modification with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA). Modified and control wood blocks were macerated to deliberate fibres, and handsheets were produced thereof. The nitrogen content of the fibres indicated that maceration removed the major proportions of DMDHEU. The stability of GA in wood during maceration was not assessed. Tensile strength determined at zero span (z-strength) and finite span (f-strength) was equal for the handsheets from DMDHEU-modified fibres and the control handsheets. The microscopic appearance of the tested finite-span paper strips from DMDHEU-modified fibres mainly indicated interfibre failure and did not differ from the fibre fracture mode of the control handsheets. In contrast, the z-strength of the handsheets from GA-modified fibres was lower than that of controls and decreased with increasing content of GA in the initial modified wood. The f-strength behaviour of the handsheets from GA-modified fibres was the opposite: it was higher than that of controls and increased with increasing GA content. The microscopic appearance of the rapture zones of the finite-span testing mainly indicated intrafibre failure for the GA-modified fibres. It was concluded that cross-linking is likely to be the major reason for tensile strength loss of GA- and DMDHEU-modified wood. In terms of DMDHEU-modified wood, the incrustation of the cell wall by the resin and the reduction in pliability could play an additional role.

  • 15.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Karageorgos, Anthony
    Passialis, Costas
    Chavenetidou, Marina
    Mathematical approach for defining juvenile-mature wood transition zone in black locust and chestnut2011Inngår i: Wood and Fiber Science, ISSN 0735-6161, nr 3, 336-342 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article defines age of transition from juvenile to mature wood in two ring-porous species, black locust (Robinia pseudoacacia L.) and chestnut (Castanea sativa Mill.). A logistic function was proposed using fiber length and ring width data of three black locust trees, aged 35-37 yr, and five chestnut coppice trees, aged 25-27 yr, from Sithonia Peninsula, Chalkidiki, Greece. The approach proved to be practical and objective in delineating maturity zones, and it was based on rate of change of yearly fiber length. The juvenile wood zone spread to the sixth growth ring from the pith in both species, whereas the demarcation of juvenile and mature wood was at age 12 and 14 yr in chestnut and black locust, respectively. Transition zone width comprised rings 7-12 in chestnut and rings 7-14 in black locust.

  • 16.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Koch, Gerald
    Johann Heinrich von Thünen-Institut, Germany.
    Wood structure and topochemistry of Juniperus excelsa2011Inngår i: IAWA Journal, ISSN 0928-1541, Vol. 32, nr 1, 67-76 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood structure and topochemical distribution of lignin and phenolic extractives in Juniperus excelsa Bieb. were investigated using a mature specimen, aproximately 80 years of age, from the Rhodope mountains, Greece. The wood of J. excelsa was found to possess the same qualitative anatomical features as those reported for other Juniperus species of the Western Hemisphere. Quantitative anatomical characteristics recorded for mature wood (heartwood and sapwood) included earlywood and latewood tracheid length, double wall thickness of earlywood and latewood tracheids, lumen diameter of earlywood tracheids and ray height. Scanning UV microspectrophotometry revealed a pronounced lignification of J. excelsa tracheids with detected absorbance values of the secondary cell wall layers being much higher in comparison to all other softwoods studied using this technique. The cell corners and compound middle lamellae were characterised by relative high UV absorbance values as compared to the S2 layers. The phenolic compounds deposited in the axial and ray parenchyma cells possessed higher absorbance values than cell wall associated lignins and had a different spectral behaviour due to the presence of chromophoric groups. According to the obtained UV absorbance spectra, more condensed phenolic compounds were deposited in the heartwood than in the sapwood.

  • 17. Adamopoulos, Stergios
    et al.
    Milios, E
    Brutia pine wood properties from young reforestations2007Inngår i: / [ed] M. Ispas, 2007, 11-18 s.Konferansepaper (Fagfellevurdert)
  • 18.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Milios, E.
    Democritus University of Thrace, Greece.
    Doganos, D.
    Democritus University of Thrace, Greece.
    Bistinas, I.
    Democritus University of Thrace, Greece.
    Ring width, latewood proportion and dry density in stems of Pinus brutia Ten2009Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 67, nr 4, 471-477 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examined basic characteristics of stem wood produced in Pinus brutia Ten. reforestations in Northeastern Greece. Sixteen dominant trees growing at good and medium site qualities were felled at 14–22 years. Site quality classification was based on site quality surrogates and confirmed by using site index curves that were created for a neighbouring area. Discs were taken at three stem positions (base, middle, top) to study variations in ring width, latewood proportion and dry density. Generally, at both good and medium sites, ring width was found to increase towards the top of the stems while latewood proportion and dry density showed a negative relationship with stem height. Radial variability trends were similar at all heights, and at both sites, revealing a rapid increase for ring width in the first 3–6 annual rings followed by a decrease towards the bark, a gradual increase for latewood proportion and no specific change for dry density. Comparisons between wood material produced during the same growth period (2005–2001) showed statistically significant differences among sampling heights in all cases except for dry density in medium sites. At the base of the stems, mean ring width and dry density were significantly (P ≤0.05) higher at good sites (3.6 mm and 0.53 g/cm3) than at medium sites (3.0 mm and 0.50 g/cm3). However, the differences between the sites are of small magnitude and therefore have limited practical impact on wood processing. The availability of such data is useful in utilising small-dimension timber of brutia pine.

  • 19. Adamopoulos, Stergios
    et al.
    Passialis, C
    Voulgaridis, E
    Prediction of bending and shear strength properties by using nondestructive parameters in fir and black locust2001Konferansepaper (Annet vitenskapelig)
  • 20.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Passialis, C
    Aristotle University of Thessaloniki, Greece.
    Voulgaridis, E
    Aristotle University of Thessaloniki, Greece.
    Oliver, JV
    Polytechnic University of Valencia, Spain.
    Grammage and structural density as quality indexes of packaging grade papers manufactured from recycled pulps2014Inngår i: Drewno, ISSN 1644-3985, Vol. 57, nr 191, 145-151 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrugated packaging production is currently facing the challenge to ensure a satisfactory strength of packaging despite the continuous increase in recycled paper as the main fibrous component. This research addresses a very common technical problem for the corrugated board industry – the difficulty of predicting the properties of paper products produced from heterogeneous sources. Grammage and structural density, being easily available data, were examined as quality parameters of the most common categories of packaging paper in Europe. Grammage, ranging from 100 to 225 g/m2, has been found to be a dominant parameter for estimating the strength properties of paper.

  • 21.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Relationship of the toughness and the modulus of elasticity in static bending of small clear spruce wood specimens2010Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 68, nr 1, 109-111 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unlike static bending, toughness is a mechanical property less commonly measured in clear wood. The paper presents results on the relationship of toughness and modulus of elasticity in static bending based on DIN standard tests on small, clear specimens of spruce, 2×2 cm2 in cross section.

  • 22.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Ring width, latewood proportion and density relationships in black locust wood of different origins and clones2010Inngår i: IAWA Journal, ISSN 0928-1541, Vol. 31, nr 2, 169-178 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cross-sectional discs were cut at breast height from 19 black locust trees aged 18–39 years of different clones and origin (Greece, Bulgaria and Hungarian clones J, U and NY). Ring width, latewood proportion and dry density were measured according to standard laboratory techniques in order to examine their relationships. Latewood proportion was found to increase (except for one tree from Bulgaria) with increasing ring width and logarithmic equations were calculated with relatively high correlation coefficients. A positive relation between dry density and latewood proportion was found in black locust of Bulgarian origin and in the Hungarian clone NY while in all other cases no meaningful relationship was observed. In mature wood, improved positive linear correlations were observed between dry density and latewood proportion with the exception of the Hungarian clone U. Regression analysis revealed low correlations between dry density and ring width and only black locust from Bulgaria had a high positive correlation. The positive correlations between dry density and ring width were slightly improved in mature wood with the exception of clone J from Hungary.

  • 23.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Karditsa, Greece.
    Passialis, Costas
    Technological Educational Institute of Karditsa, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Strength properties of juvenile and mature wood in black locust (Robinia pseudoacacia L.)2007Inngår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 39, nr 2, 241-249 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was undertaken to investigate the strength properties of juvenile and mature wood in black locust (Robinia pseudoacacia L.). Wood specimens were prepared from various stem heights, up to 9 m, of five naturally-grown black locust trees, 21-37 years old. Mechanical properties tested included moduli of rupture (MOR) and elasticity (MOE), and pure modulus of elasticity (PMOE) in static bending, stress wave modulus of elasticity (SWMOE) in dynamic strength, axial compression, and toughness. Comparisons between juvenile and mature wood specimens of similar densities (0.667-0.894 g/cm3 and 0.682-0.892 g/cm3, respectively) showed that juvenile wood had a statistically significant lower mean MOR (138.78 N/mm2), MOE (13,936 N/mm2), PMOE (18,125 N/mm2), SWMOE (16,813 N/mm2) and toughness strength (155.25 KJ/m2) than the mature wood (148.29 N/mm2, 14,747 N/mm2, 19,498 N/mm2, 17,635 N/mm2 and 181.27 KJ/m2, respectively). On the contrary, no statistically significant differences were found for the mean strength in axial compression among juvenile (63.75 N/mm2) and mature wood (66.65 N/mm2). Fractured surfaces of juvenile and mature wood specimens in static bending and toughness were classified into the "splintering tension" type of failure, while compression failures were of the "shearing type" according to ASTM D 143-83 standards. Lower strength of juvenile wood in most of the properties examined may be attributed to anatomical and chemical properties rather than density of wood specimens. The adverse influence of juvenile wood on strength properties should be considered for effective management (e.g. longer rotation age and other genetic and forest or plantation management measures that reduce juvenile wood content) and utilization of the species.

  • 24.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Moustaizis, Stavros
    Technical University of Crete, Greece.
    Kortsalioudakis, Nathanail
    Technical University of Crete, Greece.
    Petrakis, Panagiotis
    Technical University of Crete, Greece.
    Karastergiou, Sotirios
    Technological Educational Institute of Thessaly, Greece.
    Foti, Dafni
    Technological Educational Institute of Thessaly, Greece.
    Koutsianitis, Dimitrios
    Technological Educational Institute of Thessaly, Greece.
    Voulgaridou, Eleni
    Technological Educational Institute of Thessaly, Greece.
    Effect of laser drilling on mechanical properties of fir (Abies borisii regis) and spruce (Picea excelsa) wood2014Inngår i: Wood Structure, Properties and Quality – 2014: 5th RCCWS International Symposium, Moscow State University Press, 2014, 7-12 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fir and spruce wood specimens, 2×2 cm in cross section and 34 cm long, were pre-pared with true radial and tangential surfaces. All lateral surfaces of the wood specimens were drilled by laser beams to a depth of 0,4 cm (1/5 of specimen thickness) with two drilling pat-terns (distance between holes 1 × 1 cm and 1 × 2 cm). After drilling, static bending (MOR, MOE), axial compression strength and toughness were determined and compared with non-drilled control specimens. The effects of the two laser drilling patterns on mechanical proper-ties of fir and spruce wood specimens were measured and assessed. The results showed that the two drilling patterns created by laser beams on all lateral surfaces of fir and spruce wood specimens at 0,4 mm depth did not practically affect the mechanical properties of wood.

  • 25.
    Adamopoulos, Stergios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Sjöberg, Samuel
    Relationship between ultrasonic velocity and spiral grain in standing hybrid aspen trees2016Inngår i: Proceedings of the Hardwood Conference, Eco-efficient Resource Wood with Special Focus on Hardwoods, 8-9 September, 2016, Sopron, Sopron: University of West Hungary Press , 2016, 22-23 s.Konferansepaper (Fagfellevurdert)
  • 26. Adamopoulos, Stergios
    et al.
    Voulgaridis, E
    Impregnation of timber and regulations applied to preservation practice in Greece1998Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The practice of wood preservation in Greece was started about 80 years ago and refer to creosote-treated timber used in ground contact (i.e. railway sleepers, poles). At present, three creosote impregnation plants and thirteen CCA or CCB units exist in Greece treating about 90.000 m3 of wood per year. Most of the research on wood preservation has been carried out in the last 15-20 years and refer to the application of creosote and water soluble preservatives (CCA, CCB) to native wood species. However, research on a number of specific topics of wood impregnation is lacking. Impregnation of wood is of great importance for Greece, a country with great wood deficit, and, for this reason, the elongation of wood durability is strongly desirable. On the other hand, the environmentally safe impregnation of timber and the use of preservatives in a non-hazardous manner to humans or animals are gaining an increasing importance. There are some national and EU regulations applied to the use of preservatives, while the Greek Organization of Standardization (ELOT) is responsible for approving European standards. The organizations of Greek Telecommunication, Electricity and Railway apply their own standards.

  • 27.
    Adamopoulos, Stergios
    et al.
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Dimensional changes of extracted and non-extracted small wood specimens of black locust (Robinia pseudoacacia L.)2003Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 61, nr 4, 264-268 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From straight grained heartwood of black locust (Robinia pseudoacacia L.), specimens, 3 cm×3 cm in cross section and 0.5 mm (or 10 mm) in axial direction, were cut and used for the determination of dimensional changes and the rate of tangential swelling. Mean radial, tangential and axial shrinkage was 5.30%, 6.67% and 0.16%, respectively, while the coefficient of anisotropy was 1.26. Half of the specimens for the determination of the rate of tangential swelling were extracted for 48 h with distilled hot water. The tangential dimensional change and the time taken to attain half maximum swelling in air-dry and oven-dry specimens were assessed according to a common technique. Extractive removal resulted in an increase of the total magnitude of tangential swelling in both air-dry and oven-dry specimens. However, no significant differences in time taken to attain half maximum swelling between air-dry and oven-dry specimens were observed after extraction. The rate of tangential swelling was lower in air-dry specimens than in oven-dry specimens after 30 min of immersion in water when were non-extracted and after 5 min of immersion in water when were extracted. Extracted air-dry specimens had a greater rate of tangential swelling than non-extracted air-dry specimens and the same occurred for oven-dry specimens. Extraction resulted in a higher diffusion coefficient for air-dry specimens. The diffusion coefficient calculated for non-extracted air-dry specimens (0.901×10−4 cm2/min) showed that black locust is a difficult species to impregnate.

  • 28.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Effect of hot-water extractives on water sorption and dimensional changes of black locust wood2012Inngår i: Wood research, ISSN 1336-4561, Vol. 57, nr 1, 69-78 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hygroscopicity and the dimensional changes of black locust heartwood were investigated in relation to the progressive removal of hot-water extractives. Extraction in the original specimen form removed only part of the total 8.434 % hot-water extractives, 3.601 % in first extraction and 4.642 % in second extraction. As a result, the adsorption and desorption behaviour of black locust wood was little affected by the extraction and only a small increase was observed in dimensional changes at every RH from 0 % to 97 %. The mean hysteresis coefficient was also little affected by extraction and increased from 0.75 at the unextracted stage to 0.77 at the second extraction. The initial dimensional change 3.76 % of unextracted black locust wood corresponding to RH changes between 43 % and 80 % increased after the first and second extraction to the respective values of 3.96 % and 3.97 %. Extraction had no effect on the significant, very strong linear relationships between swelling or shrinkage and equilibrium moisture content (EMC).

  • 29.
    Adamopoulos, Stergios
    et al.
    Aristotelian University, Greece.
    Voulgaridis, Elias
    Aristotelian University, Greece.
    Within-tree variation in growth rate and cell dimensions in the wood of black locust (Robinia pseudoacacia)2002Inngår i: IAWA Journal, ISSN 0928-1541, Vol. 23, nr 2, 191-199 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Black locust (Robinia pseudoacacia L.) is regarded as an important natural resource almost throughout the world but relatively little is known about the within-tree variability of the anatomical characteristics of its wood. Discs 2 cm thick were cut at 2.25 m intervals, from the ground level to the top from ten black locust trees, 18–37-years-old, from the University Forest of Taxiarchi, Chalkidiki, Greece. The discs were used for the determination of growth rate and cell dimensions (fiber length and vessel member length and diameter) and their withintree variability (radial, oblique, vertical). Growth rate increased within the first 5–9 growth rings from the pith and then gradually decreased. Oblique variation of growth rate did not exhibit any clear tendency but a decrease at the top. In the case of vertical variation, growth rate decreased gradually with the year of cambium formation. Radial variability curves were found to be typical for the dimensions of cells (fibers, vessel members) especially for the fiber length. A rapid increase in cell dimensions was observed in the first 7–11 growth rings, the juvenile zone. Oblique and vertical variation of cell dimensions did not exhibit any clear tendencies.

  • 30.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Ποιότητα και μεταβλητότητα της δομής του ξύλουσε σχέση με την αξιοποίησή του: [Quality and variability of wood structure in relation to its utilization]2012Inngår i: Το Δάσος: Μια Ολοκληρωμένη Προσέγγιση: [The forest: An integrated approach] / [ed] Aristotélis Papageorgíou, Geórgios Karétsos, Geórgios Katsadorákis, WWF Greece , 2012, 213-227 s.Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 31. Adamopoulos, Stergios
    et al.
    Voulgaridis, Elias
    Passialis, C.
    Wood quality characteristics of black locust (Robinia pseudoacacia  L.)2001Inngår i: Forest Research - New Series, Vol. 14, 63-72 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 32.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Gypsum-based bricks (WoodRub BRICKS) manufactured from recovered wood and rubber2014Inngår i: Performance and maintenance of biobased building materials influencing the life cycle and LCA / [ed] Andreja Kutnar, Miha Humar, Michael Burnard, Mojca Žlahtič, Dennis Jones, 2014, 33-34 s.Konferansepaper (Annet vitenskapelig)
  • 33.
    Adamopoulos, Stergios
    et al.
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)2005Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, nr 5, 327-333 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sapwood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreasedin sapwood from the bottom to the top of the stems while the reversal occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the stems, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the stems. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom, 21.42% at the middle and 19.64% at the top.

  • 34.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Wood recycling in Europe2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Nowadays, waste wood is a valuable secondary raw material that can cover much of the wood-based panel industry's needs and a major source of renewable energy. The various categories of waste wood are described in European legislation and standards but in practice mostly followed industry practices relating to the purchase, classification and use of recovered wood. The European Panel Federation (EPF) proposes a three category classification system: untreated wood, non-hazardous treated wood, hazardous waste wood. The traditional practice of recycling in industry included mechanical handling of waste wood while new improved methods involve hydrothermal treatments. Of the total approximately 30 million cubic meters of recovered wood in Europe 38% is recycled, 34% is used for energy production and 28% ends up in landfills or composting. In the future recovered wood is expected to play an increasingly important role in the sustainability of wood-based panel industries as well as for the protection of the environment, and therefore new technologies are needed to fully explore this valuable resource.

  • 35.
    Adamopoulos, Stergios
    et al.
    Technological Edicational Institute of Larissa, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Beaver, Tim
    Composites & Textiles Pera, UK.
    Bouras, Takis
    ELKEDE Technology & Design Centre S.A., Greece.
    Properties of Microwave heat treated oak wood and impregnated with soybean oil2011Inngår i: Program & Book of Abstracts: Workshop, “Mechano-Chemical transformations of wood during Thermo-Hydro-Mechanical processing” / [ed] Parviz Navi, Andreas Roth, 2011, 145-145 s.Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The poster presents selected data on physical and mechanical properties, and gluing behaviour of microwave heat treated wood and impregnated with natural oils.

  • 36.
    Adamopoulos, Stergios
    et al.
    Technological Education Institute of Larissa, Greece.
    Wimmer, Rupert
    Georg-August-University Göttingen, Germany.
    Milios, Elias
    Democritus University of Thrace, Greece.
    Tracheid length – growth relationships of young Pinus brutia grown on reforestation sites2012Inngår i: IAWA Journal, ISSN 0928-1541, Vol. 33, nr 1, 39-49 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Brutia pine (Pinus brutia Ten.) reforestations have been successfully used for decades in restoration of degraded forest ecosystems in Greece. The future purpose of these reforestations might expand to include wood utilisation. This study provides information on tracheid length of juvenile brutia pine aged 14–22 years grown on good and medium sites in Northeastern Greece. In addition, relationships among ring width, latewood proportion, wood density, and tracheid length were evaluated by using Causal Correlation Analysis. Similar mean tracheid length values were found for good and medium sites. Radial variability of tracheid length was similar on the good and medium sites, showing the typical increase in the juvenile phase. On both site types, latewood proportion showed a strong and positive relationship with wood density. Unexpectedly and only on the good sites, a significant positive relationship was found between ring width and wood density. On the medium sites, tracheid length was negatively related to fast growth and positively to high wood density. Tracheid length on the good sites was correlated only with latewood proportion with a weak positive relationship. The overall results may provide opportunities to better understand the quality of small-dimension timber of brutia pine and to better utilise it.

  • 37.
    Adamopoulos, Stergios
    et al.
    Georg-August-University Goettingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Xie, Yanjun
    Georg-August-University Goettingen, Germany.
    Militz, Holger
    Georg-August-University Goettingen, Germany.
    Distribution of blue stain in untreated and DMDHEU treated Scots pine sapwood panels after six years of outdoor weathering2011Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 69, nr 2, 333-336 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface coating and bulk treatment of wood are two effective measures which can, individually or conjointly, protect exterior wood from deterioration. This paper reports on the blue stain attack in coated wood, untreated and modified with DMDHEU, after six years of natural exposure.

  • 38. Agnihotri, S.
    et al.
    Johnsen, I.A
    Böe, M.S.
    Öyaas, Karin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Moe, S.
    Ethanol organosolv pretreatment of softwood (Picea abies) and sugarcane bagasse for biofuel and biorefinery applications2015Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 49, nr 5, 881-896 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethanol derived from biomass has the potential to be a renewable transportation fuel that can replace gasoline. This work was carried out to establish an optimized ethanol organosolv pretreatment of Norway spruce (Picea abies) for bioethanol production (63 wt% EtOH, pH 3.5 in aqueous phase, 170–240 °C, 90 min) utilizing hydrolytic enzymes in the saccharification step. To test the generality of the method, a series of ethanol organosolv pretreatments were also performed on sugarcane bagasse (50 wt% EtOH, pH 3.5 in aqueous phase, 155–210 °C, 90–120 min). The degree of delignification increased with increasing temperature during pretreatment, and the fastest increase was observed with sugarcane bagasse. The pretreatments were carried out in a batch mode. The maximum degree of delignification of 65 % was reached at 235 °C for Norway spruce, while sugarcane bagasse reached 80 % at 210 °C. Cellulose was subjected to degradation (5–10 % points) at these temperatures. Subsequent enzymatic hydrolysis (30 FPU/g cellulose, 32 pNPGU/g cellulose, 50 °C, 48 h) of ethanol organosolv-pretreated biomass achieved complete conversion for both raw materials at the highest degrees of delignification.

  • 39.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Sweden.
    Morén, Tom
    Luleå University of Technology, Sweden.
    Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives2012Inngår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, nr 1, 85-93 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

  • 40.
    Ahmed, Sheikh Ali
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Morén, Tom
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood2017Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 63, nr 1, 74-82 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study was to investigate if these properties enhanced in thermally modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood, especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth, whereas a significant anti-mold effect was observed on Beckers oil treated samples.

  • 41.
    Alfredsen, Gry
    et al.
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Basidiomycete colonization of Scots pine sapwood quantified by qPCR and TGA2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) is an important softwood species in Northern Europe and is frequently used as material for various wood protection systems. In Europe, EN 113 is the standard basidiomycete laboratory durability test method, using mass loss as evaluation criteria. In this paper quantitative real-time PCR (qPCR) and thermogravimetric analysis (TGA) was used to characterize colonization by basidiomycetes in Scots pine sapwood, but also to learn more about the EN 113 test. Two different wood sample sizes were tested. For Gloeophyllum trabeum the largest sample size gave the highest mass loss, while for the smallest samples Trametes versicolor gave the highest mass loss. As expected, fungal DNA content and mass loss in Scots pine sapwood samples decayed by G. trabeum became higher with increasing incubation time of 16 weeks. More unexpectedly, the T. versicolor DNA content in Scots pine sapwood samples was highest at the start of the incubation period and declined during the incubation period, while mass loss increased during the 28 week incubation period. The fungal colonization in the side and middle of EN 113 samples was tested. Highest DNA contents of G. trabeum were measured in the sides during 16 weeks of incubation. The T. versicolor DNA content was higher or similar in the side compared to the middle of the samples until week 20. For weeks 20 and 22 the DNA content was higher in the middle than in the sides, while for the remaining incubation period (weeks 24, 26 and 28) it was quite similar. TGA was shown to be a useful and fast method for chemical characterization of brown rot decayed wood, but cannot be used for white rot decayed wood. For T. versicolor moisture and fungal DNA explained most of the variation in mass loss, while for G. trabeum moisture explained most of the variation in mass loss. 

  • 42. Alriksson, Björn
    et al.
    Eskilsson, Martin
    Johansson, Emma
    Lapidot, Shaul
    Norström,, Markus
    Schultz-Eklund, Ola
    Shkedi, Yoram
    Svedberg, Anna
    Svensson, Stefan
    Swerin, Agne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Europe’s first pilot facility for cellulose nanocrystals (CNC)2016Inngår i: Annual Surface and Materials Chemistry Symposium and Materials for tomorrow, ASMCS 2016, November 8-10, 2016, Gothenburg, Sweden, 2016Konferansepaper (Fagfellevurdert)
  • 43.
    Altgen, Michael
    et al.
    Georg-August University, Germany.
    Adamopoulos, Stergios
    Georg-August University, Germany.
    Militz, Holger
    Georg-August University, Germany.
    Wood defects during industrial-scale production of thermally modified Norway spruce and Scots pine2017Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 1, 14-23 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This research investigates wood defects, particularly the formation of surface cracks, during the production of thermally modified wood and its exposure to cyclic moisture changes. Boards of Norway spruce and Scots pine originating from different steps within the production of ThermoWood® were collected and wood defects were investigated at macroscopic and microscopic scale. Subsequently, the wood was exposed to capillary wetting cycles to record its sensitivity towards cracking. After the modification process, typical anatomical defects of conventional kiln-drying became more frequent and severe, with the magnitude being to some extent depending on the presence of defects in the raw material. At microscopic scale, damages to ray parenchyma and epithelial cells as well as longitudinal cracks within the cell walls of earlywood tracheids were evident in thermally modified wood. Despite a lower water uptake and higher dimensional stability, thermally modified wood was more sensitive to surface cracking during wetting cycles than unmodified wood, i.e. at the outside face of outer boards (near bark). For limiting surface cracking of thermally modified wood during service life, the use of high-quality raw material, the exposure of the inside face of the boards (near pith) and the application of a surface coating are considered beneficial.

  • 44.
    Altgen, Michel
    et al.
    Georg-August-University, Germany.
    Adamopoulos, Stergios
    Georg-August-University, Germany.
    Ala-Viikari, Jukka
    International ThermoWood Association, Finland.
    Hukka, Antti
    International ThermoWood Association, Finland.
    Tetri, Timo
    Jartek Oy, Finland.
    Militz, Holger
    Georg-August-University, Germany.
    Factors Influencing the Crack Formation in Thermally Modified Wood2012Inngår i: The Sixth European Conference on Wood Modification: Proceedings / [ed] Dennis Jones, Holger Militz, Marko Petrič, Franc Pohleven, Miha Humar, Matjaz Pavlič, University of Ljubljana , 2012, 149-158 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wood anatomical changes during a thermal modification process are likely to adverselyaffect the properties of the final product. Therefore, an anatomical investigation was performed on Scots pine and Norway spruce material coming from different steps of the regular production of ThermoWood. A macroscopic evaluation using an evaluation scale between 1 and 3 revealed typical drying defects in some of the kiln dried boards. Nevertheless, at least 50 % of the unmodified boards were defect free (CR = 1), while at least 90 % of the thermally modified boards were not defect free (CR = 2 and CR = 3), thus indicating that surface cracks become more frequent and severe after the modification process. However there was no evidence of an impact of the conditioning stage on the crack formation. Even though most of the surface cracks were removed by planing, microscopic analysis by means of light and scanning electron microscopy revealed that there might still be micro-defects within the ThermoWood. Such micro-defects were mainly associated with parenchyma or epithelial cells of the rays or the resin canals. Furthermore, longitudinal cracks within the tracheids were observed within the earlywood latewood interface or within the earlywood. During repeated drying and wetting cycles, the crack formation was higher for thermally modified wood than for unmodified, despite a lower water uptake and a better dimensional stability. After the third cycle, the average crack rating of thermally modified wood was at least twice as high as for the unmodified wood. It was concluded that this increase in the crack formation might be caused by the presence of micro-defects that potentially act as a starting point for more severe cracks during swelling and shrinkage.

  • 45.
    Andreasson, Robert
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Jansson, Pontus
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Analys av sprickdetektion vid automatisk avsyning av granvirke: med avseende på sprickors bredd, längd och djup2008Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Examensarbetet syftar till att hitta samband mellan ytliga sprickor hos virke, i form av dimensioner och karaktärer, som dagens maskinella avsyningssystem inte klarar av. Tyngdpunkten i projektet har legat på att identifiera eventuella samband mellan verkligt djup hos sprickor och de ytliga sprickmått som kan uppmätas med automatisk avsyning av WoodEye. I huvudsak har projektets praktiska undersökningar gått ut på att bestämma sprickors ytliga dimensioner, djup, typ och position med hjälp av automatisk avsyningsutrustning (WoodEye) samt genom manuell uppmätning i ett antal itusågade sprickzoner. Det provmaterial som använts i utförda försök och som legat till grund för efterföljande sprickanalyser har varit av sådan karaktär att det kunnat jämställas med konstruktionsvirke som normalt sett hållfasthetssorteras enligt europasstandard SS-EN 14081-1.

    I projektet har 568 sprickor, fördelade över 8 olika spricktyper, analyserats. Av erhållna resultat har det konstaterats att störst respektive minst medelbredd uppvisades hos kådlåpor respektive kantsprickor, störst respektive minst medellängd uppvisades hos splintsidesprickor respektive kådlåpor, samt att störst medeldjup uppvisades hos fäll-, kap- och stormsprickor. Vid analys av sprickors bredd och längd i relation till dess djup har inga entydiga samband kunnat påvisas.

  • 46.
    Arnling Bååth, Jenny
    et al.
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Giummarella, Nicola
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Klaubauf, Sylvia
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    A glucuronoyl esterase from Acremonium alcalophilum cleaves native lignin-carbohydrate ester bonds2016Inngår i: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 590, nr 16, 2611-2618 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Glucuronoyl esterases (GE) have been proposed to target lignin-carbohydrate (LC) ester bonds between lignin moieties and glucuronic acid side groups of xylan, but to date, no direct observations of enzymatic cleavage on native LC ester bonds have been demonstrated. In the present investigation, LCC fractions from spruce and birch were treated with a recombinantly produced GE originating from Acremonium alcalophilum (AaGE1). A combination of size exclusion chromatography and 31P NMR analyses of phosphitylated LCC samples, before and after AaGE1 treatment provided the first evidence for cleavage of the LC ester linkages existing in wood.

  • 47.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Mechanical properties of sound and of deteriorated softwood at different length scales: Poromicromechanical modeling and experimental investigations2011Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Due to its natural origin and its inherent heterogeneities, mechanical properties of wood are highly anisotropic and show a broad variability, not only between different wood species, but also within a tree. Similar to other biological materials, the wood mi- crostructure is well organized and hierarchically structured from the annual rings visible to the naked eye down to the wood polymers cellulose, hemicellulose, and lignin at the nanometer-scale. This thesis aims at a deeper understanding of the role of different hi- erarchical levels and their corresponding physical and chemical characteristics in relation to mechanical properties of sound wood and of deteriorated wood. This is achieved by means of micromechanical modeling and experimental analyses.

    This thesis starts with the re-formulation of an existing micromechanical model for the elastic behavior and elastic limit states of wood in the framework of poromechanics. The mechanical role of cell wall water at different hierarchical levels is investigated by means of this model. In a broader sense, the developed model allows to investigate the transition of eigenstresses from the cell wall to the softwood level. Moreover, this poromicromechanical model forms the basis for subsequent consideration of a microscopic failure criterion for lignin for the derivation of softwood failure stresses. The suitability of the modeling approach is underlined by a satisfactory agreement of the model-predicted failure stresses with experimental results of biaxial strength tests on Norway spruce.

    As a result of partly considerably different microstructural characteristics, Common yew exhibits exceptional mechanical properties compared to other softwood species. The re- lationship between microstructure and stiffness properties of Common yew and Norway spruce is investigated by means of the poromicromechanical model and mechanical tests across various length scales. Moreover, this offers the opportunity of a broader model validation. The influence of differences in microfibril angle of the S2 cell wall layer and in mass density between yew and spruce is found to be more dominant than the influence of differences in the annual ring characteristics.

    The suitability of the poromicromechanical model to predict changes in mechanical prop- erties upon fungal decay is demonstrated. For this purpose, relationships between mi- crostructure and mechanical properties of deteriorated wood are experimentally explored. Changes in mechanical properties and in the microstructure, measured at pine wood samples after standard wood durability tests using one brown rot fungus (Gloeophyl- lum trabeum) and one white rot fungus (Trametes versicolor), are presented. Transverse stiffnesses are revealed to be more sensitive to degradation than longitudinal stiffness, particularly as a result of pronounced degradation of hemicelluloses. Moreover, ultrason- ically derived anisotropy ratios of elastic stiffnesses allow to identify certain degradation mechanisms of the two considered fungi. The experimental campaign is complemented by micromechanical modeling. For this purpose, the micromechanical model is extended to take into account degradation-specific microstructural characteristics. 

  • 48.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bocquet, Jean-Francois
    University of Lorraine, France.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Lemaitre, Romain
    University of Lorraine, France.
    Numerical modeling of the load distribution in multiple fastener joints2017Inngår i: International Conference on Connections in Timber Engineering – From Research to Standards: Proceedings of the Conference of COST Action FP1402 at Graz University of Technology / [ed] Reinhard Brandner, Andreas Ringhofer & Philipp Dietsch, Graz: Verlag der Technischen Universität Graz , 2017, 136-152 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Numerical modeling approaches, for the determination of load distribution in laterally loaded joints, as well as for the assignment of stiffness properties of joints for the structural analysis, are summarized in this contribution. The effect of the nonlinearity and the load-to-grain orientation dependence of connection slip, of elastic deformation in the surrounding wood matrix, and of the deviation between load and displacement direction are discussed. Comparison of various models demonstrates the pronounced effect of the load-to-grain orientation dependence and the nonlinearity in connection slip on the load distribution, particularly in case of moment loading. The effect of elastic deformation in the wood matrix on the load distribution increases with increased size of joints, even more pronounced when joints are loaded by a shear force perpendicular to the grain. In case of normal force loading, the non-uniform load distribution due to elastic deformation in the wood matrix reduces rapidly with increased relative joint displacement. Pros and cons of the modeling approaches as well as necessary input data are discussed in relation to the design process and European standardization.

  • 49. Bader, Thomas K.
    et al.
    Braovac, Susan
    Fackler, Karin
    Hofstetter, Karin
    Stiffness Properties of the Archaeological Oak Wood from the Oseberg Ship2011Inngår i: Cultural Heritage Preservation.EWCHP - 2011: Proceedings of the European Workshop on Cultural Heritage Preservation. Berlin, Germany, September 26 to 28, 2011, Fraunhofer IRB Verlag, 2011, 164-170 s.Konferansepaper (Fagfellevurdert)
  • 50.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Braovac, Susan
    University of Oslo, Norway.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Microstructure-Stiffness Relations of the Ancient Oak Wood from the Oseberg Ship2010Inngår i: International Workshop on "Modeling Mechanical Behavior of Wooden Cultural Objects", Krakow, 2010, 22-23 s.Konferansepaper (Annet vitenskapelig)
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