Change search
ReferencesLink to record
Permanent link

Direct link
In-plane deformation of multi-layered unidirectional thermoset prepreg - Modelling and experimental verification
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-6616-2964
2014 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 56, 203-212 p.Article in journal (Refereed) Published
Abstract [en]

Sheet forming of unidirectional prepregs is gaining increased interest as a cost efficient alternative manufacturing method. Its potential lies within the use of automatically and efficiently stacked flat prepregs, which in a second step can be formed. A successful forming requires understanding of the properties of the uncured material. Here, the in-plane deformation behaviour of two different unidirectional thermoset prepregs is investigated. Experimental measurements are performed, showing the importance of stacking sequence and its effect on the forming behaviour of stacked prepreg. Finite element models are developed, using material models calibrated from bias extension tests and interlaminar friction tests. The method developed can be used to predict the reaction force and fibre reorientation during in-plane forming of thermoset prepreg, for one of the considered material systems. Further, it enables prediction of the effect of stacking sequence, which is promising for future full-scale forming simulations.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 56, 203-212 p.
Keyword [en]
Carbon fibres, Prepreg, Finite element analysis (FEA), Forming
National Category
Vehicle Engineering
Research subject
SRA - Production
URN: urn:nbn:se:kth:diva-106510DOI: 10.1016/j.compositesa.2013.10.005ISI: 000329264900020ScopusID: 2-s2.0-84887706645OAI: diva2:573965
XPRES - Initiative for excellence in production research

QC 20140131. Updated from submitted to published.

Available from: 2012-12-04 Created: 2012-12-04 Last updated: 2016-08-11Bibliographically approved
In thesis
1. Forming of stacked unidirectional prepreg materials
Open this publication in new window or tab >>Forming of stacked unidirectional prepreg materials
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To reduce cost of structural composites, the development of more efficient manufacturing methods is of great interest. An automatic tape layer (ATL) can be used to perform the layup in an efficient way for flat sheets and the second step is by pressure forming the prepreg stack onto a given mould. Sheet forming of thermoset prepreg, also known as hot drape forming, is a promising manufacturing method when combined with automatically stacked laminates. To reach the desired shape, without flaws such as wrinkles and severe fibre angle deviation, knowledge about the forming behaviour of stacked material is important. A simulation of the forming can add to the understanding of mechanisms causing defects and also how to avoid them.

A continuum mechanical finite element approach is used to model the forming of stacked unidirectional prepreg. This with the aim of finding mechanisms causing defects, such as out-of-plane wrinkling and in-plane waviness. Data from experimental characterisation of the materials are required for the constitutive material models. An experimental approach is used to investigate the intraply (within the layer) and interply (between the layers) deformation. The intraply deformation behaviour is investigated by a bias extension test, where resistance to deform and fibre rotation are registered. The interlaminar friction characteristics in the prepreg/prepreg interface are retrieved from tests performed with a specially designed rig. Measurements on the bending stiffness of the prepreg, both transverse to and in the fibre direction, are used in the out-of-plane model.

Different aerospace-grade thermoset prepreg materials are tested and major differences in behaviour are found. Since epoxy is brittle, the resin is toughened by thermoplastics, for some materials in liquid phase and for others by solid particles. These particles seem to influence both the intraply deformation modes and increase the level of friction between layers.

The experimental data from shear, friction and bending tests are used to calibrate the chosen material models. In-plane forming simulations confirm the affect stacking sequence have on the forming behaviour. Full-scale forming simulations on a joggles beam are performed with one of the tested material systems. Two different stacking sequences, with the same amount of fibre in the main directions, are analysed and compared. Both numerical and experimental forming shows that the coupling between layers, due to the interply friction, will affect the forming behaviour and in some cases create wrinkles. Wrinkles can develop both in the plane and out-of-plane, where only the in-plane waviness is present in the performed forming simulations.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. vii, 31 p.
Trita-AVE, ISSN 1651-7660 ; 2012:75
National Category
Composite Science and Engineering
Research subject
SRA - Production
urn:nbn:se:kth:diva-106269 (URN)978-91-7501-558-3 (ISBN)
Public defence
2012-12-18, E2, Lindstedtsvägen 3, KTH, Stockholm, 10:15 (English)
KEKS Kostnadseffektiva kompositstrukturerPRICE Producerbarhet i centrumXPRES
XPRES - Initiative for excellence in production researchTrenOp, Transport Research Environment with Novel Perspectives

QC 20121204

Available from: 2012-12-04 Created: 2012-12-03 Last updated: 2013-04-11Bibliographically approved

Open Access in DiVA

fulltext(1704 kB)2 downloads
File information
File name FULLTEXT01.pdfFile size 1704 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Larberg, YlvaÅkermo, Malin
By organisation
Lightweight Structures
In the same journal
Composites. Part A, Applied science and manufacturing
Vehicle Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 274 hits
ReferencesLink to record
Permanent link

Direct link