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Forming induced wrinkling of composite laminates: A numerical study on wrinkling mechanisms
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0001-8111-5202
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-6616-2964
2016 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 81, 41-51 p.Article in journal (Refereed) PublishedText
Abstract [en]

When manufacturing composite aircraft components consisting of uni-directional prepreg laminates, Hot Drape Forming (HDF) is sometimes used. One issue with HDF is that, in contrast to hand lay-up where normally only one ply is laid up at a time, multiple plies are formed together. This limits the in-plane deformability of the stack, thus increasing the risk of out-of-plane wrinkling during forming. In this paper mechanisms responsible for creating different types of wrinkles are explained. It is shown through simulations how the wrinkles are created as a result of interaction between two layers with specific fibre directions or due to compression of the entire stack. The simulations are compared to experimental results with good agreement.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 81, 41-51 p.
Keyword [en]
A. Prepreg, C. Process simulation, E. Forming
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-181434DOI: 10.1016/j.compositesa.2015.10.012ISI: 000369214600005ScopusID: 2-s2.0-84946781893OAI: oai:DiVA.org:kth-181434DiVA: diva2:900771
Funder
XPRES - Initiative for excellence in production research
Note

QC 20160205

Available from: 2016-02-05 Created: 2016-02-02 Last updated: 2016-04-25Bibliographically approved
In thesis
1. Towards defect free forming of multi-stacked composite aerospace components using tailored interlayer properties
Open this publication in new window or tab >>Towards defect free forming of multi-stacked composite aerospace components using tailored interlayer properties
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Use of lightweight materials is an important part of reduction of fuel consumption by commercial aircraft. A considerable number of structural aircraft parts are therefore built of thin layers of epoxy pre-impregnated carbon fibres stacked to laminates. Manufacturing these by hand is costly and different methods of automation have therefore been developed. One cost-effective way of manufacturing is Automated Tape Lay-up of flat stacks followed by a Hot Drape Forming operation. A well-known problem in the industry within forming is fibre wrinkling, which can cause a serious strength knock down. The focus of this thesis has therefore been on understanding how and why wrinkles develop during forming of multi-layer stacks and, based on this, investigate different methods for process and material improvements.

The work presented initially investigates the dependency between stacking sequence and wrinkle development. It is shown that wrinkle free forming can be obtained by changing the fibre stacking order. In the following investigation it is shown that the wrinkles cannot be entirely eliminated by local stiffening of the critical layers. In a, related study it is shown that different kinds of wrinkles develops during forming; wrinkles may be either due to global buckling of the entire lay-up or local compression of single layers. Global buckling is due to excessive material. Local compression occurs as the material shear during forming.

The work presented leads to an understanding of the importance of making the beneficial neighbouring fibre layers interact during forming. One way to connect neighbouring layers is to tailor the interlayer properties. A study is presented that shows how local manipulation of interlayer properties may steer the multi-layered material into a different deformation mechanisms. The manipulation in this thesis is performed using Multi Wall Carbon Nano Tubes, thermoplastic veils or consolidation of thermoplastic toughener particle interlayers.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 30 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2016:19
Keyword
Carbon Fibre, Composites, Prepreg, Forming
National Category
Aerospace Engineering
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-185694 (URN)978-91-7595-950-4 (ISBN)
Public defence
2016-06-01, Sal F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
VINNOVA, NFFP5 2010-01257VINNOVA, NFFP6 2013-01220VINNOVA, GF Demo 2012-01031VINNOVA, GF Demo 2013-04667
Note

QC 20160425

Available from: 2016-04-25 Created: 2016-04-25 Last updated: 2016-05-16Bibliographically approved

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Sjölander, JensÅkermo, Malin
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