Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Forming induced wrinkling of composite laminates with mixed ply material properties; an experimental study
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
2015 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 78, 234-245 p.Article in journal (Refereed) Published
Abstract [en]

One disadvantage of multi-layer forming of unidirectional (UD) prepreg tape is the risk of out-of-plane wrinkling. This study aims to show how mixed ply material properties affect global wrinkling behaviour. An experimental study was performed using pre-stacked UD prepreg on a forming tool with varying cross sections. Parameters studied include local interply friction, effects of co-stacking and fibre stresses in critical fibre directions. Experimental evaluation was performed on out-of-plane defect height, type and location. The study shows that fibre stresses in some fibre directions were crucial for the shearing required to avoid wrinkling. The same fibre stresses may cause wrinkling if the lamina is stacked in a non-beneficial order. Changing the friction locally, or reducing the number of difficult combinations of fibre angles, improves the forming outcome slightly. However, in order to make a significant improvement, co-stacking or different fibre stacking is required.

Place, publisher, year, edition, pages
2015. Vol. 78, 234-245 p.
Keyword [en]
Carbon fibre, Prepreg, Forming
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-176329DOI: 10.1016/j.compositesa.2015.08.025ISI: 000362605100026Scopus ID: 2-s2.0-84940757122OAI: oai:DiVA.org:kth-176329DiVA: diva2:871873
Funder
XPRES - Initiative for excellence in production research
Note

QC 20151117

Available from: 2015-11-17 Created: 2015-11-03 Last updated: 2017-12-01Bibliographically 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

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Sjölander, JensÅkermo, Malin

Search in DiVA

By author/editor
Sjölander, JensÅkermo, Malin
By organisation
Lightweight Structures
In the same journal
Composites. Part A, Applied science and manufacturing
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 148 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf