Full-Field strain analysis of compressively loaded flat composite laminates with undulated fibers

T. C. Henry, C. E. Bakis, J. C. Riddick, E. C. Smith

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations

Abstract

In filament wound composites, the existenceof undulated fibers introduces unique challenges in the prediction of compressive modulusand strength using traditional laminated composite theories. Undulations, consisting of fibers passing over and under each other,result from the interweaving process inherent in helical fiber winding patterns. In the current investigation, full field strain measurements were used to evaluate local strain distributions in the region ofa 0-deg. undulated ply in a [0n/90n]s laminate(n=2,4,6) and a 30-deg. undulated ply in a [30n/-60n]s laminate (n=2,4). Specimens were manufactured withcarbon fibers, various amplitudes of undulation, and matrix materials with three different moduli of elasticity. Full-field strains were measured on the free edge and across the width of the compressively loaded specimens using two-dimensional digital image correlation (DIC). The observed strains were highly influenced by the undulation geometry. The axial modulus of a [0n/90n]s laminate was more sensitive to reinforcement undulation when the matrix was flexible ratherthan rigid.An undulation with an amplitude/length ratio of 0.1 reduces the average axial modulus of elasticity in the undulation region by approximately 43% and 3% in laminates with flexible and rigid matrices, respectively, relative to a similar material without undulation. Observations of strain on the free edge revealed that fiber undulation caused elevated out-of-plane shear and through-thickness normal strains in regions eventually involved in the fiber microbuckling failure process. This information could not be obtained by observing strains across the width of the specimen. Comparisons with filament wound tubes indicated agreement in the failure modes.

Original languageEnglish (US)
Title of host publicationProceedings of the American Society for Composites - 29th Technical Conference, ASC 2014; 16th US-Japan Conference on Composite Materials; ASTM-D30 Meeting
PublisherDEStech Publications
ISBN (Electronic)9781605951249
StatePublished - Jan 1 2014
Event29th Annual Technical Conference of the American Society for Composites, ASC 2014; 16th US-Japan Conference on Composite Materials; ASTM-D30 Meeting - La Jolla, San Diego, United States
Duration: Sep 8 2014Sep 10 2014

Publication series

NameProceedings of the American Society for Composites - 29th Technical Conference, ASC 2014; 16th US-Japan Conference on Composite Materials; ASTM-D30 Meeting

Other

Other29th Annual Technical Conference of the American Society for Composites, ASC 2014; 16th US-Japan Conference on Composite Materials; ASTM-D30 Meeting
CountryUnited States
CityLa Jolla, San Diego
Period9/8/149/10/14

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites

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