Study of non-linear tensile behaviour of discontinuous carbon-epoxy prepreg composites

Gergely Czel, Michael R Wisnom

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

2 Citations (Scopus)

Abstract

A new manufacturing technique was developed for cut blocked ply unidirectional carbon/epoxy laminates producing very well controlled discontinuous ply model specimens.
Two different specimen types were compared, and the second with 0.25 mm ply block thickness, and 6.6 mm overlap length showed significantly nonlinear stress-strain response before failure.
The reason for different stress-strain characteristics within the different specimen types was the difference in the ply block stiffness due to the thickness and variable overlap length. The thinner ply blocks and the higher overlap length of type 2 specimens resulted in higher stress and strain to final failure, because the total area of sheared interfaces was increased. The significant increase of strain to failure caused higher mode II energy release rate in the overlap zone allowing for crack propagation on the interfaces before final failure. The sufficiently long overlap zone provided enough residual load transfer capacity after crack initiation to make propagation stable for a limited extent.
A more favourable and controlled overall stress-strain response was shown for type 2 specimens compared to that of continuous UD composites which exhibit linear behaviour before sudden failure. Almost as high initial modulus was achieved as that of continuous fibre reinforced UD specimens. The reasonably high maximum stress (above 1000 MPa) was reached after a significant reduction in stiffness, which indicates progressive damage on the ply block interfaces before final failure. These results are even more notable, considering that the specimens had no continuous fibres between the grips.
Original languageEnglish
Title of host publicationProceedings of the International Conference on Composite Materials ICCM19
Number of pages8
Publication statusPublished - 2 Aug 2013
EventInternational Conference on Composite Materials - Montreal, Canada
Duration: 29 Jul 20132 Aug 2013
http://www.iccm19.org/

Conference

ConferenceInternational Conference on Composite Materials
Abbreviated titleICCM 19
CountryCanada
CityMontreal
Period29/07/132/08/13
Internet address

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