The Effect of Specimen Size on the Compressive Str

Authors: C Soutis J Lee

Publish Date: 2002

Volume: , Issue: , Pages: 153-162

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Abstract

The effect of specimen gauge section length x width was investigated on the compressive behaviour of a T300/924C 45/45/0/903 carbon fibreepoxy laminate A modified Imperial College compression test fixture was used together with an antibuckling device to test 3 mm thick specimens with a 30×30 50×50 70×70 and 90mm×90 mm gauge length by width section In all cases failure was sudden and occurred mainly within the gauge length Postfailure examination suggests that 0° fibre microbuckling is the critical damage mechanism that causes final failure This is a matrix dominated failure mode and its triggering depends very much on initial fibre waviness It is suggested that manufacturing plays a significant role in determining the compressive strength and may be more important as the section thickness of the composite increases Additionally compressive tests on specimens with an open hole are performed The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor This suggests that the material is not ideally brittle and some stress relief occurs around the hole Xray radiography reveals that damage in the form of fibre microbuckling and delamination initiates at the edge of the hole at approximately 80 of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2–3 mm depends on specimen geometry This damage growth and failure are analysed by a linear cohesive zone model Using the independently measured laminate parameters of compressive unnotched strength and inplane fracture toughness the model predicts successfully the notched strength as a function of hole size and width

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