In this study, the effect of laminate thickness on the compressive behaviour of composite materials is investigated through systematic experimental work using the stacking sequences, [04]ns, [45/0/-45/90]ns, and [45n/On/-45n/90n]s, (n=2 to 8). Parameters such as fibre volume fraction, void content, fibre waviness and interlaminar stresses, influencing compressive strength with increasing laminate thickness are also studied experimentally and theoretically. Furthermore the stacking sequence effects on failure strength of multidirectional laminates are examined. For this purpose, two different scaling techniques are used; (I) ply-level technique [45n/On/-45n/90n]s, and (2) sublaminate level technique [45/0/-45/90]ns, An apparent thickness effect existes in the lay-up with blocked plies, i.e. unidirectional specimens ([04]ns) and ply-level scaled multidirectional specimens ([45n/On/-45n/90]ns, Fibre waviness and void content are found to be main parameters contributing to the thickness effect on the compressive failure strength. However, the compressive strength of the sublaminate level scaled specimens ([45/0/-45/90]ns,) is almost unaffected regardless of the specimen thickness (since ply thickness remains constant). From the investigation of the stacking sequence effect, the strength values obtained from the sublaminate level scaled specimens are slightly higher than those obtained from the ply level scaled specimens. The reason for this effect is explained by the fibre waviness, void content, free edge effect and stress redistribution in blocked 0° plies and unblocked 0° plies. The measured failure strengths are compared with the predicted values.

In this study, the effect of laminate thickness on the compressive behaviour of composite materials is investigated through systematic experimental work using the stacking sequences, [04]ns, [45/0/-45/90]ns, and [45n/On/-45n/90n]s, (n=2 to 8). Parameters such as fibre volume fraction, void content, fibre waviness and interlaminar stresses, influencing compressive strength with increasing laminate thickness are also studied experimentally and theoretically. Furthermore the stacking sequence effects on failure strength of multidirectional laminates are examined. For this purpose, two different scaling techniques are used; (I) ply-level technique [45n/On/-45n/90n]s, and (2) sublaminate level technique [45/0/-45/90]ns, An apparent thickness effect existes in the lay-up with blocked plies, i.e. unidirectional specimens ([04]ns) and ply-level scaled multidirectional specimens ([45n/On/-45n/90]ns, Fibre waviness and void content are found to be main parameters contributing to the thickness effect on the compressive failure strength. However, the compressive strength of the sublaminate level scaled specimens ([45/0/-45/90]ns,) is almost unaffected regardless of the specimen thickness (since ply thickness remains constant). From the investigation of the stacking sequence effect, the strength values obtained from the sublaminate level scaled specimens are slightly higher than those obtained from the ply level scaled specimens. The reason for this effect is explained by the fibre waviness, void content, free edge effect and stress redistribution in blocked 0° plies and unblocked 0° plies. The measured failure strengths are compared with the predicted values.

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