Is there a thickness effect on compressive strength of unnotched compositelaminates?

The effect of laminate thickness was investigated on the compressive behavi or of unidirectional and crossply composites. A recently developed compress ion test method for thick composites was used to test specimens from 16 to 200-plies thick. In all cases the stress-strain behavior to failure is nonl inear and failure strength is matrix dominated. Longitudinal compressive fa ilure is triggered by matrix failure accompanied by fiber microbuckling and the compressive strength is greatly degraded by initial fiber misalignment . The longitudinal compressive strength shows a mild trend of decreasing va lues with increasing thickness. It can be explained that, even if such a tr end is significant, increasing size would have a diminishing effect on comp ressive strength for initial fiber misalignments greater than 1.5 to 2 degr ees.