Crack development in graphite—epoxy cross-ply laminates under uniaxial tension

Abstract

When a graphite-epoxy laminate of cross-ply (0/90) lamination is subjected to uniaxial tension, transverse cracks in the 90° ply can be induced at strains as low as 0·3%. These cracks will continue to form in increasing numbers if the applied tension increases. At some late stage of loading, and before the breaking of fibers in the 0° ply, several other matrix-dominant cracking modes may emerge. All seem to be precipitated by the transverse cracks. The late-stage matrix cracks propagate individually in a stable manner, but can coalesce and thus cause disintegration of the laminate. The objective of this paper is to describe analytically the various cracking events in the cross-ply laminates as they occur during the course of loading. The particular laminates considered belong to the [0 2/90 n ] s , n = 1, 2 and 4 , family. Emphasis is placed on determining why a certain mode of cracking occurs while some other modes do not. Especially for the cracking modes which occur during late-stage loading, an analysis will be made to explain why they are critical to the final strength of the laminate. The analytical results are compared with experiments on laminates made from a graphite-epoxy system.