Edge delamination in laminated composites

A damage evolution theory for the effects of the rather complicated edge delamination phenomena on composite laminate response is developed. The theory is a mechanics-based formulation which quantifies the damage development of a laminate under general loading, and incorporates it directly into the laminate constitutive equations. The theoretical development attempts to describe the basic features of the edge delamination phenomena by introducing a single laminate-specific constant φ. The methodology of φ selection is presented for a [± 45/0/90]_s T300 graphite/epoxy laminate. Edge effects are demonstrated by comparing the state of the above laminate with and without edge delamination damage. The capability of the theory in predicting the volume scaling effect (the phenomenon whereby the onset of edge delamination is observed to be a function of ply thickness, when the stacking sequence is invariant) is shown through consideration of the failure strengths and strains of the [± 25 90_n]_s laminate series.