INTERLAMINAR FAILURE OF UNIDIRECTIONAL GLASS EPOXY DUE TO COMBINED THROUGH-THICKNESS SHEAR AND TENSION/

A test specimen in the form of a hoop with two 90 degrees curved secti ons is described. When loaded in three point bending, both interlamina r tensile and shear stresses arise in the curved sections. Maximum ten sile and shear stresses occur at similar locations, allowing the combi ned effect of these stress components to be investigated. Changing the geometry of the specimen alters the ratio between interlaminar shear and tension. Experimental results are presented for two sets of unidir ectional glass fibre/epoxy specimens. It is shown that it is possible for specimens subjected to combined interlaminar tension and shear to withstand higher stresses than when subjected to only tension. This is believed to be due to the smaller volume subjected to the maximum ten sile stress as a result of the stress gradient along the length of the specimen. An approach is presented to account for this effect based o n Weibull statistical theory and a quadratic interaction equation betw een interlaminar tension and shear. Using stresses from finite element analysis, satisfactory predictions of the strength of the hoop specim ens can be made. Copyright (C) 1996 Elsevier Science Ltd