Interlaminar shear strength of cloth-reinforced composites

A test specimen to define the interlaminar shear strength of cloth-reinforced composite materials is developed. The specimen is a hollow circular cylinder which is subjected to torsion. The experiment is employed for the determination of the warp-normal shear strength of a graphite-fiber carbon-matrix composite material. It is demonstrated that the proper failure mode takes place, while the problems associated with the use of strain gages on this porous material, nonlinearity, difference in tension and compression properties, and the influence of clamping effects are all discussed. The proposed experiment appears to be ideally suited to study the interlaminar shear response of cloth-reinforced composites.