Through thickness fatigue failure of fibrereinforced composites

Simple straight and curved beams of unidirectional glass-epoxy were tested in fatigue to investigate failure under overall interlaminar tension and shear combined with local stresses at cut plies. Similar behaviour was observed as under static loading, with overall and local stresses interacting to cause delamination. When normalised, all the results lay close to, or above, a line determined from previous tension tests on specimens with cut plies, suggesting that this could be used as the basis for through thickness fatigue strength calculations.