Abstract
The growth of individual transverse ply cracks during tension-tension fatigue of (0/90//2)s GFRP and (0/90//3)s CFRP has been observed using transmitted light and penetrant enhanced X-radiography, respectively. The growth rate of cracks in both laminates is independent of crack length but depends on the spacing between the cracks. Very low growth rates occur for small crack spacings or if crack branching occurs. The results are interpreted using a stress intensity factor approach.