Influence of the stacking sequence and crack velocity on fracture toughness of woven composite laminates in mode I

Woven composites are well-known for their good transverse properties and for their high fracture toughness. The damage mechanisms leading to delamination in woven composites are identified in mode I. The influence of several parameters, including the draping sequence and the fiber/matrix interface on the fracture toughness of woven composite laminates is studied. Pure mode I tests are carried out on several carbon/epoxy and glass/epoxy woven composites configurations and the differences observed are discussed from a fractographic point of view. A novel experimental method is designed to perform dynamic pure mode I tests. The study illustrates the high fracture toughness of the composites made of woven fabrics as well as the influence of the orientation of the plies, the nature of the fibers and the addition of an adhesive film on the fracture toughness in mode I. The dynamic tests prove that, on the configurations tested and for crack velocities up to 100 m/s, the crack propagation velocity has a limited effect on the value of GIc.