Mode I fracture resistance characteristics of graphite/epoxy laminated composites

Abstract Mode I crack resistance behavior of fiber‐reinforced (graphite/epoxy) composites laminated unidirectionally and anti‐symmetrically was studied. Double cantilever beam (DCB) specimens of stacking sequences, [O₁₂//O₁₂] and [(O/90)_3s//(90/O)_3s] were used where // represents the initial crack location. Resistance curves (R‐curves) were constructed for three initial crack lengths in order to determine the effects of initial crack length on the resistance behavior. The resistance force, G_R, for a crack increment was determined from the compliance calibration method. The results show that for the case of [(O/90)_3s//(90/O)_3s], the initial crack deviated from the midplane and propagated in a zigzag fashion within 13^th(90‐deg), while the crack propagated along the midplane for a [O₁₂//O₁₂] case. The results also show that for both cases, G_R was affected by the initial crack length before G_R was stabilized. However, G_R was not affected by initial crack length when G_R was stabilized for each case.