Influence of ply orientation on mode I interlaminar fracture toughness of woven carbon and glass composites

Abstract

The paper presents the study of the influence of ply orientation on mode I interlaminar fracture toughness of woven carbon and glass composites. Double cantilever beam test of mode I as performed on twill woven car-bon/epoxy and E-glass/epoxy composite systems. Speci-men stacking sequences with initial delamination at the angles of 0//0, 0//90, + 45//− 45 and 0//+ 45 were used. To define the exact instant of crack initiation the criteria of nonlinearity (NL) and 5% offset or maximum force criteria were used. The conservative Berry method and nonlinear-ity criterion that enable to determine the increase of the damages in microlevel were chosen for the result estima-tion. The evaluation of the influence of the layer rein-forcement angles on GIc disclosed that the reinforcement of the layers in the delamination plane at the angles of 0//0 and especially 90//0 was the most dangerous. Thus in the structures the layers should be reinforced at the angles of 0//+45 because GIc was by 1.4 times greater if compared with the instance of 0//0 angles.