Effect of the molding conditions on mode II interlaminar crack propagationin continuous glass fiber/polypropylene composites

The effect of molding conditions on the resistance to Mode II interlaminar crack propagation under monotonic and cyclic loading of unidirectional cont inuous glass-fiber composite, with a polypropylene (PP) matrix was studied. The distribution of the fibers and of the crystalline and amorphous compon ents of the matrix phase. the melting temperature and the amount of crystal linity are related to the molding conditions employed and to the resulting flexural strength and modulus, apparent interlaminar shear strength and You ng's modulus. Mode II crack propagation. either cyclic or monotonic, is str ongly affected by the fiber-matrix interface and matrix morphology, The dis tribution of the soft amorphous PP phase in the semi-crystalline PP matrix appears to be the controlling parameter determining the fracture and fatigu e resistance of the composite. The fractographic features clearly show the role that this phase plans during crack propagation. A relationship between the shear cusp size measured on the fatigue surfaces and the cyclic strain energy release rate is proposed.