Shrinkage artifacts in semi-spherical spherulites at the interface of glass fibre reinforced polypropylene

Shrinkage artifacts in the form of series of circumferential bands were observed at the interface in air-cooled glass fibre-reinforced polypropylene specimens. The nature of the circumferential bands was examined and the formation of the bands was explained. Experimental data indicate that unique shrinkage artifacts in the form of series of circumferential bands formed in some spherulites at the interface of glass fibre/polypropylene pull-out specimens. The circumferential bands are kink bands which form to relieve localized residual stresses in the interfacial surface of the semi-spherical spherulites. The kink bands are parallel to the tangential cross-hatched lamellae in the α form polypropylene spherulites. The kink bands exist preferentially near the outer perimeter of the spherulites where the localized residual stresses are probably highest.