HERRINGBONE FRACTURE OF A POLYCARBONATE ABS BLEND

Tensile fracture mechanisms in single edge notched injection-moulded specimens of a polycarbonate/ABS 30/70 wt % blend have been studied by fractography. When the tensile force was applied parallel to the injection direction, a herringbone pattern could be observed on the fracture surface, while for the perpendicular case, a reverse herringbone pattern was seen. At the same testing condition, the former was tougher than the latter. Fracture images and two-dimensional temperature profiles in the thickness direction were used to locate the crack initiation sites. Herringbone fracture occurred when the main crack repeatedly interacted with secondary cracks initiated along the centreline. Reverse herringbone fracture was formed in a similar mechanism but secondary cracks initiated near the edge. Anisotropy of the fracture modes was attributed to the processing-induced orientation of the polycarbonate phase near the edge.