Mixed-mode effects on the toughness of polymer interfaces

Normal, symmetric fracture toughness tests can give high values for the toughness of the joint between the immiscible polymers polystyrene and polymethylmethacrylate. These high values, which are caused by crazes growing away from the interface into the polymer with lower craze resistance, are not a fair characterization of the toughness of the joint. Much lower, and more realistic, toughness values are obtained by the use of an asymmetric test that tends to drive the crack and crazes more along the interface. © 1990 Chapman and Hall Ltd.