FRACTURE-RESISTANCE OF POLYBLENDS AND POLYBLEND MATRIX COMPOSITES .1.UNREINFORCED AND FIBER-REINFORCED NYLON 6,6 ABS POLYBLENDS/

The deformation behaviour and the fracture resistance of a range of ny lon 6,6/ABS alloys of varying composition both with and without the pr esence of glass fibres were investigated. The deformation behaviour wa s characterized by careful measurements of the volumetric strain durin g tensile tests in order to understand the relative roles of cavitatio n and shear yielding in these materials. The fracture resistance was i nvestigated in detail in the fracture mechanics sense by characterizin g the J-integral fracture initiation toughness. In materials exhibitin g stable crack growth, a new parameter, namely, the plateau value of t he J-integral fracture resistance curve, was measured directly and rep resented the resistance of the material to stable crack growth. The re sults showed that the relationship between the deformation behaviour a nd fracture resistance was related to the extent of damage that develo ped in the crack-tip zone. Substantial additional toughening was devel oped during the crack extension stage both in the presence a nd absenc e of glass fibres. Glass fibres were found to promote shear yielding a nd, as a result, enhance both the fracture initiation as well as the f racture propagation resistance of the nylon 6,6/ABS alloys.