ON THE FLOW BEHAVIOR OF CONSTRAINED DUCTILE PHASES

Effects of the matrix/reinforcement interface and the mechanical properties and size of the ductile reinforcement on the flow behavior of the constrained ductile reinforcement have been evaluated using a tensile test on a single Nb lamina imbedded in MOSi2 matrix. It was found that work of rupture of the ductile reinforcement increased with size of the ductile reinforcement and with decreasing fracture energy of the matrix/reinforcement interface. It was also found that the work of rupture normalized by size and yield strength of the reinforcement was dependent on the interfacial properties and size of the reinforcement. Based on the observation, an analytical model is developed which gives insight into the influence on the stress-displacement curve of yield strength, work hardening, fracture energy of matrix/reinforcement interface, and size of the reinforcement. A characteristic decohesion length, which is a function of size of the reinforcement, has been identified by the model and related to the measured decohesion length. The results allow the extrapolation of the work of rupture measured from the large size of constrained ductile phases to the small size of the ductile phases. As the reinforcements used in composites are usually smaller in size than those tested in such tensile tests, the extrapolation of the work of rupture allows the contribution of ductile reinforcements to the toughness of a brittle matrix composite to be calculated.