Fibre/matrix stress transfer through a discrete interphase: 2. High volumefraction systems

The effect of plasticity on the reinforcing efficiency of a broken fibre, a nd the magnitude of the strain concentration experienced by the surrounding fibres, has been assessed by the use of a 3-dimensional finite-element mod el. II was found that the occurrence of plasticity in the matrix markedly r educed the strain concentration in fibres adjacent to a fibre fracture. The effect of increasing the fibre volume fraction on the level of strain conc entration was examined and it was found that when deformation was elastic, at low applied strain, a higher fibre volume fraction led to an increase in the strain concentration. However, when plastic deformation occurred, the strain concentration factor was significantly lower and increasing the fibr e volume fraction had a negligible effect. The influences of soft or stiff interphases between fibre and matrix were also studied and, during elastic deformation, these were found to be largely insignificant in determining th e stress transfer processes, for the interphase thickness studied. At highe r strains, the occurrence of plastic deformation in either the matrix or in terphase was found to dominate the strain-transfer process and, therefore, the strain concentration. The reasons behind these dependencies are discuss ed and their effect on the failure of bulk composites considered. (C) 2001 Elsevier Science Ltd. All rights reserved.