DAMAGE PROCESS MODELING ON SMC

The damage processes taking place in SMC, which has been subjected to monotonically increasing tensile loads, are analyzed and the stress-st rain curves are calculated. SMC is viewed as a laminate consisting of fiber bundles embedded in a resin/filler matrix. The stiffness of bund les and matrix is expected to be influenced by developing cracks, whic h lead to a reduction of the total stiffness of the SMC. Crack creatio n, and consequent bundle and matrix stiffness reduction, are viewed as a statistical process. The quadratic criterion in stress space and th e maximum strain criterion are used to predict failure in the fiber bu ndles and in the matrix, respectively. Residual stresses resulting fro m the high curing temperatures, anisotropic fiber orientation, and var ying content of filler particles in the matrix, inside and outside of the fiber bundles, are taken into account. The comparison of predicted stress-strain curves to experimental results, obtained on almost 20 d ifferent SMC materials, shows very good agreement, especially at elong ations less than 1%. The model developed in this work allows us to app reciate quantitatively the influence of different material and process ing parameters on the behavior of SMC, and in this way, to optimize it s composition. (C) 1996 John Wiley & Sons, Inc.