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.