Some New Variational Mechanics Results on Composite Microcracking

Using variational mechanics we present mathematical bounds on the effective modulus of a crossply laminate containing microcracks in the 90◦ plies. An average of the two bounds provides an effectively exact solution to the modulus reduction problem. The problem of predicting microcracking is reduced to finding the energy release rate for formation of a complete microcrack. From the bounds on effective modulus we derive both rigorous and practical bounds to the energy release rate for microcracking. Again, an average of the two bounds provides an effectively exact solution to the energy release rate problem.