A progressive quadratic failure criterion, part B

The predictions for UD and laminated composites from Part A of this exercise [Compos. Sci. Technol. (1998) 1023] are compared with test data [Compos. Sci. Technol. (in press)]. Questions concerning the accuracy and flexibility of our progressive criterion are answered herein. In general, the intact and degraded models provide good agreement. So do several stress/strain curves. The selective damage scheme was found to be the source of some problems at certain loading conditions. By eliminating this selective degradation, agreement between the prediction and the test data were improved. Empirical factors are easily adjusted to close the gap between theory and data. Those factors are within the bounds set by the theory in Part A. Discrepancies do happen and some can be attributed to bad data while some have no simple explanation. All in all, the exercise has been worthwhile and may have impact on the growth of composites in the years to come. An easy to learn Excel-based program for plotting failure envelopes can be downloaded free of charge for interested parties.