A PROGRESSIVE QUADRATIC FAILURE CRITERION FOR A LAMINATE

The application of failure criteria to laminated composites is a criti cal step in the determination of the strength and safety of a point in a structure under combined loading conditions. Non-homogeneous stress es within a structure may induce a complicated failure scenario whereb y one ply at a point can initiate failure and affect other plies at th e same point or the same ply at a neighboring point. After the first-p ly failure, the stiffness of the ply is reduced by either matrix or fi ber failures. The strength of the laminate at the same point is evalua ted again to see if the laminate can carry an additional load. This pl y-by-ply analysis progresses until the ultimate strength of the lamina te is reached. The process can be extended to structures subjected to non-homogeneous stresses where both ply-by-ply and point-to-point stre ngth analyses are progressively applied. (C) 1998 Elsevier Science Ltd . All rights reserved.