Chapter 5.13 - The predictive capability of failure mode concept-based strength criteria for multi-directional laminates—Part B

Abstract

This chapter represents the author's contribution to Part B of the worldwide failure exercise. An assessment is made of the correlation between the predictions published in Part A and experimental results provided for 14 test cases involving bi-axial initial and final failure envelopes and stress–strain curves of various unidirectional and multidirectional laminates. The theory, implemented into a computer code, employs 3-D failure criteria for unidirectional (UD) laminae together with the nonlinear modeling of laminae and laminate. The criteria are based on the author's Failure Mode Concept (FMC). An improvement in the computer code and simplifications os the failure criteria are made so, that large strains to failure may be captured. Special emphasis has been put on the difference between an isolated and an embedded UD lamina. The correlation between the predictions and the test data is very satisfactory for the UD laminae, and is generally satisfactory for the laminates, especially where Fiber Failure (FF) is the dominant mode, which is the case for well-designed (according to netting theory) laminates. Discrepancy between predictions and test data is largest for the ± 55° angle ply glass/epoxy laminates and also in areas of large deformations (involving post failure progression beyond the occurrence of the various Inter Fiber Failure (IFF) modes). Further steps, including testing and modeling are identified for achieving a better understanding of failure prediction.