Some Observations on the Analysis of In-Plane Matrix Failures in Fibrous Composite Laminates

The prediction of matrix failures of fibrous composite laminates under in-plane loading is discussed. It is shown that a complete micromechanical analysis is needed to analyze such failures, even when attention is focused on significant structural damage as opposed to discontinuous microcracking. It is shown that matrix-dominated composite structures could not be certified even if they could be analyzed reliably. All that is needed is an ability to distinguish between those laminates which fail in the matrix and those which fail in the fibers since structurally significant matrix failures preceding the breaking of the fibers automatically signify inferior laminates. This permits the reliable use of failure theories very much simpler than conventional micromechanics to predict fiber-dominated strengths with no loss of accuracy. There is actually no need to calculate matrix-dominated strengths. Indeed, since fewer material properties are needed and are easier to measure than the much larger number needed for a full micromechanical assessment, physically realistic analyses confining attention to failures of only the fibers are actually more accurate than any micromechanical prediction of laminate strength under in-plane loads.