Chapter 3.1 – Prediction of composite laminate fracture: Micromechanics and progressive fracture

Publisher Summary This chapter describes an investigation on the prediction of first-ply failure and fracture in selected composite laminates made from glass/epoxy and graphite/epoxy polymer-matrix composites and subjected to uniaxial and combined loadings. Failure envelopes are generated for combined loading of these laminates on the basis of first-ply failure and laminate fracture. The chapter also presents a micromechanics-based theory and progressive fracture for the evaluation of failure envelopes. It explains an exercise organized by Hinton and Soden to confirm the current state-of-the-art for predicting failure in composites and describes the results obtained in two processes—generation of first-ply failure envelopes for combined loading by using the micromechanics-based uniaxial composite strengths and generation of laminate fracture envelopes and stress/strain diagrams for uniaxial and combined loading by using progressive fracture. The effects of residual stresses on the laminate first-ply failure are also evaluated as the differences between pristine and in situ constituent properties. The chapter explains the detailed calibration of the pristine constituent material properties to the unidirectional composite properties, so that the micromechanics used will reproduce the unidirectional composite properties provided. It discusses the specific theories and computer codes to generate the laminate failure envelopes. These computer codes integrate composite mechanics and progressive structural fracture—Integrated Composite Analyzer (ICAN) and Composite Durability Structural Analyzer (CODSTRAN). The chapter describes stress versus strain curves for all laminates as determined by progressive fracture via CODSTRAN.