Micromechanics of Failure for Ultimate Strength Predictions of Composite Laminates

A micromechanics-based constituent progressive damage model was proposed in this study to predict macroscopic failure behavior of composite laminates under multi-axial mechanical loadings as well as thermal influences. For this purpose, a micromechanics-based failure theory, named the micromechanics of failure, has been further developed not only to account for the constituent failure but also to progress damage. We first modeled the unit cell of the microstructure of a UD lamina both to derive ply properties from constituent properties and to calculate micro stresses within fiber and matrix from macro-level ply stresses using stress amplification factors. Independent failure criteria dedicated to each constituent are employed to judge failure modes of fiber, matrix, and fiber-matrix interface. Good agreement between theoretical predictions and test data was achieved.The authors thank the Stanford Composites Design Team headed by Prof. Stephen Tsai at Stanford University for technical discussion and collaboration. The development of the MMF has been partially funded by AFOSR with Dr Charles Lee as a technical monitor