Validated progressive damage analysis of simple polymer matrix composite laminates exhibiting matrix microdamage: Comparing macromechanics and micromechanics

Abstract

The generalized method of cells micromechanics theory, employing the multi-axial mixed-mode continuum damage mechanics model for the matrix of the composite, is used to predict the evolution of matrix microdamage in un-notched (simple), unidirectional and laminated polymer matrix composites. Matrix microdamage is considered to be the evolution of subscale phenomena (including micro-crack, micro-fissure, micro-void, and shear band growth) that are responsible for all non-linearity in the composite up to the onset of more severe damage mechanisms, such transverse cracking, fiber breakage or delamination. Micromechanics is used to explicitly resolve the constituents of the composite at the microscale (fiber-matrix scale). The micromechanics model is validated against experimental data for numerous different laminate stacking sequences and a previously validated macroscale (e.g, lamina-scale), thermodynamically-based, work potential theory (Schapery theory). The inputs used in the continuum damage model, which was incorporated in the micromechanics theory, were calibrated against the same three experimental stress-strain curves utilized to calculate the inputs for the macroscale model. The agreeable predictions, obtained with the micromechanics model, establishes that both the macro- and micro-models are suitable for progressive damage analysis of laminated composites, considering only matrix microdamage. Moreover, the validated micromechanics theory is utilized to study the effect of fiber volume fraction on the matrix microdamage evolution in the various lay-ups. This demonstrates a key capability of the micromechanics approach that is lacking in the macromechanics method due to the macroscale assumption that the laminae are monolithic, anisotropic materials.