Experimental and numerical damage characterization of glass/polypropylene multidirectional laminates under quasi-static loading condition

Polypropylene (PP) as a commodity thermoplastic, when reinforced with continuous glass fibers provides cost-effective composites. However, the low glass transition temperature and fabrication induced semi-crystalline morphology of PP set challenges for the experimental characterization especially when the quantification of damage mechanisms in multidirectional laminates is concerned. This paper is aimed at performing in-situ experimental observation, quantification and theoretical modeling of damage mechanisms in glass fiber reinforced polypropylene multidirectional laminates subjected to uniaxial quasi-static loading conditions. Two Stereo Digital Image Correlation systems (3D-DIC) are applied to measure the full-field strains and quantify the extent of damage mechanisms from the specimen's edge. The effects of ply thickness, off-axis ply orientation and location on damage initiation and growth are studied by testing different lay-ups. To validate the experimental measurements, a recent physics-based modeling technique is implemented that can predict the evolution of damage modes as well as their effects on the laminate properties. Good agreements are observed between the experimental measurements and simulation results which verify the accuracy of both analyses.