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Multiscale Finite Element Modeling of Carbon Fiber Reinforced Polymeric Composite Containing Void Defects



The research demonstrates the implementation of a multi-scale modeling approach for predicting the mechanical effects of porosity on carbon fiber reinforced polymer composite. Two load cases are singled out for analysis which emphasize matrix dominated mechanical response, and therefore highlighting the effects of porosity in the matrix. Microscopy is used to determine an average, idealized void morphology in both distribution and size, which in the present case gives way to ellipsoidal voids located between and within individual lamina. Macro-scale parent models of ASTM test coupons for each loading case are first used to acquire local maximum gage section strains. These strains are then applied as boundary conditions to a second set of micromechanical models containing the desired void morphology. Local strains and stresses can then be computed as a result of said local defects and or other explicitly modeled heterogeneities at the fiber level. The current work focuses on the predicted strength knockdown of simple unidirectional laminates using maximum strain criteria, and Hashin failure criteria for homogeneous-smear property approaches. These values are obtained for simulated loading cases only, but implemented in such a way as to make use of empirical results at a later stage. It is found that the Hashin damage model is particularly unsuited to deal with variations in void morphology in terms of predicting failure. This is due to the basic fact of elasticity in where stress concentrations are largely governed by inclusion aspect ratio (sharpness) and not position or size. However, the overall multiscale methodology is robust enough to allow application of alternative point-wise failure criteria and or the addition of progressive damage models at a later date.


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