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Failure Initiation Predictors for Reliability-Based Design of Hybrid Composite Materials
PI: Anthony M. Waas
Particpants: Wei Heok Ng, Ravi Raveendra [Cometacoustics, Inc.]


This project is concerned with the development of a progressive failure analysis (PFA) modeling tool for advanced composite structures that accounts for the interaction between out-of-plane failure and in-plane failure and also accounts for the material microstructure. The PFA tool utilizes a fundamental physics based approach that is devoid of empirical formulas that have dominated failure prediction tools in composites.
In the PFA tool, detailed physics of failure mechanisms will appear at the Fiber-Matrix scale, and homogenized manifestations of these will be coupled to the Lamina and Laminate scales (Figure 1) through mechanisms that operate at those scales. At the Fiber-Matrix scale, information is processed using fundamental fiber and matrix properties. Therefore, effects due to fiber debonding (interfacial failure), fiber kink banding, and matrix microcracking are now captured at a fundamental level while their influence (homogenized over the FM scale) is passed on to the Lamina and Laminate scales. The information at the Lamina and Laminate scales dictate the possibility of delamination failure, which is captured through specially designed discrete cohesive zone (DCZM) elements.

The PFA tool includes a) a robust FE based micromechanics model that includes matrix degradation, fiber- matrix debonding, local fiber rotation, fiber orthotropy and fiber failure in tension, compression (due to microfibril kinking) and shear, and b) a FE modeling strategy of a laminated composite structure using Shapery Theory, which incorporates results based on the micromechanics model, to model each lamina and including DCZM elements to account for delamination failures. Thus, interaction between in-plane and out-of-plane failure is captured.

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