Failure Criteria for Composites
Final rept. 15 Apr 1995-15 Apr 1998
MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
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Understanding the mechanisms of failure of composite structures and developing mechanism based failure criteria are important considerations in designing structures made of composite materials. The compressive response of composite materials has received considerable attention due to their significance in the aerospace industry and the complexity associated with compressive failure. Several competing failure mechanisms such as fibermatrix interfacial failure, fiber microbucklingkinking, delamination initiation and delamination buckling may become active in compressive loading. Environmental effects such as an elevated temperature can alter and affect these failure mechanisms. In this project, a micromechanics based predictive model for the notched strength of multidirectional laminates is presented and implemented via the finite element method. Experimental results to verifyrefute this model are presented at both room and elevated temperature. The in-situ shear response of the matrix, the fiber mechanical properties, the laminate lay-up and fiber volume fraction serve as input to the model. The predictions of the model are found to match favorably with experimental data. The effect of ply angle and its influence on the failure mechanism are quantified and compared with available experimental data. This work is the first development of a non-empirical mechanics based failure prediction methodology for notched strength of composite laminates.
- Laminates and Composite Materials