Non-Linear Response of Continuous Fiber Metal Matrix Composite Laminates

摘要

Metal matrix composites (MMC) offer tremendous potential for applications requiring high specific stiffness and strength materials. Continuous alumina fiber reinforced aluminum composites have demonstrated unidirectional compressive strengths of 4.5 Gpa (over 500 ksi), with strength to density ratios comparable to graphite/epoxy composite systems. The transverse and shear properties of the MMC systems demonstrate significantly material nonlinearity on the lamina or ply level. Mechanical test results demonstrate that in matrix dominated principal ply directions, MMCs can carry a substantial portion of load under the nonlinear portion of the stress versus strain curve. As a result, material nonlinearity is often observed in the effective response of MMC laminates of arbitrary architecture. Traditional linear-elastic laminate theories do not adequately predict the effective response of MMCs due to this pronounced influence of matrix dominated material nonlinearity. An accurate predictive capability is required to fully exploit the enhanced performance MMC's potentially offer. In the current work, experimental test results are presented for continuous alumina fiber reinforced aluminum composites. A nonlinear laminate analysis formulation is presented and is used to predict the effective nonlinear stress versus strain response of arbitrary MMC laminate architectures under mechanical loading. Predictions are based on an incremental formulation of a well-established three-dimensional laminated media analysis. Nonlinear ply level stress-strain curves are characterized in the longitudinal, transverse and shear directions and are used as property input into the analysis. Good correlation between experimentally measured stress versus strain response and predictions is presented for three different laminate architectures. Demonstration of this approach to accurately predict the nonlinear response of MMC laminates provides confidence in our ability to successfully design and analyze composite structures for future Army systems utilizing these advanced materials.