Fabrication, high-strain-rate constitutive behavior, and dynamic failure of MMCs

Particulate reinforced metal-matrix composites have been used in conditions involving high strain rate loadings. In this work, an approach that includes experimental characterization, numerical simulation, and theoretical modeling, has been adopted to study the high strain rate constitutive behavior and dynamic failure of metal-matrix composites (MMCs).; Aluminum 6092/(B4C)p metal-matrix composite systems fabricated by two different powder consolidation routes have been fabricated and tested over a wide range of strain rates in compression (10-4 ∼ 104 s-1) and tension (10 -4 ∼ 2 x 102 s-1). Comparisons of the constitutive behaviors are made between the composites and the unreinforced matrix materials, between compression and tension, and between low strain rates and high strain rates. Optical microscopy, SEM and TEM are used to characterize the microstructure, quasi-static and dynamic failure, and Al/(B4C)p interface. The strength of these MMCs increases with increasing volume fraction of particulate reinforcement. The fabrication route affects the strength of the matrix material, as reflected in the microstructure, and this effect carries on into the corresponding composites. The composites show significant strain rate dependence as seen in the unreinforced matrix materials. Asymmetric constitutive stress-strain behavior is observed in tension and in compression. Interface debonding plays a significant role in the dynamic failure of the MMCs.; Numerical analysis of the rate-dependent mechanical behavior of MMCs is conducted using a finite element framework where the reinforcement-matrix interface is considered imperfect and breakable according to a cohesive law. The consequences of interface failure on the overall constitutive behavior are discussed in conjunction with the influences of reinforcement volume fraction, particle shape, and aspect ratio. This numerical model captures the observed constitutive asymmetry of MMCs.; Finally, a multi-axial constitutive model for plastic deformation of MMCs is constructed by using the Mises-Schleicher criterion. The stress-strain asymmetric responses of composites under uniaxial tension and compression are used as the input of this model. A decomposed flow rule is used to determine the evolution of deviatoric and volumetric strain respectively. This analytical model is capable of predicting the pressure-dependent constitutive behavior of MMCs under various multi-axial loadings, and is evaluated with respect to torsion data.