Experimental Study and Fabric Tensor Quantification of Microcrack Distributions in Composite Materials

Abstract

In this study, the microcrack distributions of samples of a metal-matrix composite material (titanium aluminide (Ti-14Al-21Nb(α2)) reinforced with continuous silicon carbide (SiC) (SCS-6) fibers) are measured experimentally, and then quantified using the fabric tensor approach. The laminated composite material samples have two lay-up configurations: [0/90]_s and [±45]_s. These samples are tested under uniaxial tension up to different levels of loads, to understand how microcrack distributions develop with applied loads. The [±45]_s samples are shown to have more microcracks and a wider range of orientations of microcracks than the [0/90]_s samples. The microcracks can be divided into two categories: fiber microcracks and fiber-interface microcracks. Distributions of both types are shown to be similar in shape but different in orientation. In addition, microcrack distributions weighted by the microcrack lengths are presented. Fabric tensors of zero, second, fourth, sixth, eighth, and tenth order are used to approximate these microcrack distributions. Fabric tensors are seen to give a very good approximation when eighth or tenth-order fabric tensors are used for both fiber and fiber-interface microcrack distribution types. Finally, damage variable and damage evolution relations are derived in terms of the fabric tensor based on a thermodynamically consistent framework.

Keywords

microcracks fabric tensors composite materials

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