On composite-structure weaknesses: Part II. Computer experiments, identification, and correlation
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I. INTRODUCTION
ADVANCES in modeling metal-matrix composites (MMCs), particularly short-fiber composites, have led to significant understanding of the behavior of composite materials. Recent studies have focused on the elastic, mechanical, and orientational nature of fiber reinforcements.[1–8] However, local microstructural effects of the matrix material (including effects of grain orientation and geometry), especially joint effects of local fiber-matrix interaction, on the behavior of short-fiber composites still need to be investigated. One still demands a type of novel simulation that incorporates the local synergetic effects caused by the random fiber orientation, fiber size, grain orientation, grain geometry, and spatial arrangement of grains and short fibers. Recent computer experiments[9] carried out by the author have indicated that composite-structure weaknesses (CSWs) can be linked with the local status of simulated composite microstructures and correlated with local microstructures. Nevertheless, only mechanical loading was considered in those computer experiments. The effect of coupled mechanical-thermal loading on the formation of CSWs is taken into account in this research. Indeed, discerning the CSWs of a short-fiber composite material is one of the ubiquitous demands for design and assessment of MMCs. The finite-element method (FEM) is usually employed for numerical analysis of local fields associated with the constituents of a composite material. Exhaustive literature, as summarized recently,[10,11] and references contained therein have introduced finite-element approaches to the inhomogeneous behavior of stress and strain distributions XU-DONG LI, Professor, is with the College of Materials Science and Engineering, Gansu University of Technology, Gansu Province 730050, People’s Republic of China. Contact e-mail: xu dong [email protected] Manuscript submitted October 4, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS A
in composite materials. Novel applications[12,13,14] of the FEM are even notably convincing. Although the FEM is elegant in determining local stress and strain fields around a single short fiber, its effective use for a composite material entails periodic cells of a microstructure. Nevertheless, a spatial arrangement of composite constituents gives rise to a higher stress concentration in the matrix than the periodic ones, due to localization of stresses.[15] Without the periodicity, the FEM involves considerable computational expense, as one needs to take care of more short fibers individually. Therefore, our interest is in computational experiments aimed at numerical estimation of the peak mesoscopic stress distribution that might possibly occur in short-fiber composite materials, performed in an efficient way by means of the analytically-numerical–based approach.[16] The numerical computation follows three crucial steps, i.e., (1) segmentation of short fibers, (2) establishment of a geometric relation of the short fiber to the surrounding grains, and (3) the local nature of micromecha
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