Effects of changes in test temperature on fatigue crack propagation of Al6090/SiCp-Al 6013 laminated metal composites
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Effects of Changes in Test Temperature on Fatigue Crack Propagation of Al6090/SiCp-Al 6013 Laminated Metal Composites HALA A. HASSAN, J.J. LEWANDOWSKI, and M.H. ABD EL-LATIF The effects of changes in test temperature from 298 to 148 K on the fatigue crack propagation of 6090/SiC/20p-6013 and 6090/SiC/25p-6013 laminated metal composites (LMCs) tested in the crack arrester orientation were investigated. The fatigue crack propagation behavior of similar monolithic and discontinuously reinforced aluminum (DRA) materials was additionally compared to that of the laminates. The fatigue behavior of the laminates was significantly different from that of the monolithic and DRA and was affected by changes in the test temperature as well as by a thermal cycle to low temperatures (e.g., 77 or 148 K) prior to testing at either 213 or 298 K. Fatigue tests conducted either at low temperature or after a low-temperature thermal cycle exhibited significant changes in crack velocity upon traversing the individual laminae. Crack growth in these samples was accompanied by crack bifurcation and interfacial separation at high K. Attempts at modeling the effects of thermally-induced residual stresses on fatigue using a weight function approach provided reasonable estimates of the residual-stress-induced shielding in the different layers.
I. INTRODUCTION
DISCONTINUOUSLY reinforced aluminum alloys (DRA) are candidate materials for applications in which high specific stiffness and specific strength are required. The ability of using conventional processing techniques such as extrusion, forging, and rolling makes them cost effective for various applications. The relatively low fracture toughness of these composites compared to monolithic materials has prevented their more widespread use. In response, several investigators have used extrinsic toughening approaches to improve the fracture toughness of DRA.[1–11] The lamination of DRA with more ductile/tough layers is one approach that has exhibited significant improvements under static loading conditions. However, many of the applications which require high fracture toughness also require good fatigue crack propagation resistance. Unfortunately, much less work has been conducted on the fatigue crack growth resistance of the layered/laminated materials. Although some fatigue work conducted in the crack divider orientation has been reported by Huffman et al.[12,13] on 6090/SiC/25p-5182, the improved laminate toughness was accompanied by superior fatigue crack growth resistance but a lower fatigue threshold. Other work by Chawla and Liaw[14] on roll-bonded pure aluminum and AISI 304 stainless steel laminates tested in HALA A. HASSAN, Assistant Professor, formerly Graduate Student, Department of Materials Science and Engineering, Case Western Reserve University, is with the Department of Engineering, Design and Production Engineering, Ain Shams University, Cairo Egypt 11517. J.J. LEWANDOWSKI, Overseas Fellow, Churchill College, Department of Materials Science and Meta
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