Plasticity of continuous fiber-reinforced metals

Abstract

Continuous parallel alumina fiber-reinforced metals produced by pressure infiltration are tested in tension/compression along the fiber axis with a goal of measuring the influence exerted by long fibers on the flow stress of their matrix. In this configuration, the equistrain rule of mixtures, modified to take into account stresses due to differential lateral contraction, can be used to back-calculate the matrix flow stress from that of the composite. This method provides the least physically ambiguous measurement of matrix flow stress in the composite; however, experimental uncertainty can be high. This uncertainty is evaluated in detail for the present experiments, in which matrix in situ stressstrain curves are measured for cast 3M NEXTEL 610 and DUPONT FIBER FP reinforced pure and alloyed aluminum-and copper-based matrices of varying propensity for recovery and cross-slip. Within experimental uncertainty, data show no enhanced matrix work-hardening rates such as those those that have been measured with tungsten fiber-reinforced copper. It is found that the fibers alter the matrix plastic flow behavior by increasing the flow-stress amplitude of the matrix, and by rendering initial yield in compression more progressive than in initial tension. Essentially, all observed features of matrix/fiber interaction can be rationalized as attributable to dislocation emission in the matrix caused by thermal mismatch strains within the material during composite cooldown from processing temperatures.

Multi scale modeling and characterization of inelastic deformation mechanisms in continuous fiber and 2D woven fabric reinforced metal matrix composites

“…The CTE of the Nextel fibers is 8 x 10 -6 K -1 [31], and the CTE of the matrix is ~20 x 10 -6 K -1 . The resulting strain hardening due to this mismatch will alter the in situ properties of the matrix in the composite compared to the as-cast unreinforced matrix [27,[33][34][35] and needs to be accounted for in the modeling to accurately predict the properties and response of the composite. To obtain a semi-quantitative estimate of the in-situ plastic flow properties of the Al-2%Cu matrix, nanohardness measurements were conducted in the as-cast unreinforced alloy and in the as-cast MMC material.…”

Longitudinal deformation of fibre reinforced metals: influence of fibre distribution on stiffness and flow stress

“…(ii) The fibre arrangement in the complex cells is such that it allows for periodic boundary conditions (see at the end of this section). (iii) The fibre arrangement is not directly derived from micrographs of an actual composite, since these are never truly periodic; however, it is inspired from images of fibre reinforced aluminium (Isaacs and Mortensen, 1992;Bystricky et al, 1999;Moser et al, 2001). Three fibre arrangements with differing number of fibre contacts were studied for Table 2 for detailed information.…”

“…One instance is found with the inverse problem, namely extracting individual phase flow properties from the measured composite stressstrain curve. This has for example been done with fibre reinforced metals to expose size effects in metal plasticity (Kelly and Lilholt, 1969;Isaacs and Mortensen, 1992;Bystricky et al, 1999). This inverse problem is of interest because, with fibre reinforced metals stressed along their axis, phase stresses are relatively uniform in both elastic and elastoplastic deformation (Hill, 1964a,b;Mulhern et al, 1967;Dvorak, 1991;Brockenbrough and Suresh, 1990;Brockenbrough et al, 1991;B€ ohm et al, 1993;B€ ohm and Rammerstorfer, 1994).…”

Tensile and fatigue behavior of Al-based metal matrix composites reinforced with continuous carbon or alumina fibers: Part I. Quasi-unidirectional composites

“…Although complex thermomechanical models have been developed in the case of UD [17][18][19][20][21] or woven [22,23,24] composites, due to the specific geometry and behavior of these quasi-UD composites, the experimental results will be compared with those resulting from simple models (Appendix B). [25][26][27][28][29][30][31][32][33][34][35] In this respect, the behavior of the quasi-UD composites in the elastic domain (i.e., Young's modulus) is worth being compared with the results given by the simple elastic models usually used for pure UD composites, neglecting the fiber-matrix coupling (continuity at the fiber-matrix interface and Poisson's effects).…”