High strain rate deformation in particle reinforced metal matrix composites

Pure aluminum matrix composites reinforced with 40 Á/55 vol.% Al 2 O 3 particles of various sizes (5, 10, 29, and 58 mm) are produced by gas-pressure infiltration. Comparison of compressive flow stresses of these composites at quasistatic and dynamic strain rates shows that, in accord with the literature, the increase in flow stress of dynamically compressed composites results from the sensitivity of the matrix to strain rate. The accumulation of damage in the composites is quantified through high-precision density measurements. Damage accumulates primarily as a function of strain due to particle cracking followed by separation of the broken-particle segments and, to a lesser extent, by matrix cavitation. Composites reinforced by smaller particles have a higher flow stress, lower strain-rate sensitivity, and accumulate less damage, while a greater concentration of reinforcement increases the flow stress, strain-rate sensitivity, and the rate of damage accumulation. #

Section: Effect Of Volume Fractionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 58%

Section: Strain-rate Sensitivitymentioning

confidence: 83%

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Quasistatic and dynamic compression of aluminum-oxide particle reinforced pure aluminum

Marchi

Cao

Kouzeli

et al. 2002

“…As deformation of the composite begins at high strain rates (e.g., 3 1000 s-I), fibers begin to crack, causing large local strains and correspondingly high strain rates within the matrix. Bao and Lin [19] calculate that the local strain rate can reach 5 times the macroscopic strain rate and under these circumstances the matrix is deforming at a strain rate of about 4000 SK', i.e., it effectively enters a strain-rate range where it is very strain-rate sensitive (see Fig. 6).…”

Section: Discussionmentioning

confidence: 99%

High strain-rate compression testing of a short-fiber reinforced aluminum composite

Güden

Hall

1997

Compression behavior of 15-267/$/o Saffilr" short-fiber reinforced Al-l.l'iwt.%Cu alloy metal matrix composites has been determined over a strain-rate range of approximately lop4 to 2 x lo3 s-I. The strain-rate sensitivity of composite samples at 4% strain, tested parallel and normal to the plane of reinforcement, was found to be higher than that of unreinforced alloy in the strain-rate range studied. Quantitative analysis of fiber fragment lengths from samples tested to different strain levels showed that, at small strains, high strain-rate testing induced a relatively shorter fiber fragment length distribution in the composite compared to quasi-static testing. At quasi-static strain rates, the fiber strengthening effect was found to increase with increasing V?h and was higher in samples tested parallel to the planar random array. The observed anisotropy of the composite at quasi-static strain rates was also observed to continue into the high strain-rate regime.Microscopic observations on composite samples tested quasi-statically and dynamically to a range of strains showed that the major damage process involved during compression testing was fiber breakage followed by the microcracking of the matrix at relatively large strains. Fiber breakage modes were found to be mostly shearing and buckling. 0 1997 Elsevier Science S.A.

“…In a recent study Bao and Lin [8] applied finite element analysis to a particulate reinforced alloy and suggested that the main reason for the increasing rate sensitivity of the composite over the matrix alloy is due to the constraining effect of the particles. The constraint increases the local strain rate near the particulate/matrix interface, and hence pushes the composite into the high strain rate regime where the stress in the matrix increases rapidly.…”

Section: Introductionmentioning

confidence: 99%

Dynamic properties of metal matrix composites: a comparative study

Güden

Hall

1998

Three distinctly different metal matrix composites have been tested at strain rates from quasi-static to : 3000 s − 1 . It was found that the high strain rate response of each composite was determined primarily by (a) the response of the matrix in the absence of any reinforcement and (b) the damage formation and accumulation processes during deformation. High strain rate behavior of the short fiber composite was dominated by the matrix behavior at low strains but by fiber damage at high strains. The behavior of a whisker reinforced composite was dominated by the matrix properties at all strains. Re-loading tests produced increased fracture strains, indicating that adiabatic heating accelerates fracture of composites by permitting the development of local strain instabilities. © 1998 Elsevier Science S.A.