Effect of hydrostatic pressure on flow and deformation in highly reinforced particulate composites

Infiltrated particle reinforced composites combine a dense matrix with particles that are in mutual contact and can therefore transfer compressive stress directly from one particle to the next. As a result, these composites may combine characteristics of the plasticity of their matrix with those of granular matter plasticity. We measure here the influence of a 200 MPa superimposed fluid hydrostatic pressure on the flow stress of high volume fraction (56-62 vol pct) particulate Al2O3-Al composites produced by infiltration and show that the yield response of such composites is indeed pressure-sensitive. A simple analysis that transposes to metal matrix composites the theory of fluid-saturated granular media mechanics explains the phenomenon quantitatively. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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Andreas Mortensen, Maria Gabriella Tarantino, Ludger Weber
Elsevier, 2016
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https://infoscience.epfl.ch/record/222076?ln=en

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The thermal conductivity of aluminum matrix composites having a high volume fraction of SiC particles is investigated by comparing data for composites fabricated by infiltrating liquid aluminum into preforms made either from a single particle size, or by mixing and packing SiC particles of two largely different average sizes (170 and 16 mu m). For composites based on powders with a monomodal size distribution, the thermal conductivity increases steadily from 151 W/m K for particles of average diameter 8 mu m to 216 W/m K for 170 mu m particles. For the bimodal particle mixtures the thermal conductivity increases with increasing volume fraction of coarse particles and reaches a roughly constant value of 220 W/m K for mixtures with 40 or more vol.% of coarse particles. It is shown that all present data can be accounted for by the differential effective medium (DEM) scheme taking into account a finite interfacial thermal resistance. (c) 2007 Elsevier B.V. All rights reserved.

2008

Tensile flow stress of ceramic particle-reinforced metal in the presence of particle cracking

Andreas Mortensen, Andreas Rossoll, Ludger Weber

A simplified model is proposed to quantity the effect of damage in the form of particle cracking on the elastic and plastic behaviour of particle-reinforced metal matrix composites under uniaxial tensile loading: cracked particles are simply replaced, in a mean-field model, with as much matrix. Pure aluminium reinforced with 44 vol.%., alumina particles, tested in tension and unloaded at periodic plastic deformations, is analysed by neutron diffraction during each reloading elastic step, at 30%, 50%, 701% and 90% of the tensile flow stress. The data give the evolution of the elastic matrix strains in the composite and also measure the progress of internal damage by particle cracking. The test gives (i) the evolution of the in situ matrix flow stress, and (ii) the evolution of load partitioning during elastic deformation with increasing composite damage. Predictions of the present model compare favourably with relevant results in the literature, and with results from the present neutron diffraction experiments. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

2008

Damage recovery after impact in E-glass reinforced poly(epsilon-caprolactone)/epoxy blends

Amaël Maximilien Cohades, Véronique Michaud

Damage recovery after low-velocity impact has been assessed in woven E-glass fibre-reinforced polymer composites with an epoxy matrix and a blend of epoxy and 25 vol% of poly(e-caprolactone) (PCL). Impact was carried out at three energy levels (8.5, 17, 34 J) and composites with epoxy-PCL blends demonstrated similar energy absorption capacity as compared to pure epoxy composites even though the extent of damage (quantified by C-scans and optical microscopy) was higher. Ultimate compressive residual strength of the modified composites was, for the different impact energy levels, 23-33% lower as compared to unmodified composites. Healing efficiency after a thermal mending cycle at 150 degrees C for 30 min has been quantified using three complementary characterization methods; impact damage could be recovered from 20% to 100% depending on the impact energy level. These modified matrix composites are thus able to fully recover low-velocity impact damage at energy levels often met in real structures. (C) 2017 Elsevier Ltd. All rights reserved.

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