Investigation of crack-tip plasticity in high volume fraction particulate metal matrix composites

Abstract

Crack-tip strain fields in high volume fraction ceramic particle reinforced metal matrix composites are assessed using photoelastic measurements. It is shown that the size of the significant crack-tip plastic zones that form in these materials depends on the type and diameter of the reinforcement and on the matrix material. This plastic zone size correlates well with the macroscopic toughness values assessed through J -integral testing. The composites are thus ''metallic'' in the sense that their toughness is mostly composed of plastic energy dissipation around the crack tip. Plastic deformation also induces marked constraint effects that influence the shape of the surface strain fields. It is shown that finite element analysis must be three-dimensional to describe these strain fields, as two-dimensional plane-stress analysis fails to reproduce the experimental data.

Ductile-to-brittle transition in tensile failure of particle-reinforced metals

“…With toughness values that exceed 15 MPa m 1/2 in these materials, internal flaws have to be larger than a millimetre to account for the data; we have no indication of the presence of such large defects in these composites prior to mechanical loading. Running a more detailed calculation where R-curve data are available (Miserez et al, 2004c) does not alter this conclusion: their brittle tensile failure is seemingly not dominated by pre-existing defects.…”

Finite element meshes for optimal modelling of plasticity induced crack closure

“…The limit of plastic deformation zone was defined for an equivalent plastic strain of 0.2%, which is the classical limit assumed for the onset of plastic deformation in tension tests. Miserez et al [48] also estimated the plastic zone boundary in photoelastic data considering a difference of principal strains of 0.2%. However, Paul and Tarafder [49] considered a lower limit of plastic strain (0.0001%).…”

Periodic three-dimensional mesh generation for particle reinforced composites with application to metal matrix composites

“…multiphase materials consisting of an interconnected phase (referred to as matrix material) and separated particles. Examples for such materials are Al-Al 2 O 3 based metal matrix composites (Miserez et al, 2004) and Al/SiC p composites (Chawla et al, 2006a,b). While several investigations based on image recognition techniques applied to two-dimensional cross-sections of such materials have been used in FEM simulations recently (Figs.…”

“…Prominent examples for materials with such micromorphology are metal matrix composites such as the ones examined by Miserez et al (2004), Ganesh and Chawla (2005) or Chawla et al (2006c). These materials tempt to combine the thermal resistance and high stiffness of ceramic materials with the ductility observed for many metals.…”