Particle size effect in metal matrix composites: A study by the continuum theory of stress gradient plasticity

Abstract

The plastic behavior of particle-reinforced composites is studied by the continuum theory of stress gradient plasticity. This theory has been quite successful in predicting the size-dependent behavior in micro-torsion and -bending. Analyses are carried out on the axisymmetric unit cell finite element models for two sets of SiC/Al composites. Subsequent stress gradient plasticity predictions of the stress-strain curves in comparison with the corresponding experimental data show excellent agreement of flow strength for composites of varying particle size. Our results reveal that the experimental observations of particle size effect can be explained in terms of a stress gradient plasticity theory with one material length variable, which depends on the matrix microstructure. Therefore, stress gradients in the matrix-originated from the mismatch of elastic moduli between the particles and matrix-together with the matrix microstructure can control the size-dependent behavior in composites. However, the impact of this novel mechanism in competition with other well-known mechanisms can only be revealed by experimental investigations with careful attention on the matrix microstructure of composites.

Effects of particle size and oxide shell on variable stiffness performance of phase-changing materials

“…Generally, a reduction in size will result in increased material toughness and increased ultimate strength. 15,35– 37 In addition to the improved bonding characteristics from an increased interfacial surface area, the increased toughness is also usually due to the larger number of rigid particle sites available to arrest crack propagation via deflection or pinning. 37…”

“…Generally, a reduction in size will result in increased material toughness and increased ultimate strength. 15,[35][36][37] In addition to the improved bonding characteristics from an increased interfacial surface area, the increased toughness is also usually due to the larger number of rigid particle sites available to arrest crack propagation via deflection or pinning. 37 Composite specimens were manufactured from a thermoset epoxy resin consisting of Epon-828 and Jeffamine D-400 combined at the stoichiometric ratio (100:58 by weight), and then loaded with FM particle inclusions at 30 and 50 vol% for a range of particle sizes (5 specimens each).…”

Strain Gradient Plasticity-Based Modeling of Damage and Fracture

“…In this regard, it is necessary to remark that phenomenological modeling of micronscale plasticity is a field in continuous development. Current efforts are devoted to (i) overcome the physical deficiencies of present SGP models [18], (ii) explore different forms of the free energy so as to consistently capture the behavior observed in the experiments [56] and (iii) link the length scale(s) with the underlying microstructure [189,190]. The impact on fracture assessment of novel constitutive formulations must be investigated with the aim of improving crack tip characterization.…”

“…A este respecto, es necesario remarcar que la modelización fenomenológica de la plasticidad a escala micrométrica es un campo en continuo desarrollo. A día de hoy, los esfuerzos investigadores están principalmente orientados a (i) solventar las deficiencas físicas de los actuales modelos SGP [18], (ii) explorar diferentes expresiones de la energía libre que permitan capturar consistentemente el comportamiento observado en los experimentos [56] y (iii) enlazar los parámetros de escala con la microestructura subyacente [189,190]. Es preciso investigar concienzudamente el impacto sobre la evaluación de la integridad estructural de las nuevas formulaciones constitutivas con el objetivo de mejorar la caracterización cuantitativa del comportamiento mecánico en la punta de la grieta.…”

Predictive Computational Model for Damage Behavior of Metal-Matrix Composites Emphasizing the Effect of Particle Size and Volume Fraction

“…Employing the Taylor-based nonlocal theory of plasticity besides the cohesive zone model for interfacial debonding, the particle size-dependent behavior of PRMMCs is investigated [22]. In the context of the continuum theory of stress gradient plasticity, the plastic behavior of PRMMCs was studied at different particle sizes without including the interface decohesion or the particle fracture [23]. The strain gradient continuum plasticity in the context of the theoretical, experimental, and numerical investigations is comprehensively reviewed in [24].…”