Micromechanics

About: Micromechanics is a research topic. Over the lifetime, 6000 publications have been published within this topic receiving 162635 citations.

Progressive failure analysis of unidirectional fiber-reinforced polymers with inhomogeneous interphase and randomly distributed fibers under transverse tensile loading

Abstract: The effect of damage due to interfacial debonding on the post initial failure behavior of unidirectional fiber-reinforced polymers subjected to transverse tension was investigated using numerical homogenization techniques based on the finite element method. Calculations were performed for unit cells containing fibers distributed at random over the transverse cross-section with inhomogeneous interphase layers. The mechanism of progressive failure was examined at both a global and a local level. A detailed analysis of the proposed micromechanics model revealed that it is able correctly to simulate the evolution of damage and to explain the softening mechanism. It was found that the post initial failure behavior of unidirectional lamina under transverse tension is mainly controlled by the interface strength and the interphase stiffness. The present study showed that local fiber array irregularities are a significant contributor to matrix cracking through local stress concentrations and the occurrence of localization.

Elastoplastic Modeling of Metal Matrix Composites Containing Randomly Located and Oriented Spheroidal Particles

Abstract: Micromechanics-based effective elastic and plastic formulations of metal matrix composites (MMCs) containing randomly located and randomly oriented particles are developed. The averaging process over all orientations upon three elastic governing equations for aligned particle-reinforced MMCs is performed to obtain the explicit formulation of effective elastic stiffness of MMCs with randomly oriented particles. The effects of volume fraction of particles and particle shape on the overall elastic constants are studied. Comparisons with the Hashin-Shtrikman bounds and Ponte Castaneda-Willis bounds show that the present effective elastic formulation does not violate the variational bounds. Good agreement with experimental elastic stiffness data is also illustrated. Furthermore, the orientational averaging procedure is employed to derive the overall elastoplastic yield function for the MMCs. Elastoplastic constitutive relations for the composites are constructed on the basis of the derived composite yield function. The stress-strain responses of MMCs under the axisymmetric loading are also investigated in detail. Finally, elastoplastic comparisons with the experimental data for SiCp/Al composites are performed to illustrate the capability of the proposed formulation.

Micromechanical stresses in SiC-reinforced Al2O3 composites

Abstract: Applying an Eshelby (1957) approach, the internal micromechanical stresses within an SiC-inclusion-reinforced (platelet to whisker geometries) polycrystalline alumina matrix composite were calculated. The results are compared to the experimental residual stress measurements of a SiC-whisker-reinforced Al2O3 by Predecki, et al. (in press) and found to be in excellent agreement. The calculations are then extended to SiC-reinforced composites with polycrystalline mullite, silicon nitride, and cordierite matrices. It is concluded that the internal stresses are significantly influenced by the inclusion geometry as well as the thermoelastic differences between the inclusion and the matrix and also the volume fraction.

Micromechanics models for mechanical and thermomechanical properties of 3D through-the-thickness angle interlock woven composites

Abstract: In this paper, a laminate block modeling approach for three-dimensional (3D) through-the-thickness angle interlock woven composites is used to develop one finite element analysis (FEA) model and two analytical models, namely the “ZXY model” and the “ZYX model”. These models can be used to determine the mechanical properties and the coefficients of thermal expansion for 3D through-the-thickness angle interlock woven composites. A parametric study shows that there is good agreement between these FEA and analytical models. The parametric study also demonstrates the effects of the fiber volume fraction of the warp weaver (i.e., z yarn) and the space between two adjacent filler yarns on the mechanical properties and the coefficients of thermal expansion. Finally, the present models are found to correlate reasonably well with the predicted and measured results available in the literature.