Micromechanics

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

Fiber-matrix interface effects in the presence of thermally induced residual stresses

Abstract: The mechanics of transversely loaded high-temperature composites with a thermally induced residual stress field and a vanishingly weak fiber-matrix interface strength was investigated using two analytical models. In particular, the effects of several physical properties defining the performance of the constituent fiber, matrix, and interface are examined relative to their effect on composite's behavior. Both models demonstrate that, if there is a thermally induced residual stress field in the composite, the initial transverse modulus for the composite will be the same regardless of whether there is a well-bonded or an unbonded interface. 10 refs.

Micromechanical Modeling of Composite Compressive Strength

Abstract: Composite compressive failure is studied using a micromechanical (beam-on-elastic foundation) model, and the stiffness of the foundation is determined through an elasticity solution of the foundation model problem. An explicit expression has been derived for evaluation of composite longitudinal compressive strengths (CLCS). It is found that this expression predicts relatively lower CLCS compared to classical models, and closely matches some experimental data for carbon fiber/epoxy composites. It is found that a complete matrix slippage will reduce the CLCS by over 50%.

Effect of fibre sizing on the stress transfer efficiency in carbon/epoxy model composites

Abstract: The micromechanics of reinforcement of a model composite consisting of continuous high-modulus fibre embedded in epoxy resin has been investigated as a function of fibre sizing. The composite was subjected to incremental tensile loading up to full fragmentation, while the stress in the fibre was monitored at each level of applied strain with the new technique of remote laser Raman microscopy. The two systems exhibited differences in the residual stress field with the unsized fibre being in compression. The average stress in the fibre increased linearly with applied matrix strain up to first fracture. After fracture, the stress in the fibre was found to build from the tips of the fibre breaks, reaching a maximum value at the middle of each fragment. The shape of the stress transfer profiles indicated minor differences between the two systems at moderate strains. At high strains, the stress transfer profiles of the two systems were distinctly different possibly owing to the presence of two different interfacial failure modes in the two types of model composites. The maximum interfacial shear stress for both systems was of the order of 40 MPa with the sized system exhibiting slightly better adhesion. SEM examination of the fracture surfaces revealed clear interfacial failure for the unsized system whereas the sized system indicated areas of good adhesion.