Micro-Mechanics of Failure (MMF) for Continuous Fiber Reinforced Composites

Abstract

The micromechanics of failure was developed to predict the failure of continuous fiber reinforced composites. A micromechanical approach using unit cells of square and hexagonal arrays was employed to compute the micro stresses of constituents and at the fiber—matrix interface, which were used to determine the failure initiation of a unidirectional ply. The constituent properties include two tensile and compressive strengths of fiber and matrix, plus normal and shear strengths at the interface. The matrix and interfacial dominated strength properties are determined by matching the micro stresses at the constituent levels with the observed transverse tensile and compressive strengths on the macro ply level. The longitudinal shear failure is then expected to be a result of damage progression after initial failure. Based on the current MMF, in the graphite/epoxy considered in this study both transverse tensile and compressive failure are expected to occur via matrix failure. However, in the glass/epoxy the transverse tensile and compressive failures are respectively caused by matrix failure and interfacial tensile failure. These predictions are compared with predictions from other widely used failure criteria as well as experimental data. Lastly, we predicted the failure of laminates. Instead of using a unidirectional ply-based failure theory, starting with the fiber, matrix, and their interface will lead to a much simpler, more generic theory.

Is the out-of-plane shear strength an independent property? A micromechanical perspective about a macromechanical question

“…As pointed out by Ha et al 42 compressive radial traction, i.e. τ rr < 0, does not induce interface damage.…”

Micromechanics-based multiscale progressive failure simulation of 3D woven composites under compressive loading with minimal material parameters

“…Through the micro RVC, not only the elastic constants of the yarns can be according to the properties of the constituents, but also the strain and stress distribution of pure fibers and micro matrix can be determined, which makes it feasible to judge the microscopic failure based on the MMF theory [17].…”

“…This assumption is still questionable because the composite materials are actually composed of fiber and resin constituents with distinct material properties. To independently determine the damage initiations of fiber filaments and resin at the microscopic scale, Ha et al [17] proposed the micromechanics of failure (MMF) theory by employing the stress and strain amplification factor (SSAF) [18]. For different load conditions and material systems of composites, MMF theory has exhibited prominent prediction capabilities [19,20].…”

Experiment, simulation, optimization design, and damage detection of composite shell of hydrogen storage vessel-A review

“…88 In recent years, some micro failure criteria such as strain invariant failure theory 89,90,91 and multi-continuum theory 92,93 have been proposed. In the strain invariant failure theory, the first strain invariant is used as the failure criterion of volume deformation, and Von Mises stress is used as the failure criterion of twist deformation to identify the failure of the fiber and the matrix, 94 as shown in formula (2). In the multi-continuum theory, the composite material can be seen as continuum structure.…”