Composite Constitutive Model Research Articles

Novel Micromechanics-Based Woven-Fabric Composite Constitutive Model with Material Nonlinear Behavior

An averaging procedure is presented for analysis of plain-weave-fabric composites with material nonlinear behavior.Arepresentativevolumecellisassumed.Thecellisdividedintomanysubcells,andaveragingisperformed again. The effective stress-strain relations of the subcell are obtained. Using iso-stress and iso-strain assumptions, the constitutive equations are averaged along the thickness direction. As a result, a linear system of equations is formed and subsequently solved to distribute the global average strains to each subcell. In this manner, given the average strains, the global average stresses can be determined. Numerical results are generated for plain-weave composite with material nonlinear behavior. Nomenclature a = half-length of the representative cell b = half-width of the representative cell E = Young’ s modulus G = shear modulus H = height of the representative cell Ht = height of e ber tows Sij = compliance components in principal material system Sij = compliance components of constituents in global coordinate system h f = local angle between the e ll yarn and global coordinate system h w = local angle between the warp yarn and global coordinate system ( - ) = average quantities of representative volume cell

Novel micromechanics-based woven-fabric composite constitutive model with material nonlinear behavior

Novel micromechanics-based woven-fabric composite constitutive model with material nonlinear behavior

Martensitic Transformations in a NiTi Fiber Reinforced 6061 Aluminum Matrix Composite

Approximately 19.5 volume percent, 50.7 at % Ni-Ti shape memory alloy fiber reinforced 6061-T6 aluminum alloy matrix composite (SMA-MMC) and homogeneous 6061-T6 control materials were produced by vacuum hot pressing. The test materials were initially subjected to a 5.8% tensile elongation at room temperature. During this process, the shape memory alloy reinforced composite materials exhibited a bimodal yield. The initial yield was due to plastic flow in the aluminum matrix, the subsequent yield was due to the initiation of a stress induced austenite to martensite (SIM) transformation in the shape memory alloy fibers. The SMA-MMC specimens exhibited unusual positive curvature hardening during the final stages of the 25°C tensile loading resulting from the saturation of the SIM transformation. During the subsequent 25 °C to 75 °C unconstrained heating process, the SMA-MMC exhibited a nonlinear thermal contraction resulting from the martensite to austenite shape memory transformation of the NiTi reinforcement. At the conclusion of the unconstrained heating process the temperature was held constant at 75°C as the loading grips were reapplied and the test materials were tensile loaded to failure. The elevated temperature flow strength of the SMA-MMC was significantly higher than the final SMA-MMC room temperature flow strength; this increase was due to the imposition of a large longitudinal compressive stress in the composite matrix by the NiTi fiber shape memory response, and due to the increase in NiTi fiber transformation stress with increased temperature. The elevated temperature ultimate strength and final failure strain of the SMA-MMC materials were both significantly higher than that of the 6061-T6 control materials. The experimental results are analyzed by a nonlinear, one-dimensional composite constitutive model. The model provides a compact quantitative description of the SMA-MMC thermal mechanical response as a function of temperature and applied stress, and correctly expresses important experimental features.

Interface Crack in a Three-Phase Composite Constitutive Model

An arc-shaped crack in fiber-reinforced composite material is the subject of this paper. A three-phase composite cylinder is taken as the material model to take into account the effect of surrounding fibers. Using Muskhelishvili’s complex variable method, an exact elastic solution is derived based on the conventional crack opening assumption. The complex stress intensity factors for the interface crack, in the sense defined by Hutchinson, Mear, and Rice, are determined. Some numerical examples are given. It is shown that, as the volume concentration of the fiber is increased, the magnitude of the complex stress intensity factors varies considerably.

Stress-resultant plasticity theories for composite laminated plates

Abstract Constitutive laws are presented for the inelastic analysis of laminated composite plates. The implications of using an elastoplastic theory, applied in a stress-resultant formulation, are discussed and investigated. Two different stress-resultant plasticity theories are proposed, both of which overlook the matrix and fiber inelastic behavior and describe the inelastic response of the laminate as a function of overall laminate properties. Results from numerical experiments with the proposed models are compared with results obtained using a micromechanical elastoplastic composite constitutive model.