Finite Element Analysis of Thermo-Mechanical and Failure Properties of Hybrid Fiber Composites

摘要

Multiphase composite material also known as hybrids have major engineeringrnapplications where strength to weight ratio, low cost and ease of fabrication arernrequired. A high modulus material might need a replacement owing to its brittlernnature leading to sudden failure. For example considerable reduction in cost withoutrnloss of mechanical properties can be obtained using Kevlar-graphite/epoxy systems.rnAdvances in computational micromechanics allow us to study hybrid multiphasernsystems using finite element simulations. The goal of this research is to evaluate therneffective mechanical properties of hybrid composites containing graphite and glassrnfibers interspersed in an epoxy matrix. Elastic constants such as longitudinal tensilernand shear modulus and major Poisson’s ratios seem to follow the RoHM (Rule ofrnHybrid Mixtures) relation with reasonable accuracy. Transverse modulus andrntransverse shear modulus can be predicted using the Modified Halpin Tsai relationsrnfor multiphase composites. Strength properties, unlike the elastic constants showrnhigh variability with random locations of the fibers for a given volume fraction. It isrnalso observed that the stress corresponding to failure initiation of the hybrids werernlower than that of graphite/ and glass/epoxy composites. This is due to the stressrnconcentration caused by a second fiber inclusion. Effective coefficients of thermalrnexpansion and residual thermal stresses are calculated for hybrid composites andrncompared with binary composites. Progressive damage model that uses damagernmechanics based softening response for the matrix is used to model damagernprogression behavior for the hybrid composites. The damage evolution energy isrnequal to the fracture toughness of the epoxy. The results are compared to that ofrngraphite and glass epoxy bi-material composite systems.