A Virtual Testing Methodology for Characterizing Woven Fabric Laminated Composite Plates at Given Damage State

摘要

Preliminary design allowables for fiber-reinforced polymer (FRP) composite materials are mainly based on a test-driven certification procedure for which a large number of coupon tests have to be performed at various room/wet/hot conditions. A significant amount of resources will be invested in the material certification phase. Given the time and budget constraints, the test-driven material property quantification is almost infeasible to provide a material database under a given load spectrum.Accurate assessment of cumulative damage of composite structures subjected to aggressive loadings depends strongly on faithful characterization of the microstructures and the underlying deformation phenomena. The stress and strain fields predicted at a global structural level are unable to determine the damage and failure mechanisms at the constituent level and the resulting stiffness degradation. To establish a mapping relation between the global and constituent response parameters, a four-cell micromechanics model (CELLMAT) is developed for an unbalanced weave subjected to a thermal-mechanical loading. The damaged ply properties resulting from a constituent failure are then propagated into a general purpose lamination solver (VAPAS). The integration of CELLMAT and VAPAS provides an efficient and accurate material translator for a commercial finite element solver in 1) computing the smeared element properties from a given constituent damage; and 2) determining the constituent response parameters for themechanism-driven failure prediction and the subsequent material degradation.The CELLMAT model is developed based on the subcell representation of a representative volume cell. The iso-stress and iso-strain coupled with a simplified parallel-series micromechanics model is employed to characterize the thermal-mechanical response of an unbalanced woven fabric composite. CELLMAT can not only determine the thermal-mechanical properties of a woven fabric ply based on a given constituent and microstructural parameters but also perform the stress and strain decomposition in computing the stress/strain at the constituent level from the ply level.To propagate the damage from the constituent level to the ply and laminated levels, the generated ply properties at various constituent damage states are used as the input ply properties for a laminator. The VAPAS laminator is developed based on the variational-asymptotic method to provide a generalized 2D constitutive law and accurate 3D recovery relations of a laminated composite plate/shell. VAPAS calculates A, B, D (corresponding to the classical lamination theory) and G (corresponding to the transverse shear) matrices.