Shantanu S. Mulay

A detailed study on micromechanical constitutive modelling of unidirectional fiber reinforced and plain woven textile composites (PWTC) is performed. The primary objective is to compute the equivalent homogenized effective properties of PWTC through its mesoscale model. A novel parallel-series model is proposed, to compute the engineering constants in transverse plane of unidirectional composite, and validated against Chamis approaches, Mori–Tanaka and finite element method results for glass/epoxy composite. Computational homogenization of representative volume element (RVE) of transverse direction unidirectional composite is performed satisfying the periodicity of RVE. The RVE of PWTC is then approximated as cross-ply laminate consisting warp and fill plies, whose averaged properties are computed considering fiber undulations by micromechanics-based models. The bounds of the effective material properties of PWTC are determined employing Voigt and Reuss approximation. The effective engineering constants of glass/epoxy PWTC computed are compared with in-house experiments and found to be closely matching with Voigt model.

This work deals with the existence of representative volume element (RVE) for unidirectional laminated composites (with and without preexisting cracks). The RVE existence in elastic regime is studied employing periodic boundary conditions for uniaxial and shear loadings separately. RVE does exist in elastic regime for materials having discrete cracking. The numerical simulations for different sizes of RVE are performed keeping the fiber volume and crack volume fractions constant. It is observed that the elastic response is independent of RVE dimension. The RVE validity in softening regime is studied by Lemaitre ductile damage model within matrix phase.

The present work deals with the constitutive modelling and progressive failure analysis (PFA) of plain woven textile composites (PWTC). Two novel approaches, equivalent cross ply laminate (ECPL) coupled with classical laminate theory and Mori–Tanaka theory, are developed to compute homogenized properties of PWTC lamina. The PFA of PWTC lamina is performed coupling isotropic damage mechanics with ECPL theory, and meso-scale failure modes are identified. The novelty in the proposed PFA is that, the stress-based failure is detected, and the strain-based damage evolution is computed. A user-defined material subroutine of PFA of PWTC lamina is finally developed and test problems are solved in ABAQUS. All the simulation results of the proposed approaches are finally compared with experiments and found to be closely matching.

It is critical to handle geometric and material nonlinearities in a stable manner while solving the problems from solid mechanics, such that it results in a converged solution. The present work compares the suitability of generalised displacement control (GDC) and displacement control algorithms (DCA) by solving several 1D and 2D formulations. The ability of these algorithms to handle homogeneous and inhomogeneous deformations is also studied. A novel direct displacement control method (DDCM), coupled with Newton-Raphson method, is proposed and compared with GDC and DCA approaches. Appropriate conclusions are finally drawn based on the successful demonstrations of the numerical results obtained by GDC, DCA and DDCM approaches.

A damage mechanics-based progressive damage analysis (PDA) of plain woven textile composite (PWTC) is performed in this work. The primary objective is to identify the micro-scale and meso-scale failure modes, and compute the ultimate strength of PWTC under in-plane loadings. Multi-scale PDA is performed on an equivalent cross-ply laminate (ECPL) model by maximum stress theory to predict the meso-scale failure modes of PWTC. The damaged stiffness is computed by 3 different ways: 1) hypothesis of strain energy equivalence by proposed 4th order anisotropic damage tensor, 2) applying isotropic damage law, and 3) eliminating the stiffness terms. Novel multi-scale PDA approaches, applying Mori-Tanaka (MT) theory on ECPL model and on the quarter portion of representative volume element of PWTC, are performed to predict micro-scale failure modes. The macro-scale constitutive behaviour of PWTC is theoretically predicted and the corresponding strengths are computed. A user material (UMAT) subroutine is developed to validate the proposed constitutive behaviour of PWTC solving macro-scale boundary value problems in ABAQUS®. The PDA simulation results of 3D PWTC bar model are found to be reasonably matching with the in-house experiments.