A COMPLEX POTENTIAL APPROACH TO MICROMECHANICS OF UNIDIRECTIONAL COMPOSITES

Complex potential methods for the solution of two-dimensional boundary value problems in linear elasticity are used to perform micromechanics analysis of unidirectional composites. The composite microstructure is idealized as a square array of unit cells subjected to prescribed strains. Unit cell analyses are performed for plane strain and anti-plane strain conditions to study the interaction of the fiber and matrix materials. The unit cell solutions are used to derive predictions for the ply moduli, Poisson’s ratios and coefficients of thermal expansion, which are shown to agree with the results of other methods. Applications to strength prediction are briefly discussed, and the detailed stress field results that can be generated using the approach are illustrated.

MICROMECHANICAL FINITE ELEMENT MODELING OF UNIDIRECTIONAL COMPOSITES IN THREE DIMENSIONS: PREDICTION OF TRANSVERSE TENSILE & COMPRESSIVE, TRANSVERSE SHEAR & IN-PLANE SHEAR PROGRESSIVE DAMAGE BEHAVIOR

Predicting the rate-dependent non-linear progressing damage behavior of unidirectional composites from the rate dependent properties of the constituents will enable computational materials-by-design and provide the fundamental understanding of the energy dissipating damage mechanisms. In this study, micromechanical finite element models of unidirectional glass-epoxy composites have been developed with fiber volume fractions, FVF = 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, & 0.70; respectively with zero thickness fiber-matrix cohesive interfaces between the fibers and the surrounding matrix. Experimentally determined rate dependent non-linear stress-strain behavior of DER353 epoxy resin [1] (Tamrakar 2019) has been used to model the large deformation matrix behavior in conjunction with a rate dependent fiber-matrix interface traction law obtained from S-2 Glass/DER353 micro-droplet experiments & simulations [2] (Tamrakar 2019). Transverse tension, compression, in-plane shear, and transverse shear loads have been applied in predicting the progressive damage behavior of unidirectional S-2 Glass/DER353 epoxy composites.