Nonlinear flexural modeling for epoxy resin materials

Polymer composite structures are usually subjected to large flexural loadings, so the flexural behavior of these structures and their constituents are critical to their use. A novel approach for polymeric materials with strain softening model in tension and compression is developed to investigate the flexural behavior of Epon E 863. The tension and compression model consists of a bilinear ascending curve in pre-peak, strain softening followed by constant plastic flow in the post-peak response. The effects of softening localization on flexural response are considered. Local stress strain tension and compression responses, using digital image correlation system, are used for material characterization. Closed form expressions for flexural behavior are developed. The structural response of beams under three and four point bending and round plate on three symmetrical supports are studied experimentally and analytically. Results show that direct use of uniaxial tension and compression stress strain models underestimates the flexural load carrying capacity. Flexural over-strength factor obtained from inverse analysis of beam under three point bending is conservative and it could be used to modify the constitutive models for analyzing a structural system.