Multi-Linear Stress Strain and Closed-form Moment Curvature Response of Epoxy Resins
ARIZONA STATE UNIV TEMPE
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A simplified multi-linear stress strain approach has been used to obtain the closed form nonlinear moment curvature response for epoxy resin materials. The model consists of constant plastic flow in tension and constant yield in compression. The multi-linear stress strain model is described by two main parameters in addition to four non-dimensional tensile and five non-dimensional compressive parameters. The main parameters are modulus of elasticity in tension and strain at the proportional elastic limit point in tension. The nine non-dimensional parameters are strain at the ultimate tensile stress, maximum strain, post elastic proportionality stiffness, and post peak strength in the tension model and strain at the proportionality elastic limit, strain at yield strength point, maximum strain, initial elastic stiffness and post elastic proportionality stiffness in the compression model. Explicit expressions are derived for the stress-strain behavior of the polymers. Closed form equations for moment curvature relationship are presented. The results of tension, compression, and bending tests using digital image correlation technique are presented. Load deflection response of flexural three point bending 3PB samples could be predicted using the moment curvature equations, crack localization rules, and fundamental static equations. The proposed nonlinear moment curvature shows good predictions when compared to experimental results.