A piecewise-linear parametric uniaxial stress strain approach has been used to obtain the nonlinear moment curvature curve and load deflection response based on strain compatibility in bending for epoxy resin materials. It has been shown that the direct use of tension and compression stress strain models underestimates the flexural strength of epoxy resin materials in three point bending and round plate setup. The Weibull parameters were estimated using linear regression method. Fifty-two smallsized three point bending samples with grooves in the middle of epoxy resin Epon E863 were tested at room temperature. The accurate flexural over-strength factor obtained from the analytical simulation is less than the estimation predicted by the two-parameter Weibull model.