Secondary effects in the analysis of the post-buckling bending test

The post-buckling bending test can be used as an alternate to the classical three-point bending test for the mechanical characterisation of fibre-reinforced polymer composites. Its main interest is the avoidance of localised contact stress below the loading nose, which often induce the premature failure of the specimens under three-point bending conditions. The derivation of strength and modulus values from this test is based upon a mechanical analysis, which is usually developed within the frame of the classical buckling analysis. This approach is based upon some assumptions, which have been justified in the real physical situation. The validity of the beam approximation has especially been discussed for the usual specimen geometry. In addition, the correcting factors due to membrane effects and the contribution of the rigid specimen grips are considered within the frame of the beam-bending problem