Fiber nonlinear predictive model for combined bending-compression loading of an orthogonal plane weave composite laminate structure

To increase understanding of damage evolution in advanced composite material systems, a series of large deflection bending-compression experiments and model predictions have been performed for a woven glass-epoxy composite material system. Theoretical developments employing both small and large deformation models and computational studies are performed. Results (a) show that the Euler-Bernoulli beam theory for small deformations is adequate to describe the shape and deformations when the axial and transverse displacement are quite small, (b) show that a modified Drucker's equation effectively extends the theory prediction to the large deformation region, providing an accurate estimate for the buckling load, the post-buckling axial load-axial displacement response of the specimen and the axial strain along the beam centerline, even in the presence of observed anticlastic (double) specimen curvature near mid-length for all fiber angles (that is not modeled), and (c) for the first time the quantities eff - eff are shown to be appropriate parameters to correlate the material response on both the compression and tension surfaces of a beam-compression specimen in the range 0≤eff<0.005 as the specimen undergoes combined bending-compression loading. In addition, computational studies indicate that the experimental eff - eff results are in reasonable quantitative agreement with unwoven laminate finite element simulation predictions in the range 0≤eff<0.010, with the effect of the woven structure appearing to provide the key constraint for various fiber angles that leads to the observed consistency in the experimental eff - eff results on both surfaces.