Determining the Flexural and Shear Moduli of Fiber-Reinforced Polymer Composites Using Three-Dimensional Digital Image Correlation

A three-dimensional digital image correlation systemwas implemented into the flexural tests of fiber-reinforced polymer composite beams to characterize shear deformation. An optimization routine that minimized the error between the analytical and experimental data was implemented with first-order shear deformation beam theory used to compute the flexural and shear moduli using the deflection and slope of the mid-plane of the beam. A relatively coarse 814 g/m 2 woven roving E-glass fabric and a rubber-toughened vinyl ester resin system were used to fabricate the 10.0mmthick laminates in a quasi-isotropic laminate configuration. Span-to-thickness ratios of 8, 12, 16, and 24-to-1 were adopted for the laminate beams at a width-to-thickness ratio of 1.5-to-1. The full-field displacement and slope-optimization fitting methods were compared with conventional discrete point methods to determine flexural and shear moduli. Slope optimization produced consistent and reasonable values for the flexural modulus at all span-to-thickness ratios but produced higher than expected values for the shear modulus at shorter spans. Deflection optimization produced more variability in the flexural and shear moduli than slope optimization and lower than expected values of shear modulus at larger span-to-thickness ratios. Tests that used higher resolution images produced slightly larger values for shear modulus. Overall, the slope-optimization method produced the least amount of variability in the results for the flexural and shear moduli.