Characterizing Fiber Reinforced Polymer Composites Shear Behavior with Digital Image Correlation

The interlaminar and intralaminar shear properties, such as modulus and strength, are important for the design of fiber reinforced polymer (FRP) composite materials. Short beam strength is often used as a screening tool for interlaminar strength, whereas the V-Notched beam methods are considered valid for shear modulus and strength measurements. The advent of optical strain measurement techniques such as digital image correlation (DIC), provide new opportunities to generate high resolution maps of the shear strain field as a function of the globally applied strain. In this work, we show that non-contact measurements of the strain field are an important enhancement to measuring the shear properties of FRP composites. The V-Notched rail shear method is used to measure the shear modulus and strength of two different FRP composites that vary in reinforcement type (glass or carbon), matrix type (epoxy chemistry) and angle of the principle fiber axis to the shear loading axis. DIC was used to image the V-Notchrail- method samples during shear measurement to track local strains and evaluate the shear strain across the gauge length and near the notch root in these specimens. The results are compared to analytical predictions of shear modulus derived from tensile properties of the epoxy polymer matrix and the reinforcing fiber.