Experimental Investigation of Double-Sided Strain of Composites in Tensile Testing Using MultiCamera DIC

Composite materials are widely used in engineering because of their high strength, high modulus, and corrosion resistance. Accurately obtaining the mechanical properties of composites is helpful for their further development. However, in a uniaxial tensile test, the strain distribution between the front and back of the composite sheet sample may differ due to its heterogeneity, and its stress-strain curve depends on which side the strain is measured. To report the stress-strain curve more accurately, a multicamera digital image correlation (DIC) system was employed to measure the double-sided strain in this work. Two sets of 3D digital image correlation (3D-DIC) systems were placed in front of and behind the specimen to record the tensile process of the specimen, and a double-sided calibration technique was implemented to connect the two sets of 3D-DIC systems into a unified coordinate system. Young’s modulus, percent bending, and local strain history are analyzed based on the measurements of strain on both sides. The results show that the strain on both sides of the composite is not exactly same, especially in the strain concentration area. As a comparison, the strain distribution on both sides of the metal material is almost identical.