Tensile testing of carbon fiber multifilament using an advanced video extensometer assisted by dual-reflector imaging

Tensile properties of fibers are of high significance for composite materials, thus making their testing methods also highly concerned. In this work, an advanced dual-reflector-assisted video extensometer is established for accurate determination of tensile properties of carbon fiber multifilament. To validate the practicality and effectiveness of the video extensometer, three different types of carbon fiber multifilament specimens manufactured by Toray were tested. The stress-strain curves of these specimens were firstly measured for different gauge lengths, verifying that the test results are not affected by the gauge length of the video extensometer. Then, the dual-reflector-assisted and regular video extensometers were simultaneously applied to measure the tensile strains of the specimens, confirming the higher accuracy and better stability of the dual-reflector-assisted video extensometer. Moreover, the measured tensile modulus and elongation at break show good agreement with the reference values, further validating the practicality and accuracy of the technique. Due to its prominent advantages of easy-implementation, non-contact, high-accuracy, and real-time strain measurements, the proposed dual-reflector-assisted video extensometer demonstrates broad prospects in material testing of various materials.