Characterization of tensile property of high-performance fiber bundles combined with epoxy resin using advanced video extensometer

The increased desire to use high-performance fibers in the fields of industry and aerospace requires better understanding of their mechanical behaviors, especially in polymer matrix composite structure. By means of an advanced video extensometer using digital image correlation, the tensile properties of six kinds of high-performance organic and inorganic fiber bundles combined with epoxy resin were successfully determined in this paper, which have testing difficulties using contacting extensometer because of curved surface and small diameter of sample. The advanced video extensometer system was initially used for three kinds of carbon fibers impregnated and cured with epoxy resin to determine the optimum experimental conditions. The comparative tests demonstrate that the accuracy of the results is affected by light source and sampling frequency, but independent on crosshead speed. The tensile properties of other five kinds of epoxy impregnated fibers were subsequently measured using optimal conditions. The results show excellent agreement with the measurement of contacting dynamic extensometer for all studied fibers, and both relative error of Young’s modulus and elongation at break are in acceptable ranges. The capability of the advanced video extensometer system to record real-time, high-accuracy, and complete strain enables it to directly measure elongation. Then, Young’s modulus at different strain ranges was further studied. Different changing trends of Young’s modulus of various impregnated fibers with increasing strain were seen, which are related to the changes of fiber structure during testing.