Mechanical Properties Of Resin Matrix Composites

The rapid development of science of polymer composite materials, has brought new challenges and exploration to the research and examination in mechanical properties of composite materials. Because of its many merits, composite materials has been widely used in the daily life, and particularly in aerospace and military industry. Therefore, the mechanical properties testing methods become very important, especially when meeting holes, debonding and stratification inside materials during its preparation and application. Mechanical properties detection include elastic modulus, fatigue resistance, tensile ductility and deformation and strain and so on. To research the deformation and strain field distribution, a B-scan method based on a phase-contrast optical coherence tomography (PC-SOCT) was employed to dynamically measure the thermal strain fields within polymer materials. The measurement method provides a new feasible technical means for the detection of mechanical properties.The optical interference spectral domain phase control B scanning measurement technique and measurement system of resin based composite curing process, mechanical load and thermal load inside the composite out of plane displacement field and strain field distribution were measured. This article explains the experiment on theory. Focuses on the design of the structure of the measurement system, including the overall system design and experimental device. Finally experiments prove the reliability and feasibility of the measuring principle and measuring system.In this paper, the PC-SOCT theory and experimental configuration system were applied to the measurement for the solidification process of resin matrix composites, the out-of-plane displacement field and strain field distribution of the samples of epoxy resin composites with/without hole defect inside under the action of mechanical load and thermal force. The principle of optical interference in polymer composites was described, and the theoretical algorithm of PC-SOCT was presented. The design structure of the measurement system was mainly introduced, including the overall design and the step loading device. With the experiment results, it proved the feasibility and reliability of the theory algorithm and measurement system.At last, the experimental data of mechanical load and thermal load were given respectively:(a) the phase difference of silica gel solidification process (b) interference pattern of the intact and defect samples with steps loaded under the action of mechanical load; (c) interference pattern of the intact and defect samples under thermal load in the process of cooling. The data analysis are as follows:(a) extracting the amplitude-frequency characteristics and phase-frequency characteristics curve; (b) presenting the wrapped phase difference map, out-of-displacement field map and the normal strain field distribution. The experiment results were given:(a) variety of changes of out-of-plane displacement and strain near the defect part were bigger than that in other intact part; (b) only a single shot of the interferogram of the sample was needed before and after the deformation to complete the measurement; (b) a dynamical measurement was realized. In summary, the phase contrast spectral optical coherence tomography with a B scanning method is a high-precision, fast and dynamical technology, which can be applied to the mechanical properties testing as a high-performance means.