High-throughput screening the micro-mechanical properties of polyimide matrix composites at elevated temperatures

In this work, a novel high-throughput methodology based on combinations of nanoindentation, indentation creep and push-in methods, is proposed to measure in-situ the micro-mechanical properties of typical polymer matrix composites at a wide temperature range. The Young's modulus and strain rate sensitivity of a polyimide matrix and the interfacial shear strength in a quartz fiber reinforced polyimide matrix composite are measured at 25-350 degrees C for the first time. The results highlight a linear softening of the polyimide matrix at high temperatures, which is evidenced by the approximate linear decrease of Young's modulus from approximate to 5.0 GPa at 25 degrees C to approximate to 1.1 GPa at 350 degrees C. In comparison, the strain rate sensitivity of the polyimide matrix is increased, from approximate to 0.032 at 25 degrees C to approximate to 0.062 at 350 degrees C. This evidences a stronger visco-plasticity of polyimide at higher temperatures. The shear strength of the fiber/matrix interface is also temperature dependent. As the testing temperature increases from 25 to 300 degrees C, the shear strength is decreased from approximate to 147 MPa to approximate to 40 MPa. Specially, the interfacial strength is extremely low at 350 degrees C (approximate to 4 MPa), evidencing a failure of the composite at this temperature.