Mechanical performance of nanosilica filled quartz fiber/polyimide composites at room and elevated temperatures

The polyimide (PI) composites reinforced with silanized nanosilica (SNS) and/or quartz fabrics had been fabricated. Influences of the SNS dispersion on morphology, Vickers hardness, thermal stability and mechanical properties of these composites were studied. The uniform dispersion of SNS in PI resulted from the crosslink of silane pretreated on the surface of nanosilica and PI chains. The measurement results indicated that density, Vickers hardness and flexural strength were enhanced due to the addition of SNS into the PI matrix and the optimum content of SNS was 2 wt%. The thermal stability of the SNS reinforced PI composites increased with an increase in weight fraction of SNS, compared with the neat PI resin. The effects of quartz fabric on the mechanical properties of quartz fabric-reinforced PI composites with different volume fractions and effects of post-curing on the flexural strength were also investigated. Results also showed that better mechanical properties of quartz fabric-reinforced PI composites were obtained when the volume fraction of quartz fabric was 50%. The quartz fabric-reinforced PI composites containing 2 wt% SNS after post-curing exhibited the highest flexural strength and elasticity modulus by virtue of good fiber-matrix interface, and flexural strength was almost 500 MPa at 300 degrees C. It is pointed that the composites have a great application prospect as one of engineering materials with high strength and high temperature resistance.