Effect of Thermal Fatigue on Tensile and Flexural Properties of Carbon/Cyanate Ester Pultruded Composite

Abstract

The effect of thermal cycling on tensile and flexural properties of Cytec T650 carbon fiber/Lonza Primaset PT-30 cyanate ester pultruded composite rods proposed to be used for brush seals in gas turbine engines was evaluated. The thermal cycle consisted of 4min each of heating and cooling with 28min of hold at 315°C and 24min of hold at room temperature. Tension and three-point bend flexure tests were conducted after thermal cycling for 100, 200, 400, 600, and 800 cycles. Thermal cycling reduced the tensile strength and fracture strain almost linearly with the number of cycles while the tensile modulus remained unchanged. The flexural modulus did not change for the first 100 cycles and then decreased as much as 28% after 800 thermal cycles. Thermal cycling increased the Tg of the composite rods from 408 to 468°C. Optical and scanning electron microscopy analysis showed fiber/matrix interfacial separation and matrix shrinkage and oxidation due to thermal cycling.