Objective:
To evaluate the effect of environmental conditioning, namely, lubricant oil soaking, thermal cycling and their combination on mechanical properties of T650 carbon fiber/Lonza Primaset PT30 cyanate ester composite rods manufactured by pultrusion process. The composite rod is 0.5 mm ± 0.01 mm in diameter and is chosen for use in new brush seals proposed for gas turbine engines.
Approach and Results:
Three types of environmental conditioning were conducted: (1) oil soaking the rods in Mil-L-7808 and Mil-L-23699 oils for 720 hours; (2) thermal cycling the rods for 100, 200, 400, 600 and 800 cycles; (3) soaking the rods in the two oils for 720 hours and then thermal cycling the rods for 600 cycles. Soaking the rods in the two lubricant oils had little effect on tensile and flexural properties. Thermal cycling for 100-800 cycles gradually reduced the tensile strength and flexural modulus while the tensile modulus was almost unaffected. Oil soaking + thermal cycling had the same effect as no oil soaking. Fiber-matrix interfacial separation, decomposition of fiber sizing and oxidation of matrix are possible reasons for the mechanical properties degradation. Thermal fatigue increased the Tg from 408 °C to 468 °C.
Significance:
Evaluated the gas turbine environmental effect on pultruded composite rods. The results are useful for durability and life assessment of composites in oil and thermal cycling conditions.
