CURING OF POLYMERIC COMPOSITES USING MICROWAVE RESIN TRANSFER MOULDING (RTM)

The main objective of this work is to compare the difference betweenmicrowave heating and conventional thermal heating in fabricatingcarbon/epoxy composites. Two types of epoxy resin systems were used asmatrices, LY5052-HY5052 and DGEBA-HY917-DY073. All compositesamples were fabricated using resin transfer moulding (RTM) technique. Thecuring of the LY5052-HY5052-carbon and the DGEBA-HY917-DY073-carboncomposite systems, were carried out at 100 °C and 120 °C, respectively.Microwave heating showed better temperature control than conventionalheating, however, the heating rate of the microwave cured samples were slowerthan the conventionally cured samples. This was attributed to the lower power(250 W) used when heating with microwaves compared to 2000 W used inconventional heating. Study of thermal characteristics as curing progressed showed that the polymerisation reaction occurred at a faster rate duringmicrowave curing than in conventional curing for both the DGEBA and theLY/HY5052 carbon composite systems. The actual cure cycle was reducedfrom 60 minutes to 40 minutes when using microwaves for curing DGEBAcarboncomposites. As for LY/HY5052-carbon composites, the actual curecycle was reduced from 3 hours to 40 minutes. Both conventional andmicrowave heating yielded similar glass transition temperatures (120 °C forDGEBA systems and 130 °C for LY/HY5052 systems). Microwave curedcomposites had higher void contents than conventionally cured composites(2.2-2.8% and 1.8-2.4% for DGEBA and LY/HY5052 microwave curedcomposites, respectively, compared to 0.2-0.4% for both DGEBA andLY/HY5052 thermally cured composites). C-scan traces showed that allcomposites, regardless of methods of curing, had minimal defects.