Effect of heating on the structure of carbon fiber polyphenylenesulfide-matrix composite, as studied by electrical resistance measurement

Heating and cooling were found to affect the structure of carbon fiber poly phenylenesulfide-matrix composites, as shown by their effects on the DC ele ctrical resistance of the composite in the fiber direction. Matrix now duri ng first heating above Tg and thermal stress buildup during cooling in any thermal cycle caused the resistance to increase, whereas isothermal crystal lization at 180 degrees C caused the resistance to decrease. Thermal stress buildup was reversible upon thermal cycling. Prior annealing at 180 degree s C diminished the matrix flow because of improved fiber-matrix bond, and i t increased the matrix crystallinity. Annealing at 180 degrees C for 15 h o r more was sufficient to eliminate the matrix flow.