Thermal and Mechanical Properties of Short Fiber-Reinforced Epoxy Composites

A cycloaliphatic epoxy/acidic anhydride system incorporating short carbon fibers (SCF) and short glass fibers (SGF) was fabricated and thermal/mechanical properties were characterized. At low filler content both SCF- and SGF-reinforced composites showed a similar decrease in coefficient of thermal expansion (CTE), measured by a thermomechanical analyzer, with increasing loadings, above which SCF became more effective than SGF at reducing the CTE. Experimental CTE data for the SCF-reinforced composites is best described by the rule Of Mixtures at lower SCF contents and by the Craft-Christensen model at higher SCF contents. Storage modulus (E') at 30 degrees C and 180 degrees C was greatly enhanced for short fiber-filled composites compared to unfilled specimens. Scanning electron microscopy of the fracture surfaces indicated that the decreased CTE and the increased E' of the short fiber-reinforced composites resulted from good interfacial adhesion between the fibers and epoxy matrix.