화학공학소재연구정보센터
Polymer Engineering and Science, Vol.39, No.8, 1525-1533, 1999
Thermoelastic behavior of carbon fiber/polycarbonate model composites
Model composites of polycarbonate (PC) containing single, multiple and chopped carbon fibers (CF) with and without and epoxy sizing were prepared by hot pressing. The thermoelastic behavior of model CF/PC composites was characterized by stretching calorimetry at room temperature. For small strains a (i.e., epsilon approximate to 0.01) the specific mechanical work, specific heat effects and specific internal energy changes Delta U were completely reversible in stretching/contraction cycles and quantitatively obeyed the standard relationships for elastic solids. Youngs moduli E and Delta U were significantly higher, whereas the linear thermal expansivities alpha(L) were lower for model CF/PC composites compared to those for the neat PC. Smaller values of the above parameters for composites reinforced with sized CF suggested weaker CF/PC interfacial interactions. Current theoretical models of thermoelastic properties of composite materials suggest the existence of unusually stiff, highly oriented PC structures in fairly thick boundary layers around CF. The onset of inelastic deformation, as well as mechanical failure in CF/PC model composites at significantly smaller strains compared to the neat PC were tentatively explained by the yield and subsequent plastic now of the matrix polymer initiated by heat effects of fiber fragmentation processes, and by higher concentration of microvoids generated in fiber fragmentation/debonding events, respectively.