Dynamic Viscoelastic Properties of a Uniaxially Aligned Carbon Fiber Reinforced Epoxy Resin

Abstract

The dynamic viscoelastic properties of uniaxially aligned carbon fiber reinforced plastics (CFRP) containing a matrix epoxy resin composed of diglycidyl ether of Bisphenol A, nadic methyl anhydride and an aromatic tertiary amine system were measured. A new dispersion (b-dispersion) other than the dispersion (a-dispersion) of the cured epoxy resin alone was observed in a higher temperature region on the loss modulus (E“) vs. temperature curves by the addition of carbon fiber (CF) yarn. The b-dispersion tended to separate into two parts (b1-and b2 -dispersions), while the a-dispersion tended to nearly disappear with the increase of the fiber volume fraction (Vf).In particular, the intensity of the b1- dispersion observed at the lower temperature region became larger and that of the b2-dispersion at the higher temperature region became smaller with the increase of Vf. Also, the mechanical dispersion was affected by the angle between the longitudinal direction of the specimen and the fiber axis. The mechanical dispersion pattern showed only a single dispersion and its temperature range became small and it was concentrated in a specific temperature region when the angle was 45°and 90°for the specimen taken from the plain sheet which showed the b1- and b2- dispersions in the case of the 0 ° angle. From these findings, it is suggested that: 1) An interphase with a relatively strong interaction between the CF surface and matrix epoxy resin may exist, 2) The interphase may consist of two kinds of phases with different properties and one of them, namely, the b1-dispersion may be ascribed to a boundary layer with a relatively weaker interaction, and 3) The b-dispersion(b1- and b2-dispersions) may appear only in the case of the fiber arrangement where stress transfer works effectively.