Thermal and mechanical characterization of amine‐epoxy/Kevlar fibre composites

Experimental results of dynamic‐mechanical measurements and differential scanning calorimetry are compared for a pure diglycidyl‐type epoxy/tetrafunctional aliphatic amine system and for a composite containing Kevlar fibres as reinforcement. The presence of fibres had marked effects on the curing reaction, depending on the curing temperature. At low curing temperatures, the extent of the reaction was lower for reinforced than for neat formulations. For higher curing temperatures, the thermograms shifted to shorter times as the fibre content increased. In dynamic curing, an increase in the fibre content affected the curing kinetics by slightly shifting the heat flow curves to higher temperatures, and resulted also in a reduction of the glass transition temperature of the matrix if postcuring was not applied. The dependence of the dynamic‐mechanical spectra of the samples on fibre content was satisfactorily modelled with the aid of Takayanagi's block model. An analysis of the main relaxation master curve shows that relaxation broadens as fibre content increases. © 1999 Society of Chemical Industry