THE EFFECT OF TEMPERATURE ON THE BEHAVIOR OF THE INTERPHASE IN POLYMERIC COMPOSITES

The single-filament fragmentation method for measuring the fiber/matri x stress transfer was used for the identification of interphase pertur bations. This technique is based on the measurement of the fiber lengt h resulting from the multiple fracture of a single fiber embedded in a resin specimen during tensile loading. A series of single-fiber fragm entation experiments was conducted over a wide range of temperatures o n the AS4-carbon-fiber/Epon-828/PACM 20-epoxy-resin system. Critical a spect ratios, the magnitude of which is considered to be inversely pro portional to the square root of the matrix modulus, showed a significa nt increase from ambient to elevated temperatures, at temperature leve ls much lower than the glass transition point of the bulk matrix. This increase was consistent with the existence of an interphase of lower glass transition temperature than the bulk matrix. A three-concentric- cylinder elastic model was employed to correlate the effect of materia l properties.