THE MECHANICAL ROLE OF THE FIBER MATRIX TRANSCRYSTALLINE INTERPHASE IN CARBON-FIBER REINFORCED J-POLYMER MICROCOMPOSITES

Microcomposites of single-pitch-based carbon fibre reinforced J-Polymer are employed to investigate the mechanical role of the fibre matrix transcrystalline interphase. The transcrystalline interphase in this semicrystalline thermoplastic system is varied by changing the crystallization kinetics, as determined by the thermal history. The kinetics of transcrystallization under isothermal conditions are presented as an example, and are used to form different transcrystalline interphase thicknesses. These affect the fibre fragmentation process that occurs while the specimens are cooled from the crystallization temperature to room temperature. This fragmentation process is attributed to residual thermal stresses, which can be calculated by assuming that it is controlled by Weibull statistics. Tensile loading of either longitudinal or transverse microcomposite specimens results in additional fragmentation, the extent of which is determined jointly by the thickness of the transcrystalline layer and by the yield strain of the matrix.