Morphology and mechanical properties of carbon fiber reinforced composites based on semicrystalline polyimides modified by carbon nanofibers

As previous attempts to recrystallize a thermoplastic polyimide matrix, while preparing carbon fiber reinforced composites, had resulted in embrittlement of the matrix, a new concept was attempted, based on adding a small quantity of acicular nanoinclusions, namely, vapor grown carbon fibers (VGCF). The new concept was based on the expected dual action of VGCF, comprising their power to nucleate the matrix jointly with their ability to reinforce the matrix through an effective stress transfer mechanism. First, regeneration of crystallinity with 1–3 wt.% VGCF was confirmed, showing also that for such low loadings the melt viscosity remained on a practical level. Then by screening a range of mechanical properties it was shown that the reinforcing action of VGCF compensated for the loss of toughness that was associated with high crystallinity.