Interfacial toughness evaluation from the single-fiber fragmentation test

The single-fiber fragmentation rest is widely used to determine the interfacial shear strength of polymer composites. In the present study, HTA carbon fibers in an epoxy matrix are studied for the two cases of strong and weak interfaces. The average fiber length is reported as a function of strain, both plotted on logarithmic scales. As deviation from linearity is observed, interfacial debond cracks extend to significant length. Debond crack lengths at given strains are determined from experimental data. A finite-element stress analysis in combination with a fracture mechanics criterion is used to determine values of G(c), the interfacial fracture toughness. G(c) is independent of debond length, supporting the idea that G(c) is a valid fracture criterion. (C) 1996 Elsevier Science Limited