FIBER FRACTURE IN HYBRID COMPOSITE SYSTEMS

Conventional and hybrid micro-composites consisting of up to nine sing le fibers in Epon 828/Versamid 140 epoxy were constructed and pulled i n uniaxial tension. The coordination of fiber fractures for each syste m was studied as a function of interfiber spacing. E-glass, AS-4 and I M6-G carbon, and Kevlar-49 fibers were used. It was shown that fiber f racture occurred in a random pattern when fiber spacing was more than eight fiber diameters. When the fiber spacing was less than eight fibe r diameters there was coordination of fractures in adjacent fibers, wi th increased adhesion resulting in stronger coordination. The AS-4/Kev lar-49 hybrid system exhibited the least amount of coordinated fractur e. A computer model of the hybrid effect, based on local load sharing principles, predicted similar strength enhancement of the stiffer fibe rs in hybrid composites as other authors have found experimentally. It was concluded that the hybrid effect can be attributed to load sharin g between high and low modulus fibers in hybrid composites.