BASIC STUDY ON ROLES OF ENVIRONMENT AND MATERIAL ON FATIGUE CRACK PROPAGATION OF REINFORCED NYLON 46

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Influences of fillers on the fatigue crack propagation of advanced Nylon 46 at low rate near threshold in parallel to the injection direction under the equilibirium moisture were experimentally studied. Especially, with focus on the fatigue reliability of filler-reinforced Nylon 46 in practical usage, fatigue crack propagation property was estimated in parallel with the injection direction of the specimen controlled for the equilibrium moisture content under 23ﾟC and 50% room huminity. Three kinds of tested materials were short E-glass fiber-, Miker mineral- and EPM rubber-reinforced Nylon 46, which were described as G, M and R material respectively. The threshold of fatigue crack propagation, DELTAKth for short E-glass fiber-, Miker mineral- and EPM rubber- reinforced Nylon 46 was 1.4, 1.2 and 1.0 MPaROO<m> respectively.So, the resistance of E-glass fiber-reinforced Nylon 46 against crack propagation was found to be superior in all materials. The fractography using SEM showed that the fatigue crack near threshold in glass fiber-reinforced Nylon 46 propagated through the matrix in a zigzag line. Therefore, it could be interpreted that the variation in the property of fatigue crack propagation of each tested material should have been caused by the difference in the roughness of fracture surface.