IMPACT FRACTURE-BEHAVIOR OF CONTINUOUS GLASS FIBER-REINFORCED NYLON-6

The impact fracture toughness of nylon 6/continuous glass fiber composites at four levels of fiber content has been studied. The composites were produced by anionically polymerizing caprolactam within a glass mat using a vacuum injection technique. Application of linear elastic fracture mechanics to characterize the impact fracture toughness of the composites, using an energy approach (GIC), has been found to be applicable provided that a correction is made for the size of the damage zone. The concept of Jc, fracture energy per unit ligament area, has also been applied to the composites and agreement between GIC and Jc has been found to be reasonably satisfactory. The ratio of crack propagation energy to the total energy absorbed (ductility index) has also been calculated. The ductility index was found to be close to one for the composites, indicating that additional energy is involved in propagating the fracturing cracks probably due to fiber debonding and/or crack blunting and fiber pullout. Fractographic examination of the impact fracture surface confirmed the presence of these features.