The fracture behavior of rubber‐toughened, short‐fiber composites of nylon 6,6

This study critiques the use of both rubber particles and short‐glass fibers for the improvement of polymer fracture toughness ( K c ). Although dry neat nylon is brittle with only a moderate K c value (4.2 Mpa√m), additions of either second phase produce rising K R ‐curves and associated high K c values (8.1 Mpa√m for rubber‐toughened nylon, and 10.0Mpa√m for 17 vol% Glass‐fiber neat nylon). In the rubber ‐modified resin, the high K c value is associated with extensive plastic blunting at the crack tip. In the fiber‐reinforced neat resin, K c is improved due to a combination of fiber‐bridging and increased strength, the latter being associated with additional load carrying capacity of the fibers. When both rubber and fibers are added, however, no further increase in K c is noted ( K c = 9.3 Mpa√m for 17 vol% glass‐fiber rubber‐modified nylon). The extent of ductile blunting in the rubber + fiber resin is not as great as in the rubber‐only resin. Furthermore, the fracure strength of the rubber + fiber resin is not as high as the fiber‐only resin. The net result is a balance of properties for the rubber‐toughened composite.