Potassium titanate whiskers-nylon66 composites were effectively toughened with an elastic interlayer of epoxy resin. The optimal fraction of epoxy resin was 1.5 wt % of whiskers, which corresponded to an interlayer thickness of 3% of the radius of whiskers. SEM images showed that interfacial adhesion was improved with elastic interlay. The impact strength of the composite increased 132% compared with neat nylon66, whereas the bending and tensile strengths increased 55 and 48%, respectively. Digital image method was adopted to carry out fractal research of fracture surfaces of the composites. Fractal dimensional calculations were based on perimeter-area relation. It was found that with the sizes of measured slit islands increasing, calculated fractal dimensions increased first and became stable after area threshold reached about 500 eta (2) (eta was a yardstick). The toughness of composites increased with fractal dimensions, which was explained from the point of fracture mechanism. (C) 2001 John Wiley & Sons, Inc.
