Mode I Interlaminar fracture Toughness and Fracture Mechanism of Angle-Ply Carbon/Nylon Laminates

Abstract

Interlaminar fracture toughness and fracture mechanism in carbon fiber reinforced nylon laminates have been investigated. Mode I interlaminar fracture toughness tests are carried out on the double cantilever beam (DCB) specimens made of four kinds of angle-ply laminates. These laminates exhibit unstable "stick-slip" crack propagation. In order to obtain the continuous G _I resistance curve (G _I-R curve) describing the stick-slip behavior, one modification is made to Kageyama's (1997) modified compliance method. From the continuous G _I-R curves, it is found that the stable delamination is characterized by flat region of G _Istable≈ 1200 J/m² for all lay-ups except for 60° // -60° specimen which shows a rising G-R curve to final failure. The interlaminar fracture toughness of these composite laminates is considerably higher than that of carbon/epoxy laminates. Based on the continuous GC-R curves and the observation of the fracture surfaces, a mechanism is proposed in which the unstable stick-slip behavior is explained by the development of the large scale bridging of fiber-bundle or layer and its breakage.

Keywords

carbon fiber reinforced thermoplastic angle-ply laminates interlaminar fracture toughness delamination stick-slip behavior modified-nylon

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