Crack Growth At Interfaces in Bimaterial Systems and Composites


The problem of a crack impinging upon an interface between dissimilar materials is investigated using a Consistent Shear-Lag (COSL) model. The primary question to be answered is whether the crack will cross (penetrate) the interface or be deflected along it. Typically the stress and displacement fields in the vicinity of an interface create computational difficulties, especially when the elastic moduli of the adjacent regions vary greatly. The COSL model is modified to include a finite thickness interlayer region representing the interface to act as a buffer. The energy release rates for both deflected and penetrating cracks are determined. The ratio of these two quantities is then compared to that of debond and Mode I toughnesses to investigate the two scenarios for crack extension. The effect that elastic mismatch has on the energy release rates, and hence the mode of crack extension, is investigated. These results compare favorably with analytical solutions for semi-infinitc domain bimaterial problems. The effect of anisotropy is investigated to determine the relative importance of the effect of elastic constants on the energy release rate ratio. It is shown that of these, the longitudinal and transverse elastic moduli are of greatest significance. This model is applied to cracks impinging on fiber-matrix interfaces in composite materials, and it is shown that the fiber volume fraction actually has little effect on the ratio of energy release rates. © 1992.


Mechanical and Aerospace Engineering

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Article - Journal

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© 1992 Springer Verlag, All rights reserved.

Publication Date

01 Jan 1992