AN UNSYMMETRIC DOUBLE CANTILEVER BEAM TEST FOR INTERFACIAL FRACTURE-TOUGHNESS DETERMINATION

An unsymmetric double cantilever beam test is described and its suitab ility for the determination of interfacial fracture toughness is evalu ated. The test specimen consists of a beam-type geometry comprised of two materials, one 'top' and one 'bottom,' with a crack at one end alo ng the bimaterial interface. The specimen is loaded ina splitting fash ion similar to that of a conventional double cantilever beam test. Due to the dissimilar in-plane and out-of-plane deformations of the two l egs, the load vs deflection response of the specimen is found to be no nlinear. A nonlinear plate theory is used to predict the deformations of the specimen, and these results are used in a crack tip element ana lysis to determine energy release rate and mode mixity. The analytical predictions are verified by comparisons to results from two-dimension al geometrically nonlinear finite element continuum analyses for a var iety of typical materials and test geometries. It is shown that, by va rying the relative thicknesses of the two materials, the unsymmetric d ouble cantilever beam test can be used on most bimaterial pairs to det ermine interfacial fracture toughness over a reasonably wide range of mode mixities. (C) 1997 Elsevier Science Ltd. All rights reserved.