22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.5.1

MIXED MODE FRACTURE CHARACTERIZATION OF ADHESIVE JOINTS

U. Weerts, H. Kossira
Technical University of Braunschweig, Germany

Keywords: adhesive, joint, j-integral, mixed-mode, fracture

Double Cantilever Beam (DCB) and Single-Lap Joint (SLJ) specimens are investigated with regard to the fracture mechanical behavior on the basis of the J-integral [1]. The J-integral is derived in a formulation, which is useful for a coarse meshed finite element analysis. Therefore, the method bypasses the detailed determination of the strain singularity and the inelastic material behavior at the crack tip. The formulation allows a mixed-mode fracture characterization by simple determinations of the adhesive thickness and near tip adhesive stresses and strains of a continuum mechanics approach. The method is demonstrated by means of a DCB specimen and compared with a physical nonlinear analysis including the crack tip singularity. Experiments on cyclic loaded DCB and SLJ specimens are analyzed with the abovementioned theory and indicate the validity of the fracture characterization for the prediction of crack initiation.

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