Compliance Methods For Bonded Joints: Part I - Investigation Of The Standardized Methods To Obtain The Strain Energy Release Rate For Mode I

ABSTRACT The double cantilever beam (DCB) is the most acceptable geometry to obtain the critical strain energy release rate (GIc ) of adhesive joints under Mode I. However, there are still some areas of uncertainty in the standardized compliance methods recommended by the ISO and ASTM standards in terms of accuracy in estimating the compliance of a bonded double cantilever beam and, consequently, GIc . In this work, an investigation of the standardized compliance methods for fracture characterization of bonded joints under Mode I is conducted, employing a finite element model to obtain the compliance of a double cantilever beam, considering different crack lengths. The compliance values determined from the finite element model are compared with those recommended by the standards. It is concluded that the standardized compliance methods are very sensitive to issues derived from crack length measurements. The crack length correction methodology proposed by the corrected beam theory is inadequate, which can lead to a wrong interpretation of the structure’s behavior and the structural integrity assessment. The best approach to obtain the compliance of a double cantilever beam in respect of crack length is to use a compliance calibration method, fitting an expression for the experimental curve.