A COMPACT MIXED-MODE (CMM) FRACTURE SPECIMEN FOR ADHESIVE-BONDED JOINTS

Finite Element Analysis combining with the concepts of Linear Elastic Fracture Mechanics (LEFM) provides a practical and convenient means to study the fracture characteristics of adhesive-bonded joints. A Compa ct Mixed Mode (CMM) fracture specimen was developed to determine the f racture toughness under pure mode I, pure mode II and mixed mode (I an d II) loading conditions. This paper will report the parametric studie s conducted on adhesive-bonded joints by finite element analysis using models based on the Compact Mixed Mode (CMM) fracture specimen. The s tudies have investigated the adhesive layer thickness (t(a)) of 0.5 mm , 0.1 mm, 0.05 mm; crack length ratio (a/w) of 0.5-0.8 (in steps of 0. 1); and the fracture mode angle (phi) of 0 degrees (the pure mode I), 22.5 degrees, 45 degrees, 67.5 degrees (the mixed mode I and II) and 9 0 degrees (the pure mode II). From these studies, closed form solution s as well as empirical solutions using a calibration factor beta for t he stress intensity factor for the CMM specimen are derived. A range o f pure mode I, pure mode II and combinations of mode I and II Fracture load cases were investigated using the CMM fracture specimen. With th e test results, a failure assessment diagram for mixed mode fracture t oughness was proposed and compared to theoretical concepts of mixed-mo de fracture criteria. (C) 1997 Elsevier Science Ltd.