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Failure Initiation and Crack Growth in Thick Adhesive Bonded Composite Joints: Computational Mechanics Modeling and Analysis



A computational mechanics study is conducted on crack initiation, growth and instability in thick adhesive bonded composite joints. An associated experimental program was previously reported on unique features of failure modes and strength characteristics in thick adhesive bonded joints of glass fabric/vinyl ester composite. Complementary computational mechanics modeling and analysis of the thick adhesive bonded composite joint are conducted in this study to advance further our understanding of the subject. Composite joints of similar geometry but with thin adhesive bonds are also examined and results are compared to elucidate the nature of failure mechanics in the thick adhesive-bonded joints. The computational study is formulated with composite laminate mechanics, nonlinear fracture mechanics and advanced finite element methods. The following issues on failure of thick adhesive bonded composite joints are addressed: (1) crack formation and mechanisms, (2) crack growth, its driving force and failure modes, and (3) the effect of adhesive bond thickness. Local material strength criteria are used to identify crack initiation in the joint. Driving force for crack growth in the nonlinear adhesive of the bonded composite joint is evaluated by energy release rates associated with the crack. The adhesive bond thickness is found to govern crack formation and subsequent growth in the joint failure. Comparison of numerical results with experimental observations and test data are made to assess the validity of the computational mechanics approach and to better understand the complex nature of thick-adhesive bonded composite joint failure.

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