Applying fracture mechanics to adhesive bonds

Abstract Fracture, the propagation of a dominant flaw, is an important mode of failure in engineering materials, including adhesively bonded joints. The growth of pre-existing or service-induced cracks, flaws, or damage, whether through rapid propagation or slow advances due to cyclic fatigue or extended load duration, can lead to unsatisfactory performance and even catastrophic failures. The stress intensity factor or the strain energy release approach, which is more commonly used for bonded joints, can be used to quantify the likelihood of failure when compared to critical values of these parameters. Polymeric adhesives are inherently viscoelastic, so time or rate, temperature, and other factors such as moisture content and other environmental influences can affect fracture resistance, sometimes significantly. Fracture energies measured in bonded systems can depend on the mode mixity (opening and sliding components), adhesive thickness, and other factors as well.