Mode II Fracture Toughness of Adhesively Bonded Joints as a Function of Temperature: Experimental and Numerical Study

Abstract

In this work, an experimental and numerical study is performed to evaluate the effect of temperature on the Mode II fracture toughness of a high temperature epoxy adhesive. Mode II fracture testing on end notch flexure (ENF) test specimens was performed at room temperature (RT) and high temperatures (100, 150, and 200°C) and the Mode II fracture toughness, G _IIc, as a function of temperature was obtained. It is shown that at temperatures well below the glass transition temperature, the fracture toughness, G _IIc, increases with temperature and decreases as the temperature approaches T _g, while above T _g a drastic decrease in fracture toughness was observed. Furthermore, cohesive zone models, in which the failure behaviour is expressed by a bilinear traction–separation law, were used to define the adhesive behaviour in Mode II and to predict the adhesive load-displacement (P–δ) curves as a function of temperature. The simulation response matched the experimental results very well at temperatures below T _g . The sensitivity of the various cohesive zone parameters in predicting the overall mechanical response of the joint was examined as well for a deeper understanding of this predictive method.

KEYWORDS:

• End notch flexure (ENF) test specimen
• High temperature adhesives
• Mode II fracture toughness
• Temperature tests

ACKNOWLEDGMENTS

The authors would like to thank the Portuguese Foundation for Science and Technology for supporting the work presented here, through the individual grant SFRH/BD/61880/2009 and through the research project PTDC/EME-PME/67022/2006, and Nagase ChemteX (Osaka, Japan) for supplying the adhesive.

Notes

Presented in part at the 1st International Conference on Structural Adhesive Bonding (AB2011), Porto, Portugal, 7–8 July 2011.