Recent advances in debonding techniques for multi-material adhesive joints – Prof. M. Banea

Professor Mariana Banea, from CEFET/RJ - Federal Center of Technological Education in Rio de Janeiro, Brazil

The seminar will give first a brief introduction on the use of adhesive joints for automotive applications. Two main parameters that influence adhesively bonded joints performance are the adherend material and the adhesive type. Their combined effect should be taken into consideration in the design of adhesive joints. The effect of adherend material on the mechanical behaviour of adhesive joints was investigated experimentally and numerically by single lap joints (SLJs) with different adherend materials (high strength steel, low strength steel and composite). The adhesives selected were two new modern tough structural adhesives used in the automotive industry.
It was found that, for relatively short overlaps in SLJs bonded with structural modern tough adhesives, failure is dominated by adhesive global yielding and the influence of material on joint strength is not significant. For longer overlaps, the failure is not anymore due to global yielding and the effect of material becomes more important. Moreover, it was possible to evaluate which adhesive is more suited for each material.
Further the seminar proposes an overview of an originally developed methodology to assure easy debonding of adhesive joints by combining the inductive heating method and the use of thermally expandable particles (TEPs).
Debonding is a very important feature both for repair and for dismounting at the end of life. Two commercially structural adhesive systems used in the automotive industry (one polyurethane and one epoxy) were tested. First, the influence of TEPs content on the lap-shear strength of the TEPs-modified single lap joints was investigated. Further, the ability of the TEPs-modified joints to support temperature controlled debonding was evaluated. It was shown that the control of the debonding process by temperature is possible. The temperature needed for debonding is a function of TEPs content and can be lowered by increasing the TEPs content.