EXPERIMENTAL STUDY OF THE EFFECT OF CORK POWDER INCLUSION ON STRENGTH OF DOUBLE STRAP JOINT AT ELEVATED TEMPERATURES

Abstract

Adhesive joints are widely tested and investigated due to their pre-eminent mechanical properties. Different types of joints and adhesives are interest of researchers and engineers who strive to achieve maximum structural strength through adhesive joints. Double strap joint is one of the joints that could practically be used to fill the gaps and cracks in large and expensive mechanical components in addition to other fastening and welding. Strength is most critical factor to analyze before using the adhesive joint. Various techniques have already been developed and many are being developed to predict and improve the strength of adhesive joints. Addition of cork powder to the structural adhesives could improve the strength of adhesive joints through mechanical interlocking between the cork cells and the molecules of adhesive. In this study, double strap joints (DSJs) were investigated experimentally under tensile loading at four different temperatures and cork powder concentrations. The temperature used for testing were 25 oC, 50 oC, 75 oC and 100 oC. The joints were tested at these temperatures without and with cork powder concentration of 0.25 wt. %, 0.5 wt. %, 0.75 wt. % and 1 wt. %. The temperature near glass transition temperature (Tg) i.e., 100 degrees showed a slight deviation from the trend while all other temperatures showed increase in strength from 0.25wt.% to 0.75wt.% cork powder concentration and then dropped at 1wt.%. It was also observed through optical microscope (DSX1000) that the failure tends to change from mix mode to cohesive as the temperature was increased while it tends to change from mix mode to adhesive as the cork powder concentration was increased.