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Failure Analysis of Adhesive Joint of DC Glow Discharge Exposed PP to Steel

Publication Type : Conference Paper

Publisher : Fourth International Symposium on Polymer Surface Modification: Relevance to Adhesion

Campus : Coimbatore

School : School of Engineering

Department : Aerospace

Year : 2003

Abstract : The present investigation aims to analyze the failure mechanism of adhesive joint of DC glow discharge exposed PP to mild steel for attaining best adhesive joint of PP to mild steel. The as received and DC glow discharge exposed PP surfaces have been characterised by Energy Dispersive Spectra (EDS). Lap shear tensile tests have been carried out for the unexposed polymer and those exposed under DC glow discharge (i) at different power levels and (ii) for different duration of exposure. It is observed that with increasing power level lap shear tensile strength of adhesive (Araldite AY 105) joint of PP to mild steel increases till 13 W of power level, beyond which the joint strength decreases. Further, at this power level the joint strength increases with increasing exposure time upto 120 s and then joint strength decreases. At the optimized condition for the surface modification the effect of using another adhesive (Araldite 2011) on the strength of the joint has also been determined. The fractured surfaces of the specimens tested under lap shear tensile test have been examined in order to analyse the failure mechanism of the polymer to mild steel adhesive joints so that the best adhesive joint can be made. In addition, the polymer to polymer and mild steel to mild steel joints using these adhesives have also been examined. The fracture surface has been analyzed by optical microscopy and Energy Dispersive Spectra (EDS). The fracture surfaces of these joints studied under optical microscopy and Energy Dispersive Spectra (EDS), show that when unexposed polymer is joined with mild steel, the failure is confined to polymer to adhesive interface. However, when the polymer, has been modified by exposure under glow discharge the failure mode is changed. The failure is observed throughout subsurface layer of the PP. From the strength analysis of adhesive joint of either glow discharge exposed PP to mild steel, or glow discharge exposed PP to PP, it is observed that joint strength does not change with the change of adhesive and this could be possible as failure takes place throughout the subsurface layer of the PP.

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