Joining process and strength in PVC friction stir spot welding with fabricating composite material at welding area

In order to improve the strength of FSSWed PVC joint, SiC particle was compounded into the welded region at the same time with welding process. The joining process and its effect on strength of FSSWed PVC joint were investigated in joining experiment with a PVC plate having different guide hole diameter for filling the SiC particle. In case of the specimen compounded SiC particle with guide hole diameter of 8mm, SiC particle could be dispersed uniformly in the welded area. In the specimens with guide hole diameter of 5mm and 2mm, dispersion of SiC particle was not observed in side of welded area. Degradation and increase in local mechanical property was significantly observed at edge of the keyhole and inside the welded area respectively in specimen with guide hole diameter of 8mm. Width of welded area increased with increasing guide hole diameter. The joining strength was improved by fabricating composite material in welded region. The strength increased with increasing guide hole diameter. It is considered that joining strength was significantly affected by width of welded area. According to temperature distribution and observation of material flow using a high speed camera, contact between welding tool and SiC particle before plunging into a lower sheet induced increasing the heat input during the process and resulted in promoting the friction stirring. Therefore, it is considered that change in guide hole diameter leads to change in contact area between welding tool and SiC particle and also change in width of welding area then resulted in change in the joining strength.