# Quality Analysis of Bonded Joints in the Renovation of Plastic Automotive Parts
## 1 Introduction
[PERSON] investigated the effect of a corrosive environment on the mechanical properties of bonded joints, where he used Docol 1000 (SSAB, Borlange, Sweden) steel plates with a thickness of 1 mm and Araldite 420 A/B epoxy adhesive (Huntsman Advanced Materials, Basel, Switzerland). As a result, the static shear strength was affected by the exposure time to which the specimens were exposed for 120 h [61]. For the strength analysis of bonded joints, its failure is equally important. The failure analysis of GFRP joints bonded with a combination of hard epoxy and hyperelastic adhesives has been addressed by [PERSON] [62]. [PERSON] et al. [63] dealt with the problems that may occur in the bonding process such as adhesive extrusion, adhesive curing, and surface finish of the adherends. Failure analysis revealed different failure mechanisms and the effect of adhesive mixing. Finally, a failure mode map is proposed for the customized bonded joints in terms of normalized strength ratio and normalized volume of flexible adhesive. In his work, [PERSON] analysed simple interlaminated joints made of plastics that are reinforced with carbon fibre CFRP. For the experiment, he used two types of adhesives with four different adherend overlap lengths. As a result, factors such as the type of adhesive and the length of the overlap surfaces had a significant effect on the strength of the bonded joint. With increasing overlap, interface failure was observed at the edge of the overlap [64]. Currently, Japanese car manufacturers have focused on improving production processes by introducing various computer-based flexible manufacturing systems (FMS), where the purpose, according to the author, was to ensure the production of vehicles on a single line, to increase not only the automation of production, but also to improve working conditions. One of the tasks was to equally focus on the area of renovation of various components and, thus, improve the efficiency of repairing parts with respect to maintaining the required properties [65]. In the field of automotive parts, bonded joints are finding more and more applications. One of the main advantages of these joints is their non-destructive bonding, which is most used in the automotive industry. Due to the use of adhesives for the joining process, these adhesives are exposed to external operating conditions and their strength properties are reduced. It is therefore important to know to what degree, particularly when it comes to parts forming the functional unit of a car after renovation. It is therefore important to be able to understand these influences, as well as the extent to which these plastic parts are affected by external operating conditions after refurbishment, in terms of the application of bonded joints. The aim of this work was to determine the quality of selected adhesives used in the refurbishment of exterior plastic automotive parts by bonding. For the research, the three most used adhesives were selected and compared with each other, with tensile and impact tests as the evaluation tests. In addition, the quality of bonded joints after exposure to different environments was evaluated. The present paper finds application in the field of the automotive industry, as well as for the following repairs of individual components.