# Quality Analysis of Bonded Joints in the Renovation of Plastic Automotive Parts
## 1 Introduction  
The automobile as a complex element represents a concept within which the areas related to the life cycle of a product can be examined. It is a circular flow in the form of reduction, recovery, repair, refurbishment, reuse, and recycling of all components. The aim of the paper by the author [PERSON] [1] was to highlight this whole chain of processes that can be experienced and to show the importance of each of these areas, from drawing, use, repair, renovation, etc. The author [PERSON] [2] says that nowadays, the automobile, because of the different joining technologies, is subject to two trends. In the first case, we are talking about the constantly increasing demand for automobiles, and in the second case, we are talking about the customers' expectations in the form of quality and the renovation of the products themselves. In their research, the authors have focused specifically on the objectives of providing the necessary information that solves the issue of a particular phase of the product life cycle. Within the results, they were able to develop a so-called theoretical framework for the ramp-up curve (planned production rate). One of the options that also contributes to the weight reduction of the car is the method of joining them, riveting, gluing, clinching, etc. [3, 4]. Bonding is the process of joining adherends through adhesives using adhesive forces between the adherend and the adhesive and adhesive cohesion. The main advantages of adhesive bonding technology are that it is possible to bond almost any material, even heterogeneous ones, to each other, while parts made of the same materials can be of different sizes and thicknesses. The advantages and disadvantages of bonded joints are listed in Table 1.  
Bonding technology provides a large-area connection where strength, unlike riveted or welded construction, is not concentrated at a few points. If the joint is a high load-bearing joint, it is necessary to choose an adhesive that has good adhesion to the materials to be joined and good wetting of both surfaces. In riveted joints, the integrity of the material is damaged and the mechanical strength is lost because the holes for the connecting elements reduce the strength of the material [5]. Compared to welded parts, the material to be joined is not affected locally by heat, which prevents undesired changes in its structure, and the external appearance of the bonded components is maintained. In addition, under dynamic loading, the bonded joint distributes stress more consistently than any mechanical joint. Adhesive bonding technology is an advantage for repair work in the automotive industry, e.g., for the renovation of exterior plastic parts (bumper cracks, etc.). To define the parameters that are critical for the estimation of the required strength, many experimental tests are carried out in practice. Author [PERSON] [6] says that in addition to conventional joining technologies, such as gluing, riveting, and welding, in the process of manufacturing automotive parts, we also meet other technologies focusing on the field of casting or the application of CNC manufacturing. The current wide application of thermoplastic materials in the design and manufacture of automobiles is the result of the alignment of the specific requirements of automotive design and manufacturing technology with the specific material properties of plastics and their processing technologies. When studying the failure of bonded joints and, therefore, the adhesion itself, it is necessary to consider the mechanical properties of the materials being bonded. In the case of bonding, it is mainly the contact surfaces that play an important role [7]. Closely related to the contact surfaces is the pretreatment of the contact surfaces, which could increase the adhesion, which can be achieved by changing the physical and chemical properties of the bonded surface [8; 9].