# Quality Analysis of Bonded Joints in the Renovation of Plastic Automotive Parts
## 1 Introduction
In his study, author [PERSON] [27] discussed adhesively bonded joints of jute, glass, and hybrid jute/glass fibre-reinforced polymer composites for the automotive industry and found that the failure load of jute/glass hybrid joints was increased by increasing the number of outer synthetic layers, and also the effectiveness of pure synthetic bonded joints was achieved due to the optimum trade-off between the property of the adhesive material and the reduced stress state of the bond line. Author [PERSON] [28] investigated the effect of adhesive distribution on the strength of bonded joints for automotive parts. He applied non-destructive testing to quantify the joints where the adhesive was not completely bonded over the overlapping area. The adhesive area had different shapes (elliptical and circular of different sizes) and the joint with full coverage for comparison. As a result, it was found that the shape and orientation of the adhesive shape, with respect to the loading direction, influenced the failure strength. One of the most evaluated parameters related to the testing of adhesive joints is the mechanical properties of the adhesive joints forming the joint. Further, it is the effect of the load on the joint as well as the type and speed of loading [29; 30; 31]. When adhesive joints are formed, it is necessary to respect the principles of correct design of the adhesive joint and that the greatest strength of the joint must be oriented in the direction of maximum stress. Another condition is that the adhesive layer must be as uniform, continuous, and as thin as possible. Finally, we try to reduce stress concentrations to a minimum. When investigating adhesive joints, we can find a few characteristics that need to be considered in this joining method, and these are the type and properties of the adhesive, the type of methodology chosen for the purpose of investigation, the dimensions of the individual samples, the loading methods, and others [32; 33; 34]. Various nanofiber reinforcements [35] also influence the behaviour of adhesive bonded joints and their strength, or, as part of the modification of the adhesive joint properties, the incorporation of elements into the joint is used to improve adhesion or their function is to stiffen the joint [36; 37]. The author [PERSON] [38] discussed continuum theory and application in his research, focusing on moisture-induced failures of moisture-encapsulated IC devices. The result was that by increasing the bulk porosity caused by adhesion degradation at the interface, the critical stress was reduced because of moisture exposure. In his further research, author [PERSON] [39] addressed the thermal moisture analogy, where he found that interfacial adhesion degraded continuously with moisture absorption. In all phases of car production, adhesives are used for force transfer, sealing, corrosion protection, or vibration absorption functions. The most common types of adhesives used in automotive repair are listed in Table 2.  
In the industrial field, the correct bonding technology is important, as well as knowledge of the loads to which these bonded joints may be subjected [40]. In many areas of industry, different types of adhesives are used for a range of applications. To define the parameters that are critical for estimating the required strength, many experimental tests are carried out in practice. Research and a more detailed review of the different methods used for joining different types of materials have been reviewed by [PERSON] et al. [41]. [PERSON] investigated the mechanical properties of joints using tensile and hardness tests, where the materials investigated were samples produced by additive manufacturing with metallic \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Adhesive** & **Components** & **Curing Method** & **Application** \\ \hline Polyurethane & 1 & air & bodywork sealant \\ Polyurethane & 1 & hardener & bonding of face glasses \\ Epoxy & 2 & hardener & body parts bonding during repairs \\ \hline \hline \end{tabular}
\end{table}