# Use of New and Light Materials in Automotive Engineering for Towing System
## 4 Study of the Alternative Solution for the Manufacturing of Towbars
### Technological Requirements Imposed by Composite Materials  
It is known that composite materials are very difficult to recycle, reuse, and remodel, which is why, from the design phase of products made from these types of materials, the exact dimensions must be known and the manufacturing technology must be used correctly. A possible correction of the dimensions or geometric shapes of these landmarks is very difficult or even impossible to achieve after polymerization.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Advantages** & **Disadvantages** \\ \hline \multirow{4}{*}{Steel S355} & - The homogeneity of the structure; & \\  & - Stability of the obtaining process; & \\  & - Best bending performance; & -The highest specific mass. \\  & - High traction performance (lower CF). & \\ \hline \multirow{2}{*}{Carbon fiber + Sikadur resin} & - High tensile performance (lower CF + epoxy); & - Inhomogeneity of the structure; \\  & - Above average bending performance; & - Difficult obtainment process. \\  & - The lowest specific mass. & \\ \hline \multirow{2}{*}{Carbon fiber + Epoxy resin} & - The best traction performance; & - Inhomogeneity of the structure; \\  & - High bending performance (lower than S355); & - Inhomogeneity of the structure; \\  & - The lowest specific mass. & - Difficult obtainment process. \\ \hline \multirow{2}{*}{Aluminum 99.7\%} & - Continuous progress in technologies for obtaining finished products; & - The worst traction performance; \\  & - Specific mass much lower than S355, but higher than CF. & - The worst bending performance. \\ \hline \multirow{4}{*}{Al Al AlSi10 MnMg alloy} & - Continuous progress in technologies for obtaining finished products; & - Lower traction performance as S355 \\  & - Specific mass lower than that of S355; & - Lower bending performance as S355 \\  & - Superior tensile performance Al99.7\% and AlSi12 Cu1 Fe; & - Higher specific mass F. \\ \hline \multirow{4}{*}{Al Al AlSi12 Cu1 Fe alloy} & - Continuous progress in technologies for obtaining finished products; & - Tensile and bending performance \\  & - Lower specific mass S355; & inferior to S355, CF and AlSi10 MnMg; \\  & - Superior tensile and bending performance Al99.7\%. & - Higher specific mass CF. \\ \hline \hline \end{tabular}
\end{table}
Table 3: The advantages and disadvantages of each type of material.  
To manufacture the towing hook from composite materials based on CFs, a two-part mold was made, which copied the geometry of the towing hook made of steel (Figure 16). The mold was made of glass fiber polymerized with epoxy resin, with four embedded centering bushings for perfect assembly for the execution of the towing hook.  
The specimens made with both types of resins showed similar behavior in the tensile and bending tests, but the easy handling of CF mixed with epoxy-type resin (due to its low viscosity) led to the choice of making the towbar from CFs and resin epoxy L385. It should be specified that, in the structure of the CF towing hook, two metal bushings were embedded next to the fixing holes on the chassis to provide resistance both to friction with the screw threads and to the tightening of the flanges on its flattened area. Also, for the benefit of mechanical resistance regarding the tests to which the towing hook was subjected, the CFs in the structure of the towing hook were continuous, with their route being illustrated in Figure 17.  
The functional and overall dimensions of this towbar were obtained by the shape of the mold, which cannot be changed by mechanical actions or other technical solutions, as is the case with the steel towbar, whose shape can be changed by forging.