## 3 Results and Discussion  
The DMA results are summarized in Figures 3 and 4, where the real part (E\({}^{\prime}\)) of the modulus and the dissipation factor (tan\(\delta\)) are shown as a function of temperature. The waste addition increases the modulus of the materials (Figure 3) at low temperatures (<50 \({}^{\circ}\)C). Afterwards, the large drop deriving from the glass relaxation of PBT starts. At higher temperatures, all the reinforced composites still have a higher modulus than PBT. As to what concerns Figure 4, all the plots present a maximum corresponding to the glass transition of PBT. A further relaxation than the one deriving from the segmental motions of the PBT chains takes place in the reinforced materials, as evidenced by a second maximum in tan\(\delta\). This relaxation takes place at lower temperatures for CF/EP_PBT (100-125 \({}^{\circ}\)C) than for CF/EP_Blend (120-170 \({}^{\circ}\)C). The origin of this relaxation, absent in the PBT matrix, could be related to the matrix-reinforcement interphase movements. Indeed, the position of the peak (higher temperatures and intensity) can be explained with a better interaction between the epoxy coating and the blend. In the CF/EP/PC_PBT samples, the second relaxation takes place at even higher temperatures (about 160 \({}^{\circ}\)C). In this last case, the origin should be related to the glass transition of the PC layer surrounding the wastes. Indeed, after this relaxation, the modulus (E\({}^{\prime}\)) decreases rapidly since the relaxed phase (PC) separates the matrix from the reinforcing phase. A second relaxation, linked to the crystallites melting, starts in all materials at higher temperatures (about 200 \({}^{\circ}\)C). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Code** & **PBT** & **PC** & **CF/EP** & **CF 1** \\ \hline PBT & 100 & 0 & 0 & 0 \\ CF/EP\_PBT & 90 & 0 & 10 & 4.60 \\ CF/EP\_Blend & 83 & 7 & 10 & 4.57 \\ CF/EP/PC\_PBT & 83 & 7 & 10 & 4.57 \\ \hline \hline \end{tabular} \({}^{1}\) Esteemed % volume amount of carbon fibers from the average waste composition.  
\end{table} 
Table 1: Composition (wt%) and codes of the investigated materials. Table 2 shows the results of the flexural tests. In all the cases, the waste addition increases the value of elastic modulus and flexural strength. The best results are obtained in the CF/EP/PC_PBT samples. Moreover, the unnotched values of the impact strength are summarized in Table 3. In this case, the reinforcing effect of the carbon fibers is stronger, leading to an increase over the 100% in all composites. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Young Modulus** & **Standard** & **Flexural** & **Standard** \\  & **(MPa)** & **Deviation (MPa)** & **Strength (MPa)** & **Deviation (MPa)** \\ \hline PBT & 2290 & 79 & 71 & 2.5 \\ CF/EP\_PBT & 2850 & 83 & 79 & 6.1 \\ CF/EP\_Blend & 2956 & 98 & 82 & 5.8 \\ CF/EP/PC\_PBT & 3550 & 97 & 99 & 9.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Flexural properties of the investigated materials. Figure 4: Loss factor (tan8) of the investigated materials. Figure 3: Elastic modulus (E\({}^{\prime}\)) of the investigated materials. The morphology of the fracture surfaces of the composites after the flexural tests are summarized in Figure 5. A uniform random dispersion of the single fibers is detected in all samples. Almost all of them are still covered by the surrounding matrix, and thus the presence of bare fibers is rare. The interphase between fibers and matrix is a key parameter in determining the mechanical properties [32; 33]. Accordingly, the link between the fibers and the original epoxy layer seems to be the ruling interphase determining the stress transfer to the matrix.