## 4 Discussion of the Results
### Definition of Comparison Parameters  
In light of the foregoing evidence on the influence of each component (fabric, coating, matrix and dispersed short fibres) on the TRC tensile behaviour, it was deemed necessary to establish a quantitative  
Figure 10: Cracking patterns with and without short fibres for TRC composites reinforced with Fabrics: F2 (**a**); and F6 (**b**). Figure 9: Effect of short fibres addition on the uniaxial tensile response of TRC composites reinforced with Fabrics: F2 (**a**); and F6 (**b**). comparison approach between different responses to validate the observed trends in the perspective to promote the use of such materials among designers. The following considerations were made after excluding from the whole set the composites manufactured with Fabrics F3 and F5, on account of the observations drawn in Section 4.1. Two different families of values were introduced: (i) efficiency factors (\(EF\)), which quantify the global load capacity of the systems and the exploitation of the AR-glass fibres; and (ii) ductility/energy absorption parameters, which describe the behaviour of a composite system in the multi-cracking phase (regarded as significant, since in seismic retrofitting applications hysteretic energy dissipation is expected to occur mainly in this region). Ductility coefficients may also help to better underline the effect of hybrid reinforcing solutions. In addition to the standard efficiency factor, \(EF_{TRC}\), defined as the ratio between the maximum capacity of the composite and the one of the plain fabric (see Equation (3) and Figure 11a), a second factor \(EF_{TRCf}\) was introduced (see Equation (4) and Figure 11a), obtained dividing the ultimate TRC stress referred to the fabric equivalent section, \(\sigma_{TRCf}\), by the glass filaments strength \(\sigma_{fu}\):  
\[EF_{TRC}=\frac{P_{TRC,max}}{P_{f,max}}=\frac{\sigma_{TRC,f,max}}{\sigma_{f,max }}\, \tag{3}\]  
\[EF_{TRC,f}=\frac{\sigma_{TRC,f,max}}{\sigma_{fu}}=\frac{\sigma_{TRC,f,max}}{2 000\ \text{MPa}}. \tag{4}\]  
The ductility/energy absorption parameters depicted in Figure 11b are defined as: (i) the value of normalised displacement \(\varepsilon_{2}=\delta_{2}/L_{0}\) corresponding to the end of the multi-cracking phase; (ii) the total absorbed energy per unit volume \(U_{T,I-II}\) within the equivalent strain range 0-\(\varepsilon_{2}\); and (iii) the average stress \(\sigma_{I-II}\) (Equation (5)) obtained by imposing the equivalence of the area under the stress-strain curve in the first two stages of the response:  
\[\sigma_{I-II}=\frac{U_{T,I-II}}{\varepsilon_{2}}. \tag{5}\]  
The introduced parameters, averaged over each nominally identical set, are collected in Table 8.  
Figure 11: Identification of relevant mechanical parameters on the uniaxial tensile response: efficiency (**a**) and ductility/energy absorption (**b**) variables. Looking at the efficiency factors trends plotted in Figure 12, it was possible observe that:  
* A more loosely packed matrix (i.e., M2) generally implied lower \(EF_{TRC}\) (solid black dots) in the composites, thus confirming the previously drawn conclusion about the internal fabric slippage in M2-based systems (see Section 3). * The values of \(EF_{TRC,f}\) (grey crosses) were lower in the composites reinforced with greater amounts of AR-glass (F6 and F7, compared with F1, F2 and F4) and this clearly indicated a material waste, while \(EF_{TRC}\) (solid black dots) was only representative of the interaction between matrix and  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \(\sigma_{f,max}\) & \(\sigma_{TRC  
fabric. Focussing on F6-M1 and F7-M1 systems, it was possible to observe that close \(EF_{TRC_{f}}\) values did not imply similar \(EF_{TRC}\) values, probably due to different internal slippage (see Figure 6a). * The addition of short fibres implied, as expected, a general increase of the \(EF_{TRC}\) parameters.