## 3 Discussion of the Experimental Results
### Force-Displacement Curves  
The flexural strength was computed according to the standard EN 1052-2 (CEN 1999) expression, given by Equation (1):  
\[f_{b,parallel}=\frac{3\times f_{i,max}\times(l_{1}-l_{2})}{2\times b\times t_{ u}^{2}} \tag{1}\]  
where, \(f_{i,max}\) is the maximum applied force, \(l_{1}\) is the distance between OOP restrains, \(l_{2}\) is the distance between the internal OOP loading application alignments, b is the specimen width and \(t_{u}\) is the specimen thickness. The force-displacement curves of the groups HCHB150, HCHB150P10, SWM, SSM are plotted in Figure 4. The OOP displacement considered was the average of the four central LVDT measurements. Additionally, the average curve, \(\mu\), of the stress-strain results obtained by all the specimens, the average curve plus two times the standard deviation (\(\mu+2\) SD) and the average curve minus two times the standard deviation (\(\mu-2\) SD) are included for each group result. The summary of the test results is presented in Table 2. From the results, the following observations can be drawn, namely:  
* The maximum strength achieved by HCHB150 group was 0.14 MPa (see Figure 5a) with a CoV equal to 12.7%. It is possible to observe that the ultimate displacement corresponded in both tests to the displacement at the maximum force;
* The maximum strength of the HCHB150P10 group was 0.22 MPa with a CoV equal to 17.6%, as shown in Figure 5b. From the comparison between the HCHB150 and HCHB150P10 it is possible to observe that the plaster increased the flexure strength about 1.57 times;
* Regarding the SSM group, Figure 5c, the maximum strength was achieved by specimen 2 with 0.41 MPa and the minimum one was equal to 0.21 MPa, thus about 50% lower. However, as summarized in Table 2 it seems that the results obtained by specimen 1 were very different from the remaining ones, which affected the global average, CoV and standard deviation. For this, in Table 2 is also included the average, CoV and standard deviation excluding the specimen 1 results which is more representative of the real behaviour of the GFRP group;
* The OOP displacement corresponding to the maximum strength of the SSM group ranged between 0.85 and 1.7 mm (Figure 5d). On the other hand, the OOP ultimate displacement ranged between 6.4 mm and 14.65 mm. These results were affected by the mode of failure of the specimens;
* The SSM group average flexure strength was 0.34 MPa with a CoV equal to 17%;
* The maximum force reached by the SWM group specimens was 8.69 kN (see Figure 5c) and the lowest 5.93 kN. The average value equal to 7.12 kN (with a CoV of 16.81%) was achieved, as shown in Figure 5b;
* The OOP displacement corresponding to the maximum strength of the SWM group ranged between 0.55 and 1.25 mm. The OOP ultimate displacement ranged between 8.25 mm and 20.15 mm;The SWM group achieved an average flexural strength equal to 0.23 MPa with a CoV equal to 16.53%. Regarding the comparison between the results obtained by each group, it can be observed that the flexural strength reached by the SSM group was 1.48 times higher, as plotted in when compared with SWM with similar CoV;  
Regarding the ultimate OOP displacement (last OOP displacement recorded in each test), it can be observed that the SWM reached an average value equal to 14.30 mm. This result is 50% higher than the SSM group, which can be due to the higher ductility of the PP textile mesh when compared with the GFRP mesh. Figure 5: Force-displacement results: (**a**) HCHB150; (**b**) HCHB150P10; (**c**) SWM; and (**d**) SSM; and (**e**) global comparison (average curves). The comparison between the average curves of each group is plotted in Figure 5e, from which it is possible to observe that the SSM group and the HCHB150 achieved the highest and lowest flexural strength, respectively. The SSM group reached a flexure strength about 2.43 times higher than that of the SSM group. The reason for the higher flexural strength is that the SSM group is not a flexure strength.