## 4 Results and Discussion
### Mechanical Properties
#### 4.1.2 Static Bending Strength
It is possible to assume that at high temperatures in both matrix types the spatially isotropic filling can definitely be applied as long as the load exerted on the material acts at an elevated temperature. In the case of the bending strength of the vinylester (VE) composites, one may notice that the filler additives did not have a substantial influence on the strength properties. It is argued here that the application of an additive in the form of fibre, mat or basalt powder does not have a strong impact on the composite strength at an elevated temperature. The results shown in Figure 13 indicate that the epoxy composites had high Young's E modulus values at 25 \({}^{\circ}\)C. Noticeable is the fact that the composites with unoriented chopped fibres and the composites with powder exhibited very similar modulus values, which was not reflected  
Figure 12: Diagrams of \(\sigma_{\mathrm{max}}\) and corresponding elongation (L at \(\sigma_{\mathrm{max}}\)) in bending strength test for composites EP and VE reinforced with basalt powder (BP), basalt fibre (BF) and basalt textile (BT) for measurements carried out at 80 \({}^{\circ}\)C.  
in the mechanical strength. In the case of the composites with chopped fibre, the filling is oriented parallel, transversely and at an angle \(\alpha\) with respect to the load axis. It is worth mentioning that during the bending tests, on one side the material shrank in the direction surface of the cross-section centre, while it slightly stretched on the other side from the centre of the cross section outwards. When the orientation of fibres is perpendicular to the load axis, there is a phenomenon of polymer matrix overload between the transverse fibres. Therefore, in this case, the deformation of the whole composite occurs at the expense of the resin present between the transverse fibres. As a result, the fibres oriented transversely to the force acting upon the sample play a role of foreign inclusions that do not propagate stresses and the composite with a dominant fraction of such fibres is characterised by a lower strength, sometimes even lower than the strength of the reference resin. Such a situation is visible in Figure 10, where the strength of the epoxy composites with chopped fibre and powder turns out to be lower than that of the reference sample. The best properties were observed for the samples containing basalt textile, for which E was 22 GPa. It should be noticed that in reinforcement with orthotropic textiles the folding of the surface layers depends mostly on the weave type, its density and area density. The basalt textile used in this experiment was a roving type textile with a twil weave, which substantially reduced its surface folding. As a result, under a load parallel to the warp and in the weave nodes, where fibres are oriented transversely, both fibre straightening and tilting in opposite directions could have taken place up to an extent. Freezing the resin compositions down to a temperature of \(-20\)\({}^{\circ}\)C (Figure 13) gave the materials a glassy-brittle physical state where the dominant quality was elasticity, also known as energetic elasticity, given the nature of the molecular processes involved. That is why the curves being monitored during the measurements followed [PERSON]'s law with a linear relation between specific components of the stress-strain tensor. In the cases observed, an additional reinforcement of the epoxy materials with powder, textile and chopped fibre gave the compositions very high stiffness and the stress increased fast with respect to the material deformation. The mechanical strength doubled as a result of basalt powder application in comparison to the reference sample. The use of a system of fibres oriented isotropically in space allowed us to obtain the highest average values of the fracture stress and thus the bending strength as well. However, as the average values of the fracture stress increased, the standard deviations increased too.