## 3 Experimental Results and Discussion
### Tribological Properties
The authors showed above that polymer wear was accompanied by the low level of reversible strains in this case. This was due to the following reasons: (i) an increase in temperature; (ii) a decrease in specific pressure; and (iii) rising volumetric wear and, accordingly, reducing the amount of the material capable to elastic recovery. In this regard, the elastic modulus threshold value of 950 MPa was predefined. This was 250 MPa higher than that of neat UHMWPE, but 100 MPa lower than that for the \"moderate\" conditions of the metal-polymer tribological loading. Initially, it was assumed that the composite was subjected to intense strains and subsequent failure under the \"severe\" conditions of the metal-polymer tribological loading. Therefore, the requirements for tensile strength were increased and a threshold value of 35 MPa was adopted. This was the neat UHMWPE stress level at a strain rate of 400%. The threshold level for elongation at break of 350% was increased relative to the \"moderate\" conditions according to similar assumptions. This was 27% less than that of neat UHMWPE. As in the  
Figure 8:0 The range of the control parameters that ensure the physical and mechanical properties of the composites meet the specified limits for the “moderate” conditions of the metal-polymer tribological loading. previous case, the achievement of such a strain level was a clear indicator of the structure homogeneity and the composite strain stability. The regular impact loads were also unlikely under the \"severe\" conditions of the metal-polymer tribological loading. However, local impacts could be due to removing material as well. For this reason, the impact toughness threshold was raised up to \(A_{\mathrm{K}}\geq 100\) kJ\(\cdot\)m\({}^{-2}\), which was 50 kJ\(\cdot\)m\({}^{-2}\) below that of neat UHMWPE. Under the \"severe\" conditions of the metal-polymer tribological loading, the material wear was already \"controlled\" by adhesive processes, as well as oxidation, and plasticization due to the frictional heating. Therefore, the requirements for the friction coefficient value had to be slightly increased. The threshold level was predefined at 0.11, which was slightly less than that of neat UHMWPE. As in the previous case, the most critical was the wear rate parameter. In order to simultaneously improve the mechanical and tribological properties of the composite, the value was taken at WF \(\leq 2.25\times 10^{-6}\) mm\({}^{3}\cdot\)N\({}^{-1}\cdot\)m\({}^{-1}\), which was 25% lower than that of neat UHMWPE. The surfaces of the mechanical and tribological properties with the distinguished levels of their threshold values are shown in Figure 8:1  
Figure 8:2 Cont. Figure 8:3 _Cont._  
An area of the control parameter values ensuring the correspondence of the mechanical and tribological properties of the composite to the given boundaries is shown in Figure 8:4 In this case, the region filled in green was bounded on all sides. This enabled to design the composite more reliably. However, an important result was the fact that only composites with untreated wollastonite were in the range of the acceptable values. The range of their content could be quite high from 11.8 up to 19.8 wt. %. It should be noted once again that no composites loaded with silanized fibers was in the filled region. Thus, the structure and the tribomechanical properties of the UHMWPE-based composites with a variable adhesion level due to the wollastonite silanization were analyzed during these studies. Figure 8:5 Isoline patterns on the operational properties of the UHMWPE-based composites: elastic modulus E, MPa (**a,b**); ultimate tensile strength \(\sigma_{\rm U}\), MPa (**c,d**); elongation at break \(\epsilon\), % (**e,f**); impact toughness \(\alpha_{\rm k}\), kJ/m (**g,h**); the friction coefficient \(f\) (**i,g**); and wear rate I, \(10^{-6}\) mm\({}^{3}\cdot\)N\({}^{-1}\cdot\)m\({}^{-1}\) (Load = 140 N, Velocity = 0.5 m s\({}^{-1}\)) (**k,l**).