## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **E (GPa)** & **Tensile Strength (MPa)** \\ \hline L10\_CO & 2.46 \(\pm\) 0.33 & 39.56 \(\pm\) 5.70 \\ L20\_CO & 2.30 \(\pm\) 0.29 & 28.05 \(\pm\) 8.40 \\ W10\_CO & 1.36 \(\pm\) 0.52 & 13.66 \(\pm\) 10.46 \\ W20\_CO & 1.06 \(\pm\) 0.54 & 13.98 \(\pm\) 11.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 5: Comparison charts of bending curves: (**a**) PLA samples, (**b**) L20 samples, and (**c**) W20 composites. of these animal fibres, the mechanical properties decreased. Few studies have focused on the influence of sheep wool fibres on the mechanical properties of polymer matrix composite materials. Wool fibre is characterised by relatively low tensile strength compared to even natural fibres from plants (around 120 MPa). [PERSON] et al. [PERSON] et al. (2018) tested a modified composite with sheep wool fibres in an epoxy matrix and obtained a composite with improved mechanical properties of 45 MPa. Such strength values are typical for pure plastics and even some thermoplastics. Hence, the conclusion was drawn that sheep wool fibres are not suitable as a reinforcing modifier for composites, but rather as a filler or functional additive. The ageing process (degradation of the biocomposite in water) occurs quite rapidly. In other studies, the strength values decreased to a level of 30% (L20 samples experienced a 50% decrease after exposure to a humid environment) ([PERSON] et al., 2016; [PERSON] et al., 2016). Modification with cut, short natural fibres in polymer matrices results in an improvement in mechanical properties by up to 30%. The continued increase in the proportion of natural fibres in composites is associated with a slight increase in conjunction with deterioration of technological conditions (flow decrease and increased porosity of the biocomposite) ([PERSON] et al., 2016). The second test used to evaluate the mechanical properties and how they change as a consequence of the conditions and degree of degradation was a dynamic mechanical analysis (DMA), for which some of the curves are shown (Figure 6). The range to which particular attention was paid includes temperatures from \(-\)30 \({}^{\circ}\)C to 50 \({}^{\circ}\)C, as within this range, the material would be mainly used. Figure 6: Comparison charts of DMA curves: (**a**) storage modulus of PLA samples, (**b**) tan\(\delta\) of PLA samples, (**c**) storage modulus of L20 samples, (**d**) tan\(\delta\) of L20 samples, (**e**) storage modulus of W20 samples, and (**f**) tan\(\delta\) of W20 samples. From the graphs shown in Figure 6, it can be seen that a very high storage modulus was obtained for the materials immediately after manufacture. As confirmed by other tests, PLA samples subjected to composting were not significantly different from PLA samples not subjected to degradation. Therefore, the values of the storage modulus between these samples do not have significant differences, and the slightly lower modulus for the PLA sample without degradation may be due to slow degradation and physical ageing processes in the composted sample. As a result, composted PLA is characterised by higher degree of crystallinity and stiffness, and the storage modulus is higher. For each fibre, with the exception of W10, the value of storage modulus improved compared to pure PLA. It can be seen that a large content of wool fibres destabilises the material properties more quickly. In addition, the low content of fibres significantly reduces the difference in the loss modulus responsible for stress dissipation. From the available studies, it can be observed that the addition of flax fibres does not affect the glass transition temperature, but it does alter the ratio of the storage modulus to the loss modulus. Short flax fibres stiffen the composite and decrease the PLA macromolecules' mobility [21; 33; 34]. Composites with a PLA matrix containing flax fibres increase the value of the storage modulus almost twice [35].