## 3 Results and Discussion  
### Nanoindentation Behavior  
The average values of the nanoindentation experimental results obtained are summarized and tabulated in Table 1. The samples exhibit a similar, continuous and consistent loading, holding period and unloading stages, but at different loads and depth. With an increase in the fiber ARs of the samples, the material resistance to nanoindentation is found to be different. The maximum hardness and reduced elastic modulus of nearly 0.107 GPa and 1.094 GPa were recorded by sample AR_26 and sample AR_38 has the minimum hardness and reduced elastic modulus values of 0.073 GPa and 0.540 GPa respectively. This implies that sample AR_26 has the highest resistance to material plastic deformation.  
From the trend of the results presented in Table 1, it is observed that the both nano-mechanical (nanoindentation) hardness and reduced elastic modulus properties of the 5 samples were increased till maximum and threshold sample AR_26 were obtained. After this optimal sample, these two important properties began to decline until the least values were recorded by the sample AR_38, with highest fiber AR. Also, both hardness and elastic modulus of the samples determined the contact depth, as these properties decreased with an increasing contact depth among the HF/PCL biocomposite samples, especially with higher AR samples. Comparatively, it was evident that hemp fiber has a clear reinforcement effect on the PCL matrix, as observed by the increased hardness (+30%) and modulus (+100.39) of sample AR_26 when compared with the neat PCL sample AR_00. This can be attributed to the best intermolecular interaction and interfacial properties between PCL and hemp fiber AR_26, as depicted in Figure 4a,b.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multirow{2}{*}{\begin{tabular}{c} **Hardness** \\ **(GPa)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Reduced** \\ **Modulus** \\ **(GPa)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Elastic** \\ **(ROCV)** \\ **(GM)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Plastic** \\ **(MR)** \\ **(nJ)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Elastic** \\ **(nJ)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Maximum** \\ **Depth** \\ **(nJ)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Plastic** \\ **Depth** \\ **(nm)** \\ \end{tabular} } \\ \hline AR\_00 & 0.0820 & 0.5457 & 0.3886 & 0.98 & 1.05 & 1855.46 & 1336.42 \\ (Neat) & (\(\pm\)0.009) & (\(\pm\)0.042) & (\(\pm\)0.019) & (\(\pm\)0.086) & (\(\pm\)0.115) & (\(\pm\)8.12) & (\(\pm\)20.32) \\  & 0.0882 & 1.0893 & 0.2083 & 1.40 & 0.94 & 1820.97 & 1507.39 \\ AR\_1  
In addition, other properties such as elastic and plastic works of the samples recorded similar trend, having maximum values of nearly 1.21 nJ and 1.58 nJ respectively with sample AR_26. With these optimal properties, sample AR_26 was expected to possess the least indentation depth, which was approximately 1816 nm. The neat PCL recorded the highest indentation depth of nearly 1856 nm. The average maximum depth recorded by all the samples at peak load was approximately 1840 nm. These results are in close agreement with that of [PERSON] et al. [25]. They used spent neat polyamide and layered silicate as matrix and filler/reinforcement materials, respectively. Moreover, the plastic work was done during the loading stage of the indenter inside the samples, while the elastic work was recovered during the unloading stage, as previously and graphically illustrated in Figure 3. Furthermore, a small change, commonly known as 'pop out' and 'elbow' in the unloading load-depth curves only occurred from all the samples, towards the end of the cycle. This phenomenon has been similarly observed by [PERSON] et al. [45; 46] and associated with the Berkovich indenter [47] and phase transformation of materials [48].