# Evaluation of Impact Energy Absorption by Natural Fiber Composites in Motorcycle Helmets
## 4 Results and Discussion
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Type and Quantity of Fiber** & \(p\)**-Value** & **Conclusion** \\ \hline \multicolumn{2}{c}{Agave sisalana 10\%} & 0.9245 & There is no evidence to reject the null hypothesis \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Shapiro-Wilk: 10% agave sisalana (without outliers). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Free Fall (g)**} \\ \cline{2-10}  & **0\%** & \multicolumn{2}{c}{**5\%**} & \multicolumn{4}{c}{**10\%**} & \multicolumn{2}{c}{**15\%**} \\ \cline{2-10}  & **Pure PU** & \begin{tabular}{c} **Sugarane** \\ **Bagasse** \\ \end{tabular} & **Coconut** & \begin{tabular}{c} **Agave** \\ **Sisalana** \\ \end{tabular} & **Sugarane** & **Coconut** & \begin{tabular}{c} **Sugarane** \\ **Bagasse** \\ \end{tabular} & **Coconut** & \begin{tabular}{c} **Agave** \\ **Sisalana** \\ \end{tabular} \\ \hline \begin{tabular}{c} Mean \\ Standard \\ deviation \\ \end{tabular} & 71.36 & 59.76 & 57.88 & 67.10 & 63.13 & 58.86 & 67.24 & 66.23 & 62.36 \\ \
\begin{tabular}{c} Standard \\ deviation \\ \end{tabular} & 8.92 & 4.16 & 4.69 & 5.70 & 3.60 & 5.25 & 10.94 & 6.95 & 7.99 \\
\begin{tabular}{c} Outlier \\ \end{tabular} & - & - & - & 80.45 & - & - & - & - & 83.20 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: [PERSON]’s test for free-fall results. \begin{table}
\begin{tabular}{c c} \hline \hline  & **10\% Agave Sisalana (g)** \\ \hline \multicolumn{2}{c}{1 st quartile (Q1)} & 56.30 \\
3 rd quartile (Q3) & 61.85 \\ IQR (Q3-Q1) & 5.55 \\ Upper limit \(Q_{3}+1.5\times(Q3-Q1)\) & 70.18 \\ Lower limit \(Q_{1}-1.5\times(Q3-Q1)\) & 47.98 \\ Outlier & 75.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The interquartile range for free-fall results. The analyses confirmed that all datasets conform to a normal distribution. One of the analyses employed the confidence interval method at a 5% significance level in comparing the various composites to the polyurethane prototype. This method enabled the assessment of the accuracy of the sample means. Since several samples contained fewer than 30 observations and assumed a normal distribution, we utilized Student's t-distribution to determine the critical values. The standard error (SE) was computed from the sample standard deviation, minimized by the number of samples [38], as described by the following formula: \(SE=\sigma/\sqrt{n}\). The expression \(\overline{x}\pm t\times SE\) defines the CI. Table 7 presents the results for each dataset. Figure 6 illustrates the confidence intervals for each composite group, enabling a visual comparison of the variations between the materials under investigation. The analysis revealed a significant difference in performance between the pure polyurethane (PU) prototype and the composites containing varying proportions of natural fibers. As illustrated in Figure 6, pure PU exhibited both the highest mean performance, and the most significant variability compared to the fiber-reinforced composites. This result suggests that the incorporation of natural fibers enhanced the composites' performance \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Prototype** & **Mean** & \
\begin{tabular}{c} **Standard** \\ **Deviation** \\ \end{tabular} & **Samples** &
\begin{tabular}{c} **Confidence** \\ **Interval** \\ \end{tabular} \\ \hline PU 0\% & 71.36 & 8.92 & 10 & 6.38 \\ Sugarcane bagasse 5\% & 59.76 & 4.16 & 10 & 2.97 \\ Cocount 5\% & 57.88 & 4.69 & 10 & 3.36 \\ Agave sisalana 5\% & 65.61 & 3.43 & 9 & 2.64 \\ Sugarane bagasse 10\% & 63.13 & 3.59 & 10 & 2.57 \\ Cocount 10\% & 58.86 & 5.25 & 10 & 3.76 \\ Agave sisalana 10\% & 58.30 & 3.11 & 9 & 2.39 \\ Sugarane bagasse 15\% & 63.99 & 3.93 & 9 & 3.02 \\ Cocount 15\% & 66.23 & 6.95 & 10 & 4.97 \\ Agave sisalana 15\% & 61.64 & 7.07 & 29 & 2.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Confidence interval results for the different prototypes. Figure 6: Confidence interval for free fall by composite type.