1. Introduction

2. Methodology

2.2. Methods

2.2.1. Preparation of the Biocomposite

The palm kernel shell, periwinkle shell, clam shell, whelk shell and bamboo fiber were collected from the wild. It was first cleaned with water, and later, it was washed with sodium hydroxide (1% conc. NaOH) in other to remove dirt and sap in the case of the bamboo fibers. After washing with NaOH, they were rinsed with distilled water in other to maintain the PH of the specimens at 7. The shells were then crushed with hard object before with was then taken to the grinding machine for grinding. The reason for crushing is to ensure easy grinding with the machine. After the grinding, the samples were sieved at 300micron and this was done for the palm kernel shell, periwinkle shell, clam shell, and whelk shell respectively. Figures 2.1, 2.2 and 2.3 shows the crushing, grinding and sieving of the shells respectively.

Figure 2.1. crushing of the shells. Figure 2.2 Grinding of the shells. Figure 2.3 sieving of the shells.

Figure 2.1. crushing of the shells. Figure 2.2 Grinding of the shells. Figure 2.3 sieving of the shells.

2.2.2. Composite Fabrication

The epoxy was mixed according to the manufacturer's specifications, which was 2:1 for part A and part B, respectively. The molds for producing the samples were made based on flat test specimen dimensions and tolerances following ASTM E8 standard, and the composite was laminated using a hand-layup technique. Before the mold was filled with epoxy resin, it was waxed with a releasing agent (petroleum jelly). This helps to prevent the sample from sticking in the mold and subsequently makes it easier to remove the samples when they have hardened. Under randomized loading of the fiber, the composite was made with 30% volume percentage of the fiber. The volume percentage of the fiber/shell used was calculated using Equation 1.

Samples were prepared for both reinforced and unreinforced with the shells and fiber. Based on literature, the prepared samples were left to cure under room temperature for 24hours before it was removed from the mold for cutting.

$$V_f =\frac{\left(W_f/{\rho }_f\right)}{\left[\left(W_f/{\rho }_f\right) + \left(W_m/{\rho }_m\right)\right]}$$

(1)

where $V_f$ is the fiber volume fraction (%), $W_{m }$and $W_f$are the weights of matrix and fiber respectively, ${\rho }_m$ and ${\rho }_f$ are the densities (g/$c{m}^2)$ of the matrix and fiber respectively.

2.2.3. Taguchi Design

Genechi Taguchi, a statistician and engineer, created the Taguchi technique by introducing the loss function and extending trials with an outer array. Taguchi design was adopted because it helps to minimize the number of test and then maximize the effects of factors that cannot be controlled during the BSF surface treatment. For each level of treatment, the signal-to-noise (S/N) ratio was calculated using the S/N ratio formula developed by Taguchi from loss function. The goal is to maximize the treatment parameters. Therefore, the larger-the-better quality characteristic was used as shown in Equation 2.

$$S/N=-10lo{g}_{10}\frac{1}{n}\left({\displaystyle \sum _{i=1}^n\frac{1}{{{}^{\mu }}^2}}\right)$$

(2)

where $\mu$ is the responses for the given factor level combination,nis the number of responses in the factor level combination. Minitab 18 statistical software was used for the analysis. Taguchi $L_{25}$ orthogonal array of experimental design was used for this experiment. Table 1 shows the values of the percentage weight of the shells/fiber which was used in the experiment. Each experimental run was carried out three times and then the average value taken which was used in the analysis.

2.3. Determination of the Flexural Strength

The specimen sizes for the flexural test were formed according to the requirements of the flexural strength testing equipment, which are 200mm X 30mm X 4mm. The test was carried out in a Universal Testing Machine (UTM) with model number M500-25CT, according to ASTM D7264M-15 (Rochdale England). The samples were placed in the machine and then subjected to a force of 50N till they fractured. For each test, three samples were generated, and the average was used to discuss the results. The maximal bending strength was recorded, which was used for the studies. Figure 2.4 depicts the setup for the samples' flexural tests.

Figure 2.4. Flexural test setup.

Figure 2.4. Flexural test setup.

3. Results

3.2. ANOVA of the Flexural Strength

ANOVA was used to analyze the significance of the treatment parameters on the flexural strength. The ANOVA results are shown in Table 4. This analysis was done at a significance level of 5% and was determined by comparing the F-values of each treatment parameter used. The F-ratio was basically used to measure the significance of the treatment parameter on the flexural strength, at the desired significance level (5%).

From Table 4 results, the P-values shows that the periwinkle shell has statistical and physical significance on the flexural strength of the reinforced epoxy composite. Based on the F-values, the periwinkle was the most primary significant factor in the composite with a contribution of 44.90% followed by palm kernel with a contribution of 28.13%. The clam shell is less significant with a contribution of 3.45% and this can be seen from the P-value which is greater than the significance level of 5%. An R-sq value in the model summary shows that palm kernel Shell, periwinkle shell, clam shell, whelk shell and bamboo fiber gives details to 92.24% of the total variation in flexural strength response of the composite. This means that 7.76% of variations are due to other factors which are not considered in the research such as shell particulate size etc. The residual plots of the flexural strength are shown in Figure 3.2. From the normal probability plot of the residuals at top left, it is seen that the residuals are normally distributed, since the plot follow approximately a straight line. Hence, there are no violations of the ANOVA assumptions. The residuals versus observation order plot at the bottom right corner shows no pattern or trend. This means that the residuals are independent of one another. Similarly, the residuals versus fitted value plot at the top right corner shows that the residuals have constant variance and are randomly distributed.

Figure 3.2. Residual plots for flexural strength.

Figure 3.2. Residual plots for flexural strength.

4. Conclusions

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