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Abstract

Composites were manufactured from glass fiber, bagasse fly ash, and epoxy matrix and examined their mechanical and physical properties. The percentages of bagasse fine ash, glass fiber, and matrix were designed at 10%, 15%, 20%, 25%, and 30% with 30% glass fiber and conducted density, flexural strength, hardness, absorption of water, and swelling properties of thickness. Composites were prepared by manual layering. ASTM standards were followed in preparing the samples. According to the results, the bagasse fine ash percentage variation was significant in the composite but had no linear effects on its hardness and flexural strength. A 20% bagasse fine ash composite had the highest flexural strength and hardness at 27.65 MPa and 52.86 HRA, respectively, which are significantly (>0.002) higher than composites of 30% bagasse fine ash, along with the highest density. This study measured water absorption and swelling of composite samples immersed in distilled water for 192 h. As the bagasse ash content increases, these values were linearly increased until saturation occurs.

Keywords

Composite analysis manufacturing method saturation condition reinforcements matrix

Introduction

Currently, researchers are focused on composite materials and their use as alternative engineering materials. This material enhanced the following remarkable properties: lightweight, high strength, strength related to weight, corrosion resistance, high impact strength, design flexibility, part consolidation, dimensional stability, nonconductive, and low thermal conductivity.^1,2 The historical background of composite materials dates back to 1500 B.C. Egyptians and Mesopotamian settlers constructed buildings using mud and straw. The first composite bow was made with wood and bone in 1200 AD. Animal glue was used to make it bind. A series of plastics were invented in the early 1900s, such as vinyl, polystyrene, phenolic, and polyester. The first fiberglass was introduced in 1935. In the 1970s, they created an aramid fiber, which was then surrounded by carbon fiber. When coupled with a plastic polymer, a very robust and lightweight structure was developed.^3,4

Composite materials contain more than two distinct materials, one of which is a matrix and the other is a fiber or particle. Natural or synthetic fibers have found important applications in a range of areas, including construction, mechanical, automobile, aerospace, biomedical, and marine.⁵ Composite structures have demonstrated enhancements in material strength and stiffness, in addition to a significant weight reduction. It has also revealed several unexpected features, such as resistance to influence, wear, corrosion, and chemicals. These properties are variable according to the material’s composition, fiber type, and process of manufacturing.⁶

A hybrid composite material possessed higher mechanical strength compared with similar composites with individual fiber reinforcement.⁷ The hybridization of syntactic fibers with natural fibers has made them more desirable for technical applications.⁸ The products revealed excellent interfacial bonding between the fiber and the matrix hybrid composite that exhibits enrichment in the tensile and flexural properties of the material.⁵ In the hybrid composite of sisal and glass fibers, an increase in the volume ratio of sisal fibers improves the hardness of the composite but increases water absorption because of having more regions that are amorphous while the hardened polyester resin absorbs a small amount of water.⁹ This study aimed to determine the flexural and hardness properties, water absorption, and thickness swelling behaviors of an epoxy resin composite reinforced with glass fiber at 30% weight with bagasse fly ash at weight ratios of 10%, 15%, 20%, 25%, and 30%. Bagasse fly ash, the waste of the sugar industry, is discharged as solid waste. The fly ash is the fines part of the ash, and it is transported by flue gases. The chemical composition of SiO₂ in bagasse ash is relatively higher. Researchers discovered that SiO₂ is present in biomass (rich husk (86.8%), sugarcane (69.6%), rice straw (66.6%), and rod palm (64.5%)),¹⁰ woodchips, wood bark, sawdust, pellets (55%),¹¹ and coal fly ash (44.7%–61.8%).¹² The product of it is much higher in Ethiopia. Hence, sugar industries are open throughout the year, except for maintenance time. Regeneration may reduce the quantity of solid waste. It also decreases the use of natural materials. Bagasse fly ash (BFA) has some extraordinary properties, including adsorption for removal of dye, metals, and other contamination; an electrode for capacitive deionization; use in the construction industry as cement additives and substitute as cement; and preparation of briquettes, water polymers, and mesoporous silica.¹³ The application of BFA in construction was comprised of oxides of various materials.¹⁴ BFA were used to prepare pastes and mortars and increased the viscosities.^15,16 Hand lay-up of composites was performed at room temperature, with a 24-h holding period and a 25 kg load for structural application.

Material and method

Chopped glass fiber strand mat, Methyl Ethyl Ketone peroxide, and wax were purchased from World Glass Fiber Ltd, Addis Ababa, Ethiopia. Sugarcane bagasse ash was obtained from Wonj Sugar Factor, Wonj, Ethiopia. The chemical composition of the bagasse ash is shown in Table 1. The chemical composition (XRF) of the ash was determined by energy-dispersive X-ray fluorescence spectroscopy (ED-XRF) in Dangote cement industry laboratory, Ethiopia. The harvesting perspective of bagasse ash was affected by chemical composition, and physical properties.¹⁷ The physical properties of the ash was determined of 0.2 µm mean particle size and 2350 kg m⁻³ density and 2540 kg m⁻³ density of glass fiber. Figure 1 shows the preparation of sugarcane bagasse fly ash.

Table 1.

The chemical composition of bagasse fine ash.

SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO
66.45%	10.35%	5.52%	3.22%	1.25%

Figure 1.

Sugarcane: (a) Bagasse (b) ash (c) fine ash.

The conventional hand lay-up technique was utilized to produce the composite because it is convenient,¹⁸ easy to handle, and does not required more time.^19,20 The interfacial adhesion between reinforcement and matrix was improved while tensile strength and modulus, flexural strength and modulus, and impact strength were improved.²¹ Chopped glass strand mats, sugar cane bagasse ash, and epoxy resin materials were used for the production of a composite. It is cured at room temperature with a ratio of epoxy resin and hardener of 10:1^22–24 by weight percentage. A wood mold having the dimensions of 250 mm in length, 200 mm in width, and 10 mm in thickness was used for composite fabrication; it is shown in Figure 2. Then they stirred the ash with epoxy resin together and poured the mixture into the mold to complete the mixing process. Compositions of bagasse ash and glass fiber were prepared with different weight percentages. Before curing, a releasing agent was painted on the mold surface to be used to prevent sticking and make it easier to remove the composite from the mold. Roller brushes were used to remove trapped air bubbles in the mold and distribute the resin throughout the entire area. In addition, a 25 kg load was used to compact the fiber with the resin and was opened after 24 h. Finally, the samples were prepared as per the ASTM standards for flexural strength, hardness tests, and water absorption. The designations of the composites are listed in Table 2.

Figure 2.

Mold, materials, and tool for manufacturing of composite.

Table 2.

Combination of reinforcement with matrix.

Designation	Combination of composite
S1	Bagasse ash (0%) + glass fiber (30%) + epoxy resin
S2	Bagasse ash (10%) + glass fiber (30%) + epoxy resin
S3	Bagasse ash (15%) + glass fiber (30%) + epoxy resin
S4	Bagasse ash (20%) + glass fiber (30%) + epoxy resin
S5	Bagasse ash (25%) + glass fiber (30%) + epoxy resin
S6	Bagasse ash (30%) + glass fiber (30%) + epoxy resin

Determination of the density

These tests are carried out to ensure the safe behavior of the material. “Density” is a physical property of liquids and solids.²⁵ It was measured as per the ASTM D792-91 standard. According to this principle, when an object is immersed in a liquid, the apparent loss in its weight is equal to the volume of the liquid it displaces. In polymer composite materials, mass per unit volume is a crucial parameter that defines their qualities.^26–29 The developed composite was weighed using a digital weighing scale and the volume was determined using a measuring cylinder. To conduct the test, distilled water was taken as the medium. In Table 3, the measured density was shown and computed using formula (1).

D e n s i t y (ρ_{m}) = \frac{M a s s (m)}{V o l u m e (V)}

(1)

Table 3.

Density of composites.

Designation	S1	S2	S3	S4	S5	S6
Density (kg m⁻³)	1580	1460	1510	1560	1400	1380

Water absorption and thickness swelling test

ASTM D570 was used to conduct the water absorption and thickness swelling tests. The weight and thickness of each sample were determined before being immersed in the media. The water absorption value was intended by equation (2).³⁰ Three specimens for each type of composite were prepared in the following sizes: 20 × 20 × 3 mm. Under room temperature (25°C), the specimens were submerged in water media and monitored for 192 h. The digital weight balance and digital vernier caliper were used to measure the samples' weight and thickness, and the findings were analyzed using the graphical presentation shown in Figure 3. The thickness swelling (TS) was intended according to equation (3):

M a s s c h a n g e, % = \frac{W_{i} - W_{b}}{W_{b}} \times 100

(2)

T h i c k n e s s S w e l l i n g (T S) = \frac{T_{i} - T_{o}}{T_{o}} \times 100 %

(3)

Where W_i is the current specimen mass, g, and W_b is the baseline specimen mass, g., T_o is the thickness of specimens before immersion, and T_i is the thickness of specimens after 24 h of immersion in water media.

Figure 3.

The flexural strength test specimen and UTM setup.

Flexural strength test

The flexural test is one of the fundamental mechanical tests considered in designing a structure. It is used to describe a structural mechanics component that bends in response to an external force acting perpendicular to its longitudinal axis.³¹ Therefore, a meticulously prepared specimen was controlled under a three-point load for examination. By contrasting the force exerted with the strain, one may determine the flexural characteristics of a material. According to the Load Deformation Relationship, the material's elasticity depends on its response to the imposed load. Deformation is measured by the strain experienced following the imposed load. The parameters were specified, ensuring the ASTM D790 standard to acquire specimens dimension (127 × 12.7 × 3.2 mm) and the support span equal to specimen thickness times 16. The samples were prepared as shown in Figure 4.

Figure 4.

Measuring of mass and thickness changed by immersed in water media.

Polymers are most often tested using three-point flexural tests.³² Typically, a deflection is calculated using the crosshead position. Flexural strength and modulus were calculated using equation (4).

F l e x u r a l S t r e n g t h = \frac{3 P L_{o}}{2 W_{o} t^{2}}

(4)

Where P is the central load (KN), L_o is the span length of the specimen (mm), W_o is the width of the specimen (mm), and t is the thickness of the specimen (mm).

Hardness test

The Rockwell hardness test is the most widely used hardness testing method, and it is thought to be more accurate and straightforward than other hardness tests.³³ Unless the size, shape, or surface characteristics of the specimens are prohibitive, this test can be done on any metal or composite.³⁴ Hardness was assessed according to ASTM D785. A weight applies to the indentation, increasing its depth. Materials’ hardness is determined by how deeply an indenter penetrates them. To start out and hold the indenter in place, 10 kg of weight was used to achieve the first penetration. The dial was reset to zero and then a significant load of 60 kg was applied.

Result and discussion

Density of composite analysis

In composites, density plays an important role in determining their dimensional stability.^35,p-7 The correlation between the content of the bagasse ash filler and the density of the material was studied. The water displacement method was used to determine the volume of the composite. As shown in Table 3, an increase in the proportion of reinforced particles in the resin solution, i.e., bagasse ash-glass fibers, decreases density. The fact that the fibers are light in weight yet take up a lot of space might be linked to the drop in density. In the present investigation, the density of bagasse-glass fiber-filled composite was found to be the highest in S4, which is 1560 kg m⁻³.

Water absorption and thickness swelling analysis

When developing composite materials, moisture absorption should be taken into account.³⁶ In this test, a composite was exposed to a wet medium to measure its moisture absorption rate. An evaluation of the absorption rate was conducted by placing the composite sample in a distilled water container. The initial weights and corresponding thicknesses of these samples were measured. In Figure 5, the water absorption of composites with increasing immersion time was exhibited in relation to the composition parameter. It revealed that when the bagasse fly ash loading increases, the water absorption of composites also increases. The composites containing bagasse fly ash had the highest water endorsement values. Water absorption increased linearly when the relative volume percentage of bagasse fly ash increased. A composite with 30 wt.% bagasse fly ash content was displayed to have a higher water absorption rate as compared to 10 wt.%. As reported of else ware,^37,38 the excessive fillers tend to agglomerate may result void formation, reduce mechanical strength and allowing water absorption. In order to achieve decreased water absorption, mechanical performance and water resistance must be balanced. There is a strong correlation between the density and void content of a composite and the rate of water absorption.³⁹

Figure 5.

Change of water absorption.

Figure 6 shows the percentage of thickness swelling in the composite. It was observed from the result that thickness swelling in the composite increases with the increased immersion time until saturation occurs, as well as increases with the percentage of bagasse fly ash. It can be seen increase the bagasse fly ash linearly in that composite panels were more vulnerable to swelling tendency, which may be as a result of the poor interfacial adhesion occasioned by the large amount of fly ash area between the reinforcing filler and the hydrophobic matrix polymer.⁴⁰ The S1 composite showed the lowest and S6 the highest values of thickness swelling rate, whereas the lowest percentage of bagasse ash filler composites showed intermediate results.

Figure 6.

Thickness swelling.

Flexural strength analysis

Compression, tension, and shear stresses are all occurrences of composite materials during flexural strength analysis.⁴¹ The three-point flexure test was implemented to determine the bending and shearing strength that caused the failure at the 0.5 mm/s speed of the machine head. In designs of composites with glass fibers loaded, the flexural strength is higher due to the stiff glass fiber inclusion, which makes the composites more resistant to shear.⁴² As shown in Figure 7, the curve increases linearly up to a failure point and then uniformly deforms. Accordingly, S4 achieved the highest load-carrying capacity at 162N or 27.65 MPa, and a deflection at 33 mm, which is where its internal resistance to the acting load is lost. The effects of excessive loading on material cause permanent distortion; eventually, the material fails. The lowest deflection was found with glass fiber (30 wt.%) and bagasse fine ash (25 wt.%) composition, which is 14.5 mm, and the flexural stress is 21.51 MPa. However, higher content of bagasse fly ash lowered the mechanical strength of the hybrid composite. According to reports elsewhere,^43,44 fillers, particularly those of a nanoscale size, typically interrupt the adhesion between resin and reinforced fiber, thus diminishing their mechanical strength.

Figure 7.

Flexural strength test load and displacement curve.

Hardness test analysis

The Rockwell hardness test was used to determine the hardness of epoxy composites reinforced with bagasse fine ash percentage at 0.1, 0.15, 0.2, 0.25, and 0.3 wt.% and glass fiber 0.3 wt.% at room temperature by evaluating the depth of penetration of an indenter on the material. The results presented are the average of five places in a test sample. The effects of different ash content from 0 to 30 wt.% on the hardness properties of polymer composites are represented in Figure 8. It is observed that with an increase of ash content from 0 to 20 wt.%, the hardness strength gradually increased, and with 25 and 30 wt.% ash content, they decreased. This is a result of the high viscosity that the epoxy resin acquired with the high concentrations of fly ash particles added to it, which made it difficult to penetrate the epoxy to fly ash and fibers, which produced porous interstices within the composite material.⁴⁵ The neat glass fiber hardness composite was 41.52 HRA, which is the lowest strength. The designated amount of bagasse fine ash (20 wt.%) with glass fiber (30 wt.%) composite material hardness is 52.86HRA (S4).

Figure 8.

Hardness test; Hardness testing setup and hardness tested results.

Hypothesis analysis

A one-way analysis of variance (ANOVA) was conducted to analyze the data’s statistical behavior, such as the flexural strength and hardness of the composites. A factor such as “percentage composition of bagasse fly ash (BFA)” was used to classify these data. After the formulation of the data according to the one-way ANOVA, the result is tabulated as shown in Table 4.

Table 4.

ANOVA test for testing effect of factors on flexural and hardness of the composites.

Source	Degree of freedom (df)	Sum of square (SS)	Mean square (MS)	F-value	p-value
Percentage of BFA	5	1022.0	204.40	5.35	0.002
Error	24	916.3	38.18
Total	29	1938.3

Source	Degree of freedom (df)	Sum of square (SS)	Mean of square (MS)	F-value	p-value
Percentage of BFA	5	1736.2	347.24	4.82	0.012
Error	12	865.3	72.11
Total	17	2601.5

The ANOVA results for flexural strength and hardness value of composites are shown separately in the table. All the results are validated at a 95% confidence level (=0.05). In these results, the null hypothesis states that six different paints’ mean flexural strength and hardness values are equal. Because the p-values (>0.002 and >0.012) are less than the significance level of 0.05, therefore, reject the null hypothesis and conclude that some of the paints have different means.

A comparison of the percentage of bagasse fly ash content in the composite is shown in Table 5. It is tabulated by ANOVA. Differences between means that share a letter are not statistically significant. BFA_20% and BFA_0% do not share a letter, which indicates that BFA_20% has a significantly higher mean than BFA_0%. The confidence interval for the difference between the means of BFA_20% and 10% in flexural strength is 1.30 to 25.45; for BFA_20% and 0%, it is 4.99 to 29.14; for BFA_15% and 0%, it is 1.16 to 25.31; and for hardness, it is 7.15 to 53.7. This range does not include zero, which indicates that the difference is statistically significant.

Table 5.

Grouping information used the Tukey method and 95% confidence.

Flexural strength				Hardness value
Factor	N	Mean	Grouping	Factor	N	Mean	Grouping
BFA_20%	5	92.27	A	BFA_20%	3	52.86	A
BFA_15%	5	88.44	A B	BFA_25%	3	47.60	A B
BFA_25%	5	87.24	A B C	BFA_15%	3	48.50	A B
BFA_30%	5	82.43	A B C	BFA_30%	3	44.94	A B
BFA_10%	5	78.90	B C	BFA_10%	3	46.50	A B
BFA_0%	5	75.20	C	BFA_0%	3	41.52	B

Conclusion

This work was designed with the reinforcement of chopped glass fiber with bagasse fine ash based on an epoxy resin matrix. The mechanical properties of flexural and hardness strength were conducted. The composites were manufactured with different percentages of bagasse ash weight fraction and successfully developed using the hand lay-up method. These were conducted based on the ASTM standard of D792-91 for density, D570 for water absorption and thickness swelling, ASTM D790 for flexural strength, and D785 for hardness strength analysis. One-way ANOVA was used as a statistical tool to find the effect of parameter such as ‘Percentage composition of Bagasse fly ash’ on the flexural strength and hardness value of the composites. In these results, the null hypothesis states that the mean flexural strength and hardness values of six different paints are equal. Because the p-value (α > 0.002 and α > 0.012) is less than the significance level of 0.05, therefor, reject the null hypothesis and conclude that some of the paints have different means. The experimental results showed significant differences in mechanical and physical properties. The percentage of bagasse ash was increased in the composite, not linearly increasing the flexural and hardness strength. In the design of 20 wt.% bagasse ash content, the highest density and flexural stresses were found at 1560 kg m⁻³ and 27.65 MPa. The hardest value for bagasse ash is 52.86 HRA at a volumetric fraction of 20 wt.%, and the softest value is 44.94 HRA at a volumetric fraction of 30 wt.%. Water absorption and thickness swelling intensify linearly when the relative volume percentage of bagasse ash is increased. A composite with 30 wt.% bagasse ash content was shown to have a higher water absorption rate as compared to those with 10 wt.%.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Belay Taye Wondmagegnehu

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