Preparation and experimental investigations on the mechanical behavior of hybrid polymer nanocomposite with boron carbide and graphene nanoplatelets

Abstract

This paper gives an investigation into the morphological analysis of boron carbide and the mechanical properties of the Jutton-Glass hybrid polymer nanocomposites. As reinforcements, hybrid nanoparticles comprising boron carbide and graphene nanoplatelets were used. For laying the composites, the vacuum bagging technique was used with the composition of hybrid nanomaterial taken as 0, 0.25 and 0.5 wt.% of Gr and B4C, and the samples were tested for mechanical properties as per ASTM standards. The samples prepared have been subjected to various tests, and the results are reported. Before the preparation of composites, the polymer was mixed with surface-modified nanomaterial and stability tests were conducted to assess uniform dispersion with the aid of UV spectroscopy, and the outcomes showed that the samples had been exceptionally uniform over some time. It is determined that the mechanical behavior of hybrid composites, which include B4C with Gr, shows better properties than base, B4C, and Gr. However, the multi-layered samples with graphene nanoplatelets also showcased encouraging mechanical properties like hardness and tensile strength.

Keywords:

• Stability
• boron carbide (B₄C)
• graphene nanoplatelets (GNPs)
• scanning electron microscopy (SEM)
• morphological analysis
• mechanical properties

REVIEWING EDITOR:

• Swadesh Kumar Singh, Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad, India

SUBJECTS:

• Mechanics of Solids
• Mechanical Engineering
• Materials Science

1. Introduction

The growth of composites and their applications in manufacturing is a brilliant development in the history of materials. Composites are used in numerous fields with mechanical and biological backgrounds for unique applications. When two or more materials with different properties are mixed, a composite material is created. The presence of particles in a composite material adds to its mechanical properties, which include hardness, tensile strength and flexural strength (Shahinur et al., 2015). Depending on the type of matrix, composites can be categorized into three types: metal matrix composites, ceramic matrix composites and polymer matrix composites. Polymer matrix composites (PMCs) are composite materials in which a polymer matrix is strengthened by including high-strength fibers or particulate elements. The incorporation of the polymer matrix and reinforcing materials yields a composite material that demonstrates improved mechanical, thermal and occasionally electrical characteristics in comparison to the separate constituents. The properties of polymer matrix composites are determined by three constitutive factors: the type of reinforcements (particles and fibers), the type of polymer and the interface between them. Nowadays, these composites are used in various sectors such as automotive, marine, aerospace and many others due to their high specific stiffness and strength. Fiber-polymer composites, or fiber-reinforced polymer (FRP) composites, are materials made up of a strong polymer matrix reinforced with high-strength fibers (Ramesh et al., 2013). These composites merge the advantageous attributes of both the polymer matrix and the reinforcing fibers, yielding materials with improved mechanical, thermal and occasionally electrical properties (Sapuan et al., 2006). A fiber is distinguished by its significantly larger length in relation to its cross-sectional dimensions. The characteristics of the matrix, the fiber and their interaction exert a substantial impact on the properties of composites. The fibers used in polymer composites can be classified as either synthetic or natural. Frequently utilized synthetic fibers for composites include glass, aramid and carbon fibers, among others, while natural fibers consist of jute, banana, cotton, flax and hemp, among others. Various types of glass fibers are used, depending on the specific application. For instance, E-glass fibers are suitable for electrical applications, C-glass fibers are resistant to corrosive environments and S-glass fibers are used for structural purposes and in high-temperature conditions. Glass fibers are offered in several configurations, such as continuous fibers, chopped fibers and woven fibers. Natural fibers are those that are obtained from plants or other living organisms. Table 1 contains the characteristics of various fibers. Composites composed of the same reinforcing material may not exhibit superior performance due to exposure to varying loading situations over their lifespan (Bos et al., 2006; Shibata et al., 2005). Hybrid composites are the optimal choice for resolving this issue in the given applications. A hybrid composite material is formed by combining two or more distinct types of fibers, with one type of fiber compensating for the shortcomings of another type of fiber. Hybridization allows the designer to customize the material qualities to meet specific requirements.

Table 1. Physical properties of various fibers.

Type of fiber	Tensile strength (MPa)	Young’s modulus (GPa)	Elongation at break (%)	Density (g/cm^3)
Megass	292	17.5	–	1.26
Willow	221	11.5–18.2	–	0.61–1.12
Musa Paradisiac	501	13.	5.93	2.32
Coir	178	4.4–8.1	30.5	1.21
Gossypium	564	5.52–13.63	8.1–9.2	1.41–1.62
Linum	1039	28.62	2.72–3.32	1.52
Cannabis	690	73.1	1.61	1.47
Corchorus	392–778	26.52	1.51–1.82	1.20
Hibiscus Cannabinus	935	53.5	1.62	–
Agave Sisalana	521–643	9.41–23.1	2.1–2.51	1.61
E-glass	3412	73.4	–	2.51

1.2 Nano-composites

Fiber-reinforced polymer nano-composites (FRPNCs) are a sophisticated type of composite materials in which durable fibers are incorporated into a polymer matrix that is additionally strengthened with nanoscale fillers or nanoparticles. The utilization of both macroscopic reinforcement (fibers) and nanoscale reinforcement (nanoparticles) enables the augmentation of mechanical, thermal and barrier properties to a greater extent than what can be achieved with traditional fiber-reinforced polymer composites (Alexandre and Dubois, 2000; Manjunath et al., 2016). These composites can be classified into four categories: un-intercalated, interposed, exfoliated, and are manufactured using different procedures such as polymer intercalation, in-situ polymerization and melt compounding. Biomedical nano-composites are tailor-made for applications in dentistry, bone tissue regeneration, medication administration in cancer therapy, and wound care. Furthermore, the optical characteristics of composite materials can be enhanced by using a transparent matrix material. Several Nano-composites, such as Carbon Nanotubes (CNTs), Graphene and its oxides, and MoS2/Graphene, have demonstrated encouraging optoelectronic characteristics suitable for photonic applications. Srinivas et al. (2020) made investigations to assess the effect of MWCNT weight percentage on the property enhancement of nanocomposites.

1.2.1 Graphene nano platelets (GNPs)

Carbon has many allotropes, some that were discovered long ago (diamond and graphite) and some discovered 10–20 years ago (fullerenes and nanotubes). Interestingly, the two dimensional form (graphene) was only obtained very recently, bringing about a great deal of change in our current science (Katsnelson, 2007). Graphene is a carbon allotrope that consists of carbon atoms organized in a layered form with a hexagonal pattern. Graphene refers to a singular layer of carbon atoms that has been separated from the larger graphite structure. The carbon atoms in a graphene layer establish three strong intermolecular connections per atom, resulting in the development of a hexagonal planar layer with a honeycomb-like atomic arrangement (Geim and Novoselov, 2007).

1.2.2. Boron carbide

Boron carbide (B4C) has several remarkable characteristics, such as a high melting point, high hardness, low density, outstanding resistance to degradation and rusting, among others. Presently, this substance is attracting considerable interest in the field of nano-composites research due to its unique physical, chemical and electrical properties, which make it a leading contender among the materials with potential for high-performance applications (Cheewawuttipong et al., 2013). The boron carbide powder, which is extremely small in size, is obtained from a specialized supplier and then converted into particles that are even smaller, known as nano-sized particles. Carbon fiber addition leads to refinement of both ZrB₂ and SiC grains. Both the flexural strength and maximum strain value of carbon fiber reinforced ZrB₂-20v/oSiC-2v/oB₄C composite is observed to be higher than those of the base i.e. ZrB₂-20v/oSiC-2v/oB₄C composite (Das et al., 2018).

1.2.2.1. Study on natural fiber based polymer composites

Natural-based polymer composites have been used more frequently in recent years because of their many benefits, including biodegradability, flexibility, availability, affordability and light-weight nature. Many studies have been carried out by researchers to improve the mechanical properties of these composites. Yashas Gowda et al. (2018), for instance, found that composites made of jute fibers have stronger properties than those made of wood. In unsaturated polyester resin, Song et al. (2021) investigated the impact of fiber volume fraction on the mechanical characteristics of untreated jute fibers. According to Schneider and Karmaker (1995), composites made with jute fibers have better mechanical qualities than those made with kenaf fibers.

1.2.2.2. Study on non-natural fiber based polymer composites

Extensive study has been carried out by multiple researchers on polymer composites with synthetic fibers. In their study, Han et al. (2023), examined how the mechanical properties of glass/polyester composites are affected by water absorption. The breaking strength and tensile strain of the composites were found to diminish progressively as the immersion period in water increased, due to the gradual weakening of the bonding between the fiber and matrix. In their study, Yuan et al. (2013) investigated how modified jute fiber affected the mechanical properties of timber-flour/polypropylene composites. They found that the inclusion of Kevlar fiber improved the mechanical characteristics of the materials. The research conducted by Wang et al. (1995) on composites reinforced with woven Kevlar and fiberglass revealed that the choice of fiber significantly influenced the mechanical properties of the fibers. Simultaneously with Cho et al. (2007) investigating the mechanical behavior of carbon fiber/epoxy composites, they observed that the composites reinforced with nanoparticles exhibited superior mechanical properties, including enhanced shear and compressive strengths. Rajulu et al. (2002) investigated the tensile properties of epoxy toughened with hydroxyl-terminated polyester at different layers of glass rovings and reported that the tensile strength increased with an increase in fiber content.

1.2.2.3. Impression on hybrid fiber based polymer combinations

Hybrid fiber composites are composed of a mixture of natural and/or synthetic fibers, that may encompass highly-priced materials including glass, carbon and boron fibers (Jesuarockiam et al., 2019; Zhang et al., 2022). Several studies have examined the mechanical behavior of hybrid composites based on different fiber combinations, along with jute and oil palm fiber or glass and jute. Those investigations have proven that using hybrid structures can effectively beautify the tensile and dynamic mechanical performance of composites because of stepped forward fiber/matrix interface bonding (Dixit and Verma, 2012; Le and Huang, 2015). Moreover, remedies such as the conduct of jute cloth were determined to enhance the performance characteristics. Notch sensitivity has also been studied in untreated woven jute and jute-glass cloth reinforced polyester hybrid composites, with jute composites showing higher sensitivity than jute-glass hybrids. The impact of stacking sequence on mechanical features has additionally been experimentally investigated in interlaced jute and glass material bolstered polyester hybrid composites. The advantage of using HPCs depends upon the filler materials which give highest thermal conductivity. Hybrid nano-filler modified polymer matrices have created wide opportunities in research to achieve excellent thermal and mechanical properties for advances in many fields of applications. The commonly used nanoparticle-fillers are carbon nanoparticle-filler, carbon nanotubes, nano clay and silicon carbide fibres (Dyachkova et al., 2023). Since polymers have low thermal conductivity, an effort has been made to increase thermal conductivity and electrical resistivity of polymers by adding boron nitride, silicon carbides, glass Fibre, mica, aluminum nitride, alumina and zinc oxide fillers (Ramakrishna and Prasad, 2018).

1.2.2.4. Dispersion of nanomaterials in polymer

Achieving uniform dispersion of nanoparticles within the polymer matrix is crucial. Agglomeration of nanoparticles can lead to uneven properties and compromise the performance of the nanocomposite. Modifying or functionalizing nanoparticles on the surface can increase their stability in the polymer, leading to better dispersion. The compatibility of nanomaterials with the polymer matrix can be improved by applying surface treatments or coatings. This is achieved by utilizing surfactants, coupling agents, or other chemical treatments to alter the surface energy and facilitate greater dispersion. These agents can help stabilize the nanomaterials in the polymer matrix and prevent agglomeration. The dispersion stability of nanomaterials in the polymer prior to preparation of fiber reinforced polymer nanocomposites is a vital step. To assess the stability, UV Visual spectroscopy is normally employed. Dhand et al. (2013) found that graphene nanocomposites show substantial enhancements in their multifunctional aspects at low loading in comparison with conventional composites and materials.

1.3. Present work and novelty

This research aims to examine the investigation, evaluation and mechanical performance of jutton/glass fiber-strengthened epoxy hybrid composites with Nano fillers such as graphene nano platelets and boron carbide. The study investigates the impact of B₄C size, with and without surface modification on tensile and hardness properties. Additionally, the morphological and mechanical behavior as well as the stability of the composite polymer were analyzed using micrographs. Jutton fiber offer several benefits, including improved performance, enhanced durability and resistance, quick drying, reduced shrinkage and cost efficiency.

2. Materials and methods

This phase provides an overview of the processing information for the composites and the experimental procedures conducted to characterize and test the composite specimens. The raw materials utilized in this study are

2.1. Materials

Reinforcements/fibers: jutton fibers (jute + cotton), glass fibre.

Matrix/resin: epoxy (LY556) with hardener (Hy951).

Nano-fillers: boron carbide, graphene nano platelets.

Type of method: stability, surface modification.

Fabrication technique: vacuum bagging technique.

Jute is the bast fiber that has the greatest production volume and is also one of the most inexpensive natural fibers. The height of jute plants can reach 2–3.5 m. However, their fibers are fragile and have low elasticity, making them prone to breaking because of their high lignin content, which ranges from 12 to 16%. Nevertheless, jute fibers exhibit lower resilience to moisture, acid and UV light. In contrast, cotton fibers possess a delicate and cool texture, and have the ability to retain water at a ratio of 24–27 times their own weight. Additionally, they exhibit resistance to abrasion, wear and elevated temperatures. The picture depicts a graphic representation of many types of jute fibers.

Figure 1 shows the Jutton fibres are acquired from plant life and are a mixed form that comprises fibres of jute and cotton. At present, in the jute sector, it has been used and improved to a satisfactory level for use in diverse regions, particularly ground coverings, technical textiles, household textiles, handicrafts, etc. It emphasizes combining and growing the best qualities while at the same time minimizing the wicked qualities of the fibres. Mixing jute with cotton fibre may be an acceptable process of jute diversification, with the aid of which value-added merchandise may be produced. As a result, the techniques of softening and mixing have established a new class of jutton-based products. S2 Glass offers substantially greater power than conventional glass fibre, better durability, modulus of resistance, impact deformation and green processing. On further investigation using SiC instead of graphite as the filler material in E-glass reinforced thermoset composites (Gopinath et al., 2014), they found that tensile strength, flexural strength and hardness of the glass-reinforced thermoset composite increased with the inclusion of SiC filler. This has the capacity of composite parts to face up to high stages of concern and flexural fatigue. Epoxy resin has been used extensively in industries as a fiber-reinforced composite matrix and adhesive (Suresha, 2009). Epoxy LY556 is Araldite LY556 a medium-viscosity, unmodified epoxy base on bisphenol-A. It possesses tremendous mechanical properties and resistance to chemical compounds, which can be modified within wide limits by way of the use of HY951 hardeners as well as fillers. Epoxy LY556, which specifies LY as bisphenol-A, and 556 is a five-viscosity code, five-performance grade. 6-curing time (seconds).

Figure 1. 50:50 jute and cotton fiber (jutton fibre).

Nature of Epoxy resin LY-556:

1. Visual issue—self-evident, light-yellow fluid.

2. Viscosity@ 250 °C—10,000–12,000 MPa.

3. Thickness, 250 °C—1.15–1.20 gm/cm³.

4. Streak factor—1950 °C

What’s more, hardener HY951 which indicates HY as Araldite and 951 is nine-thickness code, 5-execution code, 1-relieving time (in seconds). Properties of hardener HY-951:

1. Thickness = 0.95 gm/cm³.

2. Liquefying factor = 120 °C (lit.)

3. Edge of boiling over = 266–2670 °C (lit.)

4. Water solubility = Dissolvable.

5. Streak point = 143.330 °C.

2.2. Characterization

2.2.1 Scanning-electron-microscopy (SEM)

It is used to study the morphological characterization of the composite and powder particles. SEM images have been taken of synthesized boron carbide during the milling process, with variations in timing. As the dimensions of the matter approached the nanoscale and the percentage of fragments on the surface decreased relative to the total number of molecules, the properties of the substances changed. Figure 2 shows FESEM images of (a) graphene nano platelets and (b) B4C nano materials, these are smaller, more uniform, spherical particles, as well as heavily agglomerated debris within the powder.

Figure 2. FESEM images of (a) graphene nano platelets and (b) B4C nano materials.

2.2.2 Surface modification

The hybrid composites (Burrola-Núñez et al., 2018; Chukov et al., 2019) have been extensively studied and it has been found that the composites with a jutton-to-glass ratio of 3:2 exhibit superior mechanical properties, including tensile strength and hardness, compared to untreated jutton composites. To further enhance these properties, the jutton and glass fibers are exposed to varying intensities of UV radiation. The UV-pretreated jutton and glass fibre (3:2) composite, at the most optimal intensities, demonstrates the highest mechanical properties when compared to untreated jutton and glass-based hybrid composites (Liu et al., 2009).

2.3. Preparation of the composite

2.3.1 Preparation of polymer and its stability

The stability of polymer dispersed with nanomaterials as reinforcements is a crucial aspect that determines the performance of nanocomposites and their suitability for various applications. Proper dispersion of nanofillers within the polymer matrix is crucial. The clustering of nanoparticles can result in non-uniform characteristics and jeopardize the stability of the nanocomposite (Liu et al., 2009; Merlini et al., 2011). Methods such as sonication and melt mixing are frequently used to attain homogeneous dispersion. The resilience of the interface between the polymer matrix and nanofillers is crucial during the creation of nanocomposites. Enhancing the interfacial adhesion between the matrix and the filler is crucial for effectively transferring stress, hence enhancing the mechanical characteristics and stability of nanomaterials (Dong et al., 2021). The ultra-sonication technique affects the surface and structure of nanoparticles and prevents the agglomeration of particles to form solid fluids. Adequate dispersion of short Jutton-glass fibers in a resin can be achieved without sonication. However, due to the clinginess of graphene and boron carbide, the degree of dispersion of graphene and B₄C in the resin mixture can be improved by sonicating a suspension of nanoparticles. The reasonable dispersion is much greater and effects the size of the nanopowder agglomerates.

2.3.2 Assessment of stability of polymer dispersed with nanomaterials

To assess the stability, UV Visual spectroscopy is normally employed. UV–Visible (UV–Vis) spectroscopy is a method employed to evaluate the durability of nanoparticles in polymers before creating polymer nanocomposites. UV–Vis spectra are collected to observe any alterations in the absorption characteristics of the polymer that is distributed with nanoparticles. The UV stability assessment primarily focuses on the UV range, which spans from 200 to 400 nm. UV–Vis spectra can detect absorption bands linked to the polymer and nanomaterials included within it. Alterations in these bands can signify the clustering and sedimentation of nanomaterials. Prior to subjecting the polymer dispersed with nanoparticles to UV radiation, a baseline UV–Vis spectra of the parent polymer is acquired. This spectrum functions as a benchmark for comparison and aids in the detection of any alterations in the absorption properties of the material.

2.3.3 Preparation of composite with vacuum bag method

The lamination technique is usually used for materials like glass fiber, wood, foil and plastic which are coated with thermoset or thermoplastic resin. There are four types of lamination techniques the overlay method, vacuum bagging, pressure molds and hybrid method. Picking a technique for fabricating a composite depends on the number of identical products you need, how much time can be allotted for the fabrication, and the cost of production (Mazumdar, 2001; Nagendra et al., 2017). Figure 3 indicates that vacuum bag molding is a highly effective technique utilized in composite manufacturing to produce laminated structures. This technique applies pressure to the laminate throughout its action cycle, serving various purposes.

Figure 3. Experimental setup.

• Efficiently removes any trapped air among the layers of fabric.

• Compacts the layers of fibres, ensuring sturdy bonding between them and preventing any distortion at some stage in the preparation system.

• Facilitates reducing humidity ranges.

• And most importantly, the vacuum bagging technique complements the integration of the fiber and resin in the composite.

The key to accomplishing those advantages lies in maximizing the ratio of fibre to resin. It is vital to observe the reinforcement within the fabric industry. Moreover, thermosetting resins like polyester and epoxy can end up brittle if they’re not properly strengthened in the course of the curing process. If there is extra resin inside the laminate, it’ll showcase extra habitations of the resin as opposed to the desired composite. Conversely, if there is too little resin, areas in which the reinforcement is dry will have susceptible spots. To optimize the resin content, it is essential to absolutely saturate the entire reinforcement with resin while minimizing any excess content. The essential principle in the back of the vacuum bagging technique is to “squeeze out” any excess resin so as to obtain a maximized fiber-to-resin ratio.

The composite specimens were prepared by varying the volume percentages of nanofillers like 0, 0.25, 0.5 and 1% of Gr and B₄C and base sample as shown in Figure 4. After the preparation of specimens was done then it allowed for cutting as per the ASTM standards to analyze the different properties like hardness and tensile strength.

Figure 4. A: 1%GNPs + B4C; B: 0.5%GNPs + B4C; C: 0.25%GNPs + B4C; D: Base sample.

2.4. Hardness measurement

Hardness tests measure the level of resistance to indentation and are notable for their speed, cleanliness and non-destructiveness. An indenter, together with a metal ball, is subjected to a force, and the resulting size or depth of the indentation within the material’s base is measured using a microscope. A digital Rockwell hardness testing machine is a device utilized for measuring hardness. Smaller numerical values indicate that the material is prone to being scratched easily, whilst larger numerical values imply a higher level of resistance to indentation. Tensile strength is often correlated with hardness. Functional areas are more prone to abrasion when resin composite fillings are used. Nevertheless, a notable impact on the hardness is detected after 300,000 load cycles. This exhibited entirely distinct behavior in comparison. Simultaneously, this provides an indicator of increased longevity, which must be taken into account. The study further explores the relationship between the impact of size and hardness, both with and without surface alteration, compared to hardness.

2.5. Tensile test

The tensile test measures the energy needed to fracture a sample work and the level to which it elongates before contravention. This test generates a stress-strain curve that is utilized to determine the tensile modulus. The resulting data from this testing aids in identifying the most effective materials to withstand application forces and provides crucial quality control tests for materials. The ASTM D3039 tensile test is conducted using an Instron device, which performs the test and measures the force required to break the polymer composite. Typically, the tensile test is performed on a plane specimen. In this test, a uniaxial load is applied to both ends. The tensile test is performed on a specimen of bi-directional jutton/glass FRHC with a choice of nanofillers.

3. Results and discussion

The obtained solid laminates are cut as per ASTM standards, and various characteristics are analyzed. Stability tests for the resin samples with various volume percentages of nanoparticles were performed, and the results were analysed.

3.1. Polymer and its stability

Figure 5 shows the absorbance vs. no. of days at a wavelength of incident light of the epoxy and B4C substance. If the wavelength of incident light increases, the absorbance in the respective substance reaches its maximum value and then decreases from day to day such as 1 day, after 15 days, and after 30 days as shown in Table 2.

Figure 5. Absorbance (vs.) no. of days.

Table 2. Peak absorbance.

S. no	No. of days	Peak absorbance (a.u)
1	1st Day	11.345
2	After 15 days	8.845
3	After 1 month	8.403

3.2. Effect of surface modification on the hardness of composites

3.2.1 Hardness test: hardness test without and with surface modification

The hardness tests were performed randomly on the surfaces in each sample, and mean values were reported. Hardness is found for four samples at five distinct locations in each sample, i.e., hardness above break-point (a) and below break-point (b). The hybrid composite is subjected to surface modification, for which enhanced properties were obtained. There is a substantial increase in the value of hardness. The values of hardness without and with surface modification are shown in Table 3.

Table 3. Digital rockwell hardness test (HRC values) for surface modification specimen.

Sample name	Digital rockwell hardness test (HRC values) @ near breaking points				Pictorial representation
	Without surface modification		With surface modification
	(a)	(b)	(a)	(b)
	Above	Below	Above	Below
S1: Base	306.2	325.4	NA
	318.3	241.1
	268.8	297.5
	364.9	212.6
	313.4	311.2
S2: B4C	384.5	514.7	518.5	514.7
	420.5	320.7	520.5	520.7
	325.1	419.0	525.1	519.0
	216.1	311.9	516.1	511.9
	405.0	210.5	505.0	510.5
S3: GNPs	329.5	305.8	521.7	518.1
	339.6	419.7	512.2	519.9
	384.4	327.9	514.0	527.0
	362.3	439.2	514.4	539.5
	321.1	358.3	521.6	518.0
S4: B4C + GNPs	346.6	399.5	543.5	529.5
	448.8	323.8	542.6	541.5
	343.4	448.6	545.4	548.3
	449.2	345.8	549.2	543.0
	346.4	354.7	541.8	533.2

Figure 6, shows the Rockwell hardness values of the composite without and with surface modification. It can be seen that the hardness of the samples has increased more. Sample B4C + GNPs reached the highest value of 590.74 HRC with the surface modification. The surface morphology is generally normal, and compared to the base, a lower hardness was achieved in the heat-affected region due to the sonication process. Due to the agglomeration formed and the non-uniform particle distribution, the hardness obtained is not uniform. The Rockwell hardness of the composite material without surface modification of the sample B4C + GNPs results in a higher value of 410.68 HRC compared to the other compositions of the samples. From this, it can be concluded that the sample B4C + GNPs with surface modification has a 31% higher hardness than without surface modification.

Figure 6. Hardness values without and with surface modification.

3.3 Effect of surface modification on tensile strength

The impact of surface modification of Gr and B4C nanoparticles on the GFRP hybrid composite, as depicted in Figure 7, is significant. The strong filler/matrix interaction and effective particle dispersion result in an efficient stress regulator. Consequently, the addition of nanoparticles substantially enhances the tensile strength of the composite. As a result, the percentages of nanoparticles significantly enhance the stiffness of the composite. According to the findings, the composite sample comprising B4C + GNP particles exhibited a high tensile strength of 195.63 MPa when subjected to surface modification. Furthermore, this sample displayed a greater variance in tensile strength compared to other compositions. Starting with a composite sample containing B4C with GNPs, the initial tensile strength is 126.12 MPa, however, it decreases over time. The depicted diagram demonstrates that the tensile strength of the specimen is increased by more than 35% through surface modification, as compared to the specimen without surface modification.

Figure 7. Tensile strength with and without surface modification.

4. Conclusion

Based on the results and discussion, it can be concluded that

• The production of nano-sized B₄C particles from commercially available (10-μm) boron carbide was successful. The particle size steadily declined and achieved a minimum size after 30 h of milling.

• The stability of the particles is uniform, as showcased in the absorbance, i.e., if the wavelength of incident light increases, the absorbance in the respective substance reaches its maximum value and then decreases.

• Mechanical properties like tensile strength and hardness increased tremendously at a greater rate when subjected to surface modification.

Authors contribution

VJK—data collection, experimentation, manuscript writing. VVSP—data collection and experimentation. VS—conceptualization, design, experimentation, and manuscript writing. SB—methodology and feedback. SKS—critical feedback and manuscript review. AKS—data interpretation and manuscript review. MG—data visualization, critical feedback, and manuscript review. SSA—data analysis and manuscript review.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article. Raw data that support the findings of this study are available from the corresponding author V. Srinivas upon reasonable request.