Comparative Study of the Mechanical and Water Absorption Behaviour of Basalt Fiber Reinforced Polymer Matrix Composites with Different Epoxies as Matrix for Biomedical Applications

Department of Mechanical Engineering, Malnad College of Engineering, (Affiliated to Visvesvaraya Technological University, Belagavi), Hassan, Karnataka, India Mechanical Engineering Department, Mettu University, Mettu Oromia, P.O. Box 318, Ethiopia Department of Mechanical Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61421, Saudi Arabia Mechanical Engineering Dept., Faculty of Engineering, Kafrelsheikh University, Kafr el-Sheikh, Egypt Department of Mechanical Engineering, P. A. College of Engineering, Mangalore (Affiliated to Visvesvaraya Technological University, Belagavi 574153, Karnataka, India Department of Mechanical Engineering, School of Technology, Glocal University, Delhi-Yamunotri Marg, SH-57, Mirzapur Pole, Saharanpur District, Uttar Pradesh–247121, India Mechanical Engineering Department, College of Engineering, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia


Introduction
Polymer matrix composites offer a wide range of uses due to its superior strength-to-weight ratio, corrosion resistance, less weight, adaptability, shape ability, and suitability for a variety of technical applications. Although polymer matrix composites (PMCs) were first used in the early twentieth century, they were only widely used in the second half of the century. Basalt is a clean and environmentally benign substance that originates from volcanic rocks and has a melting temperature of 1500°C to 1700°C [1,2]. e density of basalt fibers ranges between 2.7 g/cc and 2.8 g/cc. It is extremely hard compared with some conventional materials and has higher abrasion resistance [3]. It is stated that the basalt fiber could be a possible alternative compared with natural plant fibers [4]. Czigany [5] proved that the basalt could be considered as natural fiber. It is chemically inert and could be a major breakthrough as bio material. Dhand et al. [6] have considered that despite their severe mechanical qualities, basalt fiber resources are widely available around the world. ey could be manufactured using a low-energy process at a lower cost than glass and, more specifically, carbon strands. ey are created by spinning liquid volcanic basalt rock through a spinning cycle. is cycle is similar to that of making glass strands. However, in case of the basalt, no additional substances are required.
ey have concluded that the inclusion of UHMWPE fibers has increased the flexural strength considerably. Fiore et al. [12] investigated the effect of uniaxial basalt fiber on the mechanical properties of a glass fiber/epoxy composite (GFRP) intended for marine use. e presence of two outer layers of basalt in comparison to GFRP laminates has resulted in improved mechanical properties of the fabricated laminates. Lilli et al. [13] studied the effect of low temperature plasma polymerization on the interfacial behaviour of basalt fiber reinforced polymer matrix composites. A polymer coating based on pure tetra vinyl silane (TVS) or its combination with two different oxygen levels was deposited on the surface of an unsized basalt fiber using plasma-assisted chemical vapour deposition. e impact of the plasma procedure was initially investigated using a single fiber tensile test characterization, which revealed that the changed fibers had no loss of strength. Following that interfacial strength was investigated using single fiber pullout tests with an epoxy matrix. When compared with untreated basalt fibers, the addition of oxygen to the polymer film combination has shown increased interfacial shear strength (IFSS) by 79%. Many studies have previously concentrated on improving the interface for synthetic fibers, particularly glass and carbon fibers, while basalt fibers have received less attention. Goudar Santosh Gangappa and S. Sripad Kulkarni [14] have experimented and validated basalt and jute fiber reinforced hybrid polymer matrix composites. Polymer hybrid composites are created using compression moulding techniques, with polyester resin as the matrix and basalt and jute as reinforcement.
e static and dynamic behaviours are studied. It is revealed that the hybrid laminates had better damping ratio and hence could be used as vibration absorbing materials. Xing Zhao et al. [15] investigated the effect of different resin matrices on static and fatigue loading conditions in basalt fiber reinforced polymer composites. Four different types of resins were used in their study. Normal and toughened vinyl ester resins, as well as room and elevated temperature curing epoxy systems, were used. e scanning electron microscopy (SEM) system embedded in the fatigue test equipment was used to perform fractography of failed surfaces in parallel with the static and fatigue tests. e static tensile strength of the BFRP with normal vinyl ester resin was comparable with that of the BFRP with elevated temperature cured epoxy, according to the results. However, due to more matrix cracking and fiber peeling on the surface of the vinyl ester resin-based BFRP, the former had a significantly shorter fatigue life than the latter. However, the former had a significantly shorter fatigue life than the latter due to more matrix cracking and fiber peeling on the surface of the vinyl ester resin-based BFRP. Siwon Yu et al. [16] have studied the effect of plasma polymerization to improve the interfacial bonding strength and hence its effect on the mechanical properties of the developed BFRP. e former had exhibited significantly shorter fatigue life than the latter due to more matrix cracking and fiber peeling on the surface of the vinyl ester resin-based BFRP. However, due to more matrix cracking and fiber peeling on the surface of the vinyl ester resin-based BFRP, the former had a significantly shorter fatigue life than the latter. e results showed that APTES plasma-polymerized BF produced a robust interface with a 50.3 percent increase in interfacial shear strength and a 32.5 percent increase in tensile strength when compared with untreated BF. On the BF surface, the APTES was plasma polymerized for 3, 5, 7, and 9 minutes. e mechanism of reaction during plasma polymerization was investigated and compared with a traditional solution dipping method. 16

Materials.
Reinforcement used in the present investigation is basalt plain-woven fabric of 300 GSM. Details of fabrics are illustrated in Table 1. e epoxy resin and hardener combinations used are shown in Table 2.

Fabrication of Composites.
Hand lay-up approach was used for the fabrication of laminates. First, the basalt fabrics were cut to the dimensions of 300 × 300 mm 2 . en, laminates are prepared using 10 layers of fabric to maintain approximate thickness of 3 mm for different epoxy-hardener combinations as indicated in Table 2. e epoxy resin and hardener were mixed in the ratio of 100 : 10 by weight. First, wax was applied over the top of a mould, and then the fabric layers were laid one over another in the mould, simultaneously applying the measured quantity of epoxy on each layer of the fabrics. en, the epoxy was uniformly spread using roller. As soon as the last layer of fiber was properly rolled, the toughened glass slab of required size was kept on top of the mould. On the top of the glass slab, dead weights are placed and sustained in that spot for 24 to 48 hours and then withdrawn. e laminates L1 and L2 are cured in oven for a temperature range of 60 to 80°C for 2 hours, but the laminate L3 is cured at the room temperature. en, the test samples were prepared using water jet machining as per the ASTM standards.

Density Test.
For a sample of 10 mm × 10 mm × 3 mm, the mass "m" is weighed on a precision weighing scale. e volume "V" of the sample is determined using the Archimedes principle. A 100 ml beaker is partially filled with distilled water. e initial water level "V 1 " is noted at lower level of the meniscus. e samples are then dipped one by one to determine the ultimate or final water level "V 2 ." e sample volume "V" is calculated by subtracting the initial water level "V 1 " from the final water level "V 2 ." erefore, V � V 2 − V 1 . en, the density of a material is calculated using the formula as follows: where "m" is the mass of the sample in grams and "V" is the volume of the sample in cm 3 .

Water Absorption Test.
According to the ASTM D570 standard, water absorption tests are performed for 24 and 48 hours duration. e initial weight "W 1 " of a sample size of 10 × 10 × 3 mm 3 is determined. en, it is steeped for 24 hours in distilled water inside a beaker. It is extracted after 24 hours, and its final weight "W 2 " is determined. e water absorption weight percentage is calculated using the formula as follows: water absorption weight % � By dipping the samples for 48 hours duration, the same procedure is repeated.

Tensile Test.
e tensile test was performed with data capture software on a BISS-50 kN capacity Universal Testing Machine (UTM). e sample (115 × 19 × 3 mm 3 ) was chosen according to the ASTM: D638-IV standard, with a gauge length of 33 mm and a crosshead speed of 1.0 mm/min, and the test was carried out at room temperature. e results obtained are used to plot the respective graphs.

Flexural Test.
3-point bending test is conducted as per the ASTM: D790 standard using the same UTM. Testing was conducted at loading rate of 2.0 mm/min, at room temperature. e dimension of the specimen is 90 × 12.5 × 3 mm 3 , and the flexural specimens were fixed between two jaws with a gauge length of 60 mm, and the load was applied at the center. Loading is applied to the specimen until it ruptures. e flexural strength and modulus are obtained with the help of data acquisition software.

Surface Morphology.
Fractured tensile specimens were examined for microstructure using TESCAN-VEGA 3 LMU scanning electron microscope. SEM was carried out to visualize the dispersion of fibers within the matrix and the adhesion characteristics amongst fiber and matrix. In order to enhance the conductivity of the samples, the surface of the sample was coated with a thin gold film and the micrographs were captured from the fractured samples for different magnifications. Figure 2 depicts the experimental values of densities for the prepared composite laminates. Minute difference in experimental densities was observed amongst of the laminates since they are only with varied epoxyhardener combinations but prepared for a constant fiber percentage of 55% as shown in Figure 2. e L3 laminate exhibited the maximum density of 1.78 g/cc, the L2 laminate exhibited the lowest density of 1.71 g/cc, and laminate L1 exhibited a density of 1.73 g/cc.  Figure 6 demonstrates the mode of failure and fiber pullout happening during the tensile test. As seen from Figures 6(a) and 6(b) for laminates L1 and L2, respectively, the fiber pullout is occurring inappropriately. e fabric layers are peeled out during tensile testing, which indicates that the fiber-matrix adhesions are very low. Figure 6(c) depicts the tensile tested sample for laminate L3, which clearly shows the good fiber-matrix adhesion characteristics and appropriate fiber breakage and pullout. e present research revealed that the ultimate tensile strength, tensile modulus, flexural strength, and flexural modulus were seen maximum for L3 laminate [21][22][23][24][25]. Also, least water absorption percentage is seen for L3 laminate.

Morphological Studies through SEM.
Microstructural studies were conducted to visualize the failure surfaces of the fabricated laminates subjected to tensile loading. e fracture in the tested samples takes place due to the application of uniaxial tensile loading. e void content, fiber-matrix adhesion, and pullout properties are analyzed using the SEM images. All the composite specimens were coated with gold before observing them through SEM. e fractured micrographs of various laminate designations L1, L2, and L3 are shown in Figures 10(a)-10(c), respectively. It is seen that the fiber filaments are almost completely covered with an epoxy system. It showed (Figures 10(a)-10(c)) fewer amounts of voids in the fractured samples of laminates except L3 laminate. Not much interfacial deboning, matrix cracking and delamination were observed in the case of L3 laminate. It is evident from Figures 10(a) and 10(b) that the presence of voids, matrix cracking, fiber pullouts, and delamination is predominant in the case of laminates L1 and L2. Comparatively, L3 laminates had lesser amount of voids and cracks than other laminates, which helped to get better

Conclusions
Effect of three different epoxy resins on the water absorption and mechanical properties of plain-woven basalt fiber reinforced polymer matrix composites was studied for 55 wt.%. e following conclusions were drawn based on the present experimental results: laminates showed better adhesion between fibers and matrix, appropriate fiber breakage, and pullout. Also, better mechanical properties and least water absorption are observed for laminate L3. So, it is suggested to go with the LY556-HY951 epoxy hardener combination as a matrix for the basalt fiber reinforced polymer composites. (vi) SEM analysis confirmed that the L3 composite laminates showed lesser voids, better adhesion between fibers and matrix, appropriate fiber breakage, and pullout. (vii) Good water absorption behaviour and mechanical strengths are seen which make the composite developed to be used for biomedical applications.

Data Availability
e data used to support this study are available upon request.

Conflicts of Interest
e authors declare that there are no conflicts of interest regarding the publication of this article.