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Influence of Water Ageing on Mechanical Properties of CaCO3 Filler Filled Epoxy Resin and Sansevieria/Carbon Fiber Reinforced Composites

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DOI: 10.4236/ojcm.2019.91001    271 Downloads   441 Views  

ABSTRACT

The present paper studies water absorption behavior and its consequence on mechanical properties of untreated and chemically treated Sansevieria /carbon fiber reinforced hybrid epoxy (Sria/CF-Ep) composite with calcium carbonate (CaCO3) nanoparticles. Sansevieria /carbon fiber (30/5 wt%) reinforced hybrid epoxy composite with 1.5, 3 and 4.5 wt% of CaCO3 have been developed by hand lay-up method followed by heat press. The water absorption characteristics of the Sria fibers were obtained by immersing the composite samples in sea water at room temperature, until reaching their water content saturation level. The dry and water-immersed hybrid composite samples were subjected to hardness, interlaminar shear, tensile, flexural, and impact tests. The water absorption development of hybrid composites was found to follow Fickian diffusion behavior. Diffusion coefficients and maximum water uptake results were evaluated; the outcome showed that both increased with an increase in filler loading to study the consequence of water penetration in the fiber/matrix interface. The study shows that the mechanical and water-resistant properties of the Sria were improved through chemical treatment and hybridization. Nevertheless, as a result of water penetrating the fiber/matrix interface, longer water-immersion times reduced the tensile and flexural strength of the composites.

1. Introduction

The environmental awareness in addition to the government stringent rules throughout the globe has encouraged the scholarly and industrial researches to expand eco-friendly, sustainable, and biodegradable composite materials, as a result often referred to as green composites [1] . The habit of utilizing fiber reinforced polymer composites has considerably increased since last 3 decades, by glass fiber reinforced composites taking on a significant role [2] [3] . The development of glass fiber reinforced polymer composite materials and their extensive application has caused a number of ecological problems, predominantly with regards to waste management [4] . Renewable and biodegradable materials are substitute to synthetic fibers and polymers derived from petroleum used in traditional fiber reinforced polymer composites [5] [6] . The use of natural plant fibers (kenaf, jute, hemp, flax etc.) as reinforcement in matrix with little styrene substance and emissions represents a suitable explanation to this problem [7] [8] . Previous research works has shown that natural fibers have the potential to substitute glass fibers in various applications [9] . Because, natural fibers have high strength to weight ratio, abundant in nature and biodegradability, corrosion resistance, are critical at the end of life of products, and have similar specific strength and modulus as conventional glass fibers.

Areas such as automotive and construction [10] have started the manufacturing of pipelines for water desalination plants, water storage vessels, manufacture of leisure boats etc., goods using natural fiber, to develop the environmental impact of the product due to the reasonably priced of natural reinforcements. Alone natural fiber reinforced polymer composite cannot be used as promising material in mechanical applications, hence, synthetic fibers such as aramid, glass, carbon etc., can be used as reinforcements along with natural fiber to form strengthened hybrid composites. Hybridization is a technique in composites which is usually termed as the mixture of two or more reinforcing fibers in a single matrix system. Throughout proper fiber choice and plan, the stability involving price and performance of hybrid composites might be achieved all the way through hybridization [11] . For example, the integration of carbon fiber with different cellulosic fibers such as jute, abaca, hemp, and banana have been reported earlier in the literature [12] [13] [14] [15] . Experimental results show the mechanical properties of the hybrid composites being better compared to the single-fiber reinforced composites. Previously published works concerning synthetic/natural [16] and cellulosic/cellulosic [17] [18] [19] fibers based on reinforced hybrid composites. In addition, the performance of a hybrid kenaf/Kevlar composite was tested by Yahaya et al. [20] [21] discovered that the composite had the potential to be used in impact applications.

Plant fiber reinforced composites are hydrophilic and hygroscopic materials. Moisture content in plant fiber composites considerably affects their physical and mechanical properties. Moisture transfer in plant and plant fiber composites influences dimensional steadiness, viscoelastic properties, fiber play a vital role in the ageing of bio-composites in a wet atmosphere or by immersion in water and durability. These parameters lead to a lowered fiber/matrix bonding strength those results in a weaker mechanical performance of fiber/matrix hybrid composites [22] [23] [24] . Akil et al. [25] investigated that when jute/glass fibred reinforced polyester hybrid composites were exposed to moisture environments, water molecules penetrated the composites during various paths, such as: throughout the flaws at the composites interphase attributed to the poor wettability between the fiber and matrix, through micro-gaps between the polymer chains, and through the cracks in the polymer matrix induced by the fiber swelling.

Less than the fiber saturation point, moisture transport by the plant fiber is restricted by diffusion. Bounce moisture diffusion is a grouping of two movements: the vapor diffusion by void structure, and the bound water diffusion by the cell wall. A diffusion model based on Fick’s second law has been created to describe corresponding mass transfer process. The transfer of water molecules by the micro cracks that can appear in the matrix as a result of the fiber swelling. According to this mechanism, there are three cases of diffusion behaviour [26] [27] known as Fickian diffusion model, anomalous or non-Fickian, and an intermediate case between Fickian and non-Fickian.

Moisture absorption is a big hurdle in the growth to utilize natural fibers in composites because the mechanical properties of composites degrade and reduce in wet conditions. The opportunity for using these fresh materials in outdoor applications requires complete study and to evaluate their mechanical characteristic in a violent environment, mainly in a moisture environment, during a long time. In addition synthetic fibers like glass (GF) or carbon fibers (CF), short aramid fibers (AF) are adopted to intensify the compressive strength and the creep resistance of the polymer matrix composites [28] . Accumulation of fibers is to make sure the strength of the material while the matrix helps to retain the shape of the composite. Still synthetic fibers extended exposure of carbon/polyester and carbon /vinyl ester composites to seawater was observed to reason for degradation in flexural strength and modulus [29] . Lessening in fracture toughness by 30% has been listed in carbon/vinyl ester composites due to constant exposure to sea water [30] . To prevail over the hydrophilic character of natural fibers many literature have shown that the degradation of mechanical properties of plant fibers with water uptake can be reduced by the use of fiber treatment and chemical surface treatment to make the composite durable [31] .

Toughness is the ability of a material to sustain its original mechanical, thermal, physical and chemical properties for several years. For oceanic application, composites are estimated to be robust and not to be degraded in seawater for extended age of time. Owing to the viscoelastic behavior of polymeric matrix, composites exhibit time-dependant degradation in modulus and strength [32] . Alone fibers and matrix cannot withstand against sea water ageing so a little quantity of nanofillers can develop the composite properties significantly [33] . The high aspect ratio of nanoparticles produces a huge amount of surface area, which facilitates a better interaction between matrix and fiber as well as reduces the polymer chain mobility [34] . In the direction of obtaining superior mechanical properties whole exfoliation and homogeneous dispersion of nanofillers is significant.

Selection of resin is also very important parameter for designing a FRP for marine applications so epoxy resin is considered because it represents several of the highest performance resin due to the mechanical properties and resistance to environmental degradation, which leads to their almost exclusive use in aircraft components, marine application etc. Epoxies are distinct as cross-linked polymers which have cross-linking derived from chain reactions of the epoxy group. Epoxy resin typically used in coating industry as surface coating materials that combine flexibility, toughness, adhesion, and chemical resistance [35] . In count, epoxy resin also can be utilized in both laminating and molding techniques to build fiber reinforcement with better mechanical strength, chemical resistance and electrical insulating properties [36] . Epoxy resin used with reinforcing fibers for superior composites application. This is due to the ability of epoxy resin that showed superior adhesion to the embedded fiber [37] . Furthermore, epoxy resin absorbs high degree of water content which in order degrades the functional, structural and mechanical properties of the composites [38] .

Glass/polyurethane and glass/epoxy are amongst various materials suggested for use in marine infrastructure. Many researchers have investigated the consequences of moisture on glass/epoxy composites [39] [40] [41] . Absorption of sea water in glass/epoxy composites has been observed to cause changes in the mechanical, physical, and chemical characteristics of the epoxy matrix by hydrolysis and plasticization [42] [43] . Also, it has been noted that the decrease in mechanical properties and degree of damage depend on the immersion liquid. During normal working temperature, swelling and plasticization lead to relaxation of curing stresses thus compensating for any interfacial degradation that might have been caused by moisture. Koutsoubos et al. Identified that glass fibers coated with an emulsion-based size and carbon fibers are coated with epoxy-based size [29] . This showed emulsion-based size leads to absorb water at humid environment [44] for that reason; glass fiber-based composites have a more chance to debond at the fiber matrix interfacial region. The quantity of water absorption depends on the relative humidity of the environment. Moisture absorption by carbon fiber is negligible, that does not reduce carbon fiber properties significantly [45] .

Carbon/epoxy composites are appropriate for light weight structures and may be a healthier substitute to other materials presently in use in oceanic applications. Although there have been a number of work on the mechanical behavior of carbon/epoxy composites, to the best of our understanding, no studies have been reported in the literature on the effects of sea water on mechanical properties of nano-sized CaCO3 filled Sria/carbon fiber epoxy composites. The objective of this study is to investigate the effects of sea water on the mechanical properties of CaCO3 filled Sria/CF-Ep composites.

2. Materials and Methods

2.1. Materials

In the present investigation unidirectional sansevieria (Sria) plant fiber which was collected from farm near Annur, Tamil Nadu, India, using a mechanical procedure called decortication. The extracted plant fibers are weaved in mat form such that all fibers are oriented unidirectional. Unidirectional carbon fibers (CFs) woven was collected from Master Micron International, Bengaluru, India. Nanofillers like calcium carbonate (CaCO3) were obtained from Global nanotech, Kolkata, India. Epoxy (Lapox-12, K6 hardener) resin was purchased from Yuje Enterprises, Bengaluru, India.

2.2. Chemical Treatment of Sansevieria Fiber

The sansevieria (Sria) fibers were drenched in a glass tray containing 4.5% NaOH solution for 1 h. After that the fibers were washed carefully with distilled water in order to get rid of the excess NaOH content in the fibers [46] . Last washing was completed in water containing acetic acid. Fibers were dried in room temperature for 6 h and in hot air circulated at 60˚C for 2 h. later, the NaOH treated Sria fibers were subjected to potassium permanganate treatment. The Sria fibers were drenched in 0.05% potassium permanganate in acetone for 45 min [47] [48] [49] . The fibers were then decanted and dried in open air for 24 h and in hot air circulated at 60˚C for 2 h.

2.3. Preparation of Composite Slabs

The composite materials used for the existing investigation is fabricated by way of hand layup process. Sria fiber unidirectional woven mat of 300 mm × 300 mm size and unidirectional woven carbon fibers were used to put together the final slabs. The chemically handled Sria fiber mats were stored beneath daylight for 6 h and in addition dried in hot air oven for 2 h to get rid of the dampness content in the fibers. The composite slab consists of whole three layers in which carbon fibers layers are positioned at the top and backside of Sria mat. The layers of fibers are fabricated through smearing the required quantity of epoxy and hardener mix over the stacked mats and two rollers are used to trick all the air bubbles. During fabrication, the fiber orientation and alignment in the composites is maintained via two metal rollers that are always rolled on the fiber in the die. The procedure is repeated for preparation of nano-hybrid composites by way of mixing CaCO3 nanofiller with epoxy with special wt.%. Finally these stacked composite slabs are taken to the hydraulic press for curing and the period of cure is maintained for about 24 h (final size after cure: 300 × 300 × 4.5 mm3). Table 1 listing the quite a number of composites organized for the existing work.

Table 1. Designation and composition of Sria based hybrid epoxy composites.

Sria―Sansevieria Fiber, CF―Carbon Fiber, Ep―Epoxy.

2.4. Moisture Absorption Test

Water absorption tests were conducted as per ASTM D570 [50] . Initially, the specimens were flooded in a vessel filled with sea water; composite samples were immersed in a water bath until it reached saturation point. Afterward, to check the mass throughout the ageing process, the specimens were removed from the water with a gap of 24 h on regular basis, wiped dry to get rid of any surface moisture, after that weighted using a high accuracy analytical balance. For each type of composite, four specimens were tested, and then the average result was recorded. The moisture content percentage, ΔM(t), was calculated using the following equation:

Δ M ( t ) = M t M o M o × 100 (1)

MO and Mt symbolize the mass of the dry and immersed sample, at exact time. The moisture absorption percentage was plotted against the square root of time (hours). The effects of ageing on the hardness, Interlaminar shear strength, tensile, and flexural properties of the woven composites were investigated after 792 h (at saturation).

Several linear Fickian diffusion processes for composites were listed [51] [52] . As per the developed model the diffusion coefficient; D is defined as the ability of water molecules to enter through laminate composites. It is computed from the slope of moisture content versus the square root of time by:

D = π ( h 4 M ) 2 ( M 2 M 1 t 2 t 1 ) 2 (2)

where, M is the percent moisture absorbed at saturation, h is the specimen thickness; M 2 M 1 is the slope of the plot of the moisture absorption rate during the first ageing time and t 2 t 1 is the linear portion of the curve. Assuming the absorption process is linear at an early stage of immersion; times are taken at the beginning of absorption process, so that the weight change is expected to vary linearly with the square root of time.

3. Characterization

3.1. Hardness

The hardness of Sria/Ep (S1) primarily based hybrid nanocomposites was decided in accordance to ASTM D2583 standard [53] using a Barcol hardness tester. Test specimens have been used to measure the hardness of all the composite slabs prepared. The test specimens had been held firmly in position and load was applied manually by using hand. Ten indentations on every coupon at specific points were used and the mean value for each of the tested coupons used to be viewed for the investigation.

3.2. Interlaminar Shear Strength

The Interlaminar shear strength (ILSS) of the Sria/Ep primarily based hybrid nanocomposites was measured using a Universal Testing Machine (Kalpak Instruments & Control, K TEST Series, 100 kN), based on the ASTM D2344 [54] . The rectangular formed coupon was 35 × 12.5 × 4.5 mm3 and cross head speed was 0.5 mm/min. Each coupon measured for five instances have been averaged.

3.3. Tensile and Flexural Tests Sria/Ep Based Nanocomposites

The tensile tests for Sria/Ep primarily based nanocomposites had been carried out using Universal Testing Machine (Kalpak Instruments & Control, K TEST Series, 100 kN) at a cross head speed of 5 mm/min, using 4 coupons for every measurement. An extensometer with gauge length 50 mm was once used for the elongation measurements, at room temperature as per ASTM D-638 [55] . Flexural tests have been performed in the three-point bend-mode using the identical Universal Testing Machine as per ASTM D790 [56] . The effective length and cross head speed have been 60 mm and 1.5 mm/min, respectively.

3.4. Impact Testing

Izod impact test has been performed under ASTMD256 standard [57] on specimens of dimensions 64 × 12 × 4.5 mm3 using a 2.7 J pendulum at a striking velocity of 3.46 m/s. The minimum of 5 samples was once examined and the average value was used for analysis.

3.5. Scanning Electron Microscopy Observations

Fracture surfaces obtained from tensile assessments have been examined via Scanning Electron Microscopy (SEM) using JSM-7900F equipment. Prior to SEM observation, all tensile broken coupons were sputter coated with a skinny layer of gold to keep away from electric charging.

4. Results and Discussion

4.1. Water Absorption Behaviour

Water absorption of Sria/CF-Ep composites with varying percentage of CaCO3 are shown in Figure 1 with weight gain percentage as a function of the square root of time for various sample composites. From the graph it can observed that increasing in immersion time had increased the amount of water uptake by composite. In the early stage both unfilled and filled composites had significantly

Figure 1. Water absorption curves of various woven composites.

increase in water absorption and after a certain time all composites start to reduce the water uptakes from the surrounding till it reach saturation point. Saturation point is where composite absorb no more water and the water content in composite remained constant. Related work was highlighted in earlier works where the water absorption effects of natural fiber reinforced polymer composites were investigated [24] [58] [59] . Moisture uptake route of the woven composites was linear at the start, demonstrating the rapid moisture diffusion into the composite materials. Moisture uptake then slowed down and approached saturation following an extended time period. The moisture uptake is pursuing Fickian behaviour. Cellulose which is present in the order of 79.9% is a major constituent of Sria fiber, potassium permanganate treatment can alter the crystalline structure of the cellulose and thus able to restrict water absorption to a certain extent [60] . Epoxy in addition serves as a binder for reinforcement and helping to transfer the load to the fibers, also protects the fibers from harsh environments [61] .

On the other hand, while the composites are constantly exposed to water, the brittle thermosetting resin will experience micro cracking due to the swelling behaviour of the fibers. Cellulose content in the Sria fibers additional supports to more water penetrating into the fiber-matrix interphase developing stress concentration leading to failure of the composite. While, more micro cracks were found in coupons and water transport through these micro cracks [62] . The water molecules flow inside the capillary cracks and constantly assault the interface, ensuing in debonding of the fiber from the matrix. This explanation is supported by the SEM picture as shown in Figure 2.

Furthermore, the addition of nanofiller CaCO3 in composites had increased the moisture absorption rate. This might be due to the properties of the CaCO3 that have high tendency to agglomerate. It is well recognized that the smaller the

Figure 2. Matrix cracking of an immersed sample due to attacks by the water molecules (50× Magnification).

size of particle the more easily the particle to agglomerate. This agglomeration would have damaged the interfacial adhesion between the filler and matrix which therefore lead to variation in the formation of gap in interfacial region. Raising the gap in interfacial region could increase the amount of water molecules to penetrate into composite and the being trapped inside the gap.

From literature, it is understood that filler had superior tendency to produce agglomerate. Results showed that the water absorption of Sria/CF-Ep composite was increasing with addition of CaCO3 filler loading. This could be due to the higher cellulose in Sria fiber, When CaCO3 introduced in the composite; the presence of high amount of agglomeration had increased the gap in interfacial between the filler and matrix therefore increasing the water absorption of the composite. Nevertheless, the amount of cellulose in Sria fiber given more impact for water absorption properties compared to the gap appears between the filler and matrix in all filled composites. Sria fiber had the ability to absorb water due to the high cellulose content which formed high hydrogen bonding from its hydroxyl group and water molecules.

Even though CaCO3 have hydrophilic sites and polar, it may not be as fine as the cellulosic fibers of the Sria do attract water content. Also, the Sria fiber used in this study was potassium permanganate treated. Therefore, the possibility to absorb water molecule are minimal, predictable to be brought about by Sria fiber compare to CaCO3 filler loading in the hybrid composite.

4.2. Effect of Water Absorption on the Mechanical Properties

4.2.1. Hardness

Figure 3 suggests the measured hardness of all the prepared Sria composite samples. It can be viewed that the hardness of dry S2 composite will increase from 46 to 52 (Barcol hardness number) when it is stuffed with 4.5 wt % CaCO3. Similarly the hardness of water absorbed samples decreased in comparison with

Figure 3. Hardness (Barcol) of Sria based hybrid nanocomposites.

dry samples. This could additionally be credited to degree of cure of the epoxy resin, consistent dispersion and higher interfacial bonding between the CaCO3 particles in the epoxy resin. In the same way, the hardness improved for composites containing CaCO3 and their hybrid sample composites.

4.2.2. Interlaminar Shear Strength

The interlaminar shear strength (ILSS) consequences of CaCO3 crammed S2 hybrid composites are proven in Figure 4. The outcomes exhibit that the ILSS of the S2 composites has multiplied with the loading of CaCO3 nanoparticles. The outcomes confirmed similarities to studies in the literature. The experimental data acquired by He and Co-workers [63] [64] validated that the ILSS of CF/Ep layered composites can be multiplied up to 36% with the aid of 4 wt.% CaCO3 nanofiller loading. In the current experimental work, the most massive enhancement of 55.7% has been proven through 4.5 wt.% CaCO3 in S2 as in contrast to all unique composites studied. The most massive improvement of 55.7% has been proven through 4.5 wt.% CaCO3 in S2 as in contrast to all different composites studied.

This enhancement in ILSS can be credited to the uniform dispersion of CaCO3 inside the epoxy matrix, which helps in growing the bonding between the fibers and higher transfer of stress. Correspondingly the water absorbed samples ILSS decreased when compared to the same dry samples this may be attributed to the water absorption behaviour of Sria fiber and CaCO3.

4.2.3. Influence of Water Ageing on Tensile Properties of Sria/CF-Ep Based Nanocomposites

The results of the tensile properties obtained for S1, S2, and their composites are shown in Figure 5. Higher aspect ratio or unidirectional fiber as reinforcing agents provides long fiber composites with increased strength. This interprets the capability to resist creep or deformation under loads and fatigue endurance

Figure 4. Interlaminar shear strength of the dry and water absorbed Sria/CF-Ep hybrid nanocomposites.

Figure 5. Tensile strength of the dry and water absorbed nano-CaCO3 filled Sria/CF-Ep hybrid composites.

with minimum compression. Increased fiber outside region provides the ductile polymer with more capability in order to capture and transfer stress to the fiber. Further, the composite strength is considerably influenced by the orientation of reinforcing fibers within the epoxy matrix.

Figure 5 shows the tensile properties of S1, S2, and CaCO3 filled hybrid (S3 to S5) nano composites. The tensile strength of Sria based composites were notably improved with the reinforcements of CF and CaCO3 nanofiller. Under tensile loading, observed increase in tensile strength and Young’s modulus could be due the improved adhesion at CF/Sria fiber?epoxy matrix interface and along with the uniform dispersion and better adhesion CaCO3 filler ensuing in an capable load transfer from the matrix to the filler and reinforcement. The surface modification by potassium permanganate allows it to respond with the Sria fiber surface, their by forming a bridge of chemical bonds between the fiber and matrix in the hybrid composites.

For S2 composite filled with different wt.% of nano CaCO3, the tensile strength increased from 145 MPa to 240 MPa. The tensile moduli of 1.5, 3.0 and 4.5 wt.% nano CaCO3 filled hybrid composites are 39%, 61% and 67% higher than that of S2 (1.41 GPa), respectively (Figure 5). These results were regular with the general examination that the introduction of high strength carbon fiber and nano-sized CaCO3 particles into epoxy matrix increases the tensile properties. The improvement was reasonable because of the carbon fiber in S1 can carry more tensile load. In addition, the CF has high strength and stiffness when compared to the Sria fibers and the epoxy matrix, which adds stiffness to the mono-composites (S1). This data corresponded with that in the literature [65] [66] [67] . Figure 6 shows SEM Picture of water absorbed S5 sample after tensile test it shows due to complete absorption of water the diameter of sria fibers was increased leading to cracking of matrix.

4.2.4. Influence of Water Ageing on Flexural Properties of Sria/CF-Ep Based Nanocomposites

The flexural properties of S2 and their nanofillers stuffed hybrid composite are illustrated in Figure 7. As the CaCO3 loading increased, the flexural strength of the S2 improved. The CaCO3 containing composite systems (S3, S4 and S5) exhibited an extra rigid structure than the composite systems that did not contain CaCO3. The increase in the flexural modulus of the S2 used to be higher than the increase in the flexural strength. For example, the flexural modulus of the S2 with 4.5 wt.% CaCO3 accelerated by means of 261%, whilst the flexural strength improved by 21%. The flexural modulus of the S2 was once notably affected by the quantity of CaCO3. Figure 7 also indicates that the maximum flexural strength was 319.36 MPa in the CaCO3 containing 4.5 wt.% CaCO3. Similarly,

Figure 6. SEM Picture of water absorbed S5 sample after Tensile test (50× Magnification).

Figure 7. Flexural strength of the dry and water absorbed nano CaCO3 filled Sria/CF-Ep hybrid composites.

the minimal flexural strength was 263.22 MPa in the control group without CaCO3 (S2).

The flexural strength improved as the CaCO3 quantity in the hybrid nanocomposite system increased. This was attributed to the top compatibility between the CaCO3, carbon/chemically treated Sria fibers, and epoxy matrix. The outcomes confirmed similarities to research in the literature [2] [32] [64] [65] . Rong et al. [65] investigated the impact of fiber remedy on the mechanical properties of unidirectional sisal-fiber strengthened epoxy composites. However, the flexural strength and flexural modulus values of the epoxy composite multiplied due to the fact that of an increase in the alkali treated sisal fibers. This can be explained with the aid of the desirable interfacial adhesion between fiber and epoxy matrix. Reis [68] found that coconut fiber reinforcement displays a marginal increase in the flexural strength of epoxy polymer concrete in contrast to unfilled and artificial fiber bolstered materials. Yan et al. [69] investigated the impact of alkali therapy on mechanical properties of coir fiber bolstered epoxy composites. They observed that the flexural strength of treated coir fiber/epoxy composites used to be 17% greater than that of untreated coir/epoxy composites. The alkali remedy appreciably improved the flexural strength of composites. In the current work, the flexural strength of CaCO3 stuffed S2 hybrid nanocomposite will increase with increasing filler wt.% likely due to the uniform dispersion of nanoparticles, higher filler-matrix interface, chemical bonding at the interface between fiber and matrix might also be too robust to switch strength. The flexural strength of CaCO3 stuffed S2 hybrid nanocomposites (Figure 7). The viable motive is that although these samples are damaged when the most stresses was once reached. The enhancement of flexural properties of CaCO3 stuffed S2 hybrid nanocomposites is possibly due to the elimination of outer fiber surface of Sria; increase of cellulose content and interfacial adhesion through potassium permanganate treatment. However, the outcomes show that the influence of chemical therapy on flexural properties is much less than that on the tensile properties. The viable reason is that the flexural failure mode indicates much less fiber pull-out, as a consequence of the direction of the applied stress being perpendicular to the composite coupon in the three-point bending test. Flexural failure in fiber strengthened PMCs is characterized by means of the presence of compressive and tensile stresses. The deflection of 1.5, 3.0 and 4.5 wt.% nano-CaCO3 crammed hybrid composites are 1.99 mm, 2.36 mm and 2.58 mm which are greater than that of S2 (0.97 mm), respectively. According to the results, the mechanical properties of the Sria/CF-Ep composites accelerated primarily based on an increased loading of CaCO3 nanoparticles. The researchers attributed this increase to the excessive slenderness ratio of fibers and extensive surface area of the nanoparticles.

4.2.5. Impact Testing

The outcomes of the impact strength testing of S1, S2, and their nano-CaCO3 stuffed hybrid composites (S3 to S5) is proven in Figure 8. The test results confirmed that the impact strength of the S2 composites improved with increase in CaCO3 nanoparticles.

The most increase of 67% has been confirmed with the aid of 4.5 wt.% CaCO3 crammed S2 hybrid composites. Fibers and fillers play a vital role in enhancing the impact resistance of the material, which is related to the usual longevity of the material. With the increase of nanofiller loading, the interfacial adhesion between fiber, epoxy resin, and nanofiller increase, which assist in higher load transfer and promotes stress switch from fiber and filler to the matrix. Furthermore, the cause for this behaviour was the large amount of nanoparticles of the CaCO3/Sria/CF phase and their appropriate dispersion in the epoxy matrix inflicting an extended transfer of impact energy to the fiber and filler phase. This

Figure 8. Impact strength of the dry and water absorbed nano CaCO3 filled Sria/CF-Ep hybrid composites.

implies that stronger interfacial interplay between chemically dealt Sria fiber/ carbon fiber phase and CaCO3 phase improved the impact strength of the epoxy.

5. Conclusions

The mechanical properties of fabricated Sria/Ep, Sria/CF-Ep and their nano-CaCO3 stuffed hybrid composites are evaluated. The following conclusions have been derived from the experimental investigations.

・ Sansevieria fibers can be efficaciously modified by way of bodily and chemical treatments. Potassium permanganate treated sansevieria fibers brings about an active surface by means of introducing some reactive groups and grant the fibers with larger extensibility via partial elimination of lignin and hemicellulose.

・ The profitable fabrication of Sria/EP and Sria/CF-Ep composites with different share (0 to 4.5 wt %) of nano-CaCO3 filler loading can be accomplished via easy by simple hand lay up procedure accompanied by heat press.

・ The hardness and interlaminar shear strength test outcomes confirmed that the Sria/CF-Ep composite with nano-CaCO3 improved properties when compared to water absorbed Sria/Ep and Sria/CF-Ep hybrid composites. The dry composite Sria/CF-Ep with 4.5 wt.% nano-CaCO3 (S5) sequence presented the best interlaminar shear strength.

・ The tensile and flexural properties of mono-composite (Sria/-Ep, S1) multiplied with small weight share of carbon fibers (5 wt.%) and an increased quantity of nano-CaCO3 filler. The greater values may perhaps due to the fact of good dispersion of nano-CaCO3 particles in the epoxy matrix material. Also showed the decreasing trend with the water absorption for the same samples.

・ The notched Izod have an effect on tests confirmed an increase in the impact energy of both Sria/CF and CF with varied CaCO3 coupons (S2 to S5) as in contrast to the mono-composite (Sria/Ep, S1). The highest impact strength of 643 J/m used to be bought for 4.5 wt.% CaCO3 nanoparticles stuffed Sria/ CF-Ep as compared to mono-composites. These outcomes suggest that the used nano-modifier in the hybrid fiber bolstered epoxy matrix introduced a proper compatibility with each carbon/chemically treated Sria fiber, with the benefit of increasing the mechanical properties of the epoxy matrix material.

Declaration of Conflicting Interests

We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no financial support for this work that could have prejudiced its outcome.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

Cite this paper

Anjum, N. , Suresha, B. and Prasad, S. (2019) Influence of Water Ageing on Mechanical Properties of CaCO3 Filler Filled Epoxy Resin and Sansevieria/Carbon Fiber Reinforced Composites. Open Journal of Composite Materials, 9, 1-20. doi: 10.4236/ojcm.2019.91001.

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