Evaluation of Flexural Strength of Epoxy Resin Based hybrid Composites Reinforced with Jute, Banana and Flax Natural Fibers for Bio medical applications

 

Narendiranath Babu T^1*, Akash Kumar Singh¹, Anil Mandliya¹, Avneesh Singh¹, Rama Prabha D²

¹School of Mechanical Engineering, VIT University, Vellore, India.

²School of Electrical Engineering, VIT University, Vellore, India

 

ABSTRACT:

In recent days the concern for the environmental pollution and the prevention of non-renewable and non- biodegradable resources has promoted research in the field of green technologies, eco friendly, non polluting materials which can maximize energy and resource savings. In the present work Jute fibres reinforced with uniaxial glass fibres in epoxy matrix, alongside Banana fibres reinforced with biaxial glass fibres in epoxy matrix and Flax fibres reinforced with biaxial glass fibres in epoxy matrix was prepared and mechanical properties were evaluated and compared for two weight fractions, the samples were prepared by using the hand lay-up process and applying pressure at room temperature. The samples were subjected to flexural testing was performed on the samples to investigate the bending properties and to suggest a material which could compete with synthetic materials and still be easily disposed.From the results, it is easily evident that flax performs better than jute and banana for the flexural strength showing higher values for flexural strength and modulus and hence this fiber can be used for biomedical applications.

 

 

INTRODUCTION:

Presently the world is facing a tough time due to large amount of pollution, increasing levels of CO₂ emissions and as a result of which the environment is deteriorating. Hence natural fibre composites do play a suitable role here. Natural fibres are eco-friendly, renewable, possess good strength and stiffness; have good sound absorption capacity and excellent thermal properties. Authors [1] studied that removal of lignin, hemi cellulose by alkaline treatment resulted in a rougher surface, which in turn favored mechanical interlocking and bonding reaction due to the exposure of hydroxyl group in the matrix which in turn increased mechanical adhesion.Experts [2] found out that hardness of the composite increases with the increase in fiber loading.

 

The more the fiber volume fraction, higher the modulus of the composite and also did infer that higher the volume fraction of the fiber the impact transfer on the composite sample will be efficient Authors suggested that addition of jute increases the wear resistance of the composite sample and results in decreasing of the coefficient of friction values by 3.5-4.5% and a decrease in 65% of the value of specific wear rate. Compression moulding was used for the manufacture of the jute propylene composites [3]. He also concluded that the effect of the reinforcements was very little on the value of the coefficient of friction. It has been observed that the chemical resistance of jute fiber reinforced composite and the influence of void formation on the mechanical properties of the composite which proved better adhesion and mechanical properties of hybrid fibers [4]. It was also concluded that the jute fabric layer on the outer surfaces did hold maximum of the tensile strength while the oil palm core absorbed maximum of the stresses and in such a way Jute overlapping the EFB fibres were better than EFB overlapping Jute.

Authors found out that the presence of a coupling agent with the resin in the composite stimulated the adhesion in the interphase of the fiber and the matrix through chemical bonding [5]. The interphase even though it occupies a small volume of the composites still it greatly influences the mechanical properties and therefore chemical bonding around the interphase region greatly improved their properties.Authors [6] studied through experiments that in order to improve the mechanical properties of the composite hybrid reinforcement was used which involved hybridizing jute with glass fiber as a result the tensile strength of the composites increased, but there was no observable change in flexural strength or the impact energy and the composites with more of jute fibers absorbed more water than the one with high percentage of glass fibers. It is observed that treated banana fibers have a higher degree of adhesion and bonding ability with the hydrophobic resins, also that the percentage of weight loss is lower in the case of treated banana fibers when compared to untreated fibers and he concluded by stating that 60% epoxy with 40% of banana fibers have highest load bearing capacity.[7] He also observed via SEM analysis that chemically treated banana had good adhesion and better bonding and had a high crystalline index.

 

Authors [8] applied that the orientation of the banana fibers also affects their properties. Maximum increase in mechanical properties was observed in the case of plain woven banana fabric when compared with random orientated fibers. It was also observed that the strength of kenaffibre reinforced composites were better when compared to banana fibre hybrid composite. Irrespective of whatever the fibre was used plain woven fibre composites showed better properties than the twill woven fibre composites. The tensile strength of the composite is more when the fibres are oriented in longitudinal direction.Author [9] studied the vibrational behaviour of banana fiber reinforced composite, and observed that skin core type oriented treated fibers exhibited better properties when compared to skin eccentric type. Authors discussed and reviewed the friction and wear behavior of various natural fibers such as basalt fiber, banana fiber, etc.[10-17].

 

So, here in the project we are performing the comparative analysis to predict so as to which hybrid matrix would be suitable for which applications and also to study the influence of various parameters on the mechanical and tribological properties of the composite.

 

The major objectives of this research work are:

·        To study the influence of glass fibre hybridization with the natural fibres in the matrix. The increase is concentration of glass fibres in the hybrid composite would surely increase the density, tensile strength, impact energy stored in the sample but the real investigation is by how much, so the influence of glass fibre is to be studied.

·        To design a smart composite material which are highly competitive to synthetic materials in terms of wear and durability. Thereby improving the existing technologies and leading a good quality life in a clean environment.

·        To provide a composite that is green and does not deteriorate the environment. There are several legal rules and regulations on protecting the environment. The government of the country is also stressing on the need to safeguard the environment and hence the green composite greatly supports the stand.

·        To manufacture the composite material that is easily recyclable which would reduce wastage. The whole agenda of this thing is recycling the waste products into a product which can be used regularly. Just as Banana and Jute is a waste product but it can be used for automotive seating and noise isolation system.

·        To provide the best optimum material for the said application this could lead to material savings.

·        Reducing the cost incurred by people as in transportation and fuel cost. Designing natural fibre composites with the urge to reduce the overall weight of the automobile because natural fibres have high strength to weight ratio, which will in turn increase the mileage and reduce fuel consumption.

·        Incorporating composites in real life scenario like carbon fibre rackets, running shoes, furniture, cots and door panels, etc. could be easily replaced by natural fibre composites which do possess the desirable properties and are economical.

·        To study the influence of various properties influencing the wear rate like volume fraction of reinforcement, load, speed, sliding distance and to come out with the result so as to which factor dominates the wear rate.

·        To compare the best of the three hybrid composites for mechanical properties

 

Material composition:

Table 1 Weight concentration of different constituents in jute hybrid composite.

 

Table 2 Weight concentration of different constituents in flax hybrid composite.

 

Table 3 Weight concentration of different constituents in banana hybrid composite.

S No.	Banana fiber % (w/w)	Glass fiber % (w/w)	Epoxy resin % (w/w)
1	10	10	80
2	15	15	70

 

So for achieving this goal this paper was subdivided into 3 areas of interest:

(a)    Material Selection and Research

(b)   Fabrication

(c)    Testing & Analysis

 

Material Selection and Fabrication:

·        Firstly analysis on the type of matrix which will be incorporated i.e. thermosets or thermoplasts.

·        Then under thermosets which matrix to be used, there are several options available i.e. polyester resins, epoxy resins,etc. Epoxy is very widely used for polymer matrix composites and hence epoxy is taken into account.

·        Then accordingly selection of natural fibers is done on the basis of their properties, availability, cost and sustainability.

·        On the basis of the above factors 3 natural fibers were selected Jute, Banana and Flax.

·        Then the question of procurement of the fiber and the resin comes. Resin and glass fibers are purchased from a dealer in Chennai Shakti Glass Fibers, Jute and Flax fibers from local shops in Vellore and Banana fibers were purchased from Coimbatore.

 

Fabrication

·        For fabrication treatment of natural fibers with alkali was necessary hence 10% NaOH solution was purchased.

·        Purchasing releasing spray to prevent the resin from sticking to the mould.

·        Creation of the mould according to the sample dimensions, for the mechanical tests a rectangular slab was created and the samples were cut according to the dimensions from the slab

·        For the tribological testing double tube hot water pipe was purchased to make the samples.

 

Material Requirement:

The material required for this project is 3 different natural fibers: jute, banana and flax. Along with synthetic uniaxial glass fibers. The resin used is epoxy 556 and Araldite hardener ly 556. These materials are used for making the composite.

 

Sample preparation:

Firstly the natural fibers were treated with 10% NaOH solution which removes the lignin and hemicellulose layer on the fibers.The fibers are then dried in the sun and then washed with soft water then left to dry for a day.Then the fibers are compressed under a uniform load in order to give a uniform thickness.Then Epoxy and hardener are mixed in the ratio 10:1 and then mixed thoroughly to ensure that the mixture is well mixed. Then pouring time is allowed for 10 mins before a layer of mixture is applied in the mould. Then a layer of releasing agent is applied in the mould so that the sample could be easily removed from the mould.Then alternate layers of glass and natural fibers are applied in between the epoxy layers to ensure that a thickness of 4 mm is obtained. Then uniform load is applied on the sample so that the epoxy layer impregnates the fiber layers and a compact bonding is achieved. Then the sample is left to cure for 24 hrs in normal ambient conditions.Similarly samples are made for testing the tribological properties of the natural composites instead circular hot water pipes were used for moulding purpose.

 

Testing and Analysis:

·        List of all the equipments and set ups required for testing the samples and getting information about them.

·        Cutting the samples according to the dimensions and verifying it with the standards.

·        Analyzing the results and comparing it with the standard mathematical results obtained from theories.

 

Material Specifications:

Table 4 Sample numbers with their corresponding specifications.

S No.	Sample Number	Specifications
1	Jute20	10% Jute ,10% uniaxial glass fibers, 80% Epoxy
2	Jute30	15% Jute ,15% uniaxial glass fibers, 70% Epoxy
3	Flax20	10% Flax ,10% uniaxial glass fibers, 80% Epoxy
4	Flax30	15% Flax ,15% uniaxial glass fibers, 70% Epoxy
5	Banana20	10% Banana ,10% uniaxial glass fibers, 80% Epoxy
6	Banana30	15% Banana ,15% uniaxial glass fibers, 70% Epoxy

 

Table 5 Properties of different natural fibers.

Type	Density (g/cm³)	Elongation (%)	Tensile Strength (MPa)	Young’s Modulus (GPa)	Specific Gravity	Specific Modulus (GPa)
Jute	1.3-1.5	1.4-2.1	385-850	9-31	1.3-1.5	6.9-20.7
Banana	0.5-1.5	2.4-3.5	711-789	4-32.7	1.1-1.2	3.6-27.3
Flax	1.3-1.5	1.1-3.3	340-1600	25-81	1.5	16.7-54

 

Table 6 Properties of cured Epoxy 556 with Araldite LY 556.

 

Synthesizing the composite samples:

·        Firstly the natural fibers were treated with 10% NaOH solution which removes the lignin and hemicelluloses layer on the fibers.

·        The fibers are then dried in the sun and then washed with soft water then left to dry for a day.

·        Then the fibers are compressed under a uniform load in order to give a uniform thickness.

·        Then Epoxy and hardener are mixed in the ratio 10:1 and then mixed thoroughly to ensure that the mixture is well mixed.

·        Then pouring time is allowed for 10 minute before a layer of mixture is applied in the mould.

·        Then a layer of releasing agent is applied in the mould so that the sample could be easily removed from the mould.

·        Then alternate layers of glass and natural fibers are applied in between the epoxy layers to ensure that a thickness of 4 mm is obtained.

·        Then uniform load is applied on the sample so that the epoxy layer impregnates the fiber layers and a compact bonding is achieved.

·        Then the sample is left to cure for 24 hrs in normal ambient conditions.

·        Similarly samples are made for testing the tribological properties of the natural composites instead circular hot water pipes were used for moulding purpose.

 

RESULTS AND DISCUSSIONS:

Flexural Strength test:

This test involves finding the flexural properties of unreinforced and reinforced plastics, including high-modulus composites. This test is generally applicable to both rigid and semi-rigid materials. However flexural strength cannot be determined for those materials that do not break or that do not fail in the outer surface of the test specimen within the 5.0 % strain limit of these test methods. Three point loading system is used to determine the flexural strength and bending nature of the composites. Figure 2 to Figure 12 shows the results of flexural strength of hybrid composites.

 

 

Fig. 1 Experimental set up for determining the flexural strength.

 

 

 

 

 

Fig. 4 Flexural test for 20% flax hybrid Composite.

Fig. 5 Flexural test for 30% flax hybrid Composite.

 

Fig. 6 Flexural test for 20% banana hybrid Composite

Fig. 7 Flexural test for 30% banana. Hybrid Composite.

 

Fig. 8  Flexural stress vs strain for hybrid Jute composites

Fig. 9 Flexural stress vs strain for hybridflax composites

 

 

Fig. 10 Flexural stress vs strain for hybid banana composites

 

From the above three graphs it is seen that for flax and banana hybrid composites the tensile strength increases with the increase in fiber volume concentration but in case of jute the reverse happened better properties were observed for 20% fiber volume fraction than as compared to 30%. In the case of jute the value decreases for 20% it’s more and for 30% fiber volume fraction it is less this can be attributed to the reference from [2], where properties seemed to decrease and then increase. Moreover glass fibers have no significant effect on the flexural strength this was referred from a study [7], where the flexural strength was having no appreciable increment with increasing concentration of glass fibers.

 

Table 7 and table 8 shows Values for 20% and 30% of hybrid composites.

 

Table 7 Values for 20% hybrid composites

 

 

Fig. 11 Flexural stress vs strain graph for 20% hybrid composites.

Fig. 12 Flexural stress vs strain graph for 30% hybrid composites

 

Table 8 Values for 30% hybrid composites

Type	Maximum Load (N)	Flexural Stress (MPa)	Modulus (MPa)	Strain (mm/mm)
Jute	215.18	38.62	2728.66	0.05484
Banana	245.95	48.3	3230.84	0.0295
Flax	378.43	74.32	3352.18	0.0299

 

From the above graphs and table it is easily evident that flax performs better than jute and banana for the flexural strength showing higher values for flexural strength and modulus. But jute showed better properties at 20% fiber concentration but as the fiber volume fraction increases the flexural strength values for banana and flax also increases at the rate of 45% and 54% respectively.

 

CONCLUSIONS:

·        The increase in volume fraction of the glass fibers doesn’t influence the flexural properties of the composite. Hence employing it in large amounts will not improve it’s properties.

·        In case of jute 20% volume fraction composite showed better properties than the 30% volume fraction which was in close reference to a study which showed that at first the values decrease and then it increases.

·        Out of the entire three hybrid composites flax hybrid composite proved to be the best with increasing volume fraction of the reinforcements. And even it possessed higher values on account of having higher values of elastic modulus.

·        Flax composites can be used as a supporting member in trusses, lightly loaded structures on the account of it’s better flexural properties, could be employed into biomedical use.

 

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Accepted on 24.09.2017        © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(2): 547-552.