The mechanical properties of raffia palm fibre and groundnut shell particulate/epoxy (RPF/GSP/E) hybrid composites have been studied. Raffia palm fibres were treated with 10% NaOH solution at room temperature, and groundnut shell particulate of different sizes; 75 μ, 150 μ and 300 μ were also chemically treated with 10% NaOH solution at room temperature. The hybrid composite was produced by hand lay-up technique with (10%, 20%, 30%, 40%, and 50%) reinforcements of raffia palm fibre and ground nut shell particulate in the ratio of 1:1. The treated fibres were taken with required weight fractions laid into the mould of size 200 × 150 × 5 mm 3. Groundnut shell particulates were also taken with the required weight fraction, mixed with epoxy resin and the mixture was stirred thoroughly before pouring into the mould. Care was taken to avoid formation of air bubbles during pouring and the produced composite was cured under a load of 25 kg for 24 hours before it was removed from the mould. Effects of loading on the tensile, flexural and impact properties of the composite were evaluated. The significant findings of the results were that: tensile strength varied from 1.88 MPa to 9.56 MPa; Modulus of rupture (MOR) varied from 1.92 MPa to 41.6 MPa. While the modulus of elasticity, (MOE) values were in the range of 131.1 MPa to 4720 MPa and impact strength varied from 0.3 kJ/m2 to 1.6 kJ/m 2. From the results obtained, the optimum mechanical properties were obtained at 40% loading of RPF/300 μ GSP/E composite. Considering these results, the composite material can be considered as an alternative material for use in automotive interior panels such as boot liner, side and door panels, rear storage shelf and roof cover.
Composites are multifunctional material systems that provide characteristics not obtainable from any discrete material. They are cohesive structures made by physically combining two or more compatible materials, different in composition and characteristics and sometimes in form. The primary advantage of composite materials is their inherent ability to be custom tailored to a specific design situation. Constituents like fibres and matrix material can be used in different combinations, amounts, and architectures to obtain an optimal material composition.
The deployment of polymer composites with natural fibre and fillers as a sustainable alternative material for some engineering applications, particularly in aerospace and automobile applications is being pursued. Some of the common natural fibres are raffia palm, sisal, jute, hemp, coir, groundnut, bamboo and other fibrous materials. The advantages of natural fibres are low cost, light weight, easy production and being friendly to the environment [
On the other hand, there are some drawbacks to the use of natural fibres such as their low mechanical properties and high moisture absorption. The latter is due to their hydrophilic nature that is detrimental to many properties, including dimensional stability [
Some composite components (e.g. for the automotive industry), previously manufactured with glass fibres are now being produced with natural fibres. Applications including door panels, truck liners, instrument panels, interior roofs, parcel shelves, among other interior components, are already in use in European cars due to the more favourable economic, environmental and social aspects of the vegetable fibres [
Hybridization of two types of fibres can offer some advantages over using each of the fibres alone in a single polymer matrix. Hybrid composite materials offer a combination of strength and modulus that are either comparable to or better than many pure materials [
Many researchers have developed hybrid composites containing both natural and synthetic fillers. The hybrid composites showed better mechanical properties than mono filler materials [
The mechanical properties of groundnut shell reinforced urea formaldehyde composites were investigated by [
In this work, epoxy based hybrid composites were produced with raffia palm fibre and ground nut shell particulate as the reinforcing materials. To reduce the effect of moisture absorption of natural fibres and improve mechanical properties, the fibres were treated with 10% NaOH solution to improve the surface properties and provide better adhesion with the matrix. Alkaline treatment of cellulosic fibres with sodium hydroxide is a well-known method which has been employed to improve fibre-polymer matrix interfacial bonding [
Epoxy resin: Araldite LY-556 and Hardener: (2 aminoethylethane1, 2 diamine) HY 951 were obtained from Lagos, Nigeria. Raffia palm fibres and Groundnut shells were obtained locally from Ikov, Ushongo local government area of Benue State, Nigeria. Sodium hydroxide (NaOH), Distilled water, Wax, Hand gloves and Acetone were obtained from Makurdi, Benue State, Nigeria. The equipment used include: Set of standard laboratory Sieves, Monsanto Tensometer Type “W”, Universal Materials Testing Machine and Charpy Impact Testing Machine.
1) The groundnut shells were collected from a groundnut processing centre in Ushongo local government area of Benue state, Nigeria. Cleaned and dried groundnut shells were initially washed with distilled water to remove the sand and other impurities. The washed shells were sun dried and ground. The shell particles were treated using alkali treatment method by soaking the clean groundnut shell particles in 10% NaOH solution for 2 hours at room temperature and then were washed with distilled water. The washed shells were again dried under the sun. The particles were sieved through 75 µ, 150 µ and 300 µ standard test sieves to get different sizes of groundnut shell particles.
2) The raffia palm fibres were collected from raffia palm trees around a stream at Ikov, in Ushongo local government of Benue State, Nigeria. The pinnate leaves of the raffia palm were pulled out from the leaf stalks. Thereafter, the raffia fibres were taken off from the pinnate leaves. The fibres were washed thoroughly and allowed to dry under the sun. The raffia palm fibres were treated using alkali treatment method by soaking the clean raffia palm fibres in 10% NaOH solution for 1 hour at room temperature. The fibres were then washed thoroughly in plentiful of distilled water to remove the excess NaOH (or non-reacted alkali). The fibres were again sun dried and cut into fibre lengths of 10 mm to avoid fibre entanglement during production of the composite.
The fabrication of the composites was carried out by simple hand lay-up technique. A mould of 200 × 150 × 5 mm3 made of wood was used for casting the composite laminate. A mould release agent (wax), was first applied on all the surfaces of the mould, and allowed to dry. A thin film was formed on the mould when the wax dried. The thin film formed acts as the mould release agent. Raffia palm fibres of length 10 mm were laid in the mould by hand.
The epoxy resin and hardener were mixed in the ratio of 4:1 by weight. These were thoroughly mixed in a plastic container. Measured quantities of groundnut shell particulate were added in the plastic container and the mixture was again stirred for 15 minutes and thoroughly mixed before it was poured into the mould. The fibres in the mould were saturated with resin that was already mixed with groundnut shell particulate, and then were rolled using a roller to ensure good contact and freedom from porosity, and the produced composite was finally cured. The closed mould was kept under a load of 25 kg at room temperature for about 24 hours before the composite was removed from it. The composite was then post cured in air for 27 days at room temperature.
The composites were fabricated with 10, 20, 30, 40, and 50% reinforcements of raffia fibre and groundnut shell particulate in the ratio of 1:1. Samples were designated as A, B, C, D, and E respectively. Specimens of suitable dimensions were cut for mechanical testing. The produced composite is shown in
Reagents | Size | W% (Grams) | ||||
---|---|---|---|---|---|---|
Sample | A | B | C | D | E | |
Raffia fibres Groundnut shell particulate Epoxy | 10 mm 75 µ | 5 5 90 | 10 10 80 | 15 15 70 | 20 20 60 | 25 25 50 |
Raffia fibres Groundnut shell particulate Epoxy | 10 mm 150 µ | 5 5 90 | 10 10 80 | 15 15 70 | 20 20 60 | 25 25 50 |
Raffia fibres Groundnut shell particulate Epoxy | 10 mm 300 µ | 5 5 90 | 10 10 80 | 15 15 70 | 20 20 60 | 25 25 50 |
The tensile strength of the composites was measured with Monsanto Tensometer Type “W” in accordance with the ASTM D638 procedure. The test was conducted by gripping each end of a reduced section specimen and slowly pulling it until catastrophic failure occurs. Three samples were tested and the average values of tensile strength and elongation at fracture were calculated.
The flexural test was performed using a 100 kN capacity universal materials testing machine. This was done in accordance with ASTM D790 using the 3-point bending fixture, utilizing centre loading on a simple supported beam. The dimension of the sample was 100 mm × 30 mm × 5 mm. A bar of rectangular cross section rests on two supports and is loaded by means of a loading nose midway between the supports. Three samples were tested and the average values of the modulus of rupture and modulus of elasticity were calculated. The modulus of rupture (MOR) and the modulus of elasticity (MOE) of the composite specimen were determined using the following equation:
Modulus of Rupture ( MOR ) = 3 p l 2 b t 2 ( MPa ) (1)
Modulus of Elasticity ( MOE ) = p l 3 4 b t 3 ( MPa ) (2)
where, p is max. Load applied on test specimen (N):
l is gauge length (mm);
b is the width of specimen (mm);
t is thickness of specimen (mm).
The impact strength of the samples was determined using a 25 J capacity Charpy Impact Testing Machine according to ASTM standard D256. In this method, the specimen of size 80 mm by 10 mm by 10 mm is supported horizontally as a simple beam and fractured by a blow delivered in the middle of the specimen by the pendulum. Three samples were tested and the average of the values of the energy absorbed was recorded. The equation below was used to evaluate the impact strength:
I = K A (3)
where I is the impact strength of specimen in kJ/m2;
K is the energy required for fracture in kilo Joules;
A is the area of cross section in m2.
The computed tensile strength values of raffia palm fibre and groundnut shell particulate epoxy hybrid composite (RPF/GSP/E) specimens are shown in
Generally, from the results of the experiment depicted in
could be due to the agglomeration of fillers in the samples. Similar results have been reported by other researchers, that the Young’s modulus increases with an increase in reinforcement [
The result of the per cent elongation at fracture is shown in
The per cent elongation at fracture of RPF/150 µ GSP/E composite decreased as the reinforcement increased to 20%. The per cent elongation increased to a maximum at 30% loading but decreased on further loading up to 50%.
The elongation at fracture of RPF/300 µ GSP/E composite increased to a maximum at 20% reinforcement but decreased with further loading up to 50%.
Generally, from the results of the per cent elongation at fracture of RPF/GSP/E composite, the per cent elongation at fracture decreased with higher loading. It is observed that RPF/300 µ GSP/E composite gave the lowest per cent elongation at fracture except for 20% loading with an elongation of 28%.
RPF/75 µ GSP/E composite gave the highest per cent elongation at fracture except for 10 and 30% loading with elongations of 20% and 24% respectively.
While, RPF/150 µ GSP/E composite gave the highest per cent elongation at fracture at 10% and 30% loadings with elongations of 36% and 38% respectively.
The computed values of modulus of rupture (MOR) and modulus of elasticity (MOE) of the composite specimens are shown in
filler-matrix adhesion as a result of insufficient wetting of fillers by the resin for higher filler content. Similar results were obtained for RPF/150 µ GSP/E samples where MOR of samples ranged from 2.40 - 25.6 MPa. Also, for RPF/300 µ GSP/E, MOR ranged from 8.0 - 41.6 MPa. Generally, it is observed in
Similar Behaviour was exhibited by the composite samples for Modulus of Elasticity (MOE) property. MOE of samples increased with increase in filler loading which could be attributed to enhancement in stiffness of the composite with the addition of reinforcement filler, which is because reinforcing particles have higher stiffness than the weak matrix. Similar results were also reported by several authors [
MOE of the samples is in the range of 223.8 - 891.5 MPa with the sample D (40% reinforcement) of RPF/75 µ GSP/E gave a maximum MOE of 891.5 MPa. Similar trend is observed for RPF/150 µ GSP/E with MOE in the range of 172.5 - 1011.4 MPa. Same trend was observed for RPF/300 µ GSP/E, MOE of these samples, ranged from 131.1 - 4720 MPa with Sample D (40% reinforcement) having the highest MOE of 4720 MPa among all the samples.
The experimental results of impact strength of raffia palm fibre and groundnut shell particulate reinforced epoxy hybrid composite are displayed in
A hybrid composite using raffia palm fibre and groundnut shell particulate as fillers and epoxy resin as matrix has been developed. It was observed that, the addition of natural fibres to epoxy improved mechanical properties up to some weight% and further decreased with increased filler content. It was shown that, filler loading had more impact on the mechanical properties of the composite.
Sample D (40 weight% of RPF/300 µ GSP/E) gave the maximum tensile strength of 9.56 MPa. The sample E of RPF/300 µ GSP (50 wt%) gave the maximum Young modulus of 126.4 MPa. The results of the per cent elongation at fracture of RPF/GSP/E composite, showed that, elongation at fracture of the composite decreased at higher loadings. RPF/300 µ GSP/E composite gave the lowest per cent elongation at fracture except for 20% loading with an elongation of 28%.
RPF/75 µ GSP/E composite gave the highest per cent elongation at fracture except for the 10% and 30% loading with elongations of 20% and 24% respectively.
While, RPF/150 µ GSP/E composite gave the highest per cent elongation at fracture at 10% and 30% loadings with elongations of 36% and 38% respectively.
Sample D (40 weight% of RPF/300 µ GSP/E) gave the highest value of modulus of rupture (MOR) of 41.6 MPa. The analysis of Modulus of elasticity (MOE) also shows that, Sample D (40% wt of RPF/300 µ GSP/E) gave the highest MOE of 4720 MPa.
The results of the impact strength showed that, sample D (40% wt of RPF/150 µ GSP/E) gave the highest impact strength of 1.6 kJ/m2. Sample E (50% wt of RPF/300 µ GSP/E) also gave impact strength of 1.6 kJ/m2.
From the results obtained, groundnut shell particle size of 300 µ gave better mechanical properties when hybridized with raffia palm fibres. Considering the mechanical properties obtained, RPF/300 µ GSP reinforced epoxy composite samples gave optimum mechanical properties.
According to [
Nyior, G.B., Aye, S.A. and Tile, S.E. (2018) Study of Mechanical Properties of Raffia Palm Fibre/Groundnut Shell Reinforced Epoxy Hybrid Composites. Journal of Minerals and Materials Characterization and Engineering, 6, 179-192. https://doi.org/10.4236/jmmce.2018.62013