Investigation of bio-waste natural fiber–reinforced polymer hybrid composite: effect on mechanical and tribological characteristics of biodegradable composites
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The global energy crises and environmental pollution have encouraged investigators, scientist, and engineers to develop a substitute material for the conventional material. Since the availability of the natural fibers is abundant, many researchers in the worldwide are focusing their attention on the improvement of natural fiber–reinforced composites, which act as a substitute material for the synthetic natural fibers. This work examines the study of mechanical and tribological properties of tensile, flexural, impact, wear rate, and friction coefficient of the banana/hemp hybrid composites, which are calculated with the aid of NaOH-treated composite specimens. Composites were fabricated for various wt.% of the fiber content, different length of the fiber and matrix. Surface morphology of the fractured specimen of the alkali-treated fibers composites is studied by using SEM images. The effect of water absorption behavior on the mechanical properties of banana/hemp fiber composites was also determined.
KeywordsBiodegradable Mechanical properties Surface morphology Tribology
Composite materials which are produced by high-strength synthetic fibers are widely used in many commercial applications such as in the development of the automotive component, aerospace parts, construction material, medical, marine and sporting goods. But these types of composites were imported from the foreign countries and the fabrication cost of the composite will be higher. This circumstance has led to the development of substitute materials for synthetic fibers such as carbon, glass, or aramid . In a recent development, a vital amount of attention has been shown by the researcher for the potential use of natural fibers as the reinforcement material in order to replace synthetic fiber in composite materials. Even though the natural fibers are not as tough as the synthetic fibers, natural fibers are very low cost, eco-friendly, and also biodegradable material . The plant fiber structures also exhibit better insulation properties against noise and heat. Most cellulose natural fibers are harvested all over the year, so the production and supply are boundless compared with the very limited supply of the synthetic fibers which are derived from the depletion of the oil resources which produce the very high price of composite material which is reinforced with synthetic fibers. At the same time, the users of industries demand the lesser price for the composite production and which also results in better quality. The natural fibers are used as an effective reinforcement material for the polymer composites because of easy availability, inexpensive, and easy production of the composite. Hemp and banana fibers are being investigated in order to have an effective substitute material to replace the synthetic fibers in many commercial applications . Among the different natural fibers, hemp and banana fibers are used as an effective reinforcement material in the polymer matrix composites. Since the hemp and banana fibers are rich in cellulose content, so these fibers are planned to investigate the appropriate study of banana/hemp fibers as reinforcement in polymer matrix composites to manufacture lower-cost components for many applications. Dinh et al.  presented an article on recent developments in bio-composites, multiple bioplastics, and recent trends in industrial applications for natural fiber polypropylene bio-composites to provide a perspective on the possibilities and development of bio-composite materials.
Rochima et al.  explored the properties of nano-chitosan plastic composite materials reinforced by banana and glass fiber and exclusively tested their mechanical properties. Punyamurthy et al.  proposed polyester composite produced from Abaca fiber which functions as a reinforcement catalyst in which the matrix was epoxy resin. They finally concluded the composite’s mechanical properties, evaluating the specimens for tensile as well as flexural strength. It has been observed that the composite material’s tensile strength relies on the polyester strength as well as the intermolecular adhesion between reinforcement and the matrix. Prasad et al.  were using the combination of natural fiber and synthetic resin (polyester) to produce partially environmentally friendly sisal fiber–reinforced polyester matrix composite. Towards this end, on Sansevieria cylindrica, a dynamic mechanical assessment was performed. Fiber increased synthetic polyester matrix to research storage module, loss module, and damping factor. Finally, under transient temperature circumstances, the effects of fiber length, fiber loading, and chemical treatments were analyzed.
Venkateshwaran et al.  conducted a number of tests to approximate the maximum mechanical properties of the fiber size and also the weight portion. Composite specimens were generated by differing portions of fiber size (5, 10, 15, and 20 mm) and volume (8, 12, 16, and 20). In addition, sisal fibers were introduced at a various quantity proportion (25, 50, and 75%) to improve the mechanical properties of the banana/epoxy composite products. Hybridization via sisal fibers supplies mechanical properties a desirable improvement. Sharba et al.  developed a hybrid material that integrates all-natural and synthetic fiber, respectively, from kenaf and also glass fiber. Production was performed via a sheet molding substance process with an overall amount reinforcement of up to 30%. In order to recommend the maximum hybrid compound for structural application, mechanical properties were examined.
Prajapati et al.  examined the effect of coir fiber composition treatment and also noted modifications in fiber geometry and also structure. It is clear that the end results obtained from chemically refined coir fiber are a plastic scientific research reinforcement agent as well as it is appreciated doing in modern innovation as commercial material. Abdulhadi  assessed the result of various medicines on the mechanical properties of basalt fibers and also their polypropylene matrix bond properties. Use of maleic anhydride implanted PP has been examined to produce various fiber size and also matrix alteration. Basalt fiber mechanical properties examined with solitary filament tensile testing. Santhosh et al.  investigated the fiber which was treated to increase moist strength by 5% of NaOH. Both in epoxy and vinyl ester resin, banana fibers have been used as reinforcement, as well as coconut shell powder were mixed with banana fiber. This appeared to be a product of strengthening to form a synthetic hybrid.
The main objective of this research is to determine the mechanical and wear characteristics like tensile, flexural, impact, wear loss, and friction coefficient of alkali-treated natural fibers in the form of randomly oriented long banana/hemp fiber hybrid–reinforced composites. And also the identification of the optimum weight percentage of the fiber content in the composites at which the maximum mechanical properties could be obtained. The morphological behavior of the composite was studied by using the scanning electron microscope.
2 Experimental details
The output of the composites depends on the characteristics of their components and on the bonding between the matrix and the reinforcement. It is customary to test them for mechanical properties such as tensile, hardness, and flexural strength to study the performance of bio-hybrid composites. Tribological testing is performed to determine the impact of reinforcement by varying distinct loads and speeds.
2.1 Raw materials
Chemical composition of banana and hemp fiber
Hemi cellulose (%)
Physical properties of banana and hemp fiber
Moisture absorption (%)
2.2 Alkali treatment of banana and hemp fibers
2.3 Preparation of bio-hybrid composites plates
Composition of composite fiber
5% banana +5% hemp
10% banana +10% hemp
15% banana +15% hemp
20% banana +20% hemp
25% banana +25% hemp
2.4 Determination of mechanical properties
Vickers is one of several measures of the microhardness of a material. The microhardness of the bio-hybrid composites is conducted by using Vickers’s hardness testing apparatus according to ASTM E 384 standards taking a load of 80 g and a dwell time is taken as 10 s. The specimens were cut by 10 mm length and 5 mm wide to investigate Vickers microhardness. For each composition, three samples are taken and average values are reported.
2.4.2 Tensile strength
The tensile test is generally performed on flat specimens. The tests are performed as per ASTM D 3039-76 standards on a computerized Ultimate Tensile Machine (UTM) with a load of 300 kN and dwell time 15 s . All samples are cut by rectangular shape with dimensions of 10 mm wide and 120 mm total gauge length, while applying a load result in gradual elongation and fracture takes place at the end.
2.4.3 Flexural strength
The short beam shear tests are conducted of all samples at room temperature to investigate flexural strength. However, a 3-point bend test was conducted to promote failure by inter-laminar shear. The flexural strength is conducted by ASTM D 59436-96 standards. All the samples were cut by the rectangular shape of 100 mm long, 25 mm wide, and 3 mm thickness . Span length of 40 mm and the crosshead speed of 1 mm/min are taken in the present investigation. The temperature and humidity of this test are maintained at 22 °C and 50% respectively.
2.4.4 Impact strength
Mechanical properties of alkali-treated banana/hemp fiber–reinforced hybrid composites
Tensile strength (MPa)
Flexural Strength (MPa)
Impact strength (KJ/m2)
5% banana +5% hemp
10% banana +10% hemp
15% banana +15% hemp
20% banana +20% hemp
25% banana +25% hemp
It is necessary that stiffness kept to a maximum level when the desired high performance of machining would be achieved.
2.5 Water absorption test
The moisture absorption test specimens were cut from the fabricated composite plate as per the ASTM D570 . Specimen edges are sealed with the resin and it is subjected to the water absorption. In an oven at 50 °C the samples were dried and then immersed in the distilled water at 30 °C for about 5 days. At the standard time interval, the test samples were taken from the water and to remove the water present in the surface of the test specimen, it was cleaned with the filter paper and weighted with digital balance. In order to perform the continuous water absorption, the test samples were re-immersed in water until the complete saturation limit was reached. Due to evaporation, an error could occur, so that the weighing of the test specimen was done within 30 s in order to avoid such kind of errors. Percent of weight change of the samples during water absorption was determined by the following Eq. (1)
Effect of different wt.% of the fiber content on the water absorption behavior
Fiber content (wt.%)
Day1 water absorption (wt.%)
Day 2 water absorption (wt.%)
Day 3 water absorption (wt.%)
Day 4 water absorption (wt.%)
Day 5 Water absorption (wt.%)
2.6 Tribological properties
Wear test conditions
EN31 steel disc
2.7 Characterization of bio-hybrid composites
Mechanical and tribology properties are studied, and a critical concentration of compatibilizer is found to exist in the bio-composite system. Morphology of the fracture surface was also investigated by scanning electron microscopy. The bio-composite samples were ground, etched chemically, and polished mechanically by using Kroll’s reagent (a mixture of 10 ml HF, 5 ml HNO3, and 85 ml H2O). After conducting the tribology test, each sample is examined by using SEM (SEM-ZEISS SIGMA).
3 Results and discussion
Examine the effect of natural fibers and identify mechanical properties of bio-hybrid composites. To study the behavior of each phase’s surface morphology, EDS and XRD were analyzed. Effect of sliding wear behavior was identified using different parameters (applied load, sliding distance, and sliding speed) on wear loss and coefficient of friction (C.O.F).
3.1 Microstructure analysis of initial elements
3.2 Mechanical characterization
3.2.2 Tensile strength
3.2.3 Flexural strength
3.2.4 Impact strength and stiffness
The stiffness of the banana and hemp fiber with different weight fractions is presented in Table 4. The observed results are evidenced that the 20% (banana-hemp) has considerably reduced open pores and increases stiffness (3.32 Gpa) when compared with other composites. Increasing the concentration of hemp tends to improve the stiffness. The result suggests that addition of 20% (banana-hemp) is effective, due to the removal of pores and it enhances the mechanical properties of the hybrid composites. Further increasing the concentration to 25% (banana-hemp) tends to decrease the stiffness (3.27 Gpa) which is attributed to an effect of agglomeration. Therefore, A356/10%RHA-10%Fly ash hybrid composite is observed having low porosity level compared with alloy and other hybrid composites.
3.2.5 Water absorption characteristics
Figure 9 shows the increases in the percentage of the moisture absorption for 20-mm fiber length of both first and fifth day at the composite having the fiber content of 10 wt.%, 15 wt.%, 20 wt.%, and 25 wt.% were 52.24%, 75.47%, 82.21%, and 87.34% respectively.
3.3 Wear characteristics
3.3.1 Effect of sliding speed on wear loss
3.3.2 Effect of applied load on wear loss
3.3.3 Effect of sliding speed on friction
3.3.4 Effect of applied load on friction
3.4 Surface morphology of bio-hybrid composites
3.5 EDX analysis
3.6 XRD analysis
Microhardness values are much higher for the 20% (banana-hemp)–reinforced vinyl ester resin in comparison with other hybrid composites. The increased microhardness is due to a higher degree of fineness of fiber content and good wettability.
Tensile, flexural, and impact strength is increased (40%) for the vinyl ester/20% banana–20% hemp compared with other hybrid composites. The improvement of tensile strength is attributed to the presence of high silica and carbon content.
In the addition of 25% fiber, the mechanical properties of the hybrid composites were reduced due to the formation of more interfaces in the matrix and the generation of pores with voids.
For all applied load, sliding distances and sliding speeds were examined. The developed 20% bio-hybrid composite was exhibited low wear loss and low coefficient of friction at all sliding conditions.
The SEM microstructure of vinyl ester/20% (banana-hemp) bio-hybrid composite shows a pore-free compact surface. The EDS and XRD pattern confirms the formation of sisal and coir phases with their intensity of 20°,40° from the corresponding specimen.
Therefore, the vinyl ester/20% (banana-hemp) bio-hybrid composite exhibits improved wear resistance and hence resulting in longer material lifespan. This type of material is widely used in fishing rods, golf clubs, chairs, tables and all domestic purposes.
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