Mechanical Properties of Hybrid Polymer Composite Using Natural Fiber and Nanoparticle

Hybrid polymer composite were prepared by incorporating two indigenous agro-industrial waste reinforcements, sugarcane bagasse fiber (SBF) and coconut coir fiber (CCF) into epoxy resin through the hand lay-up technique. Nano-silica was also added to enhance the mechanical performance of composite materials. The alkaline treatment on the surface of natural fibers was carried out and its effects on the mechanical properties were investigated. Generally, it is found that the CCF reinforced epoxy composites exhibited higher mechanical properties as compared to the SBF reinforced epoxy composites. For hybrid composite samples, (2.5wt%SBF+12.5wt%CCF) had attained the highest mechanical performance amongst all other different ratio percentage of hybrid polymer composite.


Introduction
Conventional polymers unable to display different characteristic and properties that is required in the present modern day engineering applications. Therefore, hybrid polymers are absolutely gaining the opportunities in material science processing and production [1]. It is a high chance that hybrid polymer will replace the single material of polymer or conventional polymer.
In order to fulfill ecological and economic benefits, researchers put in a lot of effort into development and creation on high performance and strong hybrid polymer reinforced by using natural fiber and nanoparticle. Due to extraordinary mechanical properties, natural fiber reinforced with nanoparticles have shown their better potential to be used as an alternative material in replacing synthetic fiber [2]. However, there are difficulties faced by natural fiber polymer composites such as interfacial adhesion bonding between fiber and binding matrix [3]. This issue would lead to the problem of agglomeration and it would create poor stress transfer efficiencies.
Natural fibers have more advantages than synthetic fiber, so it has become the alternative solution that would apply in several reinforcement material industries [1][2][3][4][5]. The finding of this study will contribute to the benefits of society considering that natural hybrid polymer plays important role in the improvement of mechanical performances of composite materials. From this research is studying the effectiveness utilization of natural fiber (sugarcane bagasse fiber and coconut coir fiber) that embedded into epoxy resin. The incorporation of sugarcane bagasse fiber and coconut coir fiber are proven to enhance the mechanical properties of epoxy composites. In order to make further improvement on the quality, silica is introduced as additional nanoparticle into reinforcing materials as the purpose is to reduce the voids in composite materials.

Preparation of Samples
SBF and CCF were first rinsed and washed by using clean water and dried at 80°C by using an oven for 24h. The fibres were treated with 5% concentration alkaline solution. Then, the fibres were immersed into 5% concentration of sodium hydroxide (NaOH) for 5 hours at room temperatures. Subsequently, the fibres were washed with distilled water. Finally, the fibres were dried in an oven at 80 °C for 8 hours. Then the polymer composites were prepared by hand lay-up technique by mixing the SBF/CCF with the epoxy resin and stirred thoroughly for 5 minutes until the filler was completely mixed with the resin. Next, the mixture was degasified using a vacuum oven. After that, the mixture was poured into the mould and left for solidification. After solidification, composites were post-cured in an oven for 2 hours at 80°C.

Tensile & Felxural Test
Tensile and flexural testing was carried out in accordance with designation ASTM D638 and ASTM D790 respectively, by using LR Plus LLOYD Universal Testing Machine.

Water Absorption Test
Water absorption test were carried out to measure the amount of specimen immersed in water under the specific standard condition which is according to ASTM D570. Specimens were immersed in the water condition with 〖23〗^o C for 24 hours. After 24 hours, specimens are being removed and dried in the oven with 〖50〗^o C for 5 hours, and let it cool inside the desiccators until they reach the room temperature. For this procedure is to get the initial weight as the base reference of the specimens. For every 24 hours, specimens are removed from the water and wiped off the surface with a dry cloth in order to weighting system. Next, there are continues for conduct the testing with immersed specimen into distilled water for continue 14 days in order to achieve the weight percentage increase in specimen due to water absorption. Figure 1 and Figure 2 show the tensile strength and tensile modulus of composites materials versus the natural fiber content.         slightly decreased with the result collect with 3450.5MPa. For comparison between reference samples of (0wt%SBF+15wt%CCF) composite, Flexural Strength of (2.5wt%SBF+12.5wt%CCF) composite showed higher value with increment of 6%, but there is slightly decrease on Flexural Modulus by 5%. This is due to the fact that SBF has better efficiency stress transfer between two components. SCB has the properties of high porosity with the inferiority.  Figure 11 shows the moisture uptake for hybrid polymer composites. It is observed that all of the natural fiber composite and hybrid polymer composite are steadily increase with the samples immersion time. It is determine that highest percentage of weight increase is 15wt% SBF with 4.22%. The least of weight increase is reference sample of 0wt% with weight increase which is 1.23%. This is means that the least weight increase for the hydbrid polymer composites is 5wt% CCF with 1.82%. From the result shown above, it can be seen that 15wt% SBF has the increment of 243.1% when compare to reference sample, while 5wt%CCF has the increment of 47.9%. It can be concluded that when there is higher content of natural fiber reinforcement in hybrid polymer composites, the water uptake will increase. It is due to the fact that, both SBF and CCF have the component of hemicellulose. The CCF has lower hemicellulose content which are only 7.95wt% while SBF has higher percentage of hemicellulose with 28.6%.

Conclusion
Natural fiber reinforced epoxy resin composite had perform better mechanical performance (tensile properties and flexural properties) when compare to pure epoxy resin composite. Among all single natural fiber reinforced epoxy resin composite, Coconut Coir Fiber performs higher result than Sugarcane Bagasse Fiber in mechanical performance (Tensile properties, Flexural properties and Moisture properties). The (2.5wt%SBF+12.5wt%CCF) hybdrid composite samples had attained the highest mechanical performance amongst all other different ratio percentage of hybrid polymer composites.