Modeling of Kenaf Reinforced Sugar Palm Starch Biocomposites Mechanical Behaviour using Halpin-Tsai Model

Transcription

1 Modeling of Kenaf Reinforced Sugar Palm Starch Biocomposites Mechanical Behaviour using Halpin-Tsai Model M.R. Mansor 1,2, S.M. Sapuan 1, M.A. Salim, 2 M.Z. Akop, 2 and M. M. Tahir 2 1 Department of Mechanical and Manufacturing Engineering Faculty of Engineering, Universiti Putra Malaysia UPM Serdang, Selangor MALAYSIA 2 Green Technology Vehicle Research Group Centre for Advanced Research on Energy CARE Universiti Teknikal Malaysia Melaka Durian Tunggal, Melaka MALAYSIA muhd.ridzuan@utem.edu.my Abstract: - This paper presents the application of theoretical modeling approach in studying the mechanical behaviour of kenaf reinforced sugar palm starch (SPS) biocomposites. Kenaf reinforced SPS is new class of biocomposites that offered high specific mechanical property and fully biodegradable and renewable properties which is very promising for eco-friendly product applications. Halpin-Tsai micromechanical model was employed to model the final biocomposites elastic behaviour in both varying fiber contents and varying fiber length conditions. The kenaf fiber contents were varied from 0 to 50 wt% where as the fiber length was varied from 1 mm to 3 mm. Modeling results showed that elastic for final kenaf reinforced SPS biocomposites increased as the total kenaf fiber contents were increased, for both longitudinal and transverse direction. Apart from that, increased in kenaf fiber length was also shown to effect higher elastic of the due to increase in the reinforcement aspect ratio. The Halpin-Tsai model implemented in this study also proved its suitability for preliminary biocomposites design purpose in order to gain quick and cost effective information prior to experimental biocomposites characterization approach. Key-Words: - Modeling, Biocomposites, Kenaf, Sugar Palm Starch, Elastic Modulus, Halpin-Tsai Model 1 Introduction In recent years, biocomposites have made significant progress in many aspects involving materials, processes and applications due to the higher awareness towards using better sustainable resources by consumers [1] [3]. Apart from that, biocomposites also offers cost and lightweight advantages compared to synthetic composites. Kenaf natural fiber is among the most used type of reinforcement for biocomposites fabrication which is contributed to its high specific strength and as well as low cost comparable to other commodity type of natural fibers such as hemp, flax and jute [4] [6]. In addition, the emergence of matrix materials made from natural resources such as starch to replace petroleum based resins have also contribute to high potential of using biocomposites materials where fully biodegradable and renewable composites can be manufactured [7]. Among the promising type of bioresin is sugar palm starch (SPS) made from sugar palm tree which have high raw material availability especially in Malaysia. Up to date, very limited research has been reported in the application of the SPS for biocomposites application. One notable effort was reported by Sahari et al [8] whereby the SPS bioresin was used as the matrix material in combination with sugar palm fiber as the reinforcement material to formulate fully biodegradable biocomposites. Through literature review, it was also found that the application of kenaf with SPS bioresin have yet been reported in literature despite the advantage offered kenaf. Hence, the gap found have motivated the authors to explore the potential of producing kenaf reinforced SPS biocomposites and characterized its mechanical properties for this new class of biocomposite ISBN:

2 materials for eco-friendly product applications. In this study, the elastic of kenaf reinforced SPS biocomposites was determine using theoretical modeling approach. Halpin-Tsai micromechanical model was applied in assessing the final biocomposites properties at both varying fiber loading and fiber length conditions. 2 Literature Review The Halpin-Tsai model was developed in 1970s to provide alternative methods to composite practitioners in determining the final composites elastic properties using theoretical modeling approach [9]. Since its establishment, the Halpin- Tsai model was successfully applied in many composites modeling applications comprising both synthetic fibers and natural fibers especially for short fiber reinforced composites [10], [11]. The advantage of the Halpin-Tsai model is that it provide the information of the geometrical factor of the composites materials in addition the individual constituents making up the final composites as proposed in other modeling approach [12]. Furthermore, the Halpin-Tsai model is also favored for design purposes due to its simplicity and accurate prediction results for various configurations of composite materials [13]. The application of Halpin-Tsai model to model the elastic mechanical property for kenaf based natural fiber composites have been reported by many author. Mansor et al. applied the Halpin- Tsai model to study the final kenaf reinforced thermoplastic composites at varying total fiber volume and fiber aspect ratio conditions [14]. Three types of thermoplastic matrices were selected which are polypropylene, acrylonitrile butadiene styrene and polyamide 6. Modeling results showed that positive elastic improvement was able to be obtained by increasing the total fiber contents and higher fiber aspect ratio for the kenaf thermoplastic composites. Pang et al also utilized the Halpin-Tsai model to determine the final kenaf fiber reinforced plasticized cellulose acetate composite elastic [15]. In their study, the addition of higher kenaf fiber contents was shown to increase the elastic of the biocomposites. On the other hand, various authors have also reported characterization of the elastic for natural fiber composites made from natural based matrix or bioresin using the Halpin-Tsai model. Araujo et al. studied the effect of fiber contents on the elastic property of curaua leaf fiber reinforced poly-lactic acid (PLA) biocomposites using the Halpin-Tsai model [16]. Their study showed that the neat bioresin elastic was increased by the addition of curaua fibers as the reinforcement agent. They also employed Tsai- Pagano equation in addition to the Halpin-Tsai model to determine the final elastic property of the biocomposites for short-random condition. Apart from that, Fiore et al also employed the Halpin-Tsai model to study the effect of filler contents and size to the elastic of A. donax reinforced PLA biocomposites [17]. The tensile and flexural of the biocomposites was greatly increased by the addition of higher A. donax filler contents and size. Similarly, Duiguo et al. applied the Halpin-Tsai model to determine the effect of seawater aging on the flax reinforced PLA composites elastic property [18]. Test samples were prepared using injection moulded short unidirectional fiber flax reinforced PLA composites and immersed in seawater for 2 years duration. Modeling results obtained that the composites elastic performance in both longitudinal and transverse fiber directions was severely reduce as the immersion time increased. 3 Materials and Methods 3.1 Materials In the kenaf reinforced SPS biocomposites, for the varying fiber contents condition, the kenaf bast fiber length was selected at 2 mm and the total fiber contents were varied from 0 wt% to 50 wt%. Meanwhile, for varying kenaf fiber length condition, the total fiber contents were fixed at 30 wt% while the kenaf fiber lengths were varied from 1 mm to 5 mm. In both conditions, the SPS bioresin matrix used was prepared using 70 wt% sugar palm starch and 30 wt% glycerol as plasticizer. All material properties used in the analysis were obtained from literature review. Table 1 summarized the physical and mechanical property of the individual constituents for the biocomposites. Table 1: Kenaf bast fiber and SPS biopolymer material properties [19] [21] Material Density, ρ (g/cm 3 ) Tensile, E (GPa) Fiber diameter (µm) Kenaf (bast) Sugar palm starch NA ISBN:

3 3.2 Methods The elastic of single fiber/matrix composite system, E using Halpin-Tsai model is calculated using Equation (1) E = E m [(1+ζηV f )/(1-ηV f )] (1) where η is the efficiency factor and calculated using equation (2) η = [(E f /E m )-1]/[(E f /E m )+ζ] (2) where ζ is the shape fitting factor of the lamina/laminate. E f and E m are the fiber and matrix respectively. Table 3: Final kenaf reinforced SPS biocomposites elastic at varying fiber loading condition Sample Kenaf fiber loadings Elastic (GPa) wt% vol% E11 E22 SPS KF KF KF KF KF Summary of the shape fitting factor, ζ values corresponding to the different type of moduli is shown in Table 2. Composite Table 1: Shape fitting factor, ζ values [9] ζ Remarks Fiber Matrix E 11 E f E m 2(L/d) or 2(L/t)* E 22 E f E m 2 G 12 E f E m 1 Longitudinal Transverse Longitudinal shear *Note: L/d or L/t = fiber aspect ratio where L= fiber length, d= fiber diameter and t=fiber thickness 4 Results and Discussion 4.1 Effect of fiber loading on kenaf reinforced SPS biocomposites elastic The modeling results using Halpin-Tsai method in determining the effect of kenaf fiber loading on the final kenaf reinforced SPS biocomposites elastic are shown in Table 3 and Fig. 1. The application of higher kenaf fiber loadings was observed to increase the final biocomposites elastic in both longitudinal (E 11 ) and transverse directions. Significant improvement of final kenaf biocomposites elastic in longitudinal direction was also observed compared to its transverse direction (E 22 ). Fig. 1: Effect of fiber loading on kenaf reinforced SPS biocomposites elastic The findings showed good agreement with relevant study on biocomposites reinforced with similar SPS matrix as reported by Sahari et al [8]. In their study using sugar palm fiber reinforced SPS biocomposites, higher tensile and flexural were obtained using higher fiber loading. The positive effect of kenaf as reinforcement material to the elastic of biocomposites made from bioresin was also reported by Zainuddin et al [22]. Their study showed that higher kenaf fiber loading clearly increased the final kenaf reinforced cassava starch biocomposites elastic. The improving mechanism to the biocomposites is contributed to the increased of reinforcement capability to the polymer matrix [23]. Apart from that, for biocomposites made from natural fiber and bioresin matrix, the elastic improvement compared to neat bioresin matrix was also reported to be affected by the good chemical structures compatibility the between the fiber cellulose and starch matrix [24]. The presence of similar chemical structure helps to increase the hydrogen bonding between the fiber/matrix interface, and subsequently improved the ISBN:

4 fiber/matrix adhesion allowing better mechanical strength and stiffness performance for the biocomposites [25]. 4.2 Effect of fiber length on kenaf reinforced SPS biocomposites elastic The modeling results obtained also revealed similar increasing trend of kenaf reinforced SPS biocomposites elastic with increasing fiber length as shown in Table 4 and Fig. 2. The presence of longer kenaf fiber making up the biocomposites increased the final fiber aspect ratio. Higher aspect ratio for the reinforcing agent (kenaf fiber) enabled more effective stress transfer to the SPS matrix and created higher biocomposites compared to reinforcing agent with lower aspect ratio [26]. Table 4: Final kenaf reinforced SPS biocomposites elastic at varying fiber length condition Kenaf fiber Aspect Ratio length (mm) Elastic Modulus (GPa) Fig. 2: Effect of fiber length on kenaf reinforced SPS biocomposites elastic 5 Conclusions Several conclusions from the study for the kenaf reinforced SPS biocomposites are summarized as below:- i) the increase of kenaf fiber loading contents resulted in the increased of final kenaf reinforced SPS biocomposites elastic in both longitudinal and transverse fiber directions compared to unreinforced SPS ii) the increase kenaf fiber length increased the final kenaf reinforced SPS biocomposites elastic compared to unreinforced SPS iii) modeling approach implemented was also found able to provide good and cost effective estimation data to composites practitioners prior to conducting actual experimental in characterizing biocomposites mechanical properties 6 Acknowledgements The authors wish to thank Universiti Putra Malaysia and Universiti Teknikal Malaysia Melaka for the support provided throughout the completion of this research. References: [1] R. M. N. Arib, S. M. Sapuan, M. M. H. M. Ahmad, M. T. Paridah, and H. M. D. K. Zaman, Mechanical properties of pineapple leaf fibre reinforced polypropylene composites, Materials and Design, Vol. 27, No. 5, 2006, pp [2] S. M. Sapuan and M. R. Mansor, Concurrent engineering approach in the development of composite products: A review, Materials and Design, Vol. 58, No. 0, 2014, pp [3] F. M. Al-Oqla and S. M. Sapuan, Natural fiber reinforced polymer composites in industrial applications: feasibility of date palm fibers for sustainable automotive industry, Journal of Cleaner Production, Vol. 66, No. 0, 2014, pp [4] M. R. Mansor, S. M. Sapuan, E. S. Zainudin, A. A. Nuraini, and A. Hambali, Hybrid natural and glass fibers reinforced polymer composites material selection using Analytical Hierarchy Process for automotive brake lever design, Materials and Design, Vol. 51, No. 0, 2013, pp [5] I. Aji, E. Zainudin, K. Abdan, S. Sapuan, and M. Khairul, Mechanical properties and water absorption behavior of hybridized kenaf/pineapple leaf fibre-reinforced highdensity polyethylene composite, Journal of Composite Materials, Vol. 47, No. 8, 2012, pp [6] Y. A. El-Shekeil, S. M. Sapuan, K. Abdan, and E. S. Zainudin, Influence of fiber content on the mechanical and thermal properties of ISBN:

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