Abstract
Research interest has shifted from synthetic fiber to natural fiber due to environmental concerns and government regulation. This study evaluated the physical and mechanical properties of kenaf(K)/bamboo(B) fiber mat reinforced epoxy hybrid composites. Kenaf, bamboo, and kenaf/bamboo hybrid composites were prepared using the hand lay-up method at 40% wt total fiber loading. Different ratios of kenaf to bamboo fibers, such as 70:30(3B7K), 50:50(BK), and 30:70(7B3K), were used to fabricate the hybrid composites. Kenaf composite and bamboo composite were fabricated as controls. Mechanical (flexural and impact), morphological, and physical properties (thickness swelling, water absorption, and density) were examined. The density, water absorption and thickness swelling of the composites increased as the kenaf weight ratio increased. The flexural properties of kenaf composites were improved by hybridization with bamboo fiber, whereas the impact properties of bamboo were improved by hybridization with a woven kenaf mat. Hybrid composites with a 50:50 ratio showed the highest flexural and impact strength. Scanning electron microscopy (SEM) of flexural fracture showed that 50:50(BK) displayed better interfacial adhesion than the other two ratios. The woven kenaf/bamboo hybrid composite is suitable for use in the fabrication of automotive components.
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Physical and Mechanical Properties of Woven Kenaf/Bamboo Fiber Mat Reinforced Epoxy Hybrid Composites
Ahmad Safwan Ismail,a Mohammad Jawaid,a,b,* Mohamed T. H. Sultan,a,b,c and Azman Hassan d
Research interest has shifted from synthetic fiber to natural fiber due to environmental concerns and government regulation. This study evaluated the physical and mechanical properties of kenaf(K)/bamboo(B) fiber mat reinforced epoxy hybrid composites. Kenaf, bamboo, and kenaf/bamboo hybrid composites were prepared using the hand lay-up method at 40% wt total fiber loading. Different ratios of kenaf to bamboo fibers, such as 70:30(3B7K), 50:50(BK), and 30:70(7B3K), were used to fabricate the hybrid composites. Kenaf composite and bamboo composite were fabricated as controls. Mechanical (flexural and impact), morphological, and physical properties (thickness swelling, water absorption, and density) were examined. The density, water absorption and thickness swelling of the composites increased as the kenaf weight ratio increased. The flexural properties of kenaf composites were improved by hybridization with bamboo fiber, whereas the impact properties of bamboo were improved by hybridization with a woven kenaf mat. Hybrid composites with a 50:50 ratio showed the highest flexural and impact strength. Scanning electron microscopy (SEM) of flexural fracture showed that 50:50(BK) displayed better interfacial adhesion than the other two ratios. The woven kenaf/bamboo hybrid composite is suitable for use in the fabrication of automotive components.
Keywords: Composite; Kenaf; Bamboo; Natural fiber polymer composite; Physical properties; Flexural properties; Impact properties
Contact information: a: Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia; b: Aerospace Manufacturing Research Centre (AMRC), Level 7, Tower Block, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor Darul Ehsan, Malaysia; c: Department of Aerospace Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia; d: Department of Polymer Engineering, Faculty of Chemical and Petroleum, Universiti Teknologi Malaysia, Skudai, Johor Bharu, Malaysia;
* Corresponding author: jawaid_md@yahoo.co.in
INTRODUCTION
Fiber-reinforced polymer composites (FRPC) are used in various fields. Usually, FRPC contain synthetic fibers, which produce composites with superior properties. Synthetic fibers have been used in the aerospace, automotive, and wind energy industries (Rana and Fangueiro 2016). However, there are a number of environmental issues related to the industrial use of synthetic fibers, which include energy consumption during their production and products that are difficult to dispose. For example, production of glass fibers consumes a lot of fossil fuels (Abdul Khalil et al. 2007a). There are no suitable ways to dispose of FRPC, even with energy recovery using an incinerator (Okubo et al. 2004). As a petroleum-based material, synthetic fibers are non-renewable. Increasing interest in green and renewable material has encouraged researchers to study the properties of natural fiber in order to replace or reduce the use of synthetic fibers and polymers. Incorporation of natural fibers can improve the properties of composites, reduce polymer usage, and decrease production cost. In the automotive industries, natural fiber reinforced polymer composites have been used for various for interior and exterior components of vehicles (Holbery and Houston 2006).
There are three sources of natural fibers: animal, plant, and mineral. Plant fibers are commonly used as reinforcement in composite materials. Kenaf, hemp, and jute are examples of natural fibers sourced from plants. These fibers are readily and commercially available in the market. Additionally, these fibers are cheaper than synthetic fibers that are currently being used. In 1940, kenaf fiber was used to make carpet backing, packing materials, papers, and fencing (Tiwari and Srivastava 2012). Kenaf bast fibers possess striking mechanical properties that make them suitable reinforcing materials to replace glass fiber in polymer composites (Faruk et al. 2012; Paridah et al. 2011). Bamboo has been used as a structural element in pre-industrial architecture in Asian and South American countries (Tara Sen and Reddy 2011). Natural fiber reinforced polymer composite has comparable mechanical properties to glass reinforced polymer composite (Faruk et al. 2012; Krishna and Kanny 2016; Sanjay et al. 2018). The properties of natural fiber reinforced polymer composites depend on fiber selection, matrix selection, interfacial strength, fiber dispersion, fiber orientation, composite manufacturing process, and porosity (Pickering et al. 2016). Additionally, properties of natural fibers depend on the type of plant, extraction process, maturity of fiber, and locality where it is grown. Fiber selection is important since every fiber has its own unique properties. The two reinforcing elements ought to provide unique combinations of properties or synergistic effects as a “hybrid composite”, which then can be used for different applications (Hubbe 2017).
El-Shekeil et al. (2012) studied the influence of fiber content (20%, 30%, 40%, and 50%) on the mechanical properties of kenaf fiber reinforced polyurethane. This study showed that the tensile strength of the composite increased as fiber loading increased, up to 30% of fiber loading. Composites with 40% fiber loading showed the second highest tensile strength. The tensile modulus, flexural strength, and modulus increased with each increment in fiber loading. Mahjoub et al. (2014) reported that continuous unidirectional kenaf fiber reinforced epoxy composites with different fiber volumes have variable tensile strength. The 40% fiber volume, which was the highest fiber content that was tested, yielded optimum tensile properties for the composite. Similar findings were documented in their analytical analysis using the rule of mixtures (ROM). Researchers reported studies using bamboo fibre as reinforcement for fabrication of natural fiber reinforced polyester composites (Ratna Prasad and Mohana Rao 2011). Different types of fiber were used such as jowar, sisal, and bamboo. The effect of different volume fractions were evaluated and 0.4 volume fraction showed the optimum mechanical properties.
Researchers investigated how the use of more than one type of reinforcement affected the performance of different composites. Hybrid composites can be made either using natural fibers or natural fibers with synthetic fibers depending on the application. Maleque et al. (2012) studied the flexural and impact properties of kenaf/glass hybrid composites with different ratios. In this study, untreated and treated kenaf were used. Treated kenaf/glass hybrid with a ratio of 50:50 showed the highest flexural strength, while untreated kenaf/glass hybrid with a ratio of 50:50 showed the highest value of impact strength. Asim et al. (2017) studied the effect of hybridization on the mechanical properties of pineapple leaf fiber (PALF)/kenaf (K) phenolic hybrid composite. Different ratios of pineapple leaf fiber to kenaf fiber (PALF:K) were used ( 100:0, 70:30, 50:50, 30:70, and 0:100). It was shown that the optimum mechanical properties of hybrid composite was obtained when a 30:70 ratio of pineapple leaf fiber to kenaf fiber was used. Researchers have studied the effect of bamboo fiber on the physical and mechanical properties of glass/polyester composites (Vaghasia and Rachchh 2018). The percentage of glass fiber was maintain at 19%, and the percentage of bamboo was varied at 3%, 6%, 9%, 12%, and 15%. In general terms, the physical and mechanical properties increased as the percentage of bamboo fiber was increase up to 9%.
Bamboo has been utilised in composites as reinforcement; it has comparable mechanical properties to glass fiber (Rawi et al. 2013). Its high mechanical properties have attracted the interest of researchers to explore the potential for kenaf and bamboo fiber as reinforcement. This research work was intended to develop and characterize woven kenaf/bamboo hybrid composites for use in the automotive industries. In this study, bamboo mat was used to improve the properties of woven kenaf reinforced epoxy composite. Woven kenaf/bamboo reinforced epoxy hybrid composites were fabricated using the hand lay-up method with different ratios of kenaf and bamboo fibers. Mechanical properties such as flexural and impact properties were evaluated. In addition, density, water absorption, and thickness swelling of composites were carried out to study the effect of hybridization of kenaf and bamboo on physical properties.
EXPERIMENTAL
Materials
The woven kenaf fiber mat was supplied by Zul Sdn Bhd, Malaysia. The bamboo mat was procured from Shijiangzhuang Bi Yang Technology Co. Ltd, Hebei, China. D.E.R * 331 epoxy resin (reaction product of epichlorohydrin and bisphenol A) and the epoxy hardener Jointmine 905-3S (modified cycloaliphatic amine) were used in this study. Silicon spray was used as a releasing agent. The epoxy resin, commercial curing agent, and silicon spray were obtained from Tazdiq Engineering Sdn. Bhd., Selangor, Malaysia. Figure 1 shows the woven kenaf mat and bamboo mat. The properties of epoxy hardener Jointmine 905-3S and epoxy resin are shown in Tables 1 and 2, respectively.
Fig. 1. a) Woven kenaf mat and b) bamboo mat
Table 1. Typical Properties for Hardeners
Table 2. Typical Properties for Epoxy Resin
Fabrication of composites
The hand lay-up method was used to fabricate the bamboo mat, kenaf mat, and hybrid kenaf/bamboo. The bamboo mat and woven kenaf were cut according to mould size, 300 mm × 300 mm, and put in the oven at 60 °C for 24 h to remove moisture. The epoxy and hardener were mixed with a 2:1 ratio and stirred with wooden stick at room temperature for 2 to 4 min. The mould was sprayed with a thin layer of silicon spray, which acts as a releasing agent. Hybrid composites of kenaf and bamboo were prepared with different weight ratios of 70:30, 50:50, and 30:70, with total fiber loading at 40% by weight. A thin layer of epoxy was poured into the mould followed by the bamboo and woven kenaf mats. Epoxy was applied on every layer of the mats. The mould was transfer into a hot press with a temperature of 110 °C for 10 min, then transferred into a cold press for 5 min before it was demoulded. A single woven kenaf mat and bamboo mat were prepared as reference. Figure 2 shows the prepared samples.