Teknomekanik Vol.4, No.2, Dec 2021, pp. 72~77 e-ISSN: 2621-8720 p-ISSN: 2621-9980  72 Analysis of Tensile Strength of Citronella (Cymbopogon Nardus) Fiber Reinforced Composite Materials Julio Lukmanul Ardi, Hendri Nurdin, Andril Arafat and Sri Rizki Putri Primandani Department of Mechanical Engineering, Faculty of Engineering, Universitas Negeri Padang, Padang 25131, Indonesia Article Info Article history: Received Jun 18th, 2021 Revised Aug 19th, 2021 Accepted Oct 19th, 2021 Keywords: Citronella Fiber Composite Polyester Resin Tensile strength ABSTRACT The use of synthetic fibers in composite materials has a negative impact on the environment. One way to reduce this impact is to replace synthetic fibers with natural fibers. A natural fiber that has the potential as a mixed material in the manufacture of composite materials is citronella (Cymbopogon nardus) fiber. This study aims to determine the effect of volume fractions 40%, 50%, 60%, and 70% of citronella fiber with polyester resin matrix BQTN 157 on tensile strength. The process of making composites used the hand lay-up method. The specimen was formed according to the ASTM D3039 standard and the tensile strength of the specimen was tested by using a Universal Testing Machine (UTM). From the results of the study, the maximum tensile strength was found in the fiber volume fraction 70% of 77.35 MPa, the strain is 6.57%, and the modulus of elasticity is 1.177 GPa. This study indicates that fiber volume fraction affects the tensile strength of composite materials. Hence, the manufacture of composite materials which have good strength is influenced by many things such as raw materials, matrices, mixture composition, and methods. Corresponding Author: Julio Lukmanul Ardi, Department of Mechanical Engineering, Faculty of Engineering, Universitas Negeri Padang Jln. Prof. Dr. Hamka Air Tawar, Padang 25131, Indonesia Email : juliolukman53@gmail.com 1. INTRODUCTION The development of materials technology, including composites, is still in demand by the general population. It is due to the advantages of composite materials which are easily constructed, lightweight, lowpriced , and environmentally friendly [1]. The most common reinforcement fiber used by the community in composites processing is carbon, glass, and ceramics. However, the use of synthetic fibers will certainly cause damage to the environment because it is difficult to decompose naturally, therefore natural fibers appear as a substitute for synthetic fibers [2]. The mechanical properties of composite materials are influenced by several factors, including the manufacturing process and the constituent materials [3]. According to [4] one that affects the material strength is the matrix. The weakness of synthetic fiber composites is relatively overpriced and it has a tendency to damage the environment [5]. Scientists have found a replacement fiber that is environmentally friendly, non-toxic, relatively inexpensive , and its strong ability can match synthetic fibers [6]. One of the replacements for synthetic fiber is a natural fiber which has the potential to be developed into composite materials. Applications of natural fiber-reinforced composite materials have been widely used such as in connecting rods in vehicles, aerospace, shipping , and sports equipment [7]. The advantages of using natural fibers are accessible raw materials, non-toxic content, ease to recycle , and low environmental impact [8]. The tensile strength of various fibers can be seen in Table 1. Journal homepage: http://teknomekanik.ppj.unp.ac.id DOI: https://doi.org/10.24036/teknomekanik.v4i2.10472 73  Vol.4, No.2, Dec 2021, pp. 71~77 Table 1 : Tensile strength of some fibers [9] Material e-glass Carbon Hemp Kenaf Jute Tensile strength (MPa) 1200-1800 4000 350-800 400-700 300-700 Young’s modulus (GPa) 72 235 30-60 25-50 20-50 Elongation (%) 2.5 2 1.6-4.0 1.7-2.1 1.2-3.0 One type of natural fiber that has the potential to be used as a composite raw material is citronella (Cymbopogon nardus), which is one of the plants that are easy to cultivate. It has various benefits and has been used for aromatherapy, food preservatives, and perfumes [10]. The citronella plant is processed to extract the oil, and the waste from the distillation is usually used as fuel during the refining process. It is also used as animal feed and raw material for organic fertilizers. Citronella plants contain essential oils produced from distillation, in which distillation waste has the potential to be used as animal feed because it contains about 7% protein and high fiber [11]. The composition of chemical compounds in citronella stems can be seen in Table 2. Table 2 : Chemical compounds in the stems of citronella (cymbopogon nardus) [12] Chemical Compound Amount (%) cellulose 39.5 hemicellulose 22.6 lignin 28.5 The processing of citronella waste cannot be optimized because this waste is directly disposed of or burned. The use of this waste is certainly beneficial from an economic point of view in the manufacture of composite materials. Therefore, the high fiber content in citronella plants can be used as a mixture to form composite materials [13]. This study aims to utilize citronella waste for the manufacture of composite materials. 2. METHODS This research was an experimental study in which the test results were obtained directly from the specimen. Tools and materials used in the manufacture of composites include, Materials: - Citronella Fiber Figure 1 : Citronella Fiber. - Polyester Resin Yukalac 157 BQTN and Catalyst - Universal Testing Machine (UTM) Tools: Journal homepage: http://teknomekanik.ppj.unp.ac.id DOI: https://doi.org/10.24036/teknomekanik.v4i2.10472  Vol.4, No.2, Dec 2021, pp. 72~77 74 Figure 2 : Universal Testing Machine - Digital scales Measuring cup Sample Mold Ruler The manufacture of composite materials used the hand lay-up method. This study focused on the effect of fiber volume fractions 40%, 50%, 60%, and 70% with resin matrix BQTN 157 Yukalac on the tensile strength of composite materials. This test used the ASTM D3039 standard based on Table 2. Table 3 : Tensile Specimen Geometry Reqiurements [14] Parameter Compound Requirements: Shape Minimum length Specimen Width Specimen width tolerance Specimen thickness Specimen thickness tolerance Specimen flatness Tab requirement Tab material Fiber orientation Tab thickness Tab thickness variation between Tab bevel angle Requirement Constant rectangular cross-section Gripping + 2 time width + gage length As needed ± 1 % of width As needed ± 4 % of thickness Flat with light finger pressure As needed As needed As needed ± 1 % tab thickness 5 to 90, inclusive Figure 3 : Dimensions & Geometry of ASTM D3039 specimen without tabs The dimensions of the specimen were 80mm x 10mm x 5mm without tabs with a test area length of 60mm and a grips area of 10mm on each side of the specimen. Tensile testing aims to determine the mechanical properties of a material such as stiffness, ductility , and strength[15]. This test was carried out by applying a tensile load to the specimen until it was broken, and the resulting data was in the form of stress-strain curve, elongation, and modulus of elasticity. Stress is a force per unit area, and it was obtained by equation 1. Journal homepage: http://teknomekanik.ppj.unp.ac.id DOI: https://doi.org/10.24036/teknomekanik.v4i2.10472 75  Vol.4, No.2, Dec 2021, pp. 71~77 𝐹 𝜎=𝐴 (1) Strain is the increase in the length of the object per initial length. Strain was obtained by equation 2. ∆𝑙 𝜀 = 𝑙𝜊 (2) According to [16] Volume fraction is defined as a combination of fiber volume and matrix volume used to determine the composite volume, through equation 3. 𝑚𝑓 𝑚 𝑣𝑐 = 𝑣𝑓 + 𝑣𝑚 = 𝜌 + 𝜌 𝑚 𝑓 (3) 𝑚 As a control material, the fiber volume fraction can be obtained by equations 4 and 5. 𝑣𝑓 𝑉𝑓 = 𝑣 × 100% (4) 𝑐 𝑚𝑓 𝑊𝑓 = 𝑣 × 100% (5) 𝑐 2.1 Composite Manufacturing Process The raw material was obtained from the citronella distillation waste in South Limau Manis, Padang. Citronella stem waste was soaked for 3-4 days. This process was intended to let the substances attached to the fibers soften so it facilitated the separation of the fibers in the stems. The process of separating the fibers in the citronella stems was done by shaving the citronella stems repeatedly until clean fibers were obtained and then dried without sunlight. The dried fibers were soaked in an alkaline solution (5% NaOH) for 30 minutes, then the fibers were cleaned with running water and dried without sunlight. The matrix used was polyester resin yukalac BQTN 157. Composites were made by hand lay-up method. The ratio of resin and hardener was 10:1 and the fiber volume fraction (Vf) was 40%, 50%, 60%, 70%. The tensile test sample was printed using glass and it was pressed. Then the sample was cut to form a specimen according to the ASTM D-3039 standard. The specimen pieces were smoothed using sandpaper. The tensile testing used UTM (Universal Testing Machine) with a capacity of 50 kN. The results are shown in the form of the relationship between tensile properties and fiber volume fraction (Vf). 3. RESULTS AND DISCUSSION Specimen testing was carried out by using universal Testing Machine (UTM). The average tensile test results can be seen in Table 4. Table 4 : The results of average tensile test of the composite Fiber Resin Tensile Strength (MPa) 40% 60% 46.5 8.00 0.581 50% 50% 51.59 8.3 0.644 60% 40% 55.71 7.33 0.775 70% 30% 77.35 6.57 1.177 Volume Fraction Strain (%) Modulus of Elasticity (GPa) It can be seen in table 3 the results of the average tensile test on fiber volume fractions of 40%, 50%, 60% , and 70% of the resin yukalac BQTN 157. So that the graph of the relationship between stress and volume fraction is obtained in Figure 4. Journal homepage: http://teknomekanik.ppj.unp.ac.id DOI: https://doi.org/10.24036/teknomekanik.v4i2.10472  Vol.4, No.2, Dec 2021, pp. 72~77 76 90 77,35 80 Tensile Strength (MPa) 70 60 55,71 51,59 46,5 50 40 30 20 10 0 40% 50% 60% 70% Fiber Volume Fraction Figure 4 : Graph of the relationship between tensile strength and fiber volume fraction The graph shows the tensile strength in the fiber volume fraction 40% with a value of 46.5 MPa. In the volume fraction of 50% it has a tensile strength of 51.59 MPa. The fiber volume fraction 60% has a tensile strength of 55.71 MPa and the tensile strength value in the volume fraction 70% is 77.35 MPa. The above research proves that there is an effect of volume fraction on the tensile strength of composite materials. The results of this study are in line with the opinion of [17]. According to him, the tensile strength of the composite material increases with the increase in the volume fraction of the fiber. 4. 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Kamel, “Pengaruh Fraksi Volume Serat terhadap Sifat-sifat Tarik Komposit Diperkuat Unidirectional Serat Tebu dengan Matrik Poliester,” Jurnla Ilm. Semesta Tek., vol. 14, no. 2, pp. 133–138, 2011. [17] P. D. Setyawan, N. H. Sari, and D. G. Pertama Putra, “Pengaruhorientasi Danfraksi Volume Serat Daun Nanas (Ananas Comosus)Terhadap Kekuatan Tarik Komposit Polyestertak Jenuh(Up),” Din. Tek. Mesin, vol. 2, no. 1, pp. 28–32, 2012, doi: 10.29303/d.v2i1.108. 77 NOMENCLATURE 𝜎 𝐹 𝐴 𝜀 ∆𝑙 𝑙𝜊 𝑣𝑐 𝑣𝑓 𝑣𝑚 𝑚𝑓 𝜌𝑓 𝑚𝑚 𝜌𝑚 𝑉𝑓 𝑊𝑓 Tensile Stress (MPa) Force (N) Area (𝑚𝑚2 ) Strain (%) Length Increase (𝑚𝑚) Initial Length (𝑚𝑚) Composite volume (𝑐𝑚3 ) Fiber volume (𝑐𝑚3 ) Matrix volume (𝑐𝑚3 ) Fiber mass (gr) Fiber density (gr/𝑐𝑚3 ) Matrix mass (gr) Matrix density (gr/𝑐𝑚3 ) Fiber volume fraction (%) Fiber weight fraction (%) Journal homepage: http://teknomekanik.ppj.unp.ac.id DOI: https://doi.org/10.24036/teknomekanik.v4i2.10472