Tensile Strength Comparison of Polymer Composite Materials Reinforced by Three Types of Bamboo Fiber Treated With 5% aq. NaOH Solution

The specimens were prepared with polyester polymer reinforced with natural fiber from three types of bamboo, namely Gigantochloa Apus, Bambusa vulgaris, and Bambusa blumeana. Their tensile properties were compared and investigated. In this paper, the specimen utilization of hand-wet layup processes of polyester resin with natural fibers. The fibers were treated with 5% NaOH solution to remove hemicellulose and create better debonding between matrix and fiber. Bamboo-reinforced composite of 3 types of bamboo with fractions 60% volume is thorn bamboo, Bambusa vulgaris, Gigantochloa Apus, and bamboo wipe without alkali. Of the three types of bamboo, the highest tensile strength of Gigantochloa Apus was soaked using NaOH with an average value of 37.06 MPa, with a tensile strain of 4.11%. In contrast, the lowest tensile strength value is Gigantochloa Apus which was not immersed in NaOH with an average of 13.79 MPa, a tensile strain of 2.54%. This matter shows the effect of immersion on tensile strength bamboo fiber composite. The results of the tensile strength of each type of bamboo obtained in this research, among others, bamboo thorn's tensile strength of 22.81 MPa, Bambusa vulgaris tensile strength of 16.69 MPa, bamboo apus 37.06 MPa, and Gigantochloa Apus without alkali 13.79 MPa. The observations show that Gigantochloa Apuscomposites are suitable for use as alternative tensile materials.


Introduction
This paper examines the tensile properties of composite materials made from natural fibers obtained from three different types of bamboo: Gigantochloa Apus, Bambusa vulgaris, and Bambusa blumeana. To prepare the specimens, a hand-layup process was used with polyester resin and natural fibers treated with a 5% NaOH solution to remove hemicellulose and enhance bonding with the matrix. The study compared the tensile properties of the three bamboo-reinforced composites with a volume fraction of 60%. The results showed that the Gigantochloa Apus composite soaked with NaOH had the highest tensile strength, making it a promising material for tensile applications. The paper also discusses the potential of natural fiber composites as an alternative to synthetic fibers and metal materials. Indonesia has a variety of bamboo species, including Gigantochloa Apus, Bambusa vulgaris, Bambusa blumeana, and others. Natural fibers, especially bamboo fibers, have great potential to be used in composite materials that are strong, cheap, and environmentally friendly. In this study, the authors aim to investigate the effect of 5% NaOH alkaline soaking for 2 hours on natural fibers from three types of bamboo: Gigantochloa Apus, Bambusa vulgaris, and Bambusa blumeana as reinforcement for composite materials. The tensile strength results on each variation of bamboo type will be evaluated to determine the optimal percentage value of NaOH. The authors hope these natural fibers can be used as an alternative to metal materials, which have several disadvantages and are relatively expensive.
1. Epoxy resins are one type of thermoplastic resins. These resins have wide usage in chemical, electrical, mechanical, and civil industry techniques. Usually, resin-type epoxy Is used as adhesives, Coating paints, Moldings cast, and mold objects. Type resins epoxy This can be distinguished into two types that are as follows: a. Bisphenol A resin has Power suitable adhesive to material others, often used as paint for metal, as well as coating combined with fiberglass. b. Cycloaliphatic resin has a low viscosity, and equivalence epoxy is small. The material was helpful as diluent bisphenol Because of its easy handling. 2. Matrix In composite materials, the matrix in the composite structure can come from polymer, metal, or ceramic materials. The matrix is the hybrid phase with the largest (dominant) part or volume fraction. The matrix in the mixed arrangement protects and binds the fibers to work properly. The matrix also functions as a fiber coating [3]. Generally, the matrix is made of soft and clay materials. The selection of matrix and fiber materials is essential in determining the composite's mechanical properties [4].
The principal matrix must be owned by the material matrix that must forward load, so fiber must Be attached to the matrix and compatible between fiber and matrix. The generally selected matrix is the matrix that has resilience and high heat. According to [5], the matrix has functions, including: a. Transferring voltage to fiber in a manner evenly. b. Protect fiber from friction mechanics. c. Protect from the detrimental environment. d. Donate characteristic rigidity and toughness.

Types of Composite
Based on filler material, the composite material is classified into: 1. Laminated Composite Layered composites are a type of composite consisting of two or more layers combined into one, each with different characteristics. An example is Polywood Laminated Glass, a composite consisting of a fiber layer and a matrix layer, and this composite is often used as a building [6].  In particulate composites, the added material is distributed randomly or in a less controlled manner than in flake composites [8]. Composite fiber is a type of mixed using fiber as material for the amplifier. In making composites, fibers can arrange elongated (unidirectional composites) or can cut, Then placed in a random manner (random fibers) as well as can woven (cross-ply laminate). The composite fiber is used in industrial automotive and airplanes [9].
(a)Unidirectional fiber composite (b) Random fiber composite

Filled composites
Filled composites are composites with the addition of material into a matrix with a three-dimensional structure, and usually, a filler is also in the three-dimensional form [10]. The fibers can be synthetic (asbestos, glass, boron) or organic fibers (cellulose, polypropylene, polyethylene). High modulus, coconut coir, palm fiber, empty palm fruit bunches, etc. ). Based on the fiber size, fiber composites can be divided into long fiber composites and those with a diameter of <100mm; these short fibers can be oriented or randomly distributed. Long fiber composites are more accessible to train than short fiber composites, but short fiber composites have more design.
Based on the form of the composite matrix can be divided into 3, namely as follows. [11] The first condition that the material matrix must meet is its ability to withstand the load.

Polymer Matrix Composite (PMC)
This composite type consists of the polymer as a matrix, both thermoplastic and thermosetting types. Thermoplastic is a plastic that can be softened repeatedly (recycled) using heat. Thermoplastic is a polymer that hardens when cooled. Thermoplastic will melt at a specific temperature, adhere to following temperature changes, and have reversible properties to its original properties; it hardens again when cooled. Thermoplastics that are commonly used as matrices include polyolefins (polyethylene, polypropylene), vinylic (polyvinylchloride, polystyrene, polytetrafluorethylene), nylon, polyacetal, polycarbonate, and polyphenylene. Thermosets cannot keep up with temperature changes (irreversible). Once hardening has occurred, the material cannot be softened again. High heating will not ease the thermoset but will form charcoal which decomposes because of its nature which is often used as a lid for kettles, such as melamine types. Today's most widely used thermosets are epoxy and unsaturated polyester [12]. Unsaturated polyester resin is the most commonly used thermosetting matrix composite manufacturer. The hand layup method uses This resin type in the manufacturing process.

Metal matrix composite (MMC)
Metal matrix composites are one type of composite that has a metal matrix. These composites use a metal such as aluminum as the matrix and reinforce it with fibers such as silicon carbide. MMC materials began to be developed in 1996. MMC composites, produced in the automotive industry, manufacture automotive components such as engine cylinder blocks, pulleys, shafts, and axles.

Ceramic Matric Composites (CMC)
CMC is a 2-phase material with 1 phase functioning as a reinforcement commonly used in CMC, namely oxide, carbide, and nitride. One of the manufacturing processes of CMC is the DIMOX process, which is the process of forming composites with the oxidation reaction of molten metal for the growth of the ceramic matrix around the filler area.
Based on the structure of the composite matrix can be divided into two types, namely as follows. [13] 1. A laminate structure is a composite of two or more layers combined into one, each with its characteristics. 2. A sandwich structure combines two sheets of skin arranged on two sides of a lightweight material (core) and adhesive. The skin's primary function is to withstand axial loads and bending. In contrast, the core functions distribute axial loads into shear loads over the entire area due to external force loading.

Test Equipment
Tools used in this research are halat test pull and bending. To carry out the test, a universal Tensile testing machine such as the Hung Ta brand will be used in Figure 6.

Preparation of Specimens
The manufacture of composite materials reinforced with bamboo fiber (Figure 7) first treated the bamboo fiber using a 6% NaOH solution.
Combining bamboo fiber with a temporary structure with epoxy resin can be overcome by heating the epoxy resin at a temperature of 80 degrees centigrade for 15 minutes to reduce viscosity and remove trapped air. Meanwhile, the bamboo fiber is placed in the oven to ensure complete drying. Furthermore, due to the short and porous structure of the bamboo fiber, it has the potential to bring higher air into the resin during bonding. The addition of 30% more resin is the solution to remove air bubbles that are potentially trapped in the material. Finally, the resin and bamboo fiber mixture was put into the oven at 80 0 C for 2 hours. After sufficient mass was felt for fiber infiltration into the resin and all air bubbles were lifted, the catalyst mixture was added and stirred evenly for 5 minutes. Furthermore, the mixture is poured into a mold that has been prepared to form a plate composite with a certain thickness. Moreover, the material is left for at least 24 hours to get the perfect hardening. After the composite material has obtained a stable condition, the material is shaped with a high-speed saw cut to make a test specimen following ASDM D3039 for tensile testing of fibrous polymer composite materials, as shown in Figure 8.

Testing
Mechanical testing to be carried out in this study consists of two types, namely tensile testing and bending testing. Tensile test specimens follow the ASTM D3039 standard, and bending test specimens follow the ASTM D790 standard. Both tests were carried out using a universal testing machine tensile tester brand Hung Ta with a capacity of 2000 kN. The macrostructure due to material damage due to testing will be observed using a digital microscope. Observing the fracture's structure or damage can predict the causes that occur in the composite material.

Tensile Testing
Tensile testing was carried out after making bamboo fiber composites with polyester resin clear to find out the magnitude of the tensile strength of the composite with the same volume of action on the bamboo fiber reinforcement composite. Tensile testing was carried out using a universal mechanical testing machine in the material testing laboratory of the Department of Mechanical Engineering, Universitas Malikussaleh. Based on the results of the tensile test that was carried out using the ASTM D3039 standard on the reinforcing composite of three types of bamboo fiber with alkaline treatment (5% NaOH ), optimization of 60% fiber volume fraction with random Orientation with tensile stress, tensile strain, and elastic modulus, the results are shown in Table 1 to table 4 to make it easier to analyze the data from the results of this test. The results are presented in the shape of the tensile properties curve composite.     Figure 9 to Figure 12. Based on testing 4 specimens of each type of bamboo for variations of differences in 3 types of bamboo fibers using alkali treatment and without alkali treatment, it is found that there are different tensile strengths according to the type of bamboo. load and tensile strength are greatly influenced by variations in 3 types of bamboo fibers using alkali and without alkali. In Table 1, Table 2, Table 3, to Table 4. In Table 1 we can see that composites with variations of bamboo fiber thorns in a shredded arrangement with a volume fraction of 60% have the highest tensile strength of 24.51 MPa in specimen 2.
In Figure 12 we can see that the average value of MPa tensile strength of these 3 types of bamboo.  Figure 13 we can see that the average value of MPa yield strength of these 3 types of bamboo. Thorn bamboo has an average yield strength value of 3.95 MPa. And bambusa vulgaris has an average yield strength value of 3.22 MPa. Gigantochloa Apus has an average yield strength value of 3.69 MPa. Gigantochloa Apus without alkali has an average value of yield strength of 3.03 MPa.
In Figure 14 we can see that the average elongation value of these 3 types of bamboo. Thorn bamboo has an average elongation value of 3.05%. And bambusa vulgaris has an average elongation value of 2.33%. Gigantochloa Apus has an average elongation value of 4.11%. Gigantochloa Apus without alkali has an average elongation value of 2.54%. The following are the macro fracture images of the tensile testing results as shown in Figures 15, 16, 17 and 18.

Conclusion
Composites reinforced with bamboo from 3 types of bamboo with a volume fraction of 60%, namely thorn bamboo, Bambusa vulgaris, and wormwood bamboo, have the highest tensile strength in wormwood bamboo with a volume fraction of 60% with an average value of 37.06 MPa, tensile strain of 4.11%, in Bambusa vulgaris fiber shows that the tensile strength of the composite has decreased with an average value of 16.69 MPa, tensile stress of 2.33%. The results obtained in this study show that the highest tensile strength value was found in the wormy bamboo fiber at 37.06 MPa with a strain of 4.11%. The results show that the wormwood bamboo composite can be an alternative tensile material.