A skateboard is a small piece of wood shaped like a surfboard with four wheels attached to it that is used to glide on a certain track. In general, this tool is made using wood material taken from nature and vulnerable to environmental damage issues. In this research, the waste of banana stems will be processed into the main raw material for skateboarding. The type of material chosen is the type of composite material with banana stem waste selected as reinforcement and polyester resin as the matrix material. The purpose of this research is to design and manufacture a skateboard made of composite fiber reinforced banana stem fibers and to test its flexural strength to obtain the characteristics of the material formed. The design was carried out with the help of the 2007 version of Autocad software by following commercial skateboard standards.  Flexural testing was carried out at the Impact and Fracture Research Center laboratory, Faculty of Engineering, University of North Sumatra. Static static testing of polymer composite board specimens from banana stems obtained the average value data for the composition of 5% banana stems is 9.81 MPa, for the composition of 10% banana stems an average of 13.60 MPa, and composition of 15% banana stems the average is 27.20 MPa. 2. The analysis shows that the best composition is 15% of banana stems, with an average flexural strength value of 27.20 MPa. Therefore, the composition used in this study is the composition of 15% reinforcement of banana stems.

<h1>In general, household waste water pipelines use plastic pipes of PVC type that are not environmentally friendly and are relatively expensive. Therefore, this research will design molds and manufacture of composite pipes using raw materials of clampshell powder. The raw material used is clampshell powder with the composition of MgO and CaO compounds which is about 22.28% and 66.70%. The mixture of materials used consisted of clampshell powder with a size of 40 mesh, catalyst, and unsaturated polyester resin as a matrix. The objective of this study is manufacture of water pipes made from polymer composites reinforced by clampshell powder. Composite pipe manufacturing is carried out using the casting method. Pipe molds are made of stainless steel with a diameter of 40.46 mm (1.6 in) and an outer diameter of 50.8 mm (2 in). This mold size follows SNI 06-0084-2002 standards. The results of the study, water pipes from polymer composite material reinforced by clampshell powder with an inner diameter size of 40.64 mm and varying outside diameter. This variation depends on the composition of the clampshell powder in composite materials. The greater the clampshell powder composition, the more easily the maximum pipe wall thickness can be obtained. The average wall thickness variation is 3.35 mm. This variation is still included in the polymer water pipe requirements, which is a minimum of 2 mm.</h1>

<em>Typical technology for processing red onion affects the quality of red onion produced. The process of drying red onion is one of the important factors in producing the best quality of red onion. Environmentally friendly and easy operation and maintenance technology is the desired technology. In the process of engine design, the strength of the material and structure are the main factors of the building of the machine. Calculation with finite element method (FEM) is the best choice to obtain information on stress distribution on a machine structure. In this study, the calculation of the FEM method was assisted by Ansys APDL 15.0 software. The objectives of this study were: (1) calculation of the load on the tray structure, (2) the distribution of stress on the tray structure, seat, and frame for red onion dryers, and (3) analyzing the strength of the material using the Tresca and Energy Distortion methods. The input load comes from the weight of the tray and red onion. The analytical method used is the finite element method with the type of structural analysis and Beam 3Node 189 element type. Based on the FEM simulation results, the maximum stress that occurs in the tray is 1.22 MPa and the maximum deflection is 0.0055 mm. The maximum stress in the tray support structure is 33.25 MPa and the maximum deflection is 0.014 mm. The maximum stress on the frame structure of the onion drying machine is 0.89 MPa and the maximum deflection is 0.000235 mm which occurs in the middle of the machine structure. Using the Tresca and Distortion Energy theories, it is found that the stresses that occur are still far from the failure criteria for all structures. Likewise, the deflection that occurs is very small so that the construction of the onion drying machine is safe to use.</em>

<span>Komposit merupakan sejumlah sistem multi fasa sifat gabungan, yaitu gabungan antara bahan matriks atau pengikat dengan penguat. Penelitian ini dilakukan menggunakan metode kuantitatif dengan rancangan penelitian eksperimental serta membandingkan hasil pengujian pada metode elemen hingga yang dilakukan penelitian di laboratorium. Objek penelitian berupa serat tempurung kelapa yang dipilih karena melimpahnya sumber daya alam tersebut. Spesimen matriks resin dibuat dengan standar ASTM D 638 M-84 dengan bahan resin epoksi dan katalis menggunakan metode pengecoran. Teknik pengumpulan data yang digunakan adalah teknik pengujian laboratorium. Instrumen yang digunakan berupa lembar pencatatan. Dari hasil penelitian yang dilakukan didapatkan kekuatan tarik komposit tertinggi dengan tata letak random sebesar 3,38 kgf/mm2 dan perpanjangan sebesar 0,38 mm, <em>Cross</em> sebesar 3,03 kgf/mm2 dan perpanjangan sebesar 0,86 mm, <em>continuous</em> sebesar 2,24 kgf/mm2 dan perpanjangan sebesar 1,03 mm, <em>woven</em> sebesar 1,64 kgf/mm2 dan perpanjangan sebesar 0,64 mm. Bentuk patahan menunjukan bahwa hasil pengujian tarik mengalami patahan getas, karena ujung patahan terdapat patahan 900 dan kasar di karenakan adanya mekanisme <em>fiber pull out</em>.</span>

Objective of study reported in this paper is finding the optimum cutting condition respected to surface roughness (Ra), flank wear (VB) and tool life (TL) when high speed turning of aluminum alloy using uncoated carbide. Turning test was carried out by full factorial design where cutting speed (v), feed (f) and depth of cut (a) were determined as the independent variables. The high level values were set as v 1250 m/min, f 0.15 mm/rev, a 1.2 mm and for the low level were v 1000 m/min, f 0.12 mm/rev, a 1 mm. By multiple-linear regression method, the data of response variables resulted from the testing was used to developed 3 (three) mathematical models of Ra, VB and TL. Those models, φ(v, f, a), were then used as the fitness functions for finding the optimum cutting condition using Multi Objective Genetic Algorithm (MOGA) method. The results of study show that the optimum cutting condition for gaining the best roughness is at v 1000 m/min, f 0.12 mm/rev and a 1.2 mm. At that cutting condition, Ra and TL are recorded at 1.22 microns and 2.32 minutes, respectively.