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"Komposit sandwich merupakan material yang mempunyai potensi tinggi dalam aplikasi rancang bangun struktur ringan karena memiliki perbandingan strength to weight yang tinggi. Penelitian ini dilakukan untuk mencari sifat mekanik dari komposit sandwich dengan kulit kombinasi serat woven S-glass dan epoxy dan inti dari polyurethane foam. Material dibuat menjadi dua jenis orientasi S-glass yang berbeda yaitu 0°/90°/PU/0°/90 dan 0°/90°/PU/-45°/+45°. Material dibuat dengan menggunakan metode hand lay up dan vacuum bagging. Uji mekanik yang dilakukan adalah uji tekuk dan uji tekan arah edgewise. Penelitian ini memberikan hasil bahwa komposit sandwich jenis 0°/90°/PU/0°/90 memiliki sifat mekanik yang lebih baik dibandingkan dengan jenis 0°/90°/PU/-45°/+45°, dengan nilai kekuatan geser inti (74,38 ± 3,55) kPa, nilai kekuatan tekuk (1,22 ± 0,02) MPa, dan nilai kekuatan tekan (222,96 ± 8,98) kPa, serta kerusakan patahan pada citra SEM.

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Sandwich composite is a material with high potential in light weight structure because of high strength to weight ratio. Research was done to find the mechanical properties of sandwich composite with S-glass and epoxy combination skin and polyurethane foam core. The sample is divided into two different S-glass orientation, 0°/90°/PU/0°/90 and 0°/90°/PU/-45°/+45°. The sample was made by hand lay up and vacuum bagging method. Flexural test and edgewise compressive test were used to determine the mechanical properties of the sample. From the result of the mechanical test, we know that sandwich composite 0°/90°/PU/0°/90 has a better mechanical properties than 0°/90°/PU/-45°/+45°, with (74,38 ± 3,55) kPa core shear stress, (1,22 ± 0,02) MPa facing bending stress, and (222,96 ± 8,98) kPa facing compressive stress, also with a fracture in SEM image."

"Mutu beton yang diterapkan pada pengujian ini menggunakan target mutu K250 dan fc’ 20,7 MPa untuk beton beragregat polipropilena. Variasi tulangan pada balok beton tersebut terbagi menjadi A, B, C dan D. Balok jenis A merupakan beton polos, balok B beton dengan tulangan tarik, balok C menggunakan tulangan tarik dan sengkang U dan balok D menggunakan tulangan tekan, tarik dan sengkang lengkap. Jumlah sampel balok sebanyak 4 buah balok beton normal dan 4 buah balok beton ringan, sampel silinder sebanyak 3 silinder beton normal dan 3 silinder beton ringan. Material agregat kasar polipropilena dan agregat halus pasir Subang. Pengujian agregat yang dilakukan adalah analisis saringan agregat, specific gravity dan kadar organik. Mencari kuat tekan beton fc’ dengan uji tekan silinder dan menggunakan UPV. Metode uji lentur yang digunakan adalah lentur murni. Data yang akan diperoleh berupa besar lendutan (mm), besar beban luar (kg) dan pola retak. Kemudian, output yang dicari berupa pola retak balok beton, grafik kekakuan, blok tegangan beton dan grafik momen kurvatur.  Dari hasil perbandingan antara balok beton normal dan ringan, diperoleh bahwa kekakuan balok beton ringan lebih besar dibandingkan balok beton normal, dan koefisien nilai k balok beton normal tidak dapat digunakan oleh beton ringan.

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In this opportunity, the writer attempts to do a flexural test on different variation of reinforced concrete beams. This flexural test requires K250 concrete quality and fc’ 20 MPa for lightweight concrete. The variation of reinforced concrete beams are divided into 4 types, that is A, B, C and D. The A beam is a concrete beams without any steel reinforcements, B is a concrete beam using tensile steel reinforcement, C is a concrete beam using tensile steel reinforcement with an additional shear reinforments U shaped and D as a full reinforced concrete with compression and tensile steel reinforcements using full shear reinforcements. There are 8 samples of concrete beams that are used in this test. Four of them are concrete beams using dry mix concrete and the rest are lightweight concrete beams using polypropylene, and there are 3 samples of concrete cylinders using lightweight concrete and 3 samples using normal concrete. Polypropylene is used as coarse aggregate and Subang sand as fine aggregate. Aggregate tests include sieve analysis, specific gravity and organic impurities test. Cylinder concrete samples are tested using compressive test and non destructive test using UPV to find the value of fc’. The method that is used in this flexural test is pure bending. The output datas of this test are deflection (mm), external load (N) and crack pattern. The components that need to be find are crack pattern, force - displacement curve, stress distribution and curvature moment. The results from the comparation of both concretes indicates that lightweight concrete is more rigid than normal concrete, and the coefficients of stress distribution of normal concrete cannot be used to calculate lightweight concrete."