Abstract
Composite is a material composed of more than two constituent elements; composites are heterogeneous on a macroscopic scale. Each composite material has different properties, and when combined in certain compositions new properties are formed. The study of coast cottonwood bark fiber composites aims to determine the optimum bending strength of polyester composites strengthened with fiber from coast cottonwood bark with rice husk fillers by using the response surface method. The method used was to alkalize the coast cottonwood bark fibers by soaking 5% NaOH per 1 liter of water for 2 hours. The test object was made using the Hand Lay-Up and Compaction method, the fiber ratio was 35.86%, 40%, 50%, 60% and 64.14% with fillers 0.76%, 2%, 5%, 8% and 9, 24%. The bending test used the ASTM D790 standard and analyzed the data using the response surface method. The test results showed the best condition was at fiber volume fraction of 49.06% and filler volume fraction of 5.39% with bending strength values of 99.71 N / mm2. Regression equations were suitable for the response of this study: y = 99.6100 – 1.4339 x1 + 0.5107 x2 – 8.6506 x12– 2.4756 x22– 1.4325 x1* x2. Response surface method is an efficient method used to determine the independent variables levels that can optimize response.