Natural fiber was proof to be a strong material capable to substitute synthetic fiber. Natural fiber from banana stem having tensile strength of 68.44 MPa with average diameter of 0.698 mm maybe used as reinforcement for polymer composite materials. In a composite material of recycle polypropylene (RPP) matrix reinforced by fiber of banana stem, the fiber then should carry a big portion of applied load working on the composite materials. The RPP should act as a bonding for the fiber of banana

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... em, also protect fiber from damage. The optimum of volume fraction for bending test was 35% fiber : 65% matrix where bending stress 127.35 N/mm 2 , modulus of elasticity 3209.75 MPa, shear stress 2.83 N/mm 2 and flexed stress 66,48Mpa, undergo a significant and optimum change. Using SEM observation, it was seen that 35% fiber : 65% matrix volume fraction and matrix was the optimal proportion in which bonding of matrix and fiber became strong. It maybe concluded that the influence of volume fraction of fiber of banana stem as reinforcement (fiber) and RPP as bonding (matrix) in a composite materials should result in a strong and brittle material. From all the tests done, it was found that the almost optimum of volume fraction was 35% fiber and 65% matriks.