The influence of coupling agent on lnterfacial shear strength of Sansevieria cylindrica fiber-epoxy composite

Abstract

The composite strength depends on the effectivity of interface interaction between the fiber and the matrix. The chemical treatment makes fiber surfaces more compatible with a hydrophobic polymer. So, this study aims to determine the influence of silane coupling agent concentration on the interfacial shear strength in the fiber composite of the Sansevieria cylindrica fiber. The methods included fibers treatment using ethanol as a dissolving and silane coupling agent with concentrations of 2.5%, 5%, 7.5%, and 10%. Fibers were embedded into the epoxy polymer for as long as 200 μm. The interfacial shear strength test was conducted through a single fiber pull-out test. Fiber morphology, crystallinity, and the functional group were observed using a scanning electron microscope and X-ray diffraction (XRD), respectively. As a result, the morphology of S. cylindrica fibers became rougher and showed a rougher surface after a silane concentration of 7.5%, but with the proper concentration, some fiber surfaces provided a good interface. Analysis using X-ray diffraction (XRD) on S. cylindrica fibers without treatment showed a crystalline index of 66%. Increasing silane concentration by 10% and the crystalline index by 75%. The treatment with a silane concentration of 0.0%, 2.5%, 5.0%, 7.5%, and 10.0% results in interfacial shear strength of 39.936, 59.300, 76.742, 83.965, and 91.321 MPa, respectively. The interfacial shear strength increases when the concentration of silane coupling agent increases, with the highest shear strength of 91.321 MPa at a silane concentration of 10%. The silane coupling agent changes hydroxyl groups into silanol groups in fibers, making a bond between the matrix and fibers. It can conclude that the treatment of a silane coupling agent increases the interfacial shear strength of the interface of S. cylindrica fiber-epoxy composite.