Kenaf Core Sandwich Structure Composites Toughened with Modified Epoxy

This study was undertaken to enhance the properties of kenaf core epoxy matrix in sandwich structure, in addition to improve on mechanical, thermal and morphological properties. Sandwich panel was prepared by hand lay-up method. Sandwich panel were prepared in the ratio of 30wt%:70wt% from kenaf fiber and epoxy. The kenaf fiber was treated with natrium hydroxide (NaOH) to improve the interaction between fiber-matrix. Liquid natural rubber (LNR) was used as impact modifier and toughened agent in order to modify the epoxy matrix within 0wt%-5wt% of LNR. Mechanical test such as flexural, drop impact and tensile test were performed to investigate the optimum system of kenaf-core sandwich panel. All tests have been carried out according to the ASTM 365, C297, C393, and D1736. Each final data point is an average value that has been obtained based on a statistical sampling of six specimens. The main element of core structure is kenaf and the skin used in this study is aluminium type 1100. According to compression, flatwise tensile, three point bending and drop impact tests, 3wt% of LNR content exhibit as an excellent impact modifier, in modifying the mechanical properties due to rubber toughening. The mechanical properties of sandwich panel showed an increasing trend up from 0 wt% to 3 wt% of LNR content with optimum tensile strength 37.62 MPa and 21.6% increase in Young's modulus. The addition of 5wt% was substantially interrupted the system. These findings were also supported by scanning electron micrograph (SEM). SEM micrograph further showed that LNR act as impact modifier and cushioning by absorbing the energy and transfer within the matrix, preventing the crack from continuing cracking on the sandwich panel. TGA results showed that with the presence of LNR could improve the thermal stability of sandwich panel with high degradation temperature. Thus, all sandwich panels contain LNR show higher thermal stability compared to the kenaf core with neat epoxy. Water absorption was inversely proportional with the increasing of LNR composition into kenaf core epoxy matrix which was two times lower than kenaf core epoxy composite without rubber. All the results showed that the sandwich structure in the presence of LNR greatly increased the performance of sandwich structure when rubbery particles dispersed throughout the thermoset matrix.