EVALUATION OF SANDWICH COMPOSITES WITH VEGETABLE FIBERS AND HONEYCOMB MADE ON A 3D PRINTER

Abstract

In modern society, polymer composites are widely used due to their high strength-to-weight ratio, among other properties. In recent times, due to environmental issues and higher costs, most industrial and engineering sectors are trying to reduce the use of synthetic fibers by using natural fibers or lignocellulosic fibers. New composite materials using renewable materials and additive manufacturing enable better development of high-performance materials for various industries. The objective of the work was to determine the behavior of a fully biodegradable sandwich composite using sisal fiber sheets in a polyurethane matrix of castor oil and PLA honeycomb using a 3D printer (Fused Deposition Modeling FDM). Firstly, a study was carried out to determine the best alkaline treatment for the sisal fibers with which the sandwich composite sheets were made, with the aim of determining the best treatment that produces greater adhesion of the fiber to the resin and therefore better tensile effort. For this, several composite plates of polyurethane resin matrix with castor oil were made using the same amount of fiber in all plates (10%w), from which the specimens for the tensile tests were cut in a LASER cutting machine with dimensions according to the Standard for this test. After performing the tensile tests, the best alkaline treatment was determined to be a concentration of 10% sodium hydroxide and 4 hours of immersion of the dissolving fiber. To verify the efficacy of the treatment, fibers were also observed by SEM and XRD. Subsequently, sheets of the sandwich composite of castor bean polyurethane resin and sisal fibers treated with 10% NaOH dissolution and 4 hours of fiber immersion, previously determined also with 10% of w of fibers, were also made, and the cores of the sandwich composites with PLA honeycomb structure were also made,  to make a comparison, they were also made with PETG. The flexure tests demonstrated that the sandwich composites performed better with PETG. In all tests, PETG was more resistant, usually 21% to 32% more resistant than PLA. But the specific resistances are similar, with PLA compounds having a 13.8% lower core density than PETG cores. The results obtained in the study coincide with the results previously published by other authors.

DOI: https://doi.org/10.56238/sevened2025.019-024