Manufacturing, microstructure and mechanical performance of plant-based natural flax FRP-wood sandwiches for green aircraft interiors

Abstract

This Bachelor thesis is a study of the mechanical performance of flax fibre reinforced polymer (FFRP) - balsa wood sandwich panels as a potential environmentally friendly alternative to the current synthetic materials for aircraft interior components that have a high embodied energy and carbon footprint (eg. carbon or glass fibre reinforced polymers, aramid fibre or some metal alloys). The first part of the thesis consists of a literature review about composites and typical aircraft interior synthetic materials, plant-based natural fibres and their performance, as well as an insight on the application of natural materials for aircraft components. The research reveals that natural materials indeed have the potential to be used in cabin interiors. Flax has one of the highest strength and elastic modulus of all vegetal fibres, it is light and cheap and has specific mechanical properties comparable to those of glass fibre. On the other side, balsa wood is a good core candidate due to its stiffness and great lightweight. The second part consists in the manufacturing and testing of the FFRP - balsa wood sandwich panels. For this, different panel configurations have been considered based on three different core thicknesses and one and two layer FFRP facings, including the addition of two fire retardants (APP and Al(OH)3 ) in different concentrations. For the mechanical analysis, four main tests have been performed: energy absorption, axial compression, out-of-plane bending and in-plane bending. The results showed that the core thickness and number of FFRP layers have a significant influence on the mechanical performance, which varies depending on the tests and parameters. The fire retardants also show disparate effects on the load-displacement curves and mechanical properties, typically reducing them. The interface of the core and skins appeared to be very consistent, showing a good compatibility between flax and balsa wood.