Biocomposites based on a balsa wood core containing intermediate layers made of coconut and sisal

Sandwich-type composite materials of various geometries were obtained, in which the inner layer was a laminate of glass fabric, and the core consisted of natural materials: balsa wood, coconut and sisal fibres. The materials were tested to determine the type of cracking process under static and dynamic stress conditions (impact strength). The best results were obtained for hybrid balsa/glass fabric composites with a spacer made of sisal mat. This type of system allows a controlled cracking process, which is a consequence of a different stress distribution. The research shows that the combination of different materials in a single composite, depending on their volume fraction, density and layering geometry, opens the way for use in technical constructions, especially where high specific strength is required. The work contains valuable results of research on sandwich materials, their behaviour under load, their modification, and their impact on the transfer of dynamic and static stresses. For the first time, a composition was tested containing a balsa tree core with transient elastic layers made of natural cellulose fibres.