Densified delignified wood as bio-based fiber reinforcement for stiffness increase of timber structures

Abstract

Carbon fiber reinforcements are applied in timber engineering thanks to their high strength, but their fossil origin compromises sustainability. Furthermore, applications for which an increase of stiffness is beneficial, such as in slab-type elements, still remain unexploited. Here, we reinforced beech wood with an emerging bio-based fiber type, densified delignified wood (DDW). We comparatively adhered DDW, flax, and carbon fibers to wood using a polyurethane adhesive. The specimens’ stiffness was tested before and after reinforcement using bending tests, and tensile tests of the isolated fiber composites were performed for modeling purposes. Whereas no beneficial effect was reported for flax fibers, DDW and carbon fibers were able to provide a stiffness increase of up to 10.5% and 16.7%, respectively, demonstrating the potential of DDW. On this basis, a design case study conducted for a timber–concrete composite slab showed that a DDW stiffness reinforcement can be a material saving alternative.