Folded hybrid FRP-timber sections: concept, geometric design and experimental behaviour

Driven by an increasing demand for sustainable and easy-to-construct timber infrastructure, recent research at The University of Queensland (UQ) has led to the development of a new class of structures called ‘folded hybrid FRP-timber’ (FHFT) structures. In FHFT structures, FRP (fibre reinforced polymer) is combined with timber veneers to create high-performance, lightweight, easy-to-construct structural members. In such FHFT members, the fibre directions of FRP and timber are appropriately oriented to produce optimal composite properties, while the geometry of the cross section is designed to optimize the load bearing capacity for a given amount of material. This paper presents two highly innovative fabrication processes for FHFT sections that enable new geometric and material possibilities in the design of FHFT structural elements. The new fabrication processes are first demonstrated for the manufacture of regular structural hollow sections. A geometric design method is then presented for the fabrication of any folded structure with a uniform cross-section specified as a non-intersecting polygonal chain. An experimental study comparing the compressive capacity of FHFT and plywood-only columns is then presented. It is seen that the two fabrication methods produce FHFT hollow sections with similar capacities to each other and double the capacity relative to plywood-only sections. The new sections are also shown to have a weight-specific compressive strength comparable to that of existing commercial steel hollow sections.