WrapToR hierarchical space frames made from natural material composites

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Trusses and space frames are some of the most efficient structural configurations developed to date. They achieve very high levels of performance through taking advantage of highly non-linear structural scaling laws by putting small amounts of material into localised members which are spaced far away from each other, allowing them to balance large forces and bending moments with minimal stress. Such structures are typically made from metals, which provide very good performance, but require large amounts of energy and resources to extract, smelt, and form. If such structures could instead be made from natural materials then their environmental impact could be significantly lowered and they could be adopted to a much wider range of applications. However, natural materials tend to have lower mechanical performance than metallic or traditional composite solutions. One potential way of mitigating the lower mechanical properties is to further exploit geometry by creating truss structures made from members which are themselves trusses. These Hierarchical Space Frames have been shown to be very promising in previous initial work with carbon fibre composite materials, and applying them to natural materials is made tenable through adoption of a patented truss beam manufacturing method being developed at Bristol, the Wrapped Tow Reinforced (WrapToR) truss manufacturing approach.WrapToR trusses are made by using a simple adaptation of filament winding that wraps pre-made longitudinal members in a wetted composite tow to produce a rigid web of shear members when cured. These truss beams can then be made into Hierarchical Space Frames by assembling them with joint structures. This, alongside the innate hierarchical makeup of natural materials, would create a synergistic order of hierarchy from the global structure down to the material level. WrapToR trusses and spaceframes made from natural materials are currently a promising but unexplored area of research, and practical, cost effective methods for joining WrapToR beams need to be developed. This work aims to develop the WrapToR method to devise a sustainable and low cost process for producing trusses and spaceframes from natural materials. To fulfil this aim the following objectives are set:- Develop the WrapToR method to maximise structural performance of natural material truss structures, aiming to account for and exploit the unique features of natural materials. - Experimental testing of natural material WrapToR trusses to characterise unique behaviour that is produced as a result of natural materials being used, that may differ from previously tested WrapToR trusses. Determining key relationships between structural performance, structural failure, material properties and truss geometry. Then using computational modelling and optimisation to design both individual trusses and Hierarchical Space Frames.- Investigate relevant, existing contemporary and traditional methods for joining trusses and beams in order to develop a practical and cost-effective process for joining individual WrapToR trusses into hierarchical space frames.These objectives will culminate with the manufacture of a full-scale natural material WrapToR Hierarchical Space Frame demonstrator for a relevant, real world application that can be tested under realistic loading conditions.