MANUFACTURING OF NOVEL HIERARCHICAL HYBRIDISED COMPOSITES

Inspired by natural composites such as bamboo (Figure 1) or bone, the NextCOMP programme seeks toimprove compressive performance through a novel, hierarchical approach to advanced composites.Features designed to improve compressive performance are introduced at multiple length scales. Novelfibres and resins are under development, along with new approaches at the ply level.Figure 1: Illustration of hierarchical structure of bamboo. Reproduced from [1].This new approach to composites brings its own manufacturing challenges, combining multiple methodsboth automated and manual.Cylindrical struts, consisting of carbon-fibre epoxy pultruded rods of circular cross section plus aninfused resin, have previously been manufactured [2] and subjected to compression after impact testing[3]. Struts overwound with Kevlar to confine the kink bands exhibited greater compressive strength thancomparable struts without overwinding. X-ray CT images (Figure 2) show multiple smaller kink bandsin the former case compared to a single large kink band in the latter.Figure 2: Slices from XCT reconstructions of samples from experiments reported in [2]. Strut withoverwind shown left with multiple smaller kink bands, strut without overwind shown right and centrewith single kink band.Laura Rhian Pickard, Gustavo Quino, Giuliano Allegri, Michael R. Wisnom and Richard S. Trask58In the hierarchical approach overbraiding of individual rods is employed, introducing hybridisationwhere rod and overbraid fibres differ. Various materials and geometries are under test (Figure 3),including a range of rod cross section shapes and areas. These overbraided rods are then integrated intolarger structures, including but not limited to cylindrical struts.1mmFigure 3: Circular cross section carbon fibre-epoxy rods overbraided with Toray T300 carbon (left),Teijin high modulus Zylon (centre) and Teijin Twaron 2200 aramid (right).This presentation focuses on our latest investigations into the design, manufacture and compressiontesting of single and hierarchical composite overbraided architectures. Optimisation of overbraiding fordifferent test cases will be explored. The work is placed in context regarding what this new approach tocomposites may mean for manufacturing, with a look towards future challenges and opportunities.The authors kindly acknowledge the funding for this research provided by UK Engineering and PhysicalSciences Research Council (EPSRC) programme Grant EP/T011653/1, Next Generation Fibre Reinforced Composites: a Full Scale Redesign for Compression in collaboration with Imperial CollegeLondon.