Novel 3D+ Multi-axial Preforms for Complex Loaded Composite Applications

Composite materials have seen significant growth in structural applications across multiple sectors due to the high strength and low weight, enabling fuel savings. This is considered a vital component on the journey to achieving Net Zero targets set by industry and governments. To achieve this goal, development of new composite materials is required to see greater adoption of composites to structures. A key area that offers potential for significant weight saving is complex loaded structural joints such as lugs that are used to connect structural components and transfer loads. One of the primary weaknesses facing traditional laminated composites in their attempt to replace metallics in this area is the lack of through thickness reinforcement, leading to delamination and premature failure. 3D woven composites offer a desirable answer to these challenges through use of fibre in the primary xyz direction, with the "z" or binder fibre being able to carry load through the thickness and resist impact damage. Additional benefits for 3D weaving are the ability to create near net shape preforms and tailored properties. Despite the high potential benefits of 3D preforms, there are several challenges associated with it. The first is driven from the high bespoke nature of the material that creates several unknowns in how changes in the 3D architecture or weave parameters will affect the resulting composite properties. This has led to most 3D composites being manufactured in a uniform architecture and not utilising the full potential of the material. The second challenge is the absence of +/-45o or off-axis fibre that is necessary for complex loading conditions. This project aims to address this challenge through developing a new 3D+ material, by utilising the advantages of both technologies through the combination of 3D woven and 2D fibre preforming. The material will consist of a 3D woven core overlaid above and below with off-axis 2D fibre, creating a material that contains both through-thickness reinforcement and off-axis fibres necessary for complex loaded components. The 3D core will investigate the use of architecture transitions within the preform from an architecture tailored to maximise mechanical performance in the main lug body to an architecture tailored for high bearing response and delamination resistance around the lug hole. By utilising existing technologies, a high rate of production is possible with a reduced need for capital investment providing possible rapid and high impact solution for industry. This approach in material design goes against conventional methods of having a homogenised lay-up but generates a potential step change in composite design, a deeper understanding of 3D material, and potential application of composites to structures that have previously been inhibited by traditional lay-ups.