New manufacturing techniques for optimised fibre architectures

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New manufacturing techniques for optimised fibre architectures

Host Institution: The University of Manchester, The University of Nottingham

Lead Investigator: Andrew Long, Prasad Potluri

Co-Investigator: Mikhail Matveev, Shankhachur Roy, Vivek Koncherry

Aims

Textile composites produced by liquid moulding based on 3D woven preforms offer several advantages over other composites such as those based on unidirectional prepreg, including automated manufacture for complex geometries, ability to integrate geometric features (e.g. T and I sections), and delamination resistance via inclusion of through-thickness fibres. Generally in-plane fibres are orthogonal, although experimental machines have been developed which allow ±45˚ yarns. Other textile processes offer alternative fibre architectures, for example triaxial braiding which produces yarns at 0/±θ.

Like 3D weaving this is based on established textiles machinery rather than technology developed specifically for composites. This project aims to discover new 3D textile preform architectures. Computational modelling or “virtual testing” will evaluate the utility of different textile designs within an optimisation framework to determine the best solution for a particular application. This framework will not be constrained to architectures that can be produced using existing manufacturing technologies such as weaving or braiding. Optimum textile preforms will be realised either by modifying existing textile processes or, where potential benefits justify, by developing entirely new, bespoke manufacturing technologies. This will result in a step change in performance, leading to significant weight reductions and lower cycle times through routine use of automated manufacturing technologies. Earlier it was shown that, for a specific application, a weight saving of at least 50% can be achieved by relaxing constraints on binder path and in-plane fibre orientations. Here we will further relax constraints on the fibre architecture, aiming to identify and manufacture a number of classes of improved material forms.

Figure 1: 3D woven textile

Figure 1: 3D woven textile

The project aims to establish a computational framework for textile preform optimisation not limited to existing manufacturing technologies. The framework will be built and extended based on a series of case studies to identify classes of materials with improved properties. New manufacturing technologies will be developed for these materials and used to validate the predicted properties.

Progress

Implementing an effective computational optimisation framework requires the ability to create realistic models of complex textile reinforcements. Geometric models for such reinforcements can be created using TexGen software but the meshing of these geometries for subsequent prediction of mechanical and processing properties presents a problem. A novel meshing approach has been implemented within TexGen software in order to construct nearly-conformal meshes which are suitable for analysis of stiffness and strength of textile composites. The implemented meshing technique enables modelling of more complex reinforcements in an automatic way. Alongside this an analytical approach based on orientation averaging has been developed to provide fast predictions for composite elastic properties. As demonstrated through initial optimisation trials based on a genetic algorithm, this approach offers significant reductions in computation times for problems based only on elastic performance.

In order to deliver step-change manufacturing technologies, initial research has concentrated on overcoming the key limitation of commercial 3D weaving technology – inability to place tows at an angle (off-axis) to the two principal tow directions, warp and weft. The first prototype of a multi axial 3D woven fabric has been developed using a combination of robotic fibre placement and weaving principles. This approach enables us to insert offaxis tows without the need for complex rotating creel systems found in the literature. The next stage of development will create a multi-axial 3D woven architecture comparable to conventional Jacquard woven 3D weaves in terms of tow densities and appearance. Additionally, we are working on creating a multiaxial 3D woven architectures in seamless tubular form as an improvement over multi-layer 2D braiding or roll-wrapping techniques.

Figure 2: The Octree Mesh Method is used to plot and generate at high speed complex 3D solid objects

Figure 2: The Octree Mesh Method is used to plot and generate at high speed complex 3D solid objects

Key Achievements

  • A novel technique was implemented within TexGen software to support automatic generation of finite element meshes of complex textile geometries.
  • An iso-strain approach based on orientation averaging was implemented in TexGen to predict elastic properties for the candidate materials.
  • A combined fibre placement/weaving technique was developed to produce 3D textiles including off-axis fibres.
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