Virtual Un-manufacturing of Fibre-steered Preforms for Complex Geometry Composites

State of the art Automated Fibre Placement (AFP) is ideally suited for manufacturing large structures with relatively simple geometry, due to its robustness, high throughput and repeatability. However, the processing conditions, machine tolerance and tape steering in AFP has limitations for directly laying up fibre tapes onto complex 3D shapes. The need for defect-free manufacture constrains the head speed, making manufacture time consuming and thus costly. In most cases, complex geometry composite components are designed based on ideal or theoretical fibre angles, with little or no consideration of the manufacturing processes or constraints, as a result of which in-situ fibre direction in as-manufactured parts may deviate significantly from the design intent. This study focuses on the feasibility of an alternative manufacturing process, as a replacement for direct AFP processing onto complex 3D geometry, i.e. lay-flat and form processes, in which fibre tows are steered and deposited to create a flat preform; and then this flat tailored preform is formed into a 3D complex shape. The fibre path/angle of the flat tailored preform prior to forming was derived from an ‘un-manufacturing’ (i.e. un-forming) virtual process of the part with ideal fibre paths. The primary manufacturing process used in this research is a double diaphragm forming of fibre-steered prepregs deposited using the Continuous Tow Shearing (CTS) technique. With numerical process simulations of forming, un-forming and re-forming with experimental validation, this study not only showed the feasibility of the virtual un-manufacturing process in combination with ‘lay-flat-and-form’ manufacturing but also demonstrated that the proposed processes leads to a reduction wastage compared to manually laying unidirectional (UD) prepreg onto complex 3D shapes.