The AFPMeT project designed and developed a lamination tool and a transfer device for use in the automated fibre placement (AFP) manufacturing of geometrically complex helicopter side-shell sandwich panels. The initiative also investigated the possible effect of uncured material and sandwich core on AFP lamination and the transfer of the uncured honeycomb structure to the cure tool. Researchers aimed to transfer wet (uncured) shells from the lamination tool to the cure tool, while precisely holding its position to avoid warping and shrinkage. “With this type of lamination tool, managers will be able to improve the fabrication process by optimising tools for their specific function while reducing workflow time. For example, while one shell is laminated, the previous one is being cured in the autoclave,” states project coordinator Gabriella Caputo.
Innovative production methods
The team also evaluated tool material and configuration options based on several key requirements. These included low energy consumption in tools and parts fabrication, utilisation of ‘green’ or recycled materials, and the possible reuse of tool materials and components. The consortium used aluminium lost foam casting to produce a rough outline of each lamination tool before it was machined, to obtain the final shape. The lamination tool has a complex geometry and is about 4 m long, 2 m wide and 1 m high. This approach achieved good results: no vacuum leakage and reduced warpage of the raw casting. Furthermore, it reduced the need to use an alternative process such as welding. “This is a technique never used before for this kind of tool but considering the possibility of significantly reducing the amount of waste material and energy, it was considered worthwhile,” Caputo explains.
Uses outside aviation
Researchers developed a transfer process based on the use of a film and vacuum that reduces energy consumption. The cure tool, which must be heated in an autoclave, was made lighter; the lamination tool, which is used at ambient temperature, was made heavier to satisfy mechanical requirements during automated fibre placement. “The transfer must assure precise positioning of the wet shell on the cure tool to avoid any wrinkle during the transfer,” Caputo points out. Project partners also devised a method based on fast-curing adhesive infiltration to repair the lamination tool and restore air-tightness around it, as some cracks discovered on the shell prevent it from meeting airtightness requirements. According to Caputo: “The lamination tool is light and used only at ambient temperature, with lower requirements for air tightness. However, the cure tool is for use at high temperature (180 °C) and has a strict requirement for air tightness.” AFPMeT will benefit producers of large complex composite parts; the technology developed can be used in the aerospace industry to produce aircraft pressure bulkheads and fuselage panels, for instance. It also has applications in the production of large composite antennae for satellite ground stations and parts for ships, trains and the automobile sector.
AFPMeT, lamination, cure, automated fibre placement, sandwich panel, aluminium lost foam