Hot Drape Forming of Thermosetting Composites

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To automate production of composite parts using prepreg (towpreg), automated tape placement (ATL) and automated fibre placement (AFP) technologies have been developed. Many aircraft structural parts such as ribs, frames, spars or brackets are too small or too complex in shape to be efficiently and cost-effectively manufactured using automated technologies such as AFP. To take advantage of the automation (AFP) to manufacture these parts, two-step process is proposed and used. A flat stack of uncured plies with correct shape and stacking sequences is first created by automated processes such as ATL or AFP. Then flat stack is transferred to the forming set-up where it is turned into the final shape using heat and pressure (vacuum) before being cured. This is called hot drape forming. The heat applied during the process reduces the resin viscosity, while the pressure (vacuum) provides the mechanical action to form the laminate. A better understanding of forming process of laminated composite is required to capture the physics of the process and to develop models. Then models can be used to simulate and to optimize the process. Focus of this study will be on the resin role on transferring the shear load and supporting the fibres during the forming to prevent the fibres from buckling and wrinkling. Processing window has to be defined to achieve a good quality part at the end of operation. Through this two steps process, the full advantage of automation for manufacturing of small and complex parts can be explored. This will show the Canadian aerospace industry even broader advantage of automation using AFP for manufacturing different parts at lower cost.