Mitigating forming defects by local modification of dry preforms

Forming of dry fibre textile pre-forms is a commonly used technique to achieve complex shapes for light weight composite structures. Most conventional engineering fabrics can only deform through shearing. Excessive shearing often results in the formation of detrimental features, such as wrinkles, folds and fabric distortions. This paper shows the feasibility of improving formability by local modification of preforms in critical areas to enhance forming and mitigate against defects. Modification is implemented by printing localised resin patches onto textile preforms. The technique allows for continuity of fibres throughout the preform with the additional benefit that the deposited resin can be thermally staged to the desired level of cure to tune the viscosity of the region for forming and consolidation. The location and dimensions of patches are specified through numerical modelling to inform the subsequent manufacturing process. Manufacturing trials successfully demonstrate the possibility of defect mitigation using this technique.