Studying effects of preshearing on hand layup

Abstract

Advanced composites are used extensively in many high performance applications. As they are taken up in a wider range of applications, the volume of demand is pushing manufacturing methods, especially hand layup of woven prepreg cloth, to their limits. An alternative approach to hand layup over complex geometries is proposed. The regular method of layup involves generating shear using grasps and pressures in the prepreg as and when it is needed during layup, leading to a sometimes complex and time consuming process. In the method proposed, all the shear deformation is created in the ply prior to any contact between the prepreg and the mold surface. Guidelines were drawn onto the prepreg surface to enable the correct shear distribution to be ‘presheared’ by hand. These were created by processing the outputs from a simple kinematic drape simulation within MATLAB. Once preshearing was completed, the ply is laid up onto the mold using regular hand layup techniques. The process was tested alongside regular manual lamination across three example parts and using video analysis effects of the process were investigated via a variety of metrics. This revealed that significant time savings and reduced likelihood of manufacturing variations are possible with this approach. There was also a significant simplification of the layup process, leading participants to comment that a previously ‘difficult’ layup had become ‘easy’. An improved bespoke system for communicating the required preshearing was subsequently developed, and successfully trialed on a fourth example part. Preshearing has the potential to make hand layup more economically viable for years to come. As well as the productivity and cost benefits, preshearing shows promise as a training aid, especially for beginner laminators. Concepts for integrating preshearing into existing industrial practice and its further potential in the field of automation are also discussed.