Michael P Elkington

Hand layup: understanding the manual process

The hand layup of pre-impregnated woven materials is still a large part of the composite manufacturing industry, requiring the skills and experience of a human workforce to form flat plies into complex shapes. It is capable of producing high performance and complex parts, but can be an expensive and variable process. Despite its importance, there appears to have been very little research into the actual methods and techniques used by workers to manipulate flat sheets of composite material into shape during layup. This work presents the first known detailed study of the approach and techniques used by laminators. Four participants laid up onto 15 different shaped molds that replicated features commonly found on composite components. The actions used in layup were grouped into eight distinct techniques. Use of these techniques across tasks of different geometry, ramp angles, radii and drape path was identified using video analysis techniques from the ergonomics field. This revealed strong links between specific features and techniques, revealing a systematic approach to layup. This has enabled the first step toward producing a design for manufacture knowledge base surrounding hand layup. This could then be used to inform the development of the layup process, improve training methods and assist in the design of future automated solutions. Graphical Abstract

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.