Continuous tow shearing for the automated manufacture of defect-free complex 3D geometry composite parts

It has always been challenging to manufacture a composite structure with complex geometry using automated fibre placement (AFP) process. The tool surface is difficult to be tessellated using fibre tapes with a finite width, without producing gaps and overlaps, and fibre steering along non-geodesic fibre paths produces various defects such as tape buckling and pull-up. In this work, a defect-free fibre-steering process on a complex surface was demonstrated by realising the continuous tow shearing (CTS) process in three dimensions. A new head control algorithm was developed, which defines the head orientations and trajectories based on the pin-jointed net model to manipulate the fibre tow using both in-plane shear and out-of-plane twisting deformations. Fibre steering process utilising this new algorithm was tested on a doubly-curved surface, using an industrial robot arm equipped with a CTS prototype head, and its layup quality and accuracy were assessed by using a three-dimensional laser profile scanner. An experimental comparison with the conventional AFP process showed that the new control algorithm enables defect-free fibre steering on complex 3D surfaces allowing for simplifying the design and analysis of novel composite structures.