Novel Experimental Method for Microscale Contact Analysis in Composite Fabric Forming

This paper describes a novel experimental rig and associated experimental method developed to investigate composite fabric/tool contact at the microscopic scale. A key feature of this method is that it enables direct observation of real contact at the scale of fibres and the evolution of this contact under simultaneous application of shear and compression loads. To observe the contact, an optical semi-reflective coating is used. An algorithm is developed to analyse the contact images and measure the real contact length and orientation of individual fibres. The method is applied to microcontacts of carbon twill fabric. The real contact length under an apparent pressure of 1.9 kPa is surprisingly small compared to the apparent contact length. Transverse forces associated with friction are also measured. However these results are difficult to interpret as the test generates friction forces which differ from those which would be seen in conventional sliding friction tests