© The University of Sheffield

Sam Ashworth

Project Title: Performance Assessment of Machined Composites via Novel Metrics for Surface Quality

Academic Supervisor: Dr James Meredith

AMRC Supervisor: Dr Kevin Kerrigan

Carbon Fibre Reinforced Polymers (CFRP) composites are used widely in aerospace and advanced automotive industry as they offer unique strength to weight ratios compared to metallic materials.  The production process for CFRP material means that parts are nearly always formed into near-net shapes and trimming processes are required to meet the final dimensions.  Trimming can be completed using various techniques such conventional milling, laser milling or waterjet milling however all methods are subject to final surface quality controls on the trimmed edge.  The method of obtaining surface finish results has been traditionally completed using stylus-based methods where a pin is drawn across the trimmed surface and a surface roughness value known as Ra is obtained.  The Ra value is a widely used surface quality parameter that has been used throughout manufacturing to describe a surface however due to the anisotropic nature of CFRP’s, this parameter does not produce a representative value of the whole surface. 




The overall objective for the PhD is to link the long-term performance of CFRPs with machined surface quality.

The PhD is focused on identifying novel metrics that can correctly quantify an edge trimmed CFRP part.   The project will employ state-of-the-art inspection techniques including 3D surface texture analysis, micro-computed tomography and microscopy.  These will characterise fibre pull-out, delamination and other micro-scale surface features and material properties to advance knowledge in this area.  The data will help advise industry standard owners regarding the surface quality requirements of machined parts and establish a metric to define the working envelope for different tools and hence the optimum parameters required for long life composites.  The long-term performance of the composites will be achieved by mechanical testing methods within the University mechanical test labs.


Mechanical and damping properties of resin transfer moulded jute-carbon hybrid composites ( )