The Composites University Technology Centre (UTC) at the University of Bristol is a research centre supported by Rolls-Royce plc to provide a validated analysis capability for the response of composites that can be used to design and manufacture composite components. It aims to act as a focus for composites research activities, liaising with other universities to provide a coordinated programme to meet the needs of Rolls-Royce.
The Composites UTC was established in 2007 and in 2012 entered into a partnership with the Lightweight Structures UTC at TU Dresden to form the Rolls-Royce Composites University Technology Partnership (UTP).
The UTC conducts research in a number of areas relating to composites. These include projects include looking at through-thickness reinforcement, defects and features of composites, vibration and fatigue, novel structures and materials, woven textiles and composites manufacturing.
A highly complex specimen, representative of a typical composite dove-tail joint, has been designed, manufactured and tested. This has been both an exercise to understand the nature of the failure mechanisms and behaviour and to validate finite element models. The specimen, produced from unidirectional carbon fibre/epoxy pre-preg, reduces down from 147 plies at the thick end to 45 plies at the thin end. The manufacture of the specimens was in itself a complex task, with great care being taken to ensure the accuracy of the terminated ply placement and specimen symmetry. The finite element model used was a ply-by-ply representation of the layup with cohesive interface elements between each ply to be able to capture the delamination failure mode. Results show the close working of numerical modelling and experimental testing to better understand and predict the failure of a complex specimen which in turn will improve future component design.
The Surface Cut Ply specimen is a convenient test coupon for the assessment of mixed-mode fracture in composite materials. It has been designed, manufactured, tested and verified by FE Analysis for measuring the mixed-mode Gc, the critical mixed-mode Energy Release Rate (ERR), for laminated composites. The desired mode mixity can be achieved through selection of the continuous to cut ply ratio; current work has concentrated on the 5/5 configuration which is a 10 plies thick specimen consisting of 5 cut and 5 continuous plies. The specimen is loaded in the 4 Point Bending configuration and a new analytical solution has been developed to compute the mixed-mode ERR from the specimen geometry and the recorded load - deflection test data. The simplicity of the test and that the need to measure the crack length is avoided are key advantages over other mixed-mode tests.