IMX Colloquium - New test methods in support of composites manufacturing research: a tale of two fixtures

As engineers we come to rely on and sometimes take for granted the many test methods, standard protocols and test fixtures that enable us to undertake our research in materials science. This talk will recount the development process of two distinct test fixtures that have originated from my laboratory, one which has developed into an ASTM test standard, and another which was patented. The first fixture is a custom peel fixture developed specifically for measuring adhesive tack in a manner relevant to composite prepregs during automated manufacturing. The data it produces is useful in understanding how tack can be maximised during manufacture to avoid defects, coping with material out-time and environmental conditions, and generally reducing waste. The second fixture is a pin-jointed mechanism designed for carrying out equibiaxial tensile tests. This is useful in obtaining the constitutive response of materials up to large strains, and the data it produces is typically combined with uniaxial data to calibrate hyperelastic model parameters. In composites manufacturing it is used to characterise and model the behaviour of highly deformable (typically silicone) membranes used in diaphragm vacuum forming processes.

Bio: Dr Davide De Focatiis MA MEng FIMMM CSci completed his MEng degree in Engineering Science at the University of Cambridge in 1999. During his Masters research, working with Dr Simon Guest, he discovered a family of biomimetic folding mechanisms based on the folding structure of beech and hornbeam leaves, with applications as deployable structures. From 1999-2003 he studied for a DPhil (Ph.D.) at the Department of Engineering Science, University of Oxford, with Dr Zhong You. This work was concerned with the mechanics of a needle-free powder injection device developed by Oxford spin-off PowderJect Pharmaceuticals. After completing his DPhil, he was employed as a Research Assistant in the Solid Mechanics and Materials Engineering group at the Engineering Department, University of Oxford, working under the direction of Prof. C.Paul Buckley, from 2005-2008. This work was part of a large EPSRC funded collaboration following the path of well-characterised polymers from synthesis, through processing into the solid state. Major developments include the formulation of molecularly-aware and process-aware craze initiation criteria, and the development of large-deformation constitutive models for processed amorphous polymer products.
In February 2009 he was appointed to a Lectureship in the Department of Chemical and Environmental Engineering at the University of Nottingham. In September 2013 he transferred to the Department of Mechanical, Materials and Manufacturing Engineering to better align teaching and research. Besides research on polymers, he convenes the core year 1 module Statics and Dynamics, and an interdisciplinary module on Polymer Engineering (4rd year). He is the department's coordinator for peer observations.
Dr Davide De Focatiis is a part of the Composites Research Group.