Impact Engineering

Metals – Investigations of rate and temperature dependence in aerospace metal alloys.

The response of metals to deformation at high temperatures is governed by a complex interplay of mechanisms, all the more so under high strain rate loading.  Moreover, the familiar techniques with which microstructure is characterised cannot be used on the microsecond timescales involved in impacts or very high speed deformations.  This project will examine the strain rate and temperature dependence of carefully selected Titanium and Nickel alloys, with the final goal of better understanding and modelling their response to high rate and high temperature deformation.

People: Laure Bonfils, Heather Wilson, Clive Siviour

Sponsor: Rolls-Royce and EPSRC

Date:  September 2013–October 2017

Lightweight Fan System Technology Development - SILOET II Project 2

This project focuses on the development of predictive numerical modelling capability for design of lightweight composite materials and systems for components of large aircraft gas turbine fan systems threatened by impact loading. The research covers a spectrum of activities from experimental observation and quantification of relevant strain rate dependent deformation and failure mechanisms, through to development and validation of multi-scale modelling algorithms aimed at engineering of composite material architectures for optimised performance of engine components.  Topology optimisation based on the capability to simulate strain rate dependent behaviour of materials is an integral part of the materials engineering efforts.

People: Nik Petrinic, Robert Gerlach, Justus Hoffmann

Sponsor: TSB, Rolls-Royce plc

Date: October 2012-September 2016

Virtual Engine Design Systems - SILOET II Project 10

This project focuses on the coupling of isogeometric modelling with mesh-free discretisation in order to provide an all-NURBS platform for simulation of the response of solids to impact loading.

People: Nik Petrinic, Ettore Barbieri, David Hills, Mattia Montanari

Sponsor: TSB, Rolls-Royce

Date: October 2012-September 2016

Strain Rate Dependent Behaviour of Ceramic Composites MAST

This project focuses on the development of experimental methodology for characterisation of strain rate dependent behaviour of ceramics and ceramic matrix composites for armour applications.

People: Nik Petrinic, Richard Todd

Sponsor: Dstl

Date: December 2012-November 2015

Polyurethanes - Supramolecular Polyurethanes and their Composites: Properties and Engineering Performance (with University of Reading)

The project explores the mechanical response of a novel type of self-assembling polymers, recently developed at Reading.  These polymers have a number of properties that make them very attractive for use as adhesives, coatings and shock absorbing fillers; in particular, a tuneable melting temperature and very low melt viscosity.  A current weakness is their low toughness. We are investigating the temperature, frequency and strain rate dependence of the mechanical properties of these materials, integrating the mechanical testing in Oxford with the polymer synthesis in Reading, to systematically tune the chemical structure of the polymer to optimise the mechanical properties.  In addition, composites will be made with a range of fillers in order to improve the mechanical properties without adversely affecting process ability.  Finally, suitable constitutive models will be developed to describe the behaviour of the polymers and their composites.

People: Ioannis Giannakopoulos, Clive Siviour

Sponsor: EPSRC

Date:  September 2012–October 2015

Multi-Scale Penetration Mechanics of Projectiles Through Granular Media Using Neutron and X-Rays

This project focuses on the development of multi-scale computational framework for simulation of impact on wet sand protection against ballistic penetrators.  The modelling efforts are accompanied by the research into in-situ and post-mortem diagnostics systems.

People: Nik Petrinic, Ettore Barbieri, Francesco De Cola

Sponsor: DTRA

Date: July 2012-June 2015

Development of multi-scale modelling methodology for simulation of rate dependent behaviour of titanium alloys

This project focuses on the understanding of the effect of geometric and physical aspects of material microstructure upon the strain rate dependent behaviour of titanium alloys at macroscopic scale.  Observation and quantification of the response to well controlled dynamic loading regimes and detailed modelling of thus characterised behaviour are carried out in close collaboration with material manufacturers in order to enable design of alloys with advanced/controlled response to impact loading.

People: Nik Petrinic, Benjamin Cousins


Date: October 2010-March 2015

USAF - Novel techniques for characterizing and understanding the response of rubbers and rubber-based composites to impact loading

As with all polymers, the high strain rate properties of rubbers are difficult to measure because of their low modulus, and hence sound speed.  With wavespeeds as low as 100s of metres per second (as compared to 5000 m/s in Titanium and c.a. 1500 m/s in structural Engineering polymers), rubbers and biomaterials present a significant challenge.  However, their use as energy absorbers and load mitigates, coupled with the recent advances in biomaterials, means that these properties are of increasing importance.  This project is developing new techniques, combining state of the art optical analysis and bespoke experimental design, to overcome the challenge of measuring impact and high strain rate properties of these materials.  The first publications from the project will be out soon.

People: Sung-Ho Yoon, Yongchao Huang, Clive Siviour

Sponsor: USAF / EOARD

Date:  October 2012–March 2015

Multi-scale methodology for enhancing damage tolerance of composite materials in submarine environment subject to underwater explosion and depth charge attack

This project focuses on development of experimental methodology for application of blast loading representative of that imposed by underwater explosion.  In addition, experimental methodology for characterisation of strain rate dependent behaviour of water saturated composited materials at several length scales for submarine applications is being developed.  Related computational multi-scale modelling methodology is being developed and validated against the results generated by the developed experimental methodology.

People: Nik Petrinic, Vito Tagarielli, Alan Cocks, Ettore Barbieri, Andreas Schiffer, Christian Kettenbeil

Sponsor: EPSRC, Dstl

Date: September 2009-March 2015

Numerical Modelling of Impact Phenomena

This project focuses on the integration of experimental and numerical methodologies in order to provide better understanding of physical phenomena excited by impact loading.  Particular efforts are directed towards such events occurring at elevated temperatures thus drawing special attention to phase changes in materials under consideration.

People: Nik Petrinic, Antonio Pellegrino, Petros Siegkas, Kalin Dragnevski

Sponsor: Rolls-Royce

Date: December 2010-November 2014

Shard – Silk in high rate applications and research into damage tolerance (with the Oxford Silk Group)

It is well known that silks exhibit a wide range of mechanical properties, many of which are significantly better than most man-made materials.  This project initially focussed on the behaviour of silks under impact loading, but has broadened to encompass a range of mechanical properties, in particular those associated with high deformation speeds or vibration propagation.  A number of papers have been published, including the two below.

DR Drodge, B Mortimer, C Holland and CR Siviour "Ballistic Impact to access the high-rate behaviour of individual silk fibres", Journal of the Mechanics and Physics of Solids 60 (2012) 1710-1721 (doi link)

B Mortimer, DR Drodge, KI Dragnevski, CR Siviour and C Holland “In situ tensile tests of single silk fibres in an environmental scanning electron microscope (ESEM)” J Mater Sci 48(14) (2013) 5055-5062  (doi link)

People: Daniel Drodge, Beth Mortimer, Clive Siviour, Chris Holland

Sponsor: Leverhulme Trust

Date:  October 2010–March 2014

Numerical Modelling of Fragmentation, Penetration and Spallation

This project focuses on the development of algorithms for simulation of failure processes caused by impact loading.  Interaction of quasi-brittle and ductile materials is given a particular attention.

People: Nik Petrinic, Ettore Barbieri, Sascha Knell

Sponsor: Mitsubishi Heavy Industries

Date: March 2012-February 2014

Bubble Collapse by Shock Loading

This project focuses on the development of experimental methodology for shock loading of cavitation bubbles in viscous media.

People: Nik Petrinic, Yiannis Ventikos, Nick Hawker, Phillip Anderson

Sponsor: OXYNTIX

Date: February 2012-January 2014

Low Rate – Understanding high rate behaviour through low rate analogue

Understanding the mechanical response of polymers and polymer based composites is vital for future development in a range of industries, and their increased use in applications which experience impact loading means that the high rate properties are particularly important.  However, measuring and understanding these properties presents a number of experimental challenges: for polymers, because of the low modulus and strength; for composites, because of the lack of in-situ diagnostics which can be applied to high rate experiments.

This project has addressed these problems by the development of a novel experimental simulation technique, in which the high rate behaviour of polymeric materials is reproduced in low strain rate experiments through time-temperature superposition.  In particular, the use of appropriate temperature profiles allows large strain deformation to be reproduced, whilst also giving insights into specific micromechanics of the behaviour of different materials.  Initially using PVC with different levels of plasticiser as a model material, the project moved on to particulate composites.  The project also required the development of novel thermocouple and stress-gauge systems.

Michael Kendall successfully defended his thesis in October 2013.  The following journal paper has already been published, and further papers have been submitted, watch this space!

M.J. Kendall and CR Siviour “Experimentally simulating adiabatic conditions: Approximating high rate polymer behaviour using low rate experiments with temperature profiles” Polymer 54 (2013) 5058-5063  (doi link)

People: Michael Kendall, Clive Siviour

Sponsor: EOARD

Date:  October 2010–December 2013

Numerical modelling of shot peening process

This project focuses on the development of numerical algorithms and benchmarks required to provide validated methodology for simulation of shot-peening as manufacturing processing which relies upon impact loading to provide surface treatment required to reduce effect of cyclic loading upon components of advanced engineering systems such as aircraft gas turbine engines.

People: Nik Petrinic, Kovthaman Murugaratnam

Sponsor: EPSRC, Rolls-Royce

Date: May 2010-December 2013

Development of numerical modelling of failure in composite materials subjected to impact loading (SILOET 1)

This project focuses on the development of numerical algorithms for simulation of deformation in continuous fibre reinforced polymer matrix systems and related experimental support.  A combined continuum and discontinuity analysis methodology is being devised in order to simulate the effects of manufacturing induced flaws as well as those initiated during impact loading.  Algorithms for simulation of strain rate dependent behaviour hare being implemented in a multi-scale framework and are being validated against experiments at corresponding length scales.

People: Nik Petrinic, Jens Wiegand, Andreas Giebe

Sponsor: TSB, Rolls-Royce

Date: October 2009-September 2013

Understanding and Improving Ceramic Armour Materials

This project focuses on improvement of experimental techniques for characterisation of strain rate dependent behaviour of ceramics for armour applications as well as on development of computational methodology for simulation of strain rate dependent behaviour of several ceramic materials while aiming to determine if manufacturing the materials using nano-scale powders offers potential to develop better armour systems.

People: Nik Petrinic, Richard Todd, Simone Falco, Claire Dancer, Emilio Lopez-Lopez

Sponsor: EPSRC, Dstl

Date: April 2009-December 2013

Investigation of rate dependent behaviour of titanium foams

The objective of this research is to develop both the experimental and numerical methodology for characterisation and predictive modelling of the response of sintered titanium foams to impact loading.  A range of different sintered Ti foams has been characterised under compressive loading at a range of strain rates. The sensitivity of foam strength to relative density and applied strain rate has been determined.  Modelling techniques have been developed to exploit the information obtained from X-ray scans of foams under consideration. This approach has been used to develop a virtual testing framework to complement the experiments in real laboratory.  The main objective is to explore experimentally and numerically the sensitivity of the foam response to geometry, porosity, applied strain rate, with the aim of developing homogenised constitutive models for the response of sintered Ti foams to impact loading at macroscopic length scale.

People: Nik Petrinic, Vito Tagarielli, Petros Siegkas

Sponsor: EPSRC, Rolls-Royce

Date: October 2007-March 2013

Optimal fan blade design for bird strike

The objective of this research is to enable optimisation of fan blade design for bird strike.  A hierarchical ‘bottom-up’ approach has been adopted in which sub-models are used to understand the response of the blade materials at component scale.  The developed computational tools are integrated into the iSIGHT optimisation framework.

People: Nik Petrinic, Simon Read

Sponsor: Rolls-Royce

Date: October 2005-March 2013

Investigation of rate dependent behaviour of sandwich systems for open rotor applications

The main aim of this project is to generate a deeper understanding of the mechanical behaviour of cellular materials, specifically for their use in aerospace applications.  A closed-cell polymer foam material (Rohacell) of various foam densities was chosen for this investigation, and a comprehensive experimental study is being conducted to generate information for improved numerical modelling in design of lightweight components of aerospace structures.

People: Nik Petrinic, Vito Tagarielli, Prof. C.R. Siviour, Sara Poxon (Arezoo)

Sponsor: Rolls-Royce

Date: October 2007-December 2012

Investigation of texture dependent ballistic behaviour of titanium alloys

This project focuses on the understanding of the effect of material microstructure upon the ballistic properties of titanium alloys.  Microscopic characterisation of samples following rapidly applied loading (e.g. plate penetration, Taylor impact, etc.) is undertaken in order to provide better understanding of deformation and failure mechanisms for design of containment systems.

People: Nik Petrinic, Prof. C.R. Siviour, Euan Wielewski

Sponsor: TIMET, Rolls-Royce

Date: January 2008-December 2011

Experimental characterisation of dynamic Bauschinger effect

This project aims to characterise the dynamic Bauschinger effect in titanium alloys for fan blade applications.  Investigation of the effect required development of new devices for single cycle reverse loading at high rates of strain.  Two new reverse loading Hopkinson Bar systems (tension-compression and compression-tension) have been manufactured and commissioned.  The findings are aimed at improving the constitutive models for simulation of large deformation and fracture in titanium alloys subjected to impact loading.

People: Nik Petrinic, Siva Sathianathan

Sponsor: Rolls-Royce

Date: October 2004-March 2010

Experimental characterisation and development of predictive modelling techniques for simulation of the response of cellular solids to impact loading (CELPACT)

The objective of this research has been to develop improved experimental methods in support of proposed multi-scale modelling approach to simulate the response of cellular materials to impact loading.  Both metallic and hybrid cellular solutions have been investigated.  Experimental characterisation of a number of different foams and core structures has been performed, generating valuable data for the modelling aspects of the project as well as increasing the group's capability to perform experiments on low strength materials.

People: Nik Petrinic, Prof. C.R. Siviour, Peifeng Li

Sponsor: DTI, Rolls-Royce

Date: July 2006-April 2010

Impact Performance and Shock From Advanced Composites Technology (IPSoFACTo)
Partners: Rolls-Royce, Airbus, Smiths Aerospace, BAE Systems, Imperial College

The objective of this project is to develop improved experimental methods for characterisation of CFRP composites and improved numerical models for simulation of the observed and measured behaviour.  A particular focus is on development of stable algorithms for simulation of damage propagation in laminated CFRP composites for lightweight fan applications.  The experimental programme is providing data for constitutive models at several length scales.

People: Nik Petrinic, Clive Siviour, Peifeng Li

Sponsor: DTI, Rolls-Royce

Date: July 2006-April 2010

Optical metrology for characterisation of materials at high rates of strain (ARIN)

The objective of this research is to develop novel algorithms for high-speed digital 3D photogrammetry.  The method relies upon the availability of good quality high-speed digital cameras.  A systematic study of the accuracy of the approach using different surface marking schemes was undertaken.  Automation of 3D geometry reconstruction and motion tracking his also being implemented.

People: Nik Petrinic, Arin Jumpasut

Sponsor: EPSRC, Rolls-Royce

Date: November 2005-April 2010

Development of methodology for characterisation and predictive modelling of 3D reinforced composites

The objective of this research is to develop two-scale experimental procedures and numerical methods for simulating the response of 3D reinforced composites to impact loading.  A hierarchical ‘bottom-up’ approach has been used to develop macroscopic (continuum) failure criteria and damage evolution algorithms and a ‘top-down’ approach is used to optimise the material’s micro-structure.  A methodology for experimental characterisation of the individual components of 3D reinforced composites has been developed.  This focuses on resin systems, fibre yarns and on the interface between the two at meso-scale.  Implementation of such physically based constitutive modelling framework is an integral part of the project.  Virtual experiments are being used to simulate the behaviour of specific material architectures and complement the experimental work.  This approach has been applied to simulate the experimentally quantified response of composite sub-components to impact loading carried out in controlled laboratory conditions.

People: Nik Petrinic, Clive Siviour, Robert Gerlach

Sponsor: Rolls-Royce

Date: September 2006-January 2010

Ultra-high-speed digital imaging and optical metrology

The aim of this project is to select the best hardware for ultra-high-speed-digital imaging and develop the accompanying procedures for image analysis to aid the characterisation of strain-rate dependent behaviour of materials.

People: Nik Petrinic, Clive Siviour

Sponsor: Rolls-Royce

Date: January 2007-September 2009

Characterisation of composite materials and development of constitutive models in aid of lightweight hybrid fan systems (VITAL - enVIronmenTALly friendly engine)

The main objective of this project is to enable design of composite aeroengine components threatened by impact loading.  The experimental aspects of the work included initial selection of materials for aircraft gas turbine engine fan blade and containment applications as well as the full characterisation of selected materials.  Small-scale structural tests in controlled laboratory conditions have been carried out in order to provide data for validation of developed modelling tools.  Modelling aspects of the work have included evaluation of existing constitutive models and development of new algorithms for simulation of observed and quantified strain-rate dependent behaviour.

People: Nik Petrinic, Jens Wiegand

Sponsor: EU

Date: January 2005-September 2009

Development of new artificial bird material for bird strike on jet engine fan blades (STEFAN)

The main objective of this research is to develop novel artificial material whose behaviour will be qualitatively and quantitatively comparable to that of real birds in aeroengine impacts.  A secondary objective is to improve experimental methods for characterisation of such material(s) and numerical methods for predictive modelling of material behaviour.  A new hybrid material has been developed which comprises cellulose sponge and low density gelatine.  This has exhibited excellent behaviour when compared with real bird tissue.  Full experimental characterisation for generation of data for constitutive modelling is being carried out.  Numerical models based on a Lagrangian monolithic solid and on an assembly of particles are being developed to enable accurate simulation of bird strike events.

People: Nik Petrinic, Stefan Schwindt

Sponsor: CSL-IBRG

Date: September 2004-October 2007