Understanding and Improving Ceramic Armour Materials
Lead Research Organisation:
Loughborough University
Department Name: Materials
Abstract
Ceramic materials are used for both personnel and vehicle armour since they can be very effective at stopping ballistic projectiles by breaking and eroding them. However, such armour is generically fairly heavy and does not have multihit capability due to its fragmentation during impact. The development of new ceramics for armour is further hindered by the limited understanding of the mechanisms involved in their success and therefore what the characteristics of the ideal ceramic should be. Challenges to improving the situation include: the difficulties in defining initial material state (defects and damage); experimental characterisation of short-lived impact events; the fragmented nature of the specimens left behind; and the importance of the whole system to the dynamic failure process (e.g. impact resistance depends inherently on the shape and size of the component unlike conventional materials properties). This hinders the comparison of reports of competing materials from different labs. Previous work has included the use of a range of mechanical testing equipment (from quasi-static, low velocity hydraulic and gas gun actuated split- and direct-impact Hopkinson bar systems to intermediate-, high- and hyper-velocity gas and powder guns) and aimed to quantify the impact response by means of high-speed photography. There have also been attempts to simulate experiments using a range of modelling techniques. However, most of the available literature uses particular techniques and materials in isolation. No work has yet demonstrated the use of an integrated experimental-numerical, multi-scale approach to understanding and predictively modelling deformation and fracture of ceramics subject to impact loading.A holistic approach to developing an understanding of the high strain rate performance of ceramics is proposed. Modelling plays a dual role, which is both to design the experiments employed to understand the materials' behaviour on a macroscopic scale and to give insight into the role of micromechanisms in determining ballistic performance. Model input will be provided by materials property data determined before testing (e.g. basic information such as grain size and hardness and detailed surface and subsurface characterisation of the defect population using advanced microscopy). The models will be developed by comparing their predictions with the output of instrumented laboratory tests covering a wide range of strain rates (10 exp -4 to 10 exp 6 /s), ballistic tests (through DSTL) and with the results of novel post mortem characterisation. The latter will include detailed characterisation of the fragments ejected from the surface and the remnants of the main specimen. This will include assessments of fracture mode and origin using SEM, dislocations and twinning by TEM, particle size distributions by laser scattering and the use of optical luminescence microscopy for the first time in this context to measure residual stresses in the specimens with a spatial resolution of 2um and to measure dislocation densities. This quantitative information can be compared directly with the predictions of the models. This approach will be used on a range of ceramics with systematically differing characteristics and will give comparative information about which microstructural features and mechanical properties successful ceramics possess, as well as enabling the development of a fundamental understanding of the high strain rate performance. The materials used will include both existing armour ceramics and, for the first time, novel nano-grained and nano-composite ceramics which quasi-static tests indicate to have interesting properties for armour applications (e.g. the ability to undergo much more plastic deformation before crack initiation). The outcome will be the ability to design ceramic microstructures and armour systems with improved performance. The final task will be to begin making such structures.
Publications
Wade-Zhu Y
(2021)
The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) and alumina ceramics
in Journal of the European Ceramic Society
Wade J
(2015)
Contact damage of silicon carbide ceramics with different grain structures measured by Hertzian and Vickers indentation
in Journal of the European Ceramic Society
Huang S
(2014)
Quantitative analysis of the residual stress and dislocation density distributions around indentations in alumina and zirconia toughened alumina (ZTA) ceramics
in Journal of the European Ceramic Society
Falco S
(2014)
A new method for the generation of arbitrarily shaped 3D random polycrystalline domains
in Computational Mechanics
Dancer CEJ
(2011)
Measurement of deformation in alumina samples indented at high strain rates
in Proceedings of the 35th International Conference on Advanced Ceramics and Composites
Dancer C
(2019)
Characterisation of damage mechanisms in oxide ceramics indented at dynamic and quasi-static strain rates
in Journal of the European Ceramic Society
Dancer C
(2019)
Characterisation of damage mechanisms in oxide ceramics indented at dynamic and quasi-static strain rates
in Journal of the European Ceramic Society
Description | This project consisted of four related activities,viz. i) The thorough characterisation of microstructure and mechanical behaviour at high and low strain rate of a wide range of ceramic materials. ii) A systematic, post-impact analysis of ceramic remnants with electron microscopy techniques with the aim of establishing the damage mechanisms for a range of armour ceramics under various impact conditions. The above two activities led to a much greater understanding of the processes that occur during ballistic impacts with ceramic materials, including the microstructural deformations that occur. This knowledge can be used to develop improved armour materials. iii) The processing, characterisation and assessment of nanostructured ceramics as potential armour materials. The nano zirconia toughened alumina developed displayed excellent performance during gas gun tests and so has now been scaled up (under another project funded by MAST) and is due to undergo actual ballistic evaluation in late 2014. iv) Development of methodology for experimental characterisation of strain rate dependent behaviour of ceramics and corresponding modelling at two distinct lengths scales, thus resulting in improved understanding of the intrinsic behaviour of ceramic materials as well as in improved modelling capability to design improved armour systems. toughened aluminas. Potentially the most exciting part of the project, this work fed off the first two items above to develop models that would predict the performance of ceramic materials under ballistic impact conditions. More work has been undertaken at Oxford University (I was not involved). Reports suggest that this has taken the whole area a massive step forward, with Unicam underpinning the work. As a result of the above work, we have also been working on boron carbide-based armour materials through funding from DSTL and the US Army Research Labs. This could lead to superior B4C armour; the work is still ongoing. |
Exploitation Route | The work on nano ZTA resulted in an armour material that was more effective at stopping bullets but the extra mass involved with the armour made it no more effective overall than alumina armour, though there was greater consistency. |
Sectors | Aerospace Defence and Marine |
Description | This project consisted of four related activities,viz. i) The thorough characterisation of microstructure and mechanical behaviour at high and low strain rate of a wide range of ceramic materials. ii) A systematic, post-impact analysis of ceramic remnants with electron microscopy techniques with the aim of establishing the damage mechanisms for a range of armour ceramics under various impact conditions. The above two activities led to a much greater understanding of the processes that occur during ballistic impacts with ceramic materials, including the microstructural deformations that occur. This knowledge can be used to develop improved armour materials. iii) The processing, characterisation and assessment of nanostructured ceramics as potential armour materials. The nano zirconia toughened alumina developed displayed excellent performance during gas gun tests and so has now been scaled up (under another project funded by MAST) and is due to undergo actual ballistic evaluation in late 2014. iv) Development of methodology for experimental characterisation of strain rate dependent behaviour of ceramics and corresponding modelling at two distinct lengths scales, thus resulting in improved understanding of the intrinsic behaviour of ceramic materials as well as in improved modelling capability to design improved armour systems. toughened aluminas. Potentially the most exciting part of the project, this work fed off the first two items above to develop models that would predict the performance of ceramic materials under ballistic impact conditions. More work has been undertaken at Oxford University (I was not involved). Reports suggest that this has taken the whole area a massive step forward, with Unicam underpinning the work. As a result of the above work, we have also been working on boron carbide-based armour materials through funding from DSTL and the US Army Research Labs. This could lead to superior B4C armour; the work is still ongoing. |
First Year Of Impact | 2014 |
Sector | Aerospace, Defence and Marine |
Impact Types | Societal |
Description | DSTL £45,479 Extension to Silicon Stabilised Boron Carbide Armour, SiBA (2018-19) |
Amount | £45,479 (GBP) |
Organisation | Defence Science & Technology Laboratory (DSTL) |
Sector | Public |
Country | United Kingdom |
Start | 06/2018 |
End | 03/2019 |
Description | MAST |
Amount | £300,000 (GBP) |
Organisation | Defence Science & Technology Laboratory (DSTL) |
Sector | Public |
Country | United Kingdom |
Start | 09/2012 |
End | 03/2016 |
Description | Nano transparent alumina |
Amount | $66,000 (USD) |
Organisation | ONRG Office of Naval Research Global |
Sector | Public |
Country | United States |
Start | 09/2012 |
End | 03/2015 |
Description | Nano transparent alumina |
Amount | £50,000 (GBP) |
Organisation | Defence Science & Technology Laboratory (DSTL) |
Sector | Public |
Country | United Kingdom |
Start | 09/2012 |
End | 03/2015 |
Description | Understanding and improving ceramic armour materials |
Organisation | Defence Science & Technology Laboratory (DSTL) |
Country | United Kingdom |
Sector | Public |
PI Contribution | See outline of the project. |
Collaborator Contribution | DSTL provided technical input and ballistic testing; Morgan provided technical input. Both attended meetings. |
Impact | See publications. |
Start Year | 2009 |
Description | Understanding and improving ceramic armour materials |
Organisation | Morgan Advanced Materials |
Country | United Kingdom |
Sector | Private |
PI Contribution | See outline of the project. |
Collaborator Contribution | DSTL provided technical input and ballistic testing; Morgan provided technical input. Both attended meetings. |
Impact | See publications. |
Start Year | 2009 |
Description | Invited paper ICACC 2018 Jan 2018. |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Invited paper 'Processing of boron carbide-based armour', Ceramic, Composite and Optical Materials Center (CCOMC), Armor Ceramic Subgroup Program, held during the 42nd International Conference on Advanced Ceramics & Composites (ICACC 2018), Daytona Beach, Florida, January 2018. |
Year(s) Of Engagement Activity | 2018 |