New Journal Paper Published! "Surface Engineering Alumina Armour Ceramics with Laser Shock Peen
It brings a great pleasure to publish a new journal paper, on our recent work entitled “Surface Engineering Alumina Armour Ceramics with Laser Shock Peening”, in the Material and Design journal. This journal is a highly reputed in the area of material science and related areas, and has an excellent impact factor (4.364, August 2017), for engineering and material science fields. The work in the paper shows novel finding with respect to modification of an important property of a ceramic - fracture toughness (KIc), microstructural examination, hardness, compresive stress induction, which all-in-all, not only shows rigour, but it also has the significance, as it is focused on an important subject such as Improving the strength of armour ceramics. The comments of the reviewers were extremely encouraging and motivational:
"This study is valuable because it gives the information on the improvement of the armor ceramic elements that is extremely topical in our current fight against terrorism".
"Systematic test data has been presented which showed some clear effect of the laser peening on hardness, indentation toughness. More obvious effect was observed on the residual stresses. This represents a new direction of work for further research".
"The significant improvement of the mechanical properties of the ceramic plates was reached after laser pulse treatment. The experimental conditions used for the sample preparation and physical properties observation are given in detail that opens a possibility for future testing of the results by other researchers".
The experiments were undertaken using a pulse Nd:YAG laser to induce compressive stress in a fine grain, brittle alumina ceramic of a level 4 bullet resistant vest. Further work is ongoing in this line of research and will be reported shortly. I would like to thanks the contributors from home institution and both Loughborough University and the University of Cincinnati. Please see abstract and the online link to the paper below:
Laser shock peening (LSP) of Al2O3 armour ceramics is reported for the first-time. A 10 J, 8 ns, pulsed Nd:YAG laser with a 532 nm wavelength was employed. The hardness, KIc, fracture morphology, topography, surface residual stresses and microstructures were investigated. The results showed an increase in the surface hardness by 10% which was confirmed by a reduction in Vickers indentations size by 5%. The respective flaw sizes of the Vickers indentations were also reduced (10.5%) and inherently increased the KIc (12%). Residual stress state by X-ray diffraction method showed an average stress of − 64 MPa after LSP, whilst the untreated surface stress measured + 219 MPa. Further verification with the fluorescence method revealed surface relaxation with a maximum residual stress of − 172 MPa after LSP of the Al2O3 armour ceramic. These findings are attributed to a microstructural refinement, grain size reduction and an induction of compressive stress that was relaxing the top/near surface layer from the pre-existing tensile stresses after LSP. Further process refinement/optimization will provide better control of the surface properties and will act as a strengthening technique to improve the performance of armour ceramics to stop bullets for a longer period of time and protect the end-users.
Shukla, P., Robertson, S., Wu, H., Telang, A., Kattoura, M., Nath, S., Mannava, S.R., Vasudevan, V.K., and J. Lawrence, (2017), ‘Surface Engineering Alumina Armour Ceramics with Laser Shock Peening’, Materials and Design, In Press