The Surface Treatment of Advanced Ceramic Materials for Improved Adhesive Bond Strength in Armour Applications.

Lightweight ceramic armour is desirable to reduce mass of armoured vehicles. Alumina and silicon carbide are the two most frequently used ceramics and they are incorporated into the system using adhesive bonding technology, which historically has proved problematic. Thus, in this work, a range of surface treatments have been investigated with the aim of increasing the strength of the bond between alumina or silicon carbide and a toughened epoxy adhesive, in ballistic applications. Three surface conditions for each ceramic have been characterised; as-fired and laser processed samples as well as grit blasted alumina and refired silicon carbide. Physical and chemical changes to the surface were investigated using scanning electron microscopy, profilometry, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and the sessile drop technique. After grit blasting alumina it was found that the surface had been contaminated. For silicon carbide it was observed after refiring that the surface was oxidised. It was found after laser processing alumina and silicon carbide that the treated surfaces had a greater concentration of hydroxyl groups and for the silicon carbide surface it was found also to have been oxidised. These chemical changes were tentatively linked to the improved wettability and more specifically, the increased polar component of the surface energy. These surfaces demonstrated the greatest improvements in bond strength in comparison to the as-fired, grit blasted and refired samples. Ballistic tests were performed on a range of processed alumina and silicon carbide tiles. The results were consistent with the predictions made on the basis of the quasi-static testing, in that the damage to the laser processed tiles resulted in less debonding and hence better ballistic performance than the control samples. Thus, this study has shown that the laser processing of the ceramic surface has the potential to improve the performance of ceramic armour systems