Strength of transparent ceramic composites with spinel

Protective windows have to be very hard and possess a certain thickness to provide a good wear resistance, as well as low weight and cost to be used economically. But, common transparent systems like bulletproof glass are quite heavy because they need a minimum thickness to provide protection. Therefore, laminate systems consisting of a thin transparent ceramic layer with a very high hardness and a low-cost as well as a lower-weight transparent substrate are considered in the current work as an alternative solution to thick monolithic ceramics. Since reliability is a main aspect for the application, mechanical characterization is carried out using ring-on-ring bending tests for different laminate structures. Apart from various commercially available hardened and unhardened glasses, also a polymer material is taken into account as thicker substrate material for a thin spinel ceramic. In particular, polycarbonate as well as float glass, B270 and Borofloat^® by Schott or Gorilla glass^® 3 by Corning are used as substrate materials. Tests are carried out with either ceramic or substrate material under tension. Properties derived using laminate theory are compared and discussed with respect to the properties of the individual materials. The Young’s moduli of the monolithic materials are measured via an impulse excitation technique. In an outlook, implications for the application of the laminates are discussed.