Functionally layered cement composites against projectile impact

This study is about the original development of functionally layered system comprising cementitious and polymer materials, based on shock physics analysis considerations, to improve penetration resistance and reduce radial damage. The design approach was based on the bio-inspired impact resistance and energy absorption characteristics of turtle shells, and builds on a previous research by the main author to employ the concept of functional layering using shock physics considerations. It entails the use of cementitious materials and orthotropic polymers that would lead to the development of a functionally layered protective system comprising (1) High strength plain mortar (similar to 85 MPa) as the first layer to convert most of the projectiles kinetic energy into the creation of fracture surfaces, and heat, (2) An orthotropic polypropylene geotextile polymer as a second layer to delay and spread the compressive shock waves, (3) High energy absorption rubberised mortar as the third layer to absorb the remaining transmitted kinetic energy through cell collapse and volume change, and (4) Base plate for confinement of the relatively weak energy absorber, as the 4th layer. In this study, the use of rubberised mortar, in combination with geotextile, reduced crater diameter by up to 28% with a moderate average increase of 2% in penetration depths. There exists a minimum thickness required of a high strength plain mortar as a first layer to take the first impact of a projectile. Geotextile, as wave spreader, has the effect of reducing crater diameter by up to 25% without significantly affecting the penetration resistance of a target.