Mitigating impact failure of masonry boundary walls using auxetic composites

Masonry boundary walls protect buildings of national significance and residences by obstructing intruding vehicles. As masonry is weak in tension, impact induced tensile stresses damage the walls locally sufficient for the impacting vehicles intruding. Strengthening masonry walls using various forms of fiber reinforced plastics (FRP) can prevent intrusion but would generate excessive acceleration that can endanger the occupants of the unintended impacting vehicle; furthermore, prevention of local damage would force the whole wall participation that can increase the impact force and affect the global safety of the wall. Energy absorption properties of the mitigating system is, therefore, more important than the strength properties. To reduce the accident severity and save the lives, use of Auxetic materials possessing negative Poisson’s ratio is promising and hence used as a mitigating measure in this research. Auxetic fabric embedded in fiber cement matrix is used as composite render on both sides of the boundary wall. The wall, supported on three edges except the top to simulate the boundary wall profile, was modelled using a layered shell element. Masonry was modelled as a homogenised orthotropic nonlinear brittle material with embedded mortar joints; the wall was modelled with and without the auxetic composite render. This paper will describe the modelling method and results.