BALLISTIC TESTING OF CROSS-LAMINATED TIMBER LAYUPS TO FURTHER DEVELOP PROTECTIVE PANELS

Abstract

Though ballistic projectile penetration of wood has been studied for centuries, standard models overestimate the thickness of wood required to stop projectiles, often by a large margin. Adhesive lamination via contemporary manufacturing methods can produce mass timber panels of unprecedented thickness, yet industry standard layups of softwood cross-laminated timber (CLT) cannot stop projectiles traveling at velocities specified by current protective design requirements. To develop mass timber panels that comprehensively mitigate blast, ballistic, and forced entry threats, seven reinforced or hardened CLT layups were manufactured to compare their ballistic performance with that of a baseline 7-ply softwood CLT layup. Three calibers of ammunition were fired at each panel specimen, and entry and exit velocities were recorded with high-speed cameras. For projectiles that did not fully perforate the panel, the depth of penetration was determined by radiography. Four of the eight tested layups stopped all projectiles. Among the successful layups, three included embedded steel reinforcements. The other successful layup was made entirely of hardwood laminations. Steel-plate-reinforced softwood CLT proved the most cost-effective option.