Advanced Sealant for Next-Generation Transparent Armor Service Life

The U.S. Marine Corps are trained, organized, and equipped as a force in readiness, and their ability to operate with agility and efficiency depends on a well-equipped fleet of armored vehicles. One portion of this operational readiness is for the transparent armor in these vehicles to perform effectively. Transparent armor provides ballistic protection and visible transparency for the Warfighter. Transparent armor consists of layers of glass and polycarbonate autoclaved together with a interlayer adhesive.  The multi-layer laminate is then autoclaved, secured into metallic frames using a potting sealant or gasket, and attached to the vehicle structure. Existing transparent armor is experiencing early-life delamination, creating a significant cost for the Marine Corps and other branches of the military. These failures impede the Warfighters’ ability to visualize threats and the environment and reduce both vehicle and mission readiness. To compound the problem, existing stocks of transparent armor can delaminate before they are deployed, resulting in additional cost burdens and increased operational risks. This is especially problematic for the Marine Corps, where cost-effective agility is critical in maintaining superiority. While numerous failure modes exist, Luna Labs determined that delamination is primarily driven by 1) thermal cycling and humidity, which can cause thermo-mechanical stress on the laminate and adhesion loss in the interlayer adhesives, and 2) chemical incompatibility between the potting sealant (or gasket) and the edges of the laminate. In Phase I, a contaminant-free sealant was developed with improved environmental durability, moisture resistance, and adhesion. Using a high temperature and humidity accelerated aging test protocol, Luna Labs demonstrated the sealant’s effectiveness for reducing early-stage delamination, preventing moisture and thermal cycling from accelerating delamination, and extending the service life of small transparent armor coupons. In the Initial Phase II, our team refined the potting sealant and demonstrated its ability to reduce delamination on HMMWV transparent armor windshields in ATPD-2352 Revision U accelerated life testing. Windshields passed 8 out of the eventual 12 cycles that will be required for future ground vehicle transparent armor and Luna Labs secured purchase orders for over 600 gallons of the initial sealant product (GlassLock). In the Sequential Phase II, Luna Labs will optimize the GlassLock sealant for extended service life on a variety of ground vehicle platforms while enabling multiple original equipment manufacturers to qualify armor through all 12 cycles of the ATPD-2352 Revision U accelerated life test.