Stress failure of airborne optical assembly resulting from rigid, high modulus epoxy adhesive and quality improvements

摘要

Up to 40% failure odds on an airborne optical assembly were found during finalizing the design-production phase. It resulted in lens splitting, cracking, and shattering. The combined stress of residual stress originated from solidification shrinkage and deformation stress and from temperature changes that drastically caused the failures. The optical assembly was composed of aluminum shell, rigid epoxy adhesive layer, and glass lens. Mechanism and affecting factors of the failure were investigated on process, operation, and materials. A series of comparative trail experiments were carried out. It was recommended to prevent the failures by redesigning match clearance between duralumin wall and lens, replacing rigid epoxy adhesive with flexible polyurethane adhesive. Via these new measures, all optical assemblies made hereafter succeeded and passed all military environmental tests and inspections, with a zero percent failure odds. (c) 2005 Wiley Periodicals, Inc.