Published: Jan 1981
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Two parameters used to quantify the nondestructive inspection (NDI) of adhesive lap-joint bonds are useful as reliable indicators of adhesive bond strength in certain inspection applications. The two indicators, local bond integrity index (LBI) and bond merit factor (BMF), will be defined and their relationships to bond strength demonstrated and discussed.
The LBI indicator is obtained from readings of local bond integrity made with a commercially available bond tester. The readings were made on local bond regions approximately 2.5 cm2, with a bond tester that had been calibrated to a desired sensitivity by using an appropriate reference specimen. The reference specimen was selected by a simple statistical and physical test procedure, and its use provides a reproducible relationship between LBI and bond strength. Destructive test results have shown good correlations (r = 0.9) of lap-shear strength with LBI readings for a given sample set.
The BMF indicator is an easy-to-obtain, time-efficient indicator of adhesive bond coverage. It is computed for a bond line region, generally 15 to 40 cm long, using disbond detection data obtained for instrument sensitivity based on the LBI of the reference specimen. These regional inspection results have shown fair correlation (r = 0.7) with the sum of local lap-shear strengths over the region.
nondestructive evaluation, nondestructive inspection, nondestructive testing, adhesive bond NDE, adhesive bond NDI, adhesive bond NDT, ultrasonic inspection, quality assurance, adhesive bonds, composites, composite materials, fiber reinforced plastics, fiberglass, bond-joint strength, FRP assemblies, bond strength evaluation, ultrasonic testing, sonic inspection, bond testing
Senior research engineer, Ford Motor Co., Detroit, Mich.