Practical Bond Strength Inspection for Aerospace Composites

Composite airframe designs benefit significantly from incorporation of adhesive bond joints rather than metal fasteners. Adhesive bonds can be exceptionally strong and lightweight, but require careful process control to form. In order to rely on such joints, both the Air Force and commercial manufacturers require a non-destructive test method to verify the quality of as-built joints. The only known test is shock-loaded bond inspection, in which a brief, high amplitude stress wave is coupled into the joint to interrogate its strength. The current standard for performing this inspection requires a massive pulsed laser to produce the mechanical shock. This system works well in the laboratory, but the expensive 10,000 pound laser and unwieldy articulated arm make the system completely impractical in a production environment. We have developed a novel transduction mechanism to replace this laser. Our mechanism is orders of magnitude smaller and more efficient, as well as dramatically simpler and more reliable, but produces precisely the same stress wave in the tested part. A shock-loaded bond inspection system incorporating our novel transducer will enable truly practical measurements on the aircraft production floor using a simple, handheld transducer.