Nondestructive Inspection for Quality Assurance of Fiber Reinforced Plastic Assemblies

THE QUALITY ASSURANCE OF FIBER reinforced plastic assemblies is accomplished at several Ford company and supplier facilities by the implementation of inspection technology developed to assure the integrity of adhesive bond joints and the adherend material of which the assemblies are made.

A low-frequency ultrasonic inspection method for the adhesive joints has been developed into a production-compatible method and was reported in references 1, 2, and 3. It uses a 25 kHz commercially available bond tester calibrated with reference specimens selected by a statistical procedure. Certain strength-related characteristics of the adherend material of the assembly, such as fiber orientation, can also be evaluated by measuring changes in the Lamb-wave velocity of 25 kHz acoustic waves propagated in the material by the bond tester. Glass concentration can be determined nondestructively by measuring the velocity of longitudinal ultrasonic waves propagated through the thickness of the material.

The development and implementation of this inspection technology has provided an effective NDI method for determining the tensile strength of the material, in a given direction, by indicating such strength-related properties as glass fiber concentration and orientation.