DETECTION AND QUANTIFICATION OF FIBER WAVINESS IN THICK COMPOSITE COMPONENTS

As the usage of composite materials in the design and fabrication of complex flight critical components evolves, the ability to provide an accurate assessment of the integrity of these components must also evolve. New families of anomalies have emerged that are not readily detected with conventional nondestructive methods. One such anomaly is fiber waviness/marcelling, which, when introduced during manufacturing processing of thick composites, imposes several negative effects on the material properties of components. Bell Helicopter has identified the need for the development of NDE methodology to enhance detection and enable quantification of this condition. Existing and newly emerging NDT techniques have been explored. With the incorporation of radiographically opaque tracer materials embedded in the lamina, radiation-generating methods have shown the greatest promise (with the lowest impact to the manufacturing process) in detecting marcels. Under a Bell-funded R&D grant, the Mechanical Engineering Department at Southern Methodist University has developed PC-based visualization routines using computer-assisted tomography. A computer program has been developed that enables the user to view, analyze, and interact with the 3–D representation of individual composite layers. Data were used that were obtained from several CAT-scans of specimens that have been impregnated with tracers. Specialized software routines were developed to reconstruct ply representations from the tracer images. A unique aspect of the graphical output is that it captures the geometric features of in-plane as well as out-of-plane marcels. The user can easily navigate to any given location within the scanned part and “set analyze” the scan with varying degrees of complexity.