Non-Destructive X-ray Computed Microtomography Inspection of Composites Containing Manufacturing Defects

摘要

Honeycomb sandwich constructions are used extensively in the aerospace industryrnto increase stiffness of composite structures without adding significant weight. As partrnof the manufacturing process, immersion ultrasonic non-destructive inspection (NDI)rnis typically conducted in order to validate compliance of components. Ultrasonic NDIrnis relatively cost effective. Attenuation variations from baselines (known goodrncomponents) indicate non-compliance of manufactured components, but the source ofrnattenuation is often unavailable from ultrasonic inspection. Examples of sources ofrnattenuation of ultrasonic signals include porosity in the bondline or laminate,rndelaminations between the core and facesheets, and foreign objects that entered therncomponent during manufacturing. In order to improve manufacturing processes andrnreduce the costs associated with non-compliant components, a relatively new (torncomposites manufacturing) NDI technique, X-ray computed microtomography (CμT)rnis used. The advantages and limitations of CμT are discussed via investigation of noncompliantrncomponents.rnUltrasonic NDI results of non-compliant cored composite aircraft components arernpresented. Regions of non-compliance are further investigated via CμT. The CμTrninvestigation reveals unanticipated defects, blistering within the honeycomb core cellrnwalls, at the locations that ultrasonic NDI indicated as non-compliant. As part of thernCμT process, 3-dimensional digital volumes of the components are created. Fromrnthese volumes, virtual cross-section cuts are created, including the creation of videosrnshowing the ability to make “infinite” section cuts, which allow defects within therncomponent to be investigated. Finally, results of destructive investigation arernpresented to confirm the blistering observed via the CμT investigation.