Inspection of Complex Composite Components

Carbon Fiber Reinforced Plastics (CFRP) are increasingly being used in both military and commercial aircraft due to the high strength-to-weight ratio, fatigue performance, corrosion resistance, and the ability to create complex geometries. From a manufacturing perspective, these advantages can only be achieved when the layers (plies) of the composite construction are properly bonded and there are no defects within the structure. To ensure this quality and precision, all structural CFRP parts must be 100% inspected as part of the manufacturing quality processes.

Technical Requirements

The inspections of CFRP components require Non-Destructive Testing (NDT) methods that can rapidly scan components of all sizes, providing quantitative data on the material construction. This is typically achieved with Ultrasonic Inspection. Ultrasound inspection methods require a coupling medium, such as water, to transmit the ultrasonic energy into the part and then interpret the reflected or transmitted sound waves to assess the integrity of the material. These inspections can be performed in an immersion tank or with more sophisticated systems such as squirter or bubbler systems with mechanical scanner systems.

Such inspections can be performed using conventional single-channel or Phased Array equipment and methods. With Ultrasound Phased Array (UTPA), an array of transducers is electronically controlled by powerful and sophisticated electronics, allowing the sound energy to be steered or focused. UTPA increases the scanning coverage and speed of inspection, generating richer data sets and better probability of detection. Another advantage of UTPA is the diagnostic imaging of the part and defect areas for clearer interpretation and detection.

Sophisticated UTPA techniques are constantly being developed to increase the accuracy and productivity of production inspection for composite aircraft components. An example of an advanced UTPA solution is Parallel B-scan mode, where all elements of a large aperture are fired and received at the same time. This technique is ideally suited to corners and other outside radii features, where the incident sound energy is not entering the part at the ideal 90° angle to the part surface. This allows the inspection a large part with a single flat probe. Eliminating the need to switch to customized probes for outer corners of other complex radii simplifies the inspection and allows increased throughput in high volume manufacturing settings.

Ultrasound Phased Array inspection of composite panels with Automated Robotic Testing Machines from GE Inspection Technologies.

Additional innovations have been developed to inspect a number of subcomponents in one single scan. Using batch scan technology, the inspection of the numerous different components are taught in advance to the automated UTPA system and control electronics. Many components are grouped into a batch container of components to be scanned.

Each component has its own UT- and scan parameters, but the inspection equipment performs them in series, by group. This approach is implemented at a major aircraft manufacturer, employing an automated loading area, NDT area and unloading area fully integrated into the serial production cycle. This system has been designed for highly loaded production cycles and was successfully qualified for 100% test for delaminations and porosity.