Aerospace Composite Testing Solutions using Industrial Robots

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1 18th World Conference on Nondestructive Testing, April 2012, Durban, South Africa Aerospace Composite Testing Solutions using Industrial Robots Albrecht MAURER 1, Walter DEODORICO 1, Roland HUBER 1, Thierry LAFFONT 2 1 GE Inspection Technologies, Alzenau, Germany albrecht.maurer@ge.com; walter.deodorico@ge.com; roland.huber@ge.com 2 GE Inspection Technologies, Limonest, France; thierry.laffont@ge.com Abstract Due to the higher volumes of Composite materials in structural airframe components, automated ultrasonic testing (UT) is been requested not only for large surface areas, but also for smaller and more complex geometrical components. Beyond the cost advantage of automated vs. manual testing, full availability and documentation of results in B-or C-scan format is another advantage of automated testing. Phased Array in full parallel mode allows additional advantages in both test capability of complex components and versatility. This paper describes the incremental testing capabilities with advanced Phased Array technology vs. conventional testing. Advanced Phased Array technology and its implementation into production-type aircraft testing machines is presented. Beyond the testing capabilities, automated evaluation procedures of defects are described. Additionally, industrial scanners are presented both in customized design solutions as well as in the use of standard industrial robots. These innovative composite-testing solutions help our customers to cost-effectively adapt their NDT test cell for program changes. As testing machine development and delivery time has been highly reduced versus traditional gantry system, it allows the users to order the inspection solution when the component s final design is known with a full confidence to be ready for the production start date. The potential use of new-generation ultrasonic matrix arrays opens a complete new range of applications. Keywords: Phased array, automated testing machine, industrial robots, aerospace, carbon fiber composite, CFC 1. Introduction New civil aircraft types are designed for improved operations and higher fuel efficiency. One of the main factors influencing these parameters is the weight of the aircraft. State-of-the-art carbon fiber composite (CFC) components offer superior strength parameters as well as the capability to design according to individual load. Component integrity is mainly affected by proper bonding of the individual CFC layers. Ultrasonic testing has proven to be the optimum NDT method to test CFC components for factors weakening its strength, mainly influenced by delamination and porosity. Automated testing provides both high throughputs, improved probability of detection (P.O.D.) and a proper document proving the quality of the tested components. While testing of simple, shaped parts is state-of-the-art, more complex components are being tested manually, causing higher cost and lacking of documented test results. This paper describes advanced testing features for automated inspection of complex-shaped components as well as the use of off-the-shelf robotic scanners to serve as transducer manipulators. 2. Challenges While large-surface-area components can be easily tested with large-area scanners, their productivity is mainly affected by their throughput speed and versatility. Rather than providing individual application specific adaptations, parallel B-scan Phased Array technology offers extremely high productivity, easy adaptation to complex geometry curvature, as well as, together with matched bubblers, automated testing of part sections usually tested manually.

2 3. Sample applications In the following samples of automated testing, complex component sections are presented: 3.1. Large surface areas with slight curvature and variable-thickness cross section A bubbler probe (local immersion coupling device) for large area inspection including specific flange edges is designed for a scan width of 64 mm in one single scan, allowing coverage of 40 m² per hour with a sensitivity of 3 mm delamination tested in a 2x2mm matrix. This capability is achieved through parallel B-scan technology. Up to 128 ultrasonic transducer elements are pulsed and received in parallel. Through this feature, both pulse-echo and pitch-catch techniques are possible, i.e. the phasedarray technology returns signals back to the firing elements, but is also capable of receiving signals reflected from neighboring elements, without losing important information. Figure 1: Send/receive on non-parallel front surface Figure 2: Send/receive on non-parallel component section Example of a non-parallel cross section shows a B-scan recorded in parallel B-scan mode without making part-specific settings on the instrument: Front Surface Anomalies Rear surface Figure 3: Cross sectional B-scan of a CFC component with a curved front-and-rear surface The above-described parallel B-scan technology covers a significant amount of complex-surface testing requirements.

described in the enclosed example: R Part R VP Figure 4: Curved component testing with linear phased-array (left) and A- and B-scan result featuring automated adaptation of cycling to the part

3 Array Probe width 3.2. Curved-radius areas In addition, Parallel B-scan technology has potential to be upgraded to support corner inspection using the same linear array probe, but with additional adaptive-phasing method as described in the enclosed example: R Part R VP Figure 4: Curved component testing with linear phased-array (left) and A- and B-scan result featuring automated adaptation of cycling to the part curvature (right) 3.3. Automated test of stringer sections Specific tooling has been engineered to perform automated testing of stringers, which, in the past, have been tested manually despite availability of automated test machines for the outer skin. This feature adds productivity, improved P.O.D. as well as UT image data to the quality records. Figure 5: Tooling for automated testing of stringers in a single-path using parallel B-scan Phased Array ultrasonic technique 3.4. Stringer Root Inspection

The stringer root requires a specific test procedure, which is transformed into an automated test unit using a curved Phased Array probe with bubbler following the contour and detecting, lack of,

Porosity Evaluation Apart from geometric-section inspection for delamination, the content of porosity in a CFC component is of vital influence to the component s integrity.

Figure 7: C-Scan of a porosity reference component having a known porosity content. The area is divided in a section with and without detected porosity 3.6.

4 The stringer root requires a specific test procedure, which is transformed into an automated test unit using a curved Phased Array probe with bubbler following the contour and detecting, lack of, bonding in the stringer root section ( noodle ). Figure 6: Equipment for stringer root inspection (left) and C-scan of a stringer root inspection with suspect (right) areas Porosity Evaluation Apart from geometric-section inspection for delamination, the content of porosity in a CFC component is of vital influence to the component s integrity. Porosity can be detected from the attenuation of the ultrasound in a known volume section: In the example shown, the equipment is capable of detecting areas of porosity exceeding a predefined level. Figure 7: C-Scan of a porosity reference component having a known porosity content. The area is divided in a section with and without detected porosity 3.6. Technical solution in a production testing machine In the current example, all necessary probes and bubblers are integrated into the probe head and can be selected by operator choice. Selection may include the sequential use of all probes/bubblers for the test of representative areas of the part. The process can be programmed into a batch file to enable a complete automated scan process.

Figure 8: Squirters and application-specific bubblers integrated into a

1. Customized solutions Customized scanner designs have been and are still

Different designs have been realized to meet specific needs.

5 Figure 8: Squirters and application-specific bubblers integrated into a single probe head for uninterrupted automated testing. 4. Scanning systems 4.1. Customized solutions Customized scanner designs have been and are still in use to meet user s inspection requirements. Different designs have been realized to meet specific needs. Examples are shown below: Figure 9: Full-Fuselage Through-Transmission Scanner Figure 10: Dual-manipulator scanner with turntable

Figure 11: Scanner unit in box design 4.2.

solutions, industrial robots have become a valid scanning-system option in the aerospace industry.

solutions, resulting in shorter delivery times and lower-cost solutions.

Receiver probe water column Robot Figure 12: Industrial robot for through-transmission testing of a

6 Figure 11: Scanner unit in box design 4.2. Robot-based solutions In view of the high degree of customization for application-specific scanner solutions, industrial robots have become a valid scanning-system option in the aerospace industry. Their versatile capabilities allow a high variety of applications using standard industrial solutions, resulting in shorter delivery times and lower-cost solutions. A number of scanning solutions have been established, shown in the pictures below: Pulser probe Receiver probe water column Robot Figure 12: Industrial robot for through-transmission testing of a narrow fuselage nose section Figure 13: Industrial robot with linear scanning capabilities. A rack of interchangeable specific bubbler types can be automatically connected to the robotic end effector.

7 Figure 14: Dual industrial robot scanning system for through-transmission operation 5. Conclusions The increased use of carbon fiber composites in airframe design and manufacture follows the need for automated, application-specific sensor and sensor head solutions, as well as matched scanning-system solutions. The use of the Parallel B-scan phased array technology increases testing productivity and eases mechanized testing solutions for complex geometries. Further, industrial robots have proven to be valid substitutions for legacy customized scanner systems. 6. Accomplishments The authors would like to thank the GE Sensing & Inspection Technologies teams from Alzenau, Germany, and Lewistown, PA, USA for their strong contribution to the results presented in this paper.

Automated Inspection of Complex Composite Components in the Production Cycle

17th World Conference on Nondestructive Testing, 25-28 Oct 2008, Shanghai, China Automated Inspection of Complex Composite Components in the Production Cycle Albrecht MAURER 1, Wolfgang HAASE 1, Rudolf