By Dr. Adam Brant, Project Manager at RE2 Robotics
Throughout numerous industries, the use of composite materials is continuously increasing, due to the fact that they are typically stronger, lighter and less expensive than metals like steel, aluminum, and titanium. Made of two or more combined materials, the properties of the composites are usually stronger than the original, individual materials.
The Significance of Composites for the Aerospace Industry
The aerospace industry, in particular, is increasing the use of composite materials in the design and building of aircraft. Less weight on an airframe means better fuel economy and, therefore, lower operating costs. Aircraft wings, tailfins and fuselages are increasingly being built with composite materials, as they are typically more durable and lighter weight than metals.
Safety, of course, is paramount in the aerospace industry. As the use of composites grows, so does the need for innovative methods for testing and inspecting them. Visual inspection is the most common method for inspecting composites, but that method only provides information on what the inspector can see with his or her eyes.
Non-Destructive Testing for Aerospace Applications
In response to the increased use of composites, Non-Destructive Testing, or NDT, is being used more often. NDT refers to any type of test on a material, component or device that does not result in damage or destruction of what is being tested.
When you perform NDT, that component or material can still be used normally after the test. By using ultrasound to inspect an aircraft beneath its surface, NDT provides an economical and reliable method of ensuring the safety of the materials from which aircraft are built. This method can also be used at the manufacturing stage to test newly built material, in the maintenance shop to help diagnose problems, or on the flightline for routine inspection prior to flight.
NDT is beneficial to the aerospace industry because it does not compromise the material’s structural integrity the way that standard, destructive testing does. Destructive testing can only be conducted in situations where there are multiple specimens available for “sacrificial” testing. Destructive testing also does not account for sample-to-sample variances. This means that if failures are not found during testing, they can still occur in a fielded product due to slight manufacturing variances or unknown disruptions in the supply chain.
NDT, on the other hand, allows materials to be tested without being removed from the aircraft, which saves time and also eliminates the need to perform flight worthiness tests, which are required when components are removed from the aircraft for testing. NDT also allows for the material or component that is being tested to immediately be fielded. Therefore, there is direct knowledge of the testing outcomes of that particular aircraft component, thus higher confidence in its performance.
How Mobile Manipulation Enhances NDT
The use of robotics can help to augment NDT processes in a number of ways. For instance, robotic manipulator arms can be configured to maneuver in tight spaces, allowing robots to easily reach areas of the aircraft that humans cannot access without first removing parts. Second, mobile robots offer repeatability. A robot can be programmed to perform the exact same test on the exact same regions of an aircraft, eliminating opportunities for human error. Robotics-based NDT also can more easily facilitate the automated transfer and processing of test data and results. Deploying robotic arms for NDT testing provides users with robust test results no matter where they are implemented, including areas that have complex geometries or that are difficult or even dangerous for humans to access.
Mobile manipulation enhances NDT by providing increased repeatability and robustness for a measurement. Oftentimes, measurements made with NDT sensors are highly dependent on the relative placement of the sensor on the material that is being inspected. If two measurements differ in placement by even a small amount—such as less than an inch--the results can be quite different, and this could cause false positive or false negative readings.
RE2’s manipulator arms can perform a highly repeatable measurement more accurately and more quickly than a human can. Additionally, adding vision sensors can assist inspectors in viewing hard-to-reach or hard-to-see areas. This increases the speed of work while reducing risk to the inspectors. All of these advantages lessen the physical burdens of an aging aircraft maintenance workforce, therefore reducing the overall cost of aircraft maintenance.
As composite materials continue to evolve, so will the need for enhanced NDT methods. Composite material development is a growing field, with many different research groups dedicated to the development of stronger, lighter and cheaper materials. Robotics-based NDT will allow the industry to keep pace as increases in automation and data processing requirements are realized.
About Dr. Adam Brant
Dr. Adam Brant is a project manager at RE2 Robotics. After earning his Ph.D. in physics from West Virginia University, Adam began working on a variety of Department of Defense Small Business Innovation Research (SBIR) programs. He has completed research in magnetic resonance spectroscopy for the U.S. Air Force as well as research and development into non-destructive evaluation technologies for missile systems. He has also managed defense programs in nondestructive evaluation of electronics and has experience in three separate R&D areas: magnetic resonance, RF sensors, and now robotics.