Inventors win award for nondestructive inspection method for composites

Roger M. Crane, an alumnus of University of Delaware, was honored by the U.S. Office of Naval Research (ONR) for work developing the nondestructive inspection method known as SIDER.

Roger M. Crane, who earned his Ph.D. in materials science at the University of Delaware in 1991 under the advisement of the University’s Center for Composite Materials (CCM) Director Jack Gillespie, was recently honored by the U.S. Office of Naval Research (ONR) for developing a nondestructive method that can detect flaws and anomalies in composite materials. Crane is now a senior composites materials engineer in the Structures and Composites Division at the Naval Surface Warfare Center, Carderock Division.

With co-inventor Dr. Colin P. Ratcliffe, professor of mechanical engineering at the U.S. Naval Academy, Crane received the 2006 Vice Admiral Harold G. Bowen Award, which recognizes inventions patented by Navy personnel that have been "of great benefit to the Navy.”

Rear Admiral William E. Landay, Chief of Naval Research, presented the award to Ratcliffe and Crane at a ceremony in Arlington, Virginia, on November 27, 2007. In presenting the award, Landay noted that detecting damage early on, before a structure fails, has the potential to save lives.

The novel technique known as SIDER (Structural Irregularity and Damage Evaluation Routine) is used to find damage in composite ship structures. The method can be used anywhere, eliminating the need to cut samples from the material and send them to a laboratory for inspection.

SIDER involves exciting a composite structure with a modally tuned impact "hammer"and recording the vibration response using accelerometers. This information is input into a frequency analyzer, where the frequency response function (FRF) is determined. Conventional NDE vibration methods use either mode shape or frequency shifts to determine whether damage exists. These methods can detect damage only when it is extensive.

With SIDER, the FRF is used to obtain the operational deflection shape from which the operational curvature shape can be determined. Ratcliffe and Crane's research has shown that curvature is much more sensitive to minimal levels of damage. "For example,"Crane says, “SIDER was capable of identifying the area on a 4-inch by 36-inch 0.0125-inch thick steel beam where a 0.002-inch groove was machined across the width of the beam.”

The other significant feature of the SIDER method is that the identified damage areas can be mapped with great precision onto an image of the structure, allowing anomalies to be located quickly.

Crane and Ratcliffe have used SIDER to inspect the composite vertical stabilizers of the F-18 Super Hornet aircraft, the twisted rudder on the DDG guided missile destroyer, and the hull of the Office of Force Transformation M80 Stiletto all-composite ship. In addition to these military platforms, SIDER has been used to inspect a composite road bridge on Route 896 in Delaware; a composite bridge deck in Dayton, Ohio; and an A320 composite vertical stabilizer.

"The cool thing for me is that the initial validation on large-scale composite inspection using SIDER started with the University of Delaware on the 896 bridge,"Crane says. "Success there piqued the Navy's interest in using it on other structures. Researchers at CCM had the foresight to see its value and allow us to take the risk to try the technique out.”

Following successful validation of the technique on the Delaware bridge in 1998, Crane continued to collaborate with CCM on work related to SIDER through the ONR-funded Advanced Materials Intelligent Processing Center (AMIPC) Program.

"Over the years, we have worked closely with Roger, applying this technology to other projects, including the Airbus tail and the HEMTT armored truck,"says Gillespie. "It's very gratifying to see him become a successful branch chief and to be recognized for his pioneering research and creation of a new large-scale NDE technique.”

A current project in CCM's CART (Composites Applied Research and Technology) program with the Army is addressing composite armor NDE. "The concept allows simple post-manufacturing and depot-level evaluation,"says CCM Assistant Director Dirk Heider. "Potentially, the SIDER approach could enable in-service health monitoring using vehicle vibration, allowing optimized maintenance scheduling and improved battlefield awareness.”

Crane and his colleagues, including Ratcliffe as well as Bill Marr of the U.S. Naval Academy and Maureen Foley of the NSWC Carderock Division, recently published the results of a proof-of-concept demonstration of the use of SIDER underwater. Foley is also a CCM alum; she earned her Ph.D. in materials science under Gillespie's advisorship in 2004.

"Removing such structures as composite rudders for inspection, or dry docking an entire ship just to inspect them, is expensive and time consuming,"Crane says. "A detailed inspection method that could be used underwater to assess the structural health of components would be very valuable.”