Tests conducted on composite aircraft fuselage test panels show that new sensing technology from Luna Innovations Incorporated (NASDAQ: LUNA) offers aerospace manufacturers and operators greater insight into the condition of composite structures.

Highly distributed strain sensing is now available with Luna's ODiSI (Optical Distributed Sensor Interrogator) instrument. According to tests conducted by the University of California-San Diego and the FAA Airworthiness Assurance Center operated by Sandia National Labs, the ODiSI measures the performance, tolerances and failure mechanisms of structures and vehicles.

Researchers fired ice balls of approximately 2.5 inches in diameter onto two carbon fiber-epoxy test panels representative of composite surfaces found on a range of modern aircraft such as the B787, A350 or A380. In one panel optical sensing fiber was embedded within the composite laminate during layup and co-cured; in the second panel sensing fiber was surface bonded to the panel skin.

Results showed residual, lasting strain after the impact, offering better insight into how the impact of debris and collisions affects composites. Looking at the residual strain in the fiber as it is mapped to the panel surface, the impact location is identifiable in a single scan of the laser by the strain left in the fiber. Current inspection techniques are labor intensive and require examination of the surface in small sections at a time.

"Our technology gives manufacturers and operators the ability to know what is happening inside composite structures and see damage even if it's not visible," said My Chung, CEO. "The tests demonstrate that composite structure testing is not only possible but that manufacturers and operators can test the condition of composite structures like never before."

ODiSI provides a constant picture of a structure's load distribution with a sensor mass of only a few grams. It utilizes low-cost optical fiber for unprecedented sensor density for strain or temperature sensing applications and delivers hundreds of measurement locations per meter of fiber with resolutions of a few microstrains.

With sensors suitable for surface bonding or embedding in composites, ODiSI can be used either during manufacturing or later installation.

First introduced in August 2011, ODiSI supports the exacting standards of the aerospace, automotive, energy and other composites industries where high-density strain or temperature measurements are required for structural or mechanical testing. The product is sold under the company's test and measurement equipment brand name Luna Technologies.

"Luna Innovations is improving the way composite materials are tested and validated for peak performance and safety, particularly in the aerospace and energy markets, and customers are starting to embrace our technology around the world," Chung said. "ODiSI is an integral part of our corporate strategy to grow revenue that focuses on serving high-growth industries with new-technology solutions."

Composite materials have seen increased usage in the aerospace industry due to weight-saving initiatives. For example, the new Boeing 787 is nearly 80 percent composites by volume. Safety concerns with widespread composites use have arisen because these materials do not visibly show fatigue and impact damage the way traditional materials do.

ODiSI applications include composite structure design and model verification, design improvement, manufacturing process verification, structural health monitoring and performance optimization. ODiSI provides a sensing solution that is rich in data content, lightweight, robust, easy to install, and does not require expensive fiber containing Fiber Bragg Gratings (FBGs).