NDT

Honeywell Sensors to Detect Composite Failures

Honeywell Automation and Control Solutions (ACS) is currently working on a new type of sensor system that can provide non-destructive inspection information to maintenance personnel regarding the health of an aircraft's composite structures.

According the Lee Burtelson, director of marketing and sales for ACS's Aerospace, Transportation, Ordinance, and Marine Division, the sensors use ultrasonic Lamb wave technology to detect minute changes in composite structure, which can alert maintenance personnel to immediate or future repair needs. The Lamb wave sensor arrays can be embedded within the composite layers or bonded to the structure or skin surface.

"With composite material, structural failure is more difficult to determine because it's not like solid aluminum where you can see a crack and use it as a guideline for maintenance or repair," said Burtelson. "So the issue is how to establish maintenance criteria on something that you may or may not be able to see."

Lamb waves are guided ultrasonic waves capable of propagating long distances in plates and laminated structures such as aircraft skins, storage tanks, and pressure vessels. An array of sensors placed at regular intervals determines a baseline for Lamb wave propagation; wireless transmitters output sensor information on demand or after certain events, such as hard landings. Comparing current Lamb wave propagation to the baseline can reveal structural repair needs. The system can be configured to interface with ground-based maintenance diagnostics equipment.

"Ultimately we want to provide a maintenance-on-demand feature," said Burtelson, "As long as the aircraft operates within a set of parameters, you could [delay] maintenance until maintenance needed to occur. For instance, after a landing condition, you could have the system give an indication of whether the landing sustained reasonable forces or not, and thus potentially avoid the downtime to assess the situation."

Lamb waves have been used for non-destructive testing and inspection of defective parts and small structures for more than a decade, but this is apparently the first attempt to use permanent Lamb wave-based sensor arrays to monitor the health of an entire composite aircraft structure. Honeywell is currently working with an undisclosed customer to develop the Lamb wave-based sensor array technology, which is not limited to aircraft but could ultimately be used on any composite structure where failure is an issue. Burtleson estimates that these sensors should be available to the commercial aviation maintenance market within three years. - By Kim Rosenlof