Nondestructive Evaluation Technique Utilizing Embedded Thermal Fiber Optic Sensors

Abstract

We investigated a thermal nondestructive evaluation (NDE) technique based on thermography that uses optical fiber thermal sensors to detect damage within a laminated graphite epoxy composite specimen. Two sets of composite samples were used for testing, one set had fiber optic sensors embedded between the layers while the other relied on thermocouple sensors attached to the exterior. A simulated impact system was used to induce damage of varying degrees into the samples. The damage was confirmed either with X-ray or C-scan imaging. The test apparatus in addition to the test data obtained from both sets of samples are presented. The data confirms that the fiber optic thermal sensors can not only detect the presence of damage, but can measure the severity of damage as well. This is the first known attempt to use in situ fiber optic point sensors with thermography to detect damage.