N102-143 TITLE: Nondestructive Inspection Technique Capable of Detecting and Characterizing Bridging

TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: PMA-261: H-53 Heavy Lift Helicopter Program

OBJECTIVE: Develop a nondestructive inspection technique capable of detecting and characterizing bridging in graphite/epoxy and fiberglass/epoxy laminate parts with tight radii.

DESCRIPTION: Ply bridging in laminate materials with tight radii can result from improper manufacturing processes. Bridging is an area within a laminate material with tight radii in which the plys are not completely filling the radius. Bridging reduces structural strength, and its detection and characterization is of importance to the Navy. Having a means of detecting and quantifying bridging would significantly improve the quality control process of thick composite parts subject to defects of this kind. While computed tomography radiographic techniques have been used in the past, they are expensive, generally limited to parts less than two feet in width, and unreliable when the plies are nearly in contact with each other. For these reasons, an affordable nondestructive tool is desired to reliably detect, measure, and characterize bridging in tight radii. The primary materials of focus are graphite/epoxy and fiberglass/epoxy laminates of various geometries and up to 0.75 inch thick. Detection of bridging throughout the thickness of the part is required. Consideration also should to be given to other materials or obstructions that may exist between layers in a part. Composite bridging must be detectable in and around molded-in metal sections of the component under inspection.

PHASE I: Develop and demonstrate feasibility of an innovative technology that detects and measures bridging in graphite/epoxy and fiberglass/epoxy laminate materials with tight radii. Manufacture or procure necessary laminate samples for feasibility demonstration.

PHASE II: Develop, construct and demonstrate a prototype for characterization testing and evaluation, capable of detecting and quantifying bridging. Demonstrations should be performed using samples that are manufactured or procured and that are representative of what can be expected in the Fleet.

PHASE III: Transition the developed nondestructive evaluation (NDE) device to interested platforms and commercial interests.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Quality control process improvements from this technology would be applicable to any industry that is using composite material construction; i.e.; automotive, wind turbines, ship building, and commercial aircraft.

REFERENCES:
1. Krishnamurthy, C. V., Shankar, M., Vardhan, J. V., & Balasubramaniam, K. (2006). The 2004 ultrasonic benchmark problem - sdh response under oblique incidence: Measurements and patch element model calculations. Review of Progress in Quantitative Nondestructive Evaluation. Volume 25B, 25B, 1820-1827.

2. Walker, J. L., Russell, S. S., & Workman, G. L. (1998). Thermographic qualification of graphite/epoxy instrumentation racks. Paper presented at the Proceedings of SPIE: Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware II. San Antonio, TX; USA; 31 Mar.-2 Apr.; Proceedings of SPIE: Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware II, San Antonio, TX; USA. 141-148.

3. Muralidhar, C., Lukose, S. N., & Subramanian, M. P. (2007). Evaluation of turbine blades using computed tomography. Journal of Nondestructive Testing, 12(3)

KEYWORDS: bridging; radius; composite; nondestructive inspection; nondestructive testing; void

** TOPIC AUTHOR (TPOC) **

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