NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Investigation of Fiber Waviness in a Thick Glass Composite Beam Using THz NDEFiber waviness in laminated composite material is introduced during manufacture because of uneven curing, resin shrinkage, or ply buckling caused by bending the composite lay-up into its final shape prior to curing. The resulting waviness has a detrimental effect on mechanical properties, therefore this condition is important to detect and characterize. Ultrasonic characterization methods are difficult to interpret because elastic wave propagation is highly dependent on ply orientation and material stresses. By comparison, the pulsed terahertz response of the composite is shown to provide clear indications of the fiber waviness. Pulsed Terahertz NDE is an electromagnetic inspection method that operates in the frequency range between 300 GHz and 3 THz. Its propagation is influenced by refractive index variations and interfaces. This work applies pulsed Terahertz NDE to the inspection of a thick composite beam with fiber waviness. The sample is a laminated glass composite material approximately 15mm thick with a 90-degree bend. Terahertz response from the planar section, away from the bend, is indicative of a homogeneous material with no major reflections from internal plies, while the multiple reflections at the bend area correspond to the fiber waviness. Results of these measurements are presented for the planar and bend areas.
Document ID
20080014177
Document Type
Conference Paper
Authors
Anastasi, Robert F.
(Army Research Lab. Hampton, VA, United States)
Date Acquired
August 24, 2013
Publication Date
March 9, 2008
Subject Category
Composite Materials
Meeting Information
SPIE Smart Structures and Materials and Nondestructive Evaluation and Health Monitoring(San Diego, CA)
Funding Number(s)
WBS: WBS 377816.06.02.03.02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

NameType 20080014177.pdf STI
No Preview Available