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Detection of CFRP Composite Manufacturing Defects Using a Guided Wave ApproachNASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered waves are in phase over the overlap boundaries.
Document ID
20160005999
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Hudson, Tyler B. (North Carolina State Univ. Raleigh, NC, United States)
Hou, Tan-Hung (NASA Langley Research Center Hampton, VA, United States)
Grimsley, Brian W. (NASA Langley Research Center Hampton, VA, United States)
Yuan, Fuh-Gwo (North Carolina State Univ. Raleigh, NC, United States)
Date Acquired
May 10, 2016
Publication Date
May 18, 2015
Subject Category
Composite Materials
Report/Patent Number
NF1676L-19900
Meeting Information
Meeting: SAMPE Baltimore 2015
Location: Baltimore, MD
Country: United States
Start Date: May 18, 2015
End Date: May 21, 2015
Sponsors: Society for the Advancement of Materials and Process Engineering
Funding Number(s)
WBS: WBS 544163.04.03.07.03
Distribution Limits
Public
Copyright
Public Use Permitted.

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