Original Date: 10/14/1988
Revision Date: 01/18/2007
Information : The Effects of Defects In Composite Materials
Bell Helicopter Textron, Inc. (BHTI) has developed the ability to correlate ultrasonic inspection results to the mechanical properties of graphite/epoxy composite materials. They currently use this information during the accept/reject decision-making process for composite parts that do not meet nondestructive inspection (NDI) acceptance criteria. This information may also be used to redefine the NDI acceptance criteria used for production parts.
BHTI's study of the "Effects of Defects" on composites may ultimately reduce part rejections by providing quantitative data to the Material Review Board (MRB) for use in the assessment of a part's structural integrity. Without a quantitative assessment of defects, every flaw must be considered potentially fatal.
Specifically, dispersed intralaminar porosity was investigated. It was found that porosity content varied linearly with ultrasonic signal attenuation in IM6/3501-6 laminates. Furthermore, interlaminar shear strength and open hole compression strength were shown to decrease linearly as ultrasonic attenuation levels increased. The initial studies of fatigue properties show a similar trend. Further investigations of fatigue properties will be performed in the future, as well as investigations of the effects of delaminations, measles, and other defects.
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