Authors:

B. Boro Djordjevic

Publication:

Materials Evaluation, Volume 72, Issue 7

Publication Date: 1 July 2014Testing Method:

Ultrasonic Testing

,

Guided Wave

,

Laser Testing

Composite mechanical damage is typically in the form of delaminations or disbonds (laminate-to-laminate or laminate-to-core), broken fibers due to impact, fatigue damage that affects the zone of composite material via micro cracking, fiber delaminations, fiber breaks and overall loss of mechanical modulus. It can be caused by thermal damage from fire, engine bleed air leaks, and prolonged exposure to heat above resin cure temperatures, as well as a combination of environmental effects due to extreme operational conditions. Ultrasonic testing (UT) enables extensive characterization of the composite materials’ integrity, and many ultrasonic methodologies are in current use for the inspection of large-scale composites. Challenges for UT of composites are more complex and require better understanding of the ultrasound signal attenuation, ultrasonic signals frequency dependent behavior and consideration of ultrasonic signal modality. UT of composites for optimized operations requires additional consideration of the inspection parameters and a fresh evaluation of applicable UT modes. It is improper to extrapolate metals UT experience to the composite structures.

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