Location

La Jolla, CA

Start Date

1-1-1991 12:00 AM

Description

Nondestructive evaluation (NDE) of thick composites is a difficult task. If ultrasonic techniques are used, such factors as attenuation (preferentially high frequencies); dispersion which causes the ultrasonic wave to change shape as it propagates in the composite; anisotropy (sound velocity a function of direction); material variation (inhomogeneities in composition); and transducer beam spread must be taken into account. Radiographic techniques depend on density differences to produce images. However, in many instances, the density differences produced by defects in composites are not great with the result that many defects go unnoticed. Thermography and shearography are two relatively new NDE techniques but heat flow considerations (for thermography) and stressing a large-thick composite structure sufficiently (for shearography) limit the application of these methods. Regardless of the technique used, the two principal aspects of NDE in a manufacturing environment are defect location and defect sizing.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

10B

Chapter

Chapter 6: Engineered Materials

Section

"Thick" Composites

Pages

1583-1590

DOI

10.1007/978-1-4615-3742-7_58

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Defects in Thick Composites and Some Methods to Locate Them

La Jolla, CA

Nondestructive evaluation (NDE) of thick composites is a difficult task. If ultrasonic techniques are used, such factors as attenuation (preferentially high frequencies); dispersion which causes the ultrasonic wave to change shape as it propagates in the composite; anisotropy (sound velocity a function of direction); material variation (inhomogeneities in composition); and transducer beam spread must be taken into account. Radiographic techniques depend on density differences to produce images. However, in many instances, the density differences produced by defects in composites are not great with the result that many defects go unnoticed. Thermography and shearography are two relatively new NDE techniques but heat flow considerations (for thermography) and stressing a large-thick composite structure sufficiently (for shearography) limit the application of these methods. Regardless of the technique used, the two principal aspects of NDE in a manufacturing environment are defect location and defect sizing.