Location

La Jolla, CA

Start Date

1-1-1987 12:00 AM

Description

The use of ultrasonic backscatter to characterize anomalous states in fiber-reinforced composites has received considerable attention in recent years. The ultrasonic backscatter from composites with oriented fiber reinforcement, unlike that from monolithic materials, displays a strong angular dependence. Hence, three independent variables are available over which to analyze the backscatter. These are the azimuthal angle ∅ (the rotation orientation of the composite plate about the perpendicular), the elevation angle θ (the angle between the ultrasonic beam and the perpendicular to the insonified composite plate), and time. Bar-Cohen and Crane [1] considered various ways of exploiting the angular dependence of backscatter to examine anomalies in composite laminates such as fiber misalignment, cracks, and porosity. Several other efforts employing similar approaches have followed [2–4]. This paper addresses specific questions concerning the angular dependence of backscatter and the use of this angular dependence to assess porosity levels. Additionally, problems inherent in the analysis of the temporal behavior of backscatter are discussed, and an approach to the spectral analysis of backscatter for porosity assessment is demonstrated.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

6B

Chapter

Chapter 6: Advanced Composites

Section

Defects

Pages

1147-1156

DOI

10.1007/978-1-4613-1893-4_131

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Porosity Characterization in Fiber-Reinforced Composites by Use of Ultrasonic Backscatter

La Jolla, CA

The use of ultrasonic backscatter to characterize anomalous states in fiber-reinforced composites has received considerable attention in recent years. The ultrasonic backscatter from composites with oriented fiber reinforcement, unlike that from monolithic materials, displays a strong angular dependence. Hence, three independent variables are available over which to analyze the backscatter. These are the azimuthal angle ∅ (the rotation orientation of the composite plate about the perpendicular), the elevation angle θ (the angle between the ultrasonic beam and the perpendicular to the insonified composite plate), and time. Bar-Cohen and Crane [1] considered various ways of exploiting the angular dependence of backscatter to examine anomalies in composite laminates such as fiber misalignment, cracks, and porosity. Several other efforts employing similar approaches have followed [2–4]. This paper addresses specific questions concerning the angular dependence of backscatter and the use of this angular dependence to assess porosity levels. Additionally, problems inherent in the analysis of the temporal behavior of backscatter are discussed, and an approach to the spectral analysis of backscatter for porosity assessment is demonstrated.