Nondestructive inspection of load induced damage in fiber reinforced polyphenylene sulfide

• Main Author: Fields, Richard Elliot
• Other Authors: Engineering Mechanics
• Format: Others
• Language: en_US
• Published: Virginia Polytechnic Institute and State University 2018
• Subjects: LD5655.V855 1982.F545; Thermoplastics > Testing; Laminated materials > Testing
• Online Access: http://hdl.handle.net/10919/82605

The present work presents the results of an investigation of properties of polyphenylene sulfide (PPS) reinforced with random, continuous glass fibers, approximately 30% by weight. The investigation included both characterization of the mechanical properties and nondestructive inspection of the material. The objectives of the nondestructive inspection program were twofold: i) to determine nondestructive testing techniques were most responsive to developing damage and ii) to identify the damage modes using the nondestructive testing methods. The mechanical testing program involved the study of three types of specimens: straight sided tensile coupon, dogbone, and streamline. The streamline specimen typically fails in the narrow region and therefore appears to be relatively unaffected by stress concentrations induced by the specimen geometry. Results are given for all three specimen types and comparisons made for the measured mechanical properties. Several nondestructive testing methods, including C-scan, ultrasonic attenuation, acoustic emission, X-ray radiography, and edge replication, were applied to study the damage developed under quasi-static tension loading of this material. The C-scan, edge replication, and X-ray radiography tests were performed both initially and after intermediate stages of loading. These three tests appear to be unresponsive to the developing damage. That is, these techniques were unable to detect any distinctive patterns around the regions of final failure. The most responsive NDT techniques are ultrasonic attenuation and acoustic emission. Both of these methods yield quite distinct changes with increasing load. The acoustic emission tests, for example, show an extremely rapid rise in count rate at loads of about two-thirds of ultimate. The ultrasonic attenuation measurements display maxima and minima when taken in real-time as the specimen is loaded. In an effort to determine the damage mechanisms in the material and to understand the results of the NDE tests, virgin and damaged specimens were destructively examined with the aid of a scanning electron microscope (SEM). The SEM appears to show that the acoustic emission production is corning from cracking of the transverse glass fibers. The results of all tests to date are presented together with recommendations and conclusions for the application of nondestructive test methods to PPS. === Master of Science