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Fatigue Behavior and Nondestructive Testing of Thermoformed High-Performance Thermoplastics with Discontinuous Carbon Fiber Reinforcement

In the course of this study, uni- and bidirectional polyetherketoneketone-(PEKK)-Iaminates with aligned, discontinuous, AS-4 fibers were deformed to various plastic deformation states (3 %, 6 %, 9 %, 12 %) by thermoforming. It appeared that the DAF-material (DAF-Discontinuous Aligned Fibers) has a natural tendency to local thinning when stretched. Local necking resulted in areas of insufficient consolidation. Therefore, it was necessary to deter­ mine a new processing window which differs from that recommended by the manufacturer. This window includes a higher temperature and pressure Ievel. Static tensile tests and fatigue tests were carried out depending on the plastic deformation. It was found that the mechanical properties improved with increasing plastic deformation as long as the consolidation quality was satisfactory.

Nondestructive testing methods (ultrasonics, X-ray, thermography) as weil as image processing techniques were employed for two reasons: to determine quality criteria for thermoforming and to characterize the darnage accumulation during fatigue. The evaluation of these experiments showed an obviously different darnage accumulation behavior for DAF­Iaminates in comparison with continuously reinforced thermosets.

In order to use ultrasonic testing, which is regarded to be the most powerful state-of-the-art nondestructive testing tool, research on the signaVnoise-ratio was performed to determine a standard for the proper selection of transducers prior to ultrasonic testing. In addition, it was shown that pattern recognition is a weil suited method for identifying and characterizing defects.

The experimental results obtained from thermoforming, static-, and fatigue testing were accurately modelled.

Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Author
 Jens Schuster

Jens Schuster
Institut für Verbundwerkstoffe GmbH
Universität Kaiserslautern

Information

Free keywords: Thermoforming, fatigue test, tensile test, fiber orientation, signal-noise-ratio, C-scan, frequency analysis, pattern recognition, X-ray-testing, thermography, modeling
Institute / chair: Fachbereich Maschinenwesen der Universität Kaiserslautern
Language: German
Technical consultant for expert services: Prof. Dr.-Ing. K. Friedrich (Betreuer), Prof. Dr.-Ing. M. Neitzel
Publication year: 1995
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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