Paper number 438

ENVIRONMENTAL EFFECTS ON THE MECHANICAL PROPERTIES OF PLAIN WEFT KNITTED CF/PEEK AND GF/PET COMPOSITES

Roland Reber¹, Joop de Haan¹, Joerg Mayer¹ and Erich Wintermantel¹

Jolanta Janczak-Rusch2 and Lukas Rohr2
1Biocompatible Materials Science and Engineering, Department of Materials
Swiss Federal Institute of Technology Zurich, Wagistrasse 23, 8952 Schlieren, Switzerland
http://www.biocomp.mat.ethz.ch
2Swiss Federal Laboratories for Materials Testing and Research,
Feuerwerkerstrasse 39, 3602 Thun, Switzerland
http://www.empa.ch

Summary

The effects of hygrothermal exposure on the mechanical properties of knitted fabric reinforced composites (KFRCs) was investigated with respect to their environments in potential applications. Knitted CF reinforced PEEK was immersed in water and simulated body fluid (SBF) at 37, 60 and 90°C for exposure times up to 50 weeks, whereas knitted GF/PET was immersed in water at 90°C for a maximum of two weeks. While no significant effects of long-term exposure on flexural properties, out-of-plane fracture toughness and failure behavior of CF/PEEK were determined, a severe reduction of matrix and fiber/matrix interface properties was observed in GF/PET. Matrix embrittlement and low interfacial adhesion dominated the failure behavior, studied in 4-pt bending and push-out tests. Results suggest that knitted CF reinforced PEEK is highly appropriate for load bearing implants, whereas the application of GF/PET composites is critical in environments involving moisture and elevated service temperatures.

Keywords

environmental fffects, thermoplastics, textiles, knitted fabric reinforced composites (KFRCs), interface degradation, CF/PEEK, GF/PET.