Thermoplastic matrix composite polyetheretherketone (PEEK) reinforced with carbon fibers
The macroscopic behavior of composites depends not only on the properties of their individual constituents but also on the elastic–plastic interaction between the different phases,
such as fiber and matrix. During processing of a polymer
matrix composite material, the interaction between the surfaces of the fibers and the polymer matrix may create various chemical and morphological inhomogeneities. These are typically discussed in terms of two distinct regions,
namely, the interface and the interphase zones. The interface is defined at the atomic scale as the layer of the immediate chemical bond between the fiber and the polymer matrix. The interphase region is much larger. It is formed by local
changes of the polymer matrix in the vicinity of a fiber. In this region local properties like morphology, thermomechanical behavior and chemical composition can differ from the corresponding values observed in the bulk polymer matrix. It is obvious that the overall mechanical properties of fiber-reinforced polymer composite materials are influenced by the micromechanical behavior of both the interface and the interphase regions.
Godara, A.; Raabe, D.; Green, S.
Published: MAR 2007
Acta Biomaterialia 3 (2007) 209 PEEK_bon[...]
PDF-Dokument [1.0 MB]
The effect of sterilization on the structural integrity of the thermoplastic matrix composite polyetheretherketone (PEEK) reinforced with carbon fibers (CF) is investigated by nanoindentation and nanoscratch tests. The use of the material as a medical implant grade requires a detailed understanding of the micromechanical properties which primarily define its in vivo behavior. Sterilization is a mandatory process for such materials used in medical applications like bone implants. The steam and gamma radiation sterilization processes employed in this study are at sufficient levels to affect the micromechanical properties of some polymer materials, particularly in the interphase region between the polymer matrix and the reinforcing fibers. Nanoindentation and nanoscratch tests are used in this work to reveal local gradients in the hardness and the elastic properties of the interphase regions. Both methods help to explore microscopic changes in the hardness, reduced stiffness and scratch resistance in the interphase region and in the bulk polymer matrix due to the different sterilization processes employed. The results reveal that neither steam nor gamma radiation sterilization entails significant changes of the reduced elastic modulus, hardness or coefficient of friction in the bulk polymer matrix. However, minor material changes of the PEEK matrix were observed in the interphase region. Of the two sterilization methods used, the steam treatment has a more significant influence on these small changes in this region and appears to increase slightly the thickness of the interphase zone.