Carbon Fiber Reinforced Polyetheretherketone Composites Research Articles

The influence of sterilization processes on the micromechanical properties of carbon fiber-reinforced PEEK composites for bone implant applications

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.

Solid particle erosion of unidirectional carbon fibre reinforced polyetheretherketone composites

The solid particle erosion behaviour of unidirectional carbon fibre (CF) reinforced polyetheretherketone (PEEK) composites has been characterised. The erosion rates of these composites have been evaluated at different impingement angles (15–90°) and at three different fibre orientations (0, 45, and 90°). The particles used for the erosion measurements were steel balls with diameter of 300–500 μm and impact velocities of 45 and 85 m/s. The unidirectional CF reinforced PEEK composites showed semi-ductile erosion behaviour, with maximum erosion rate at 60° impingement angle. The fibre orientations had a significant influence on erosion rate. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.

Long-range effects of carbon fiber on crystallization of semicrystalline thermoplastics

Non-isothermal crystallization of carbon fiber reinforced polyetheretherketone composites was studied with differential scanning calorimetry and Fourier transform infrared spectroscopy. Composite prepregs prepared by a solution pre-impregnation method with the matrix of different molecular weights were employed in the present work as the main model materials. Analyses of the different dependencies of non-isothermal crystallization on melt residual time in these systems revealed that carbon fibers had long-range effects on bulk crystallization of matrix polymer, which is rooted in the fact that the fibers tend to promote strain-induced nucleation in polymer. Comparison of the crystallization behavior of prepregs with that of the composite laminates indicated the importance of wetting and absorption to the effects of fiber on matrix crystallization, coinciding with the mechanism that short-range interaction formed the boundary to the flow under thermal stress.

Suitability and limitations of carbon fiber reinforced PEEK composites as bearing surfaces for total joint replacements

The suitability and limitations of carbon fiber reinforced polyether ether ketone (PEEK) composites as bearing surfaces for total joint replacements are investigated. The wear behaviour of the composites is studied under both high-stress non-conforming contact and low-stress conforming contact conditions. The former mimics the total knee contact conditions while the latter simulates the total hip contact conditions. For each contact geometry, the study focuses on the effects of carbon fiber type, carbon fiber loading and counterface material on the wear behaviour of the composite.

Micromechanics and Creep Behavior of Fiber-Reinforced Polyether-Ether-Ketone Composites

A micromechanics formulation of composite properties in terms of the constitutent properties using Eshelby's inclusion principle and Mori-Tanaka's mean field method. A linear four-element Burger mechanical model has been employed for application to viscoelastic polymers. The influence of volume fractions of inclusions on the overall creep strain of a polyether-ether-ketone (PEEK)-matrix composite is investigated. The creep rate of the PEEK-matrix which depends linearly on the creep strain and the primary creep, resulting from the viscous flow of creep deformation, is also considered in addition to the usual steady state, or secondary creep. In order to examine the applicability of the model to pure PEEK resin and carbon/PEEK, a series of experiments on PEEK 150P and unidirectional carbon fiber-reinforced PEEK composites has been carried out, which included constant rate of tensile tests and constant load tensile creep tests. It is found that the pure PEEK resin and its composite satisfies the four element Burger model, and that the model agrees with the experimental results extremely well. Also, it is demonstrated that this simple, albeit micromechanic theory is capable of predicting the volume fraction dependence of the time dependent creep, with a characteristic consistent with the known elastic behavior.

Matrix fractography of fibre-reinforced thermoplastics, part 2. shear failures

This paper describes the various features which are characteristic of shear failures in carbon fibre-reinforced polyetheretherketone composites and considers their significance in the analysis of the failure of structures fabricated from such material.