Fabrication of PEEK/carbon fibre composites by aqueous suspension prepregging (original) (raw)
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Interlaminar fracture morphology of carbon fibre/PEEK composites
Journal of Materials Science, 1987
The interlaminar fracture morphology of a carbon fibre/poly(ether-ether-ketone) composite (Aromatic Polymer Composite, APC-2) has been examined. The techniques used included scanning electron microscopy on fracture surfaces and on polished and etched sections. Two types of interlaminar fracture are observed: stable and unstable fracture. Both fracture surfaces exhibit microductility but it is more extensive for stable fracture. The fracture surfaces are not planar but have surface roughness. Fibre breakage and peeling are also observed and a quantitative examination enables the fracture energy contributions from the various processes to be calculated. The use of an etching technique reveals the spherulite texture and the presence of a deformation zone which extends into the bulk of the composite from the fracture surface. The extent of this zone is greater in the stable fracture region than in the unstable region and its presence indicates that the volume of composite which can be brought into the energy absorbing process extends well beyond the interlaminar region. The size of the zone has also been calculated using the fracture energy contributions and there is moderate agreement between calculated and observed zone size. Patterns of microductility on the fracture surface are seen to be due to spherulite texture, however the spherulite boundaries do not influence the fracture path.
Interface morphology of carbon fibre/PEEK composites
Journal of Materials Science, 1990
The morphology of high-performance thermoplastic composites (APC-2) based on continuous carbon fibres embedded in a poly-ether-ether-ketone matrix is studied by means of scanning electron microscopy. Samples with different degrees of crystallinity obtained using different thermal treatments are investigated. The effect of the crystallinity content seems to be crucial for fibre/matrix adhesion, as can be detected by SEM analysis.
Relationships between microstructures and fracture energies in carbon fibre/PEEK composites
Composites
The aim of this investigation was to characterize the fracture surfaces of a series of similar composites, and to relate the features observed to the fracture modes. The materials used in this study were based on the ICI material APC-2, being uniaxially aligned composites of carbon fibre in a matrix of poly-ether-ether-ketone, PEEK. The fracture method chosen for this comparative study was to propagate cracks in the weakest plane of the materials, so that the samples split under the wedging action of a blade driven into the material. The fracture surfaces are thus representative of cracks propagating parallel to the fibres and normal to the prepreg layers. Fracture energies were obtained from analysis of the geometry of the crack without the need for any load measurements using a specially developed technique, the razor blade test 1'2. The fracture surfaces were prepared from the slivers of material split off in the test, and were examined in the scanning electron microscope (SEM). They were thus taken from the same region of material which yielded the data on fracture energy. The principal microstructural factors identified as being significant were the matrix ductility and the fibre/matrix adhesion.
Impact characterization of polymer composites based on peek and carbon fibres
2014
Considering the constant expansion of the areas of application of composite materials, is increasingly crucial to deepen the research for the correct evaluation of the potential application of these materials. In this job, the determination of the impact strength value, as well as the maximum load and the rigidity of the material, has been obtained by means of an instrumented pendulum impact test. More in details, the characterization of four different composite materials, based on a polymeric matrix and reinforced with carbon fibres, will be presented. The materials tested will differ for the type of the reinforcement and the degree of crystallinity of their matrix. The influence of these factors on the aforementioned impact properties will be the presented and discussed, leading to the identification of the composite material with the best impact properties for a specific application.
Materials
Due to the non-polar nature and low wettability of carbon fibers (CFs), the interfacial adhesion between CFs and the polyetheretherketone (PEEK) matrix is poor, and this has negative effects on the mechanical properties of CF/PEEK composites. In this work, we established a modification method to improve the interface between CFs and PEEK based chemical grafting of aminated polyetheretherketone (PEEK-NH2) on CFs to create an interfacial layer which has competency with the PEEK matrix. The changed chemical composition, surface morphology, surface energy, and interlaminar shear strength were investigated. After grafting, the interlaminar shear strength (ILSS) was improved by 33.4% due to the covalent bonds in the interface region, as well as having good compatibility between the interface modifier and PEEK. Finally, Dynamic Mechanical Analysis (DMA) and Scanning Electron Microscopy (SEM) observation also confirmed that the properties of the modified CF/PEEK composites interface were en...
Polymers
Laminated composites based on polyetheretherketone (PEEK) and polyimide (PI) matrices were fabricated by hot compression. Reinforcing materials (unidirectional carbon-fiber (CF) tapes or carbon fabric) and their layout patterns were varied. Stress–strain diagrams after three-point flexural tests were analyzed, and both lateral faces of the fractured specimens and fractured surfaces (obtained by optical and scanning electron microscopy, respectively) were studied. It was shown that the laminated composites possessed the maximum mechanical properties (flexural elastic modulus and strength) in the case of the unidirectional CF (0°/0°) layout. These composites were also not subjected to catastrophic failure during the tests. The PEEK-based composites showed twice the flexural strength of the PI-based ones (0.4 and 0.2 GPa, respectively), while the flexural modulus was four times higher (60 and 15 GPa, correspondently). The reason was associated with different melt flowability of the use...
Wear performance of PEEK–carbon fabric composites with strengthened fiber–matrix interface
Wear, 2011
Powder-prepreg method was used to develop composites with untreated and cold remote nitrogen–oxygen (0.5%) plasma (CRNOP) treated carbon fabric (CF) (67–68 wt%) and poly-ether-ether-ketone (PEEK) followed by the evaluation of physical and mechanical properties. Tribo-evaluation in adhesive wear mode was done by sliding a composite pin against a mild steel disc under various loads. It was observed that surface treated fabric composites were excellent in mechanical (tensile, flexural and ILSS – interlaminar shear strength) and tribological properties. A low coefficient of friction (0.21–0.28) and wear rates (1–12 × 10−15 m3/Nm) were recorded for these composites. An enhanced fiber–matrix adhesion was found to play a key role for improvement in performance properties. Raman spectroscopic and SEM studies on worn composites were done and correlated with the wear performance.
Acta Biomaterialia, 2007
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.
Fibre-reinforced composites with tailored interphases using PPE/epoxy blends as a matrix system
Composites Part A: Applied Science and Manufacturing, 1996
In this study poly(2,6_dimethyl-1 ,Cphenylene ether) (PPE) is introduced as a ductile thermoplastic matrix for high-performance carbon fibre-reinforced composites by using epoxy resin as a reactive solvent. An interesting feature of this reactive composite processing route is that the epoxy resin acts not only as an effective solvent, lowering the viscosity and processing temperature of the polymer matrix, but also provides an essential structural part of the final composite material. Upon curing and subsequent phase separation, a morphology of epoxy-coated fibres in a nearly pure PPE matrix results. This phenomenon is not only of great importance with respect to the possibility to drastically improve the adhesion between the fibres and the thermoplastic matrix, but also creates the challenge to tailor the mechanical properties of these in situ formed interlayers by changing the chemistry of the epoxy phase.
Influence of fibre–matrix interface on the fracture behaviour of carbon-carbon composites
Journal of the European Ceramic Society, 2003
This paper studies the fracture behaviour of unidirectional carbon fibre reinforced carbon matrix composites and its relation with the type of fibre-matrix interface developed in the composite. Model unidirectional carbon-carbon composites were prepared using the same type of fibre and different pitches as matrix precursors. These included both commercial pitches and synthesized in the laboratory ones. The chemical composition of the matrix precursor determined the type of microstructure developed in the composite, this microstructure seems to govern the fibre-matrix bonding and in turn controls the fracture behaviour of the composite. In general, a matrix texture of mosaic (small size) seems to yield a good fibre-matrix bonding, making the materials to have higher interlaminar shear strength but having at the same time brittle fracture behaviour. On the other hand, composites where larger textures were developed in the matrix seem to have a poorer fibre-matrix bonding. This made the composites to have lower strength, but it allowed debonding of fibre and matrix during fracture. As a result, these materials showed pseudo-plastic failure behaviour. Other examples of both types of fracture behaviour associated with the change in microstructure and fibre-matrix interface are discussed. #