Neat Polyetheretherketone Research Articles

The abrasive wear behaviour of continuous fibre polymer composites

The dry abrasive-dominant wear behaviour of several composite materials consisting of uni-directional continuous fibres and polymer matrices was investigated. Seven materials were examined: neat epoxy (3501-6), carbon fibre epoxy (AS4/3501-6), glass fibre/epoxy (E-glass/ 3501-6), aramid fibre/epoxy (K49/3501-6), neat polyetheretherketone (PEEK), carbon fibre/PEEK (APC2) and aramid fibre/PEEK (K49/PEEK). The wear behaviour of the materials was characterized by experimentally determining the friction coefficients and wear rates with a pin on-flat test apparatus. First, the effects of the operation variables apparent normal pressure, sliding velocity and apparent contact area were observed. The dimensionless wear rate increased linearly as the apparent normal pressure increased and decreased as the apparent contact area increased. Second, through microscopic observations of the worn surfaces and subsurface regions, basic wear mechanisms were identified as a function of fibre orientation. Observations of fibre-abrasive particle interactions allowed for the differentiation of the dominating wear mechanisms. Finally, a network of data was compiled on the wear behaviour in terms of the three material parameters: fibre orientation, fibre material and matrix material. This enabled the systematic selection of an ideal low wear composite material which would consist of a PEEK matrix reinforced with aramid fibres oriented normal to the contacting surface and carbon fibres oriented parallel to the contacting surface.

Thermal Sonic Analysis of Polymer Matrices and Composites

A commercially available sonic Pulse Propagation Meter (PPM-5R) was utilized in this study to monitor kinetic changes of matrix polymers that may be encountered in process ing operations of fiber-reinforced composites. Both thermoplastic polyetheretherketone (PEEK) and thermosetting epoxy resins and their carbon fiber composites were examined. During cure, the epoxy samples displayed obvious velocity changes at the initial softening and final cure transitions. For the neat PEEK samples, the sonic velocity decreased slowly as the temperature increased and the velocity dropped rapidly at a transition temperature of 160°C. Samples of carbon fiber-reinforced epoxy and PEEK composites were also in vestigated to examine the effect of fibers on the sonic velocity responses. The results show that the reinforcing fibers whose orientation coincides with the probe orientation have the most dampening effect on the detection of transitions using the sonic technique. Overall, the sonic technique for process monitoring is discussed in this paper.

Annealing effects on the crystallinity of polyetheretherketone (PEEK) and its carbon fiber composite

AbstractThe degree of crystallinity of polyetheretherketone (PEEK) has been measured using both the density gradient technique (DGT) and differential scanning calorimetry (DSC). The difference in results between the methods was shown to depend on crystallization taking place during the heating scan in the DSC. By freezing the sample at different stages of the DSC thermogram and measuring its crystallinity in the density gradient column, the existence of induced crystallization for PEEK was established. Though this induced crystallization is not visible in the DSC thermogram, it must be taken into account when comparing the degree of crystallinity measured by the two methods. The induced crystallization was in turn interpreted as a result of an increase in crystal perfection that is also commonly observed during the initial stages of the annealing process. Accordingly, the effect of annealing on the crystallinity was also investigated. DSC scans on annealed samples exhibited a small endothermic peak at approximately 10°C above the annealing temperature. This peak was observed in both neat PEEK and its carbon fiber‐reinforced composite. Annealed PEEK shows, therefore, two melting transitions, a low one which depends on the annealing temperature and a high one which is independent of annealing temperature conditions. Collectively, the results of this study demonstrate that processing conditions and morphological features must be considered in characterizing semicrystalline‐based matrix polymers for high performance composites.