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The thermal stability of carbon fiber-reinforced polyetheretherketone (PEEK/CF) in air and its influence on consolidation are characterized under simulated processing conditions. The changes in dynamic shear modulus, melting temperature, heat of fusion and glass transition temperature due to chemical reactions and morphology changes were monitored by dynamic rheological analysis and differential scanning calorimetry. Thermal decomposition in air and simultaneous thermooxidative reaction of PEEK resin exposed to temperatures slightly higher than normal processing temperatures were observed by thermogravimetric and dynamic rheological analysis. The initial stage of this thermo-oxidative reaction, under isothermal and non-isothermal conditions, was modeled by a exponential-based Arrhenius expression. The consolidation of PEEK/CF is affected by the thermal oxidation of the resin, which delays time to intimate contact between the plies. A consolidation model, predicting the degree of intimate contact, is extended to also take into account the rheological changes of the system. Finally, a processing limit regarding the thermal stability is defined based on the model and the experimental results.

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Modelling is increasingly relied upon for the design and qualification of ultrasonic inspections applied to safety-critical components. Numerical methods enable the simulation of the ultrasonic interaction with realistic defect morphologies; however, the computational requirements often limit their deployment. The hybrid simulation technique, which combines semi-analytical and numerical methods, realises the potential of high fidelity numerical modelling without the limiting computational factors. The inspection of thick section components for near-backwall surface-breaking defects results in large propagation distances across, making them a key application of hybrid modelling. This work presents a methodology for efficiently simulating the ultrasonic inspection of complex surface-breaking defects using a hybrid model. The model is initially verified against full numerical simulation; further validation is presented by comparison to an experimental scan over an artificially machined surface-breaking notch. The potential of the new hybrid method is then demonstrated by carrying out a Monte Carlo analysis on the scattered field from surfacebreaking defects with randomly rough surfaces and the results are compared to the Kirchhoff approximation.