A study has been carried out on the influence of extrusion and drawing related process parameters with an object of obtaining high modulus poly ether ether ketone yarns that can be tailor made to meet critical requirements of aerospace applications. The influence of the interaction between rheological properties, spinning process variables, and drawing conditions has been given special attention to engineer a yarn that exhibit excellent structure property relationships. The wide angle X-ray diffraction results suggest that drawing carried out above glass transition temperature (T g ) influences the structure that include unit cell parameters, density, and mechanical properties. The degree of orientation characterized in terms of sonic velocity measured as high as 3 km/s with sonic modulus of 105 gpd. With progressive increase in draw temperature, crystallinity was found to increase, and useful properties were observed at an optimum draw temperature of 200 C (may be region of maximum crystallization rate) primarily attributed to the maximum crystallization temperature and the heat setting effect. Thermal studies (TGA) indicate that these materials can be used in high temperature applications (up to 250 C) for long time exposure and 500 C for short term exposure.

Poly ether ether ketone (PEEK) polymer was extruded into filaments and cowoven into unidirectional hybrid fabric with glass as reinforcement fiber. The hybrid fabrics were then converted into laminates and their properties with special reference to crystallization behavior has been studied. The composite laminates have been evaluated for mechanical properties, such as tensile strength, interlaminar shear strength (ILSS), and flexural strength. The thermal behavior of the composite laminates were analyzed using differential scanning calorimeter, thermogravimetric analyzer, dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA). The exposure of the fabricated composite laminates to high temperature (400 and 500 C) using radiant heat source resulted in an improvement in the crystallanity. The morphological behavior and PEEK resin distribution in the composite laminates were confirmed using scanning electron microscope (SEM) and nondestructive testing (NDT). Although DMA results showed a loss in modulus above glass transition temperature (T g ), a fair retention in properties was noticed up to 300 C. The ability of the composite laminates to undergo positive thermal expansion as confirmed through TMA suggests the potential application of glass-PEEK composites in aerospace sector.

The extruded poly ether ether ketone (PEEK) and glass fiber yarns were used to obtain the co-weaved hybrid fiber fabrics. Compression molding technique was employed to obtain the glass-PEEK composites from the hybrid fiber fabric. Composites having different thickness values of 3.3, 3.6, and 4.5 mm have been fabricated by varying the number of layers (15, 17, and 20 layers) of co-weaved fabrics. The mechanical properties such as flexural strength and inter laminar shear strength as a function of number of layers of fabric have been evaluated. Low-velocity (2.1 m/s) repeated drop weight impact tests were carried out on the fabricated composites at 5 and 10 J incident energy. The number of drops to failure was observed to be more in 5 J compared to 10 J incident energy. Effects of frequency on the viscoelastic behavior were investigated using dynamic mechanical analyzer by sweeping at different frequency and temperature ranges. Master curves were generated by time-temperature superposition of the experimental data at a reference temperature of 156 C. The dielectric properties such as relative permittivity and loss tangent of glass-PEEK composites was found to be less dependent on the frequency (8-13 GHz) and temperature (50-300 C), which is an indication for its use in typical aerospace applications such as radomes.

The extruded poly ether ether ketone (PEEK) and glass fibre were used to obtain the co-woven hybrid fibre fabrics and converted into composites using compression moulding technique. The effect of shear stress and shear rate on the shear viscosity of PEEK was investigated to optimise the process conditions for converting hybrid fabrics into composites. The mechanical properties such as flexural strength and inter laminar shear strength (ILSS) as a function of number of layers of fabric have been evaluated. Low velocity (2.1 m/s) repeated drop weight impact tests were carried out on the fabricated composites at 5 and 10 J incident energy. Dielectric properties as a function of temperature and frequency have been carried out. Flammability behaviour of composites has been carried out using cone calorimeter. The data generated shows that glass-PEEK based composites are excellent potential materials for advanced structural composites.

The effect of heat flux levels on burning behavior and heat transmission properties of hybrid fabrics and composites has been investigated using cone calorimeter and heat transmission techniques. The hybrid fabric structures woven out of E-glass (warp) and polyether ether ketone (PEEK) (weft) and E-glass (warp) and polyester (weft) have been studied at high heat flux levels keeping in view the flame retardant requirements of structural composites. The performance of the glass-PEEK fabric even at high heat flux levels of 75 kW/m 2 was comparable with the performance of glass-polyester fabric evaluated at 50 kW/m 2 . The results further demonstrate that glass-PEEK hybrid fabrics exhibit low peak heat release rate, low heat release rate, low heat of combustion, suggesting an excellent combination of materials and fall under the low-risk category and are comparable with the performance of carbon fiber-epoxy-based systems.