INFLUENCE OF CROSSLINKING DENSITY ON THE MECHANICAL PROPERTIES OF DIFFERENT POWDER EPOXIES FOR COMPOSITES APPLICATIONS

Powder epoxy composites are a very promising option for the manufacturing of large composite structures for applications such as tidal stream turbine blades, due to their low exotherm and viscosity, a suitability for out-of-autoclave manufacturing, the ability to perform a separate melting and curing phase and a very high toughness. Reinforcing fibres can be glass, carbon or basalt and high mechanical properties combined with ease of processing can be achieved. This study investigates six different experimental powder epoxies with the following characteristics: fire retardancy, different curing agent to base resin ratios, different chain lengths and a commercial powder epoxy system (PE6045) for comparative propose. These powder epoxies are reactive "solid" resin systems, with almost infinite shelf life. The resins can be stored at room temperature indefinitely and are suitable for out-of-autoclave industrial processes. For each of the cured powder epoxies, mechanical and thermal properties were evaluated using tensile testing, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) respectively. The crosslink density of each powder was calculated and validated with the obtained mechanical and thermal test results. A higher crosslink density improved the stress at break slightly and the strain at break more consequently.