Examination of various out of autoclave vacuum infusion techniques used in aviation applications and development of an innovative alternative infusion model: Dynamic infusion process (DIP)

The use of continuous fiber-reinforced advanced composite materials (FRPCs) instead of traditional engineering materials has been gradually increasing in the aviation, space, and defense industries, since the properties of advanced composite materials, such as specific strength and specific stiffness, are superior to those of traditional engineering materials. The most widely used method in the production of FRPCs for these sectors mentioned above is autoclave composite production. On the other hand, the initial investment and operating costs of autoclaves are quite high compared to other advanced composite material production methods. Since the autoclave process is a batch process, as the autoclave size increases, part loading and unloading cycles cause a bottleneck in the production rate. Manufacturers are determined to overcome the drawbacks of the use of autoclaves due to these handicaps. It is for this reason that studies in literature performed on the development of out-of-autoclave production methods have gained massive attraction in recent years. In the framework of this PhD study, the Dynamic Infusion Process (DIP), an innovative and brand-new derivation of the Vacuum Infusion Process that is deemed to be an alternative to proven methods such as CAPRI and SCRIMP, has been proposed to produce carbon fiber-reinforced composites. Moreover, this study proposes a new method based on the use of TGA in calculating the fiber volume fraction of FRCPs that was developed and compared with the data obtained by using optical-based and wet-chemistry acid digestion analysis-based methods, which are widely used in the literature. The proposed method proves to be highly promising and even better than other techniques in terms of both measurement accuracy and analysis time. The effect of production techniques on the final mechanical properties of the composites was evaluated and discussed based on the 3-point bending test findings. It has been concluded that the recommended DIP technique is a promising approach considering the theoretical and experimental studies performed in this thesis, thus having the potential to produce quality FRPCs that can be employed in aviation applications regardless of the complexity of the part geometry.