Additive manufacturing and characterization of high temperature thermoplastic blends for potential aerospace applications

Here, we study the thermomechanical and microstructural properties of a carbon fiber (CF)-reinforced blend of poly ether ketone (PEEK) and polyether imide (PEI) used in the Fused Filament Fabrication (FFF) additive manufacturing (AM) process. The reinforced PEEK/PEI blend material was prepared by melt mixing in an extruder and used as filament feedstock for FFF printing and for the injection molding of test specimens for comparison purposes. The effect of the manufacturing process, CF reinforcement and mechanical testing temperature were investigated through mechanical tensile testing and microstructural analysis. Reinforced specimens printed in longitudinal direction demonstrated the highest modulus, 17.9 GPa, which was slightly more than the value of 16.9 GPa obtained for the injected specimens. The measured modulus was mostly constant up to 120 degrees C, while the ultimate tensile stress (UTS) showed an important drop from 129 MPa at 120 degrees C to 77.3 MPa at room temperature. Micro-tomography was executed, depicting porosity, carbon fiber length and orientation, for deeper understanding of the material microstructure and their effect on the mechanical performance. The microstructural analysis revealed that the porosity of the blend is -4%, the maximum fiber length is -600 mu m, and the CFs are mainly aligned along the printing direction. According to our experimental measurements, our composite blend material shows a very strong potential for the aerospace sector, even for operating temperatures up to 120 degrees C.