Properties of sustainable composites based on bio-based polyamides and recycled carbon fibers under static and cyclic loads

Abstract

The demand for high-performance materials increases in the last decade and sustainability of materials becomes more important as well. Different bio-based polyamides of type x.10 were compounded with 30wt% recycled carbon fibers to achieve a material with high mechanical properties with low CO2 emissions. The micro structure was evaluated by using high-resolution tomography (voxel size under 1μm) and scanning electron microscopy (SEM). Mechanical tests were done to characterize the quasi-static and fatigue performance of the composites. The carbon fiber composites show a significant increase of Youngs' Modulus and tensile strengths compared to the neat polyamides. The fatigue strength measured by an increasing stress fatigue test is approx. 67% of the tensile strength of each studied composite. Besides the short carbon fibers (mean value about 80μm) larger impurities from the recycled carbon fibers were observed. Due to that and the fiber recycling process, the tensile strengths of these sustainable composites are lower compared to composites with virgin carbon fibers and approximately on the level of glass fiber reinforced polyamides.