OUT-OF-AUTOCLAVE MOLDING OF THICK CARBON FIBER REINFORCED TUBES BY USING SHRINKABLE TUBES

Carbon fiber reinforced (CFR) tubes for aeronautic and aerospace are manufactured by wrapping and autoclave curing. These technologies present technological and cost barriers for the automotive and urban air mobility (UAM) sectors. Autoclave molding is an expensive process because of the time, energy and materials involved. In this study, an out-of-autoclave (OOA) process is proposed by using shape memory polymers (SMPs). Composite tubes have been prototyped by winding CFR prepregs on a rigid mandrel, and agglomeration has been achieved in oven by the pressure of a thermo-shrinkable tube. Final composites have 11, 19 and 26 CFR plies, with thickness from 3.2 mm to 7.2 mm and internal diameter of 28 mm. Ring samples with a width of 15 mm have been cut from the molded samples to observe its section and to perform transverse compressive tests. Defects have been found as wrinkles and porosity, but a good agglomeration has been already reached, and improvements are possible by using vacuum bagging and internal SMP cores. The proposed technology has the potential to manufacture thick CFR tubes by tailoring the consolidation pressure with higher production rate and lower cost than autoclave, as necessary to sustain the future automotive and UAM market.