Magnetic-assisted alignment of reinforcing functionalized-fibers in a composite for lightweight structures

Localized reinforcement of composites employed to manufacture parts for the transport industries is making possible the lightweighting of components that have a much sought-after effect in the reduction of CO2 and NOx emissions. However, its realization, through the removing of mass where it is not required and reinforcement added to areas more prone to stress from working loads, relies on the development of novel manufacturing processes that can create structures whose performance is on a par with their solid counterparts, but at a fraction of the weight and at an affordable production cost. In this work we exploit the use of a very weak and safe magnetic field to control the location and orientation of functionalized discontinuous carbon fibers within a polymeric structural (polyurethane) foam to create performance-optimized composites. Two wet-chemistry methods (i.e. in-situ precipitation-deposition and amine-co-adjuvated electrodeposition of magnetite) to transform commercial carbon fiber into a magnetically active form were explored. The resulting fibers were analyzed and characterized through a set of physico-chemical tests. The functionalized fibers were then embedded at 3 different %vol contents in the polymeric matrix at given locations and with a desired alignment. Their mechanical performance (incl. compression, tension) was assessed and benchmarked against both a similar %volumetric content but non-functionalized-reinforcement (i.e. randomly distributed) composites and to non-reinforced matrices. In the two sets of reinforced composites (random and aligned) there is a positive correlation between stiffness, yield strength and strain with increasing %vol content. Both sets outperformed the non-reinforced matrix, demonstrating good fiber adhesion within the matrix and successful load transfer from matrix to fiber. The magnetically aligned composites generally outperformed the non-functionalized ones in terms of stiffness and strength at yield.