Multi-material suspension A-arm and swing arm: advanced CAE modelling and comparison

Mass reduction plays a fundamental role in modern suspension components design. In addition to keeping the unsprung mass fraction as low as possible to improve comfort, the trend towards lightweight parts is the result of the upcoming restrictive regulations in terms of CO2 emissions. Although for different reasons, both combustion and electric vehicles benefit from a reduction in mass. A lighter ICE (Internal Combustion Engine) vehicle means lower fuel consumption that results in lower CO2 emissions. Likewise, for electric vehicles mass reduction is a key factor in increasing vehicle range. Therefore, automotive industry is challenging OEMs towards innovative technologies. In this context the idea that a multi-material approach can offer further lightweight potential is becoming increasingly convincing. This thesis is focused on the design and comparison of two multi-material solutions - which will be often referred to as hybrid - for two different suspension control arm geometries. The objective is to further investigate multi-material design potential in developing lightweight structural automotive components. The design of a multi-material control arm is always linked to a metal counterpart to which it is compared the so-called baseline geometry. The baseline components used as reference in this work are: - A hypercar aluminum casted wishbone which will be often referred to as A-arm - A C-segment stamped steel control arm which will be often referred to as swing arm. These components have been subjected, through FEM analysis, to a series of operational, special and misuse load cases calculated according to the principles of vehicle dynamics and reference vehicle data. Their characterization also in terms of mass and stiffness has been necessary to define the targets for the hybrid solutions. Then, starting from the aluminum casted control arm a multi-material arm made of an aluminum core and two CFRP (Carbon Fiber Reinforced Plastic) covers has been handsketched, CAD designed, and FEM tested. Both the original position of the hard points and the original size of the bushing sleeves have been integrated into the new hybrid design. The same procedure has been followed to obtain the hybrid swing arm maintaining the baseline hard points and bushing sleeves. The approach used is referred to as tailored design because employs a combination of metal and continuous fiber reinforced plastics. Before running the FEM simulations for the hybrid solutions, two balanced stacking sequence of the continuous carbon fiber layers have been developed to compare the behavior of two different unidirectional fibers: a high strength and a high modulus one. From the evaluation of the results it was agreed to proceed with the optimization of both metal and composite of the hybrid control arms in which the high strength unidirectional carbon fiber was used. Finally, the optimized hybrid A-arm and swing arm designs achieved and even exceeded the 20% of mass reduction target ensuring at least the same performance as baselines in terms of longitudinal and lateral stiffness.