Vibration analysis of metal - polymer sandwich structure incorporated in car bonnet

The weight of the car material plays an important role in its performance in terms of fuel efficiency, speed and smoke emission. Especially in hybrid electric vehicles, lightweight materials are important for balancing the weight of its electrical components and also to enhance vehicle speed on account of its comparative low mileage. Nowadays, aluminium, magnesium and Carbon Fibre Reinforced Composites (CFRP) were introduced in making of car body panels since those materials can improve its performance. Yet the material costs, fibre orientation and fabrication techniques in case of CFRP in mass production remains a question. Also, the interior of the car panels was filled with vibration barriers or isolators with considerable thickness which can also add weight to the car. Hence a sandwich structure is presented in this work where the polyurethane foam of higher thickness (core) is bonded between two thin metallic face sheets (skin). The polyurethane foam was chosen as the core because of its low density, porosity and viscoelastic behaviour where it can provide better damping capabilities. Hence, the foam can also help in reducing the volume of internal vibration isolators. Since the car bonnet receives the vibration from sources like aerodynamic exposure to air during travel and mechanical movements within the vehicle (engine operation), it was chosen as the subject for vibration analysis.