Design of 5.4L 3V thermoplastic composite engine cover for NVH improvement

As a cost-effective lightweight material, thermoplastic composites have been increasingly used in the automotive industry, but mostly for nonstructural applications. Recently, thermoplastic composites have been used for under-the-hood structural components such as cylinder-head covers, oil-pans, etc. To compete with other lightweight materials such as aluminum and magnesium, the thermoplastic composite has to demonstrate sound structural performance such as long-term durability and NVH performance. In the present study, the NVH performances of production 5.4L 3V engine cylinder-head covers were studied. The covers were made of thermoplastic, aluminum and magnesium. The first phase of this work involved the design and analytical processes during the development. In the final phase of this program, the experimental parts were prototyped and tested in a Ford F150 vehicle for NVH performance. The test was carried out on a vehicle chassis dynamometer in an anechoic chamber under loaded wheels and operating drive conditions. NVH data was processed for sound pressure, vibration, transmissibility, coherence, and for psychoacoustic parameters such as articulation index, loudness and sharpness of the sound as one hears inside the vehicle cabin. All tests were completed for both full and semi isolation of the covers. The study demonstrates that a well-designed thermoplastic cam cover can achieve similar structural requirements (NVH) as the metal cam covers while providing substantial cost saving and weight reduction.