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The opportunity for composites in engine closure systems such as valve covers, oil pans, and timing belt covers is expanding rapidly. The primary driving forces are lighter weight finished components, integrated designs, improved isolation of engine noise, improved materials systems, and matured manufacturing processes for composite materials. Thermoset-based composite materials, particularly those based on high-temperature resistant epoxy vinyl ester matrices, offer improved performance with respect to thermoplastic and thermoset polyester-based composites and can be manufactured using different processing methods. This paper presents the current state-of-the-art design, engineering and optimization techniques for engine closure systems. The performance requirements of different systems such as valve covers and oil pans are explained in detail. Techniques for long-term structural stiffness evaluation, vibration performance assessment and noise transmission estimation are described.

The market for composite engine oil sealing components, such as valve covers and oil pans, continues to expand, replacing traditional metal stamping and die casting materials. As the market for these composite components grows, so must the understanding of the material performance characteristics and the relationship of these characteristics to the design of the part. Unlike metals, composites are viscoelastic in nature, exhibiting time-temperature dependant properties. Therefore, the traditional design approach utilizing static property data to predict long-term performance under load and over a wide temperature range will not sufficiently characterize the nonlinear property response of polymeric-based composites. A robust composite sealing design requires complete materials characterization, including long-term creep performance as a function of temperature, loading, and cycling.

Continuously improving the physical and thermal properties of under-the-hood composite materials is a challenging requirement facing today's resin manufacturer. Providing meaningful data, so that the best material is selected for each application, is also a challenging task. Long-term performance data is typically unavailable due to time and economic constraints. Traditional short-term data, such as static physical properties, cannot predict the performance of these materials with time, under load, and/or in harsh chemical and thermal environments. This paper illustrates how short-term dynamic mechanical analysis (DMA) testing can simulate long term behavior of vinyl ester resin SMC materials. In particular, it will be shown how creep characteristics, typically requiring lengthy, expensive testing, can be achieved with the DMA by acquiring data over relatively short (thirty minute) time intervals and applying time-temperature superpositioning to make long-term performance predictions.

Under-the-hood components with composites are currently making headway in the automotive arena. The corrosive environment these components are often exposed to, such as elevated temperature motor oil, is an important design consideration; however, as yet there is little commercial experience on the performance of composites under such conditions. This study investigates the effects of hot (160°C) “used” motor oil on vinyl ester glass fiber reinforced sheet molding compound (SMC) materials, simulating an extremely accelerated aging process indicative of under-the-hood conditions. Several SMC formulations were examined which varied in resin identity, filler type, and filler loading. All materials were evaluated for changes in appearance, weight and thickness, flexural properties, and thermal performance at one, three, and six month intervals. In addition to harsh environmental conditions, engine components must exhibit some degree of flame retardance.