Automotive Under-the=Hood Applications in Vinyl Ester Resin SMC/BMC 900633

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. Although the automotive industry as yet has set no specific standards to evaluate this material property, this paper examines the flammability resistance of vinyl ester composites using the UL 94 burn test. Again, SMC compounds varying in resin and in filler type and loading were examined. Specifically, alumina trihydrate, a widely used filler for flame control, was compared to calcium sulfate dihydrate, a less expensive filler often cited for its flame and smoke resistance.

Composites must do more than just match the performance of traditional materials in order to become the material of choice for selected engine compartment components - automotive engineers mandate they must out-perform conventional materials to warrant their developmental time, effort, and expense. Composites not only can withstand the same excessive heat and corrosive environments metals see under-the-hood, they surpass metals in areas such as pricing through reduced manufacturing costs and weight reduction, design flexibility, and acoustic emissions. This paper will also examine these effects on the total engine performance of a specific passenger car engine.