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As automakers struggle to meet often conflicting safety, weight, styling, and performance requirements, engineering thermoplastics (ETPs) are making increasing inroads into applications that once were the exclusive domain of metals, glass, and thermosets. A good example of this is in the door systems area, where the performance, design flexibility, aesthetics, parts integration, and lower specific gravity offered by ETPs are allowing highly integrated and efficient modules to be created that, in turn, increase assembly efficiency and reduce mass, part count, warranty issues, and systems costs. This paper will use several case studies on innovative door hardware modules and door panels to illustrate the advantages offered by this versatile class of engineering materials.

Engineering thermoplastics are widely used in a variety of automotive components systems because of their excellent balance of mechanical performance, design flexibility, aesthetics, parts integration, and low specific gravity. This combination of properties allows for the creation of highly integrated modules, which can increase assembly efficiency and reduce mass, part count, warranty and ergonomic issues, and systems costs. As a result, the use of engineering thermoplastic materials can enhance market competitiveness at a time of increased global competition. To evaluate the economic advantages of polymers in a specific vehicle system, a design for assembly (DFA) case study was conducted with the goal of determining the variable system cost case for a generic thermoplastic door module system vs. conventional-build door systems based on assembly savings gains. This paper will describe the study and show the results achieved.

The thermal performance of an automotive forward-lighting assembly is predicted with a computational fluid-dynamics (CFD) program. A three-dimensional, steady-state heat-transfer model seeks to account for convection and radiation within the enclosure, conduction through the thermoplastic walls and lens, and external convection and radiation losses. The predicted temperatures agree well with experimental thermocouple and infrared data on the housing. Driven by the thermal expansion of the air near the bulb surface, counter-rotating recirculation zones are predicted within the enclosure. The highest temperatures in the plastic components are predicted on the inner surface of the shelf above the bulb where airflow rising from the hot bulb surface impinges.

The consumption of blow molded bumpers for passenger vehicles is increasing, particularly for small to mid-size vehicles. The performance required for bumpers in this class of vehicles varies by geographic region, as “global” vehicles are increasingly specified outside of the United States. For this reason, it is important to understand the impact performance provided by materials that could be blow molded into bumpers for this class of vehicles. This paper will compare the relative performance of polycarbonate/polybutylene terephthalate (PC/PBT) alloys vs. polyolefins for impact protection, weight, and processing performance.

Automotive styling trends point to reduced bumper overhang, greater sweeps, and reduced overall package space for the bumper system. At the same time engineers are charged with improving bumper performance to reduce collision repair costs and enhance occupant safety further. Two key performance parameters for the bumper to meet these conflicting objectives are fast but controlled loading and efficient energy absorption (EA). The majority of today's North American passenger-car bumper systems consist of a reinforcing bar either of steel, aluminum, or composite construction, and an energy absorption media. The most widely used energy-absorber construction is made from an expanded-polypropylene foam (EPP). Honeycomb energy absorbers, which are made from an ethylene vinyl acetate (EVA) copolymer, are also still used on some of today's cars. This paper will address an alternative to the bumper energy absorber systems described above.

The I-Section bumper design has evolved over the past 10 years into a lightweight, low cost, high performance alternative to traditional bumper beams. Initial I-Section Bumpers were developed with 40% Chopped fiberglass GMT. Through the development of lower cost Mineral-Filled/Chopped fiberglass GMT, improved static load and dynamic impact performance results have been achieved in I-Section Bumper Designs.

Current accelerated weathering protocols such as SAE J1960 or ASTM G26 do not provide reliable, predictive results for engineering thermoplastics. Correlation factors among resin types and even different colors of a single resin have variations that are 60-100% of the mean at the 95% confidence level, making these tests useless for lifetime prediction or even reliable ranking of materials. We have developed improved conditions using CIRA/sodalime-filtered xenon arc, a more rain-like water spray, and occasional sponge-wiping of the samples. The data for gloss loss and color shift agree very well with Florida data giving a correlation factor of 3100±680 kJ/m2 (at 340 nm) per Florida year at the 95% confidence level. The acceleration factor is 7.6x.