DuPont Develops Plastic Side-Impact Door Beam

Aluminum, carbon fiber and high-strength steel alloys have dominated the automotive materials discussion in recent years, but DuPont is reintroducing the topic of plastics with a number of significant breakthroughs.

A plastic side-impact door beam is the supplier’s latest showcase technology. Developed with PSA Peugeot Citroen, it is up to 60% lighter than a comparable part made from ultra-high-strength steel, depending on size and design. With a beam in every door, that adds up to a significant weight savings. The plastic beam is expected to enter production in a high-volume PSA model in 2017.

The component is made from “Vizilon,” a thermoplastic composite. The safety beam, which protects occupants from vehicles and objects intruding into the passenger compartment during a crash, passed PSA’s crash tests and proved itself in temperatures ranging from -40° F to 194°F (-40°C to 90°C). Vizilon is a Polyamide 6.6 thermoplastic reinforced with continuous fiberglass strands.

The first design for the impact beam was produced in two steps, the first consisting of thermo-stamping the thermoplastic continuously glass reinforced composite sheet, followed by a process in which a network of strengthening ribs are injection-molded over the basic structure. This design is 40% lighter than a comparable steel beam, says Stéphane Delalande, PSA’s polymer materials chief.

However, finite element analysis and other computer simulation techniques allowed engineers to optimize the structure’s design and eliminate the second manufacturing step. That provided a cost reduction and made the part 60% lighter than a UHSS steel beam, Delalande says.

The impact beam is designed to be treated like a conventional steel part in the assembly plant, says Craig Norrey, technical programs manager, DuPont Performance Polymers. The part can be attached to the vehicle body-in-white prior to the painting process. That means it can withstand the high heat of anti-corrosion E-coat dips and paint baking ovens during vehicle assembly, processes that typically challenge plastics.

Despite the cost savings, the plastic beam still is more expensive than a conventional steel part. Nevertheless, auto makers are under so much pressure to improve fuel economy and reduce vehicle emissions, they are willing to pay a premium for materials and components that reduce weight, Norrey says.

DuPont has been a major supplier to the auto industry since the 1920s, but the company has been shifting its focus away from automotive to higher-margin business sectors related to agriculture and biotechnology.

The supplier sold off a chunk of its auto-related business earlier this year for $4.9 billion, its low-margin automotive paint business, but it remains bullish about advanced polymers.

Hok Hoh Wong, regional director-North America for DuPont Performance Polymers, still sees promise in the historically low-margin auto-supply business.

“The more innovative something is, the higher the returns will be,” he says.

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