Lightweight composite materials have been a key part of developing more fuel-efficient vehicles, as data from the Department of Energy’s Vehicle Technologies Office indicates that a 10% reduction in vehicle weight can lead to a 6% to 8% improvement in fuel economy. However, as vehicle component manufacturers have found new ways to shave off weight, they’ve also learned to maximize composites’ other notable characteristics, including their tremendous strength and moldability.
But the tempting design freedom that CFRP and GFRP materials offer has been challenged by production scalability. That too is beginning to change. Developers are focusing on simplifying the number of components to assemble and reducing the need for secondary assembly or finishing to speed the entire manufacturing process at a more competitive cost.
That work seems to be paying off. Research firm Global Market Insights projects that the automotive composites market will grow at a compound annual growth rate of more than 6.7% from 2020 to 2026. Much of that growth will be due to work building off innovations now coming to market, such as the four composite applications profiled here.
Simplified Trunk Floor Production
The Hyundai Creta, India’s top-selling SUV, makes ample use of lightweight carbon fiber, from its front fender to the passenger seat cowl. However, it’s the SUV’s trunk floor that pushes the envelope in the use of composite materials.
When Brazil-based Tier 1 automotive supplier DPA Moldados began looking for a thermoplastic sandwich core solution to replace its previous thermoset option, it turned to EconCore, a specialist in thermoplastic honeycomb core technology, to help. Together, the material and component suppliers developed a compression molding process that replaces the conventional use of a multi-step thermoset polyurethane, glass fiber, paper honeycomb sandwich lay-up with a low-cost and environmentally-friendly thermoplastic honeycomb alternative.
In the past, such modular trunk floors were made out of two or three molded parts that were then connected into foldable sections with a hinge – yet another separate piece. With the new process, the supplier extrudes a thermoplastic material that is directly converted into the honeycomb core. The core is compression molded with thermoplastic glass fiber mat composite skins, all from a single sheet of sandwich preform, and the decorative thermoplastic carpets are added on the surface of the part at once. The hinge connecting the foldable sections is created in the same process by accommodating a mold gap design. The soft, preheated thermoplastic honeycomb core is calibrated into a “V” profile, creating a living hinge.
By reducing the need for secondary finishing, the supplier is able to speed production of this single part from a 90- to 120-second cycle to a 45- to 50-second cycle, a time savings that helps lower the overall cost of using a high-performance material.
Today, DPA sources the honeycomb core independently of the skins, but Tomasz Czarnecki, COO of EconCore, predicts that this process could be further streamlined by molding all panel components at a single location. “In the future, subject to high enough production volume, the compression molding step can be integrated with the continuous honeycomb sandwich panel production,” he says.
Czarnecki estimates that one high-capacity honeycomb line can create products for 10 or more different car models, a flexibility that adds to the solution’s overall value.
There’s one more notable benefit for the new Creta – a 20% reduction in weight by using the honeycomb trunk floor compared to the material used in earlier models. By using less material, the component reduces its weight and its impact on the environment. This part pushes environmental friendliness further as well.
“Our product, and the thermoplastic finishing carpets that automotive parts require for decorations, are recyclable,” Czarnecki explains. “Upon molding and integration of the carpets into the sandwich structure, they are not contaminated by other materials such as polyurethanes or thermoset glues, so at the end of the product’s life they can be fully recycled.” He adds that in certain cases, when the carpet and panel are made of the same thermoplastic material, the company can further simplify the recycling process and avoid any mechanical separation of components.
The production team is considering using ThermHex recycled PET thermoplastic honeycomb core in future iterations to further improve upon the product’s environmental friendliness.
CarbonPro Sees Mass Production
Rapid production speed is also a key benefit for the carbon fiber pickup bed first launched on General Motors’ 2019 Sierra Denali 1500 and Sierra AT4 1500, although that’s hardly been the focus of pickup enthusiasts. Advertising has focused on the fact that the lightweight CarbonPro box offers 10 times greater impact resistance than its steel counterparts, allowing it to stand up to hurricane Category 1 projectile testing. Early testing of the carbon fiber composite included dropping heavy loads, from cinder blocks to 450-pound water-filled steel drums, into the bed. The steel drums took a beating, but left little impact on the tough composite material.
Automotive component manufacturers, however, are more likely to be interested in the technology that supports high-volume production of this structural carbon fiber reinforced thermoplastic (CFRTP) component. The Japan-based composites technology supplier Teijin developed the production equipment to mold each CFRTP part in approximately one minute. An entire CarbonPro box – about 23 CFRTP pieces altogether – can be built in about 10 minutes. The boxes are assembled at Teijin subsidiary Continental Structural Plastics’ (CSP) Indiana facility.
Although GMC manufactured fewer than 500 of its roughly 200,000 2019 Sierras with the CarbonPro box, demand has pushed that number to closer to 20,000 in 2020, Automotive News reports.