Gary J. Smyth, Ph.D., executive director, Global R&D Laboratories, GM Global Research & Development, will be the keynote speaker at CAMX 2015 (Oct. 26-29, Dallas, TX, US), discussing the carmaker's material and manufacturing strategies as it pursues lightweighting in new-car development. CompositesWorld offers this Q&A with Smyth, as a preview to the live event, Tuesday, Oct. 27, 9:00-10:30 a.m.
CW: What are the major lessons learned at GM from the Corvette?
GJS: From its fiberglass body, introduced in 1953, to today’s aluminum frame, carbon fiber hood and roof panels, carbon-nano composite underbody, and range of composite, aluminum, magnesium, and titanium components, the Chevrolet Corvette has a track record for introducing lightweight materials. Low curb weight plus high horsepower equals exhilarating performance – a combination that has defined the Corvette for six decades. Obviously, one of the major lessons learned is to never focus on just one material. We are constantly looking for the best materials structure, powertrain, and chassis to improve Corvette performance.
Another key learning is that we can do high-volume Class A carbon fiber panels, as demonstrated with the hood and roof. However, there are still significant challenges remaining in process cycle time and surface quality that make the business proposition for Class A carbon fiber very challenging. There is also a need to continue to develop the supply base for both material supply and molding.
CW: There is much talk in the automotive composites industry about a mixed-material strategy for composites application. How does this fit with GM's materials strategy?
GJS: Lightweighting and mixed materials are key pieces of GM’s materials strategy. We want to apply a smart mix of innovative lightweight materials to our vehicles, combined with new joining and manufacturing technologies, to achieve the strength, performance, and efficiency our customers need and want. There is no “one size fits all’ for mass reduction. There are cases where an advanced lightweight material is needed to meet performance requirements efficiently – for example, for high strength, stiffness, or energy absorption. There are other cases where cost is the most important factor. Optimization of the overall design is critical, with trade-offs driven by performance, efficiency, CO2 regulation, cost, and most importantly customer acceptance.
An automobile, by definition, is “mixed material.” We use the right material in the right location depending on its performance and cost targets: copper for wiring, glass for windows, fabric for interiors, etc. In addition, we are seeing a steady increase in electronic systems. A single car today can contain 50-75 different electronic control units, which govern functions like acceleration and braking.
Recently, the term mixed materials has been used specifically in reference to the body structure where materials like high-strength steel, aluminum, magnesium, or composites have been chosen for different vehicles. Composites play a role as a candidate for body and closure applications, but there are technical and financial challenges which must be overcome for them to see significant introduction into the industry. Today, on average, we use about 300 lb of polymer composites on a vehicle – or just under 10% of its mass.
CW: What do you see as the composites industry's greatest strengths and weaknesses in regards to automotive manufacturing?
GJS: Among the strengths are lower mass, the ability to make complex shapes with integrated parts, less corrosion than metals, and styling advantages. The composite body strategy used for the new, seventh-generation Corvette resulted in a 15-25% reduction in mass compared to the previous generation, and its doors have surface contours that cannot be stamped out of metals.
Among the biggest challenges is high material and processing costs in terms of dollars per kilogram saved. Other hurdles include cycle time, dimensional tolerances (e.g., fit and finish), longer durations for joining (there is no analog to resistive spot welding of metals), and damage prediction and repair. In addition, constitutive models for all material and process combinations, including joints made with those materials, are required.
Finally, there is need for industry alignment. This is a key commercial challenge. When we try to source a part, we get a mixed bag of materials and processes from different suppliers, so it’s difficult to compare apples to apples.
CW: Some automakers say they can meet CAFE standards without lightweighting, but that lightweighting provides longer battery range and "cascading" weight benefits. What is your reaction to this?
GJS: Lightweighting is important to provide the performance the customer demands and to meet global CO2 regulations. Automobiles will be lighter in the future, but you have to remember that lightweighting is only part of an overall vehicle performance and compliance plan. This is especially true when making the decision to use premium materials that increase cost. This cost of lightweighting has to be compared to the cost of other CO2 enablers like aerodynamics, powertrain technologies, tires, etc. Each automaker has a different fleet mix, and slightly different strategies to achieve performance and compliance. As a result, you may see some OEMs pursue advanced materials more than others.
At GM, we believe lightweight materials will continue to have a large role. With new safety standards and increasing customer content, automakers have to work very hard to avoid adding mass. In this environment, lightweighting, use of multiple materials, and smart design are all critical.
CW: The composites industry does not have a history of providing high-volume, JIT manufacturing services. If GM increases composites use, how will it cope with this challenge?
GJS: This is a significant issue and compounded by the complexity of the composites value chain. In the metal world, we buy sheet metal and stamp it into a part or, in some cases, buy a pre-made assembly. In the composites world, there can be a resin supplier, a fiber supplier, a molder, and then a component assembler or finisher/painter. This makes it very difficult to manage the whole value chain. One approach would be to bring the technology in-house; another is to closely partner in the plant, much as we do for the paint shop today. What is clear is that to enable true high-volume implementation, the right decisions need to be made early in part and process design to optimize material use and minimize manufacturing issues.
CW: What composite and material combinations do you think have the greatest potential for automotive, and why?
GJS: I don’t think there is a clear answer to this question, in part because there is so much development still required from a material and process perspective in the composite, aluminum, and steel industries. Composites have challenges being the primary structural load path for vehicles and require a higher ductility metal to facilitate energy absorption, so bonding composites to high-strength/high-ductility steel and aluminum is an attractive combination from a performance standpoint.
The next big frontier is structural carbon fiber, but many challenges must be addressed, including lower-cost processes to produce the carbon fiber material as well as lower-cost manufacturing processes, faster cycle times, and predictive modeling. No high-volume application of carbon fiber in the dominant load path has been done to date.
CW: Similarly, how does GM view thermoset vs thermoplastic composites use?
GJS: Both thermosets and thermoplastics have potential in the automobile. Thermoplastics are attractive due to recycling, joining, and molding; however, their mechanical properties as a function of temperature will limit where they can be used in the car. Thermosets offer the best chance to realize the highest mechanical properties with composites from a strength and stiffness perspective, but recycling, ductility, and damage tolerance are concerns. In both materials, we need to develop better finishing and painting systems.
CW: What advice do you have for composites fabricators who seek greater involvement in the automotive supply chain?
GJS: GM would be happy to engage with composites fabricators who can meet automotive requirements. We have a number of partners in this area and are always looking for more opportunities to collaborate on advanced materials that will help take weight out of the vehicle. We also do pre-competitive research on these technologies with the USCAR partners through the Automotive Composites Consortium. I would suggest working with Global Purchasing and Supply Chain to introduce your capability and then become part of the bidding process on future components. You should also reach out to technical leaders so they are aware of your capability. One key to getting GM’s attention is to clearly communicate the value or uniqueness that you bring as a supplier and to quantify that value. This often is done through a well-described case study for components you have produced for other industries or OEMs where you demonstrated improved performance or lower cost or better global reach.