The automobile industry has been constantly pushing towards enhancing automobile features to meet increasing mileage and emission requirements. This is being approached through the use of innovative materials and manufacturing processes. The major approaches towards achieving these objectives include reducing aspects such as aerodynamic drag, driveline and transmission losses, tire rolling resistance, and electrical parasitic and vehicle weight. Among these, reducing vehicle weight seems to be the most cost-effective. OEMs are now gearing up towards light-weighting a vehicle in order to increase performance and efficiency while decreasing emissions and maintaining safety and comfort. Global efforts towards CO2 reduction and fuel optimization have given impetus to the current concept of Lightweight Vehicles.
For an average automobile, the weight contributed by individual components such as chassis, powertrain, body and other exterior components is approximately 80% of the total weight. Hence, most of the automakers and OEMs are focusing on such components to achieve overall weight reduction. Studies are being conducted to identify materials that can solve the critical issue of component weight. According to information sources, approximately 10% reduction of vehicle weight contributes to 6-8 % reduction in fuel consumption and 5-6% in emission volume reduction. Though not a huge number, in the growing competitive market, these figures can hugely add to the OEM’s market promotions.
For regular passenger vehicles, replacement of certain traditional materials with lightweight materials could result in overall weight reduction. A few examples are given in Table 1.0.
Table 1.0 Components & Alternate Materials
|Target Components||Alternate Materials|
|Firewalls and rear kick-up panels, floor panels, "A" and "B" pillars, energy-absorbing bumpers, side-impact door intrusion bars, front crash rails, space frame components and roll bars, and blast mitigation panels in military vehicles.||Aluminum|
|Instrument panel, seat frame, steering wheel core parts, cylinder block heads, transmission cases, clutch housings, lower crank cases, intake manifolds, and brake and gas pedals.||Magnesium Alloys (Mg-Al-Si, Mg-Al-RE, Mg-Al-Ca, Mg-AlSr)|
|Connecting rods, piston pins, driveshafts, diesel engine pistons, cylinder liners, brake drums and brake rotors.||Metal Matrix Composites|
While Powertrain electrification has already helped achieve vehicle weight reduction by partially or totally eliminating ICE (Internal Combustion Engines) practical challenges such as meeting long-range, efficiency and safety still exist. For a BEV (Battery operated Electric Vehicle), the regular lithium-ion, lead–acid, nickel–metal hydride batteries that act as primary sources of energy will contribute to significant vehicle weight and can be considered as a target component for further study on weight reduction. Manufacturers are looking at alternate materials for long-range batteries. Aluminum- and zinc-air batteries are cheaper, lighter and safer than conventional batteries, and are expected to hit the market by the end of 2019.
While discussions on improvements in current battery design and material compositions have been in progress, researchers at Sweden’s Chalmers University of Technology have come up with an innovative concept of “structural battery” using carbon fiber, which means a vehicle’s structure itself works as a battery if proper design parameters are achieved. The team is currently experimenting with ways to increase the composite thickness in order to overcome the mechanical challenges while boosting total energy storage capacity. The other innovations that are happening in the battery area are listed below:
|Aluminum-Air Flow Battery||Ulsan National Institute of Science and Technology in S.Korea has developed a new catalyst for aluminum-air flow battery which could help EV drivers with replaceable long range lightweight batteries.|
|Membrane Technology for Fuel Cell Vehicles||Hydrogen fuel cell vehicles are comparatively lighter than other designs; however, transportation of hydrogen has many challenges. These are addressed using an ammonia-to-hydrogen membrane reactor incorporated into a modular unit that can be installed at the point of delivery, including a fuel-cell car refueling station. CSIRO has successfully road-tested its ammonia-to-hydrogen technology for a fuel-cell-powered Toyota vehicle.|
A few examples of successful trials on weight reduction of automobiles are given below:
Graphene - The next generation material that can be employed in composite car components is expected to sweep the market in the next seven to eight years, leading to much lighter and more energy-efficient cars. The University of Sunderland claims to be the first one to physically test a car bumper made using graphene combined with carbon reinforced plastic, resulting in 40% more energy absorption characteristics.
iSTREAM® Carbon: A Gordon Murray concept is to be the world’s first affordable high-volume carbon fiber chassis structure, claiming to reduce the weight by 50%. This system combines a high strength aluminum frame with advanced carbon fiber composite panels, bringing formula one materials and technology within the reach of the common man.
2019 GMC Sierra CarbonPro Carbon Fiber Box - The upscale variant of the GMC 2019 Sierra has the most impressive spec – the cargo box (Truck Bed) made of Carbon Fiber, which claims to save 62 pounds compared to the steel version, adding to the 360 pounds weight savings of the outgoing Sierra.
Safe light regional vehicle (SLRV): An innovative concept for small vehicles developed by researchers from the German Aerospace Center uses a sandwich design which is light, yet very sturdy. Plastic foam panels with an aluminum top layer replace conventional steel panels, ensuring a low gross load weight of around 90 Kg. for the chassis.
Generative design using Autodesk simulator -General Motors is the first automaker using generative design software by Autodesk (based on cloud computing and AI algorithms) to develop the next generation of lightweight vehicles. According to the automaker, the new technology will be a key factor in developing more efficient, alternative-fuel cars with zero emissions.The user can simulate component design by using multiple materials and can then 3D print the component.
Gazella Tech, a France based startup and first builder of suburban vehicles all composite, has developed a patented Aerocell self-supporting composite body technology while maintaining comfort and safety (2007).
German startup Compredict has developed a software that can predict failures and perform real time load monitoring in lightweight models and thus help accelerate the design process of automotive components (2016).
AREVO, based in Silicon Valley has a software to support design, simulate and optimize parts and their material composite to bring out best solution for product design and enable 3D printing prototype and products (2013).
Germany based Carbon TT has developed carbon fiber reinforced plastic (CFRP) for manufacturing components that weigh 50-70% lighter than steel and 30% lighter than aluminum at the same strength.
Black Wave is specialized in Carbon-SMC (sheet moulding compound) process for realizing substitution of complex metallic structures for lightweight components. Black Wave’s carbon rim designed specifically for racing vehicles is 51% lighter than aluminium rims.
|Company||Component manufactured||Material used||Weight Reduction Achieved|
|VOLKSWAGEN||Vehicle’s Body Structure||Multi-material approach||85 Kg|
|CHEVROLET & GENERAL MOTORS||Alloy wire in place of heavy motorized component||Shape memory alloy||1.1 pounds|
|FURUKAWA||Spring to activate CVT continuously||SMA-NT (NiTi)||-|
|FAURECIA||Automotive Seat||Steel + thermoplastic, High quality Foam & HSS||2.5kg|
|GENERAL MOTORS||Individual components||Aluminum (Quick Plastic Foaming)||35 % lighter|
|GORDAN MURRAY||Chassis||High strength Aluminum and Carbon Fiber||Up to 50 % lighter|
|SAMYANG GROUP||Car sunroof frame||Carbon–long fiber thermoplastics (CLFT)||-|
Lotus Engineering’s lightweight vehicles successfully passed the virtual crash test with their design meeting or exceeding federal standards in all front-, side- and rear-impact tests, plus roof-crush testing.
|Results of Crash test|
|Front Impact||Intrusion towards passenger compartment limited to 0.8 ins, footwell intrusions < 0.4 inches|
|Side-Impact Pole Testing||Intrusion at the vehicle’s door is 6.3 ins|
|Front Impact Rear Impact Test||No evidence of intrusion into the fuel tank or battery pack|
Tata Nexon: India’s safest car Tata Nexon achieved 4-star Global NCAP crash rating with its shell said to be manufactured smartly using high-steel strength with lesser weight along with adapting mix of metals and alloys for vehicles structures.
Jaguar's all-electric I-Pace SUV, engineered with a lightweight aluminum body structure and integrated batteries with structural aluminum frame has scored 5 star rating in Euro NCAP Crash Test offering 91 % for adult occupant protection and 81% for child occupant protection
The wiring technology inside an automobile is designed to withstand higher temperatures and deliver large currents to installed equipment. Currently the gross weight of electrical wiring in a conventional car is around 30Kg out of which 30% can be reduced using weight saving electric wires. A few weight reducing cables developed recently are:
Aptive PLC, a global auto parts company, has employed SMC (Selective Metal Coating) technology for a special coating of connection systems enabling use of copper and aluminium in an electrical-electronic on-board network by replacing cable looms with aluminium without corrosion problems. It has also reduced the wiring weight by 2kgs.
Leoni AG is using innovative conductive materials such as aluminium, copper magnesium, copper silver, copper tin, copper-clad steel and brass in their cables, having crimping properties similar to copper, thus contributing to weight reduction in automobiles.
Zuken has launched a new solution to optimize cabling harness which is a complex task and requires skilled labor. The software can import connectivity data from industry standard formats to create an optimum topology of cabling harness with reduced weight and cost in a 3D environment. This tool can be used by anyone without any special training for creating and evaluating different architectures
Kromberg & Schubert, a German wiring manufacturer has developed a lightweight battery cable made of aluminum by using self-bonding liquid silicone rubber (LSR) to seal the aluminum wire connection with tin-coated battery terminal to address the concerns on corrosion.
The emerging alternative lightweight materials for automotive components will continue to be an interesting area for automakers. Material innovations such as graphene and carbon fiber have been promising, but still there is a gap due to cost effective engineering and production of these materials. Also, multi-material design and multi-objective optimization are needed to be rolled out for commercial production. Efficient and reliable techniques must be developed for testing with regard to passenger safety. Current material testing technologies need to be upgraded keeping in mind the upcoming multi-material scenarios, and an in-depth analysis is required to comply with real time functionality. Successful optimization of cost of production, component design and testing is still needed to meet the industry standards.