1. How is my car held together?
particles - where science matters
  • New innovations in manufacturing change how your car is held together

    By Sue Casement, 3M Storyteller

    Sparks fly as a car is worked on

    • A car that had 30 linear feet of adhesive in 2001 has 400 feet today.

      Automotive manufacturers have a lot of priorities to balance. Fuel economy, safety, cost, increased customer expectations and keeping manufacturing efficient are all important, and manufacturers are looking at a stream of new innovations come into play. Many countries are implementing laws that make low emissions and high fuel economy an imperative. At the same time, safety is a top priority, and drivers expect a range of amenities like vented seats, built-in Wi-Fi and infotainment systems. Self-driving features require connectivity and sensors, and electric vehicles carry batteries that weigh upward of 500 pounds.

       

    • “Companies that are successful increase fuel economy and reduce weight without reducing content.” – Jay Baron, Center for Automotive Research

      Many of these new features add weight to the vehicle, which detracts from fuel efficiency. To balance out the added weight, automakers need to find new ways to be efficient, reduce emissions and lighten weight in other areas of the car.

      Increased production of electric vehicles can reduce the number of gas-guzzling vehicles on the road to help bring CO2 emissions down, but cars still need to be efficient to make it from one charging station to another. Regardless of the power source, lightweight materials are a key to reducing energy consumption in any mode of transportation. To stay on top of changing demands, car manufacturers are looking at materials, parts and processes in new ways.

      The auto industry has worked for decades on perfecting processes for working with different materials. From fabrication to joining parts and painting, manufacturers have built solid expertise in the art and efficiency of creating the perfect machine. The shift to make lighter parts – parts that can also be recycled at the end of the car life – impacts many steps in the manufacturing process.

      Jay Baron, of the Center for Automotive Research says that with pressures for both lightweighting and recycling, manufacturing processes and technologies have become much more complex. Automakers may need to go to more suppliers to provide niche materials for every part. Adding more suppliers and steps is the opposite direction of where they want to go – instead of simplifying the process, it complicates it.

      “The manufacturers will tell you that this is out of their comfort zone,” Jay says. What does he think is the logical next step? Possibly finding tier one suppliers to build some of the components.

       

    • Infographic showing the increase in cost for lightweighting vehicles

      The cost of lightweighting

      Engineers design components with multiple, and often competing, objectives. Near the top of the list? Avoiding risk. Since vehicles are mass-produced, the consequences that can come from failing parts can be catastrophic. Automotive design engineers work diligently to ensure that parts are tested and retested to meet this number one goal.

      Making lightweight components is also on the list of objectives – after meeting the needs for safety and performance. Manufacturers can meet all those needs for lightweighting, safety and performance, but it comes with an increase in cost.

      Materials in the mix

      To meet the mix of needs, automotive manufacturers are using more materials with higher strength-to-weight ratios and stiffness-to-weight ratios.

      Steel is still the most common material used in cars – it’s strong, cheap and easy to work with, and automakers have built up expertise and processes to work with it. It comes in multiple grades of thickness. Advanced high-strength steel and ultra high-strength steel have thinner-gauge sheeting, so it’s lighter but not as easy to work with. The strongest steel is typically used where the most reinforcement is needed, like protecting the cockpit for crash-resistance.

    • Image showing the inside of a car door held together by adhesives

      Aluminum is another go-to material – and growing more popular each year. It is light, strong and rust-resistant and is often used in hoods, trunk lids and doors. It can reduce the weight of a component by up to 60 percent, according to energy.gov. It adds significantly to the cost of the vehicle, because it’s a more expensive material and more challenging to work with. It has limits on formability and can be difficult to join to other materials. More expensive cars tend to use more aluminum and lower cost cars tend to use more steel.

      Carbon fiber is half the weight of steel and four times stronger, according to energy.gov, and it can potentially reduce the weight of a car by up to 70 percent. The barriers? High cost, low availability and difficulty in joining. It is also more complex to recycle than steel and aluminum.

      Carbon fiber is more commonly used in aviation, and is becoming increasingly popular in premium cars for passenger enclosures, hoods and frames.

      Magnesium has the lowest density of metals used in cars and is currently used primarily in the powertrain. It was used in the 1970s and, because it’s easier to work with than other lightweight materials, it could see a resurgence in use. However, it is expensive, lacks crashworthiness and is not readily available in large quantities.

       

    • Infograhic showing that the use of mild steel in the car shell may shrink from 55 to 5 percent
      According to Energy.gov, the use of mild steel in the car shell may shrink from 55 to 5 percent.


      Titanium is used in some parts like exhaust systems and can withstand heat well. It has high strength, but is costly.

      Plastics are used throughout the interior of the car and in areas like the bumpers. It’s tough, lightweight and cheap. High-strength glass bubbles can be added to plastic car components and make it even lighter without sacrificing performance.

      Other materials will likely come into the mix. Researchers are working hard to test other alloys and composites. Titanium alloys, nickel-based alloys and metal matrix composites all look promising and have qualities that other materials can’t match.

      When automakers find a way to make new materials work in mass production, they may have additional options to add to the already complex manufacturing process.

      The types of materials used can make a huge difference in the weight of each component and in the overall weight of the car.

      As mixed materials are used more in vehicles, one of the biggest issues engineers deal with is bonding them together. How do you marry a steel component to an aluminum or carbon fiber composite part? You probably use adhesives.

      According to Shashank Modi, a research engineer at the Center for Automotive Research, certain car models used 30 linear feet of adhesive in 2001. Today, those same models contain more than 400 linear feet of adhesive. Welds, screws or rivets are still used, but mixed materials are increasingly held together with adhesives.

    “There is no generic approach to lightweighting. It’s all about the material mix. If you remove weight, auto makers are happy.” –Daniel Suttor, 3M Global Key Account Manager

    • Infographic showing the expected shifts in material distribution in the U.S. fleet by 2040
      Source: Center for Automotive Research

      Adhesives solve a lot of issues when welding won’t work to join dissimilar materials. Bolts or rivets add weight or open materials up to corrosion where adhesives provide a continuous bond. The right adhesive can create a stiff seam that strengthens the entire structure. The adhesive can also seal gaps, reducing noise, vibration and harshness inside the vehicle.

      Just as different metals, alloys and composites work best in different parts of the vehicle, there are a wide variety of adhesives and tapes. Automakers may want to connect an aluminum panel to a steel panel, or they may want to attach a mirror to the inside of the windshield.

      There are many types of double-sided tapes, epoxy film adhesives and heat curable tapes for different applications.

      As consumer expectations change and as legislation evolves, automakers and their suppliers will continue to find new processes and technologies to meet those needs. Whether it’s a solar-powered car, a driverless shuttle or a gasoline-powered truck, efficiency will most likely be near the top of the list of needs.

    Explore lightweighting

    As consumer expectations change and as legislation evolves, automakers and their suppliers will continue to find new processes and technologies to meet those needs. Whether it’s a solar-powered car, a driverless shuttle or a gasoline-powered truck, efficiency will most likely be near the top of the list of needs.