As the automotive industry embraces composite materials, vehicles are becoming lighter, more efficient and more sustainable. For load-bearing elements, aluminum is still the material of choice, but there are high-performance alternatives on the market. Composites offer several advantages for OEMs looking to apply the benefits of lightweighting to engine and powertrain mountings.
The highly glass filled grades of Ultramid® from BASF are an economical way to achieve the highest possible modulus, a critical aspect of NVH performance. Damping— the ability to dissipate energy, such as physical vibration and airborne noise — is equally important. Ultramid’s viscoelastic matrix provides damping, while its glass fiber offers stiffness, essentially functioning as a shock absorber. As a result, Ultramid provides 10–30 times the amount of damping effects (measuring loss factor) as die-cast aluminum in working range of automotive temperatures (80–100 degrees Celsius).
Powertrain mounts and brackets built with composite materials at BASF can bear loads in excess of 30 kilo-Newtons — that’s over 6,500 pounds. This is accomplished through BASF’s proprietary analytical software ULTRASIM®, which works in conjunction with finite element solvers to establish the material’s behavior during the analysis based on conditions the material is exposed to.
As an anisotropic material, the composite’s performance varies based on direction. To improve its physical properties, composites are heavily loaded with fiber. ULTRASIM, which maps the fiber alignment, assigns material properties based on temperature, moisture and strain rate. Because ULTRASIM’s methodology offers such a high correlation to the empirical test result, a high level of weight optimization is achieved through improved accuracy.
A composite solution typically weighs 40 percent less than aluminum occupying the same volume — even with up to 60 percent glass fiber content. This allows for a comparable or better strength-to-weight ratio, depending on environmental conditions. Even at the highest fiber loading, Ultramid has a 40 percent lower density than aluminum, enabling mass to be used sparingly and only applied in areas where it’s actually needed.
In 2017, BASF received the Automotive Innovation Award in the Chassis Category by the Society of Plastics Engineers® International (SPE) in recognition of its development of a lightweight engine clevis bracket in collaboration with Hutchinson. Manufactured for General Motors, the brackets were constructed from Ultramid after metal alternatives failed to meet weight and NVH targets. The brackets were up to 45 percent lighter than die-cast aluminum.
Composite solutions are typically created through an injection molding process, which affords greater design freedom and flexibility. The complex geometries can be processed for thinner walls and ribs, the latter of which are placed in multiple directions to support the loading conditions. Die-cast aluminum, alternatively, requires thicker ribs to ensure flow and allow more tool steel to support the injection pressures.
Although a composite solution for engine and powertrain mountings typically costs more than aluminium in terms of raw materials, it also reduces overall material usage. The injection molding process, for one, requires less processing steps than die-cut alternatives. This enables OEMs to eliminate processes like trimming, machining, cleaning, sandblasting and priming, ultimately resulting in lower overall costs.
With increased structural performance, inherent damping, competitive overall parts costs and greater design freedom, composite solutions offer a clear advantage over aluminum alternatives for engine and powertrain mounts. OEMs who take advantage of these benefits can manufacture vehicles that are lighter and more fuel efficient. As the automotive industry continues to embrace innovation and sustainability, lightweighting will help manufacturers meet energy savings goals at a reduced cost.