Exploring the Advantages and Applications of Composite Bearing Materials

A bearing helps reduce friction between machine parts for easier movement. It guides and supports machine parts in transferring motion and force. A bearing typically consists of two rings with raceways, rolling elements (balls or rollers), and a cage to guide the rolling elements.

The inner and outer rings are usually high-carbon chromium steel for strength and durability. Modern bearings are also made from engineered plastic composites, which are lighter and suitable for various industries like aerospace, automotive, and construction, requiring durable yet lightweight equipment.

Using Engineered Composite Materials for Bearings 

Viable composites with fiber reinforcement are replacing bearings made from metals and alloys. This is largely because composite materials offer several unique properties that make them better for various applications. Their composite-bearing materials are often made from thermoset resins implanted with synthetic fibers, such as phenolic resins. Many grades also contain thermoplastics like polyoxymethylene (POM) or polytetrafluoroethylene (PTFE), along with graphite or molybdenum disulfide evenly distributed throughout the material. Due to its low friction coefficient, molybdenum disulfide often serves as a lubricant for bearings in these composites.

Composite bearing materials can be designed to present certain properties that include: 

• Acid, chemical, corrosion, fire, radiation and/or other resistances within material
• Can be lubricated by almost any fluid
• Durable and tough
• High ratio of weight to strength
• Ingredients don’t include toxic substances
• Low absorption rate for water
• Low natural friction coefficient
• Machinable and can be made to tight tolerances
• Retains excellent dimensional stability even when wet
• Weight of about 1/6 that of steel

The use of these composite bearing materials offers manufacturers an alternative that’s attractive to design engineers. Their excellent dimensional stability, lightweight, and machinability make composite bearings extraordinarily useful for certain products, while other properties can be built into these composites by varying the resin or fabric used.

Advantages of Composite Bearing Materials 

Due to their innate flexibility and strength, equipment manufacturers increasingly replace bronze and copper in bearings with composite materials. These qualities also mean they require less maintenance. The heavy-duty nature of these composites makes them ideal for load-bearing applications under difficult operating conditions. They often outperform both bronze and copper in many applications.

Advantages of composite bearing materials include: 

• Corrosion resistance: Unlike bronze, copper, steel, or other metals used traditionally in bearings, composite bearing materials are highly resistant to corrosion from water and chemical solutions, with only nominal pitting or expansion. 
• Customizable: Because plastic resins can be fabricated into various dimensions, design possibilities are more flexible with a composite; bearing materials that use plastic resins can be more easily reinforced or layered, while also making it easier to vary the thickness of a component’s walls and other features.
• Friction Coefficient: With many composites having self-lubricating properties, friction coefficients are significantly lower, which also presents cost savings as continuous lubrication isn’t necessary for many applications. 
• Load-bearing: Composite bearing materials’ intrinsic elasticity allows them to withstand heavier loads better. 
• Moisture absorption: Certain bearing composite materials have moisture absorption rates as low as one-hundredth of one percent. This negligible amount allows their use in pumping systems and other applications where bearings are exposed to water.
• Regulatory compliance: Composite bearing materials meet various food and medical standards, including for FDA (Food and Drug Administration) compliance regarding work environments requiring elevated sanitation, such as the food processing or pharmaceutical sectors; this also includes the EU’s RoHS (Restriction of Hazardous Substances) and REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulatory standards.
• Shock resistance: Unlike copper or other metals, composite bearing materials are better able to resist shock from impacts without deforming.
• Temperature range: Composite bearing materials can operate well continuously or recurrently within temperatures that range from cryogenic to 330°F (165.6°C), which makes them suitable for a wide range of applications involving temperature extremes in which metal-based bearings are more likely to fail.
• Weight: Using composite bearing materials lowers weight considerably compared to metals and alloys, while lighter-weight components enhance energy efficiency.

Offering better performance and reliability due to their ability to self-lubricate, using composite bearing materials leads to improved efficiency and lower expenditures for maintenance and repair. This makes these composites incredibly useful for various types of bearing applications.

Applications for Composite Bearings

Innumerable applications can benefit from bearings made from an engineered plastic composite. Bearing materials’ various characteristics offer manufacturers countless variations on composites that can be applied to various situations, environments, or conditions.

Automotive Applications

Automakers value composites to improve fuel efficiency as a significantly lighter material than any metal or alloy. Composite bearing materials lower weight, but their strength and durability also make them useful throughout the vehicle, including for steering, belts, door hinges, and seat mechanisms. One key characteristic of bearings made from engineered composites is that their split ring design enables press fitting, so there’s no need for excessive force or adhesives during assembly.

Steering 

At the interface between the steering rack and steering column is a bearing situated in the vehicle’s steering yoke, which prevents the rack and column from separating while enabling sufficient steering movement. Using a composite bearing material reduces friction in the steering yoke, giving drivers a better feel of the road and augmenting maneuverability.

Timing Belt

Within a belt tensioner, a spring-like device maintains tension on an engine’s timing belt, oscillating at about sixty cycles every minute at two degrees. Composite bearing materials ensure consistent torque and damping while an engine runs to maintain the right tension.

Door Hinges

Bearings are positioned between the housing and hinge pin to ensure a vehicle’s doors open and close smoothly. Due to their corrosion resistance and durability, composite materials are often used for vehicle hinge systems. Certain composite bearing materials also help ensure superior paint finishing, making them more conductive. This allows the transfer of electricity to the hinges, facilitating electrostatic painting. These materials’ hydrophobic characteristics also repel paint, keeping excessive droplets from ruining the paintwork.

Seat Mechanism

Seat mechanisms feature a bearing positioned between the pin and linkage to adjust for the height and legroom of a driver or passenger. These mechanisms are constructed to impart enough torque to adjust the seat’s positioning smoothly. Bearings made from engineered composites allow for easy adjustment and more comfortable seating.

Bicycle Applications

As with motorized vehicles, designers of bicycles seek to reduce weight to increase performance without sacrificing strength or quality. For this reason, engineered composite bearing materials are often used to enhance overall performance.

Fork

The fork on a bicycle is important for rider comfort, especially on rough terrain. It allows the shaft attached to the bicycle’s frame to slide along the housing connected to the wheels. The bearing positioned between the housing and shaft is often made from engineered composites to reduce weight and increase performance. These help absorb shock, acting to cushion impact while riding.

Shock Absorbers

Certain types of bicycles have suspensions with front shocks that smooth the ride and reduce the impact from bumps. Composite materials are often used to sit the bearing between the outer housing and inner shaft to provide optimal performance while absorbing excessive vibration.

Headsets

Like a vehicle’s steering mechanism, a headset is the bearing assembly that connects the fork to the rest of the frame, allowing the rider to turn the handlebars connected to the fork to allow the rider to steer. Composite bearing materials are used in the headset to reduce the overall weight of the bicycle.

Pedals

Bicycle pedals must have bearings that reduce friction, which is ideal for a low friction coefficient composite. Bearing material made from an engineered composite allows the pedals to rotate more smoothly when they connect the spindle to the pedal’s body and the crank’s end.

Derailleurs

Used in a bicycle’s gear system, a derailleur helps the rider switch gears by changing the tension on the gear cabling to “derail” the chain to move smoothly into another gear. Pivot points on the derailleur often use bearings that require moderate lubrication, which benefit from the lower weight and self-lubricating properties of many engineered composites.

Solar Applications

For solar plants, one of the main reasons that composite bearing materials are used is to ensure they last as long as the plant does. As a concentrated solar power array’s life expectancy is four decades, components need to be durable enough to last until a solar plant’s decommissioning. Engineered plastics offer a solution.

Solar Tracking System

Certain types of solar power plants use concentrated solar radiation to produce electricity. Solar trackers work to concentrate solar reflectors towards the sun, with bearings positioned at the pivot points. Composite bearing material is designed to resist corrosion, heat, ultraviolet radiation, and weather, and it can last longer. This helps better support the structure within the parabolic trough that rotates the mirrors and points them at the heliostats. Additionally, the low friction coefficient of these composites can keep the mechanism from sticking.

Construction Applications 

Construction equipment like loaders or excavators that are used to build highways mainly move with the help of hydraulic transmission systems. Driven by a combustion engine or electric motor, off-highway equipment for construction uses energy that’s converted mechanically into hydraulic energy via hydraulic piston pumps.

Piston Pumps

The piston pump’s shaft features mounted bearings that transfer torque energy that then makes the machinery move. The bearing’s role in this case is to decrease energy use and ensure the construction equipment runs smoothly. Using an engineered composite bearing material with properties like self-lubrication to reduce friction helps optimize energy use while reducing the need for maintenance.

Composite Materials for Bearings 

There are many different types of composite bearing materials. Generally, the standard thermoplastic resins used for bearings are PTFE and POM, each suitable for different applications. Both are used with other materials that are impregnated into the composite. Bearing materials also normally include a steel sheet backing and a sintered layer of metals like bronze, copper, and/or tin. Thermoset phenolics are also used for composite bearing materials as they work well with steel and bronze when lubricated with water, oil, or other fluids.

Examples of composite bearing materials include:

• Bronze featuring PTFE deposition overlay
• Coarsely woven Kevlar® fabric formulated with high-temperature phenolic resin
• Epoxy resin matrix with fiberglass filaments
• Fibers made from PTFE and polyester with liners featuring self-lubricating materials supported by epoxy resin and fiberglass matrix
• Fine weave cotton fabric containing high-temperature phenolic resin with self-lubricating molybdenum disulfide filler
• Formulation of high-temperature phenolic resin with finely woven cotton fabric and graphite filler for self-lubrication
• High-temperature phenolic resin within a fine cotton weave fabric
• Jute fabric with a ‍coarse weave formulated within high-temperature phenolic resin and self-lubricating graphite filler
• Phenolic composites with cotton and polyester fibers
• PTFE composite with metallic mesh and self-lubricating carbon fiber
• Specialty resins that incorporate modern aramid fabrics

These are just a few composite bearing materials, with others continually being developed based on customer needs and specifications. The future for engineered plastics in bearings is almost limitless, only constrained by the testing necessary before using new materials.

Composite Bearing Material by Spaulding

Spaulding Composites Inc. is a manufacturer of both composite bearing materials and customized composite bearings. Spaulding makes bearings suitable for propeller shafts on ocean-going craft and heavy equipment. The company’s composite ball bearings are known for their flexural and compressive strength and machinability. Spaulding’s materials for composite bearings include phenolic resins containing medium-weave cotton canvas, medium-weave canvas, and medium-weave cotton. To learn more about Spaulding’s composite capabilities for bearing material, contact us today.