Composite materials like carbon fiber and fiberglass are becoming increasingly popular for many applications. Compared to traditional materials like steel or aluminum, composites offer high strength and stiffness while being lightweight. However, the tradeoff is often a higher cost. So is composite really that expensive? There are several factors to consider when evaluating the costs of composite materials.
Upfront Material Costs
The base materials for composites, like carbon fiber cloth or fiberglass mats, are more expensive per pound than steel or aluminum. Carbon fiber in particular is costly to manufacture, driving its raw material price up. According to CompositesWorld, carbon fiber tow can range from $5-50 per pound depending on the grade. Fiberglass is cheaper at around $0.75-3 per pound. In comparison, aluminum costs around $1 per pound and steel $0.25 per pound.
So clearly the raw material costs for composites are higher. But when looking at the finished composite part, material cost is only one contributor to total part cost.
Manufacturing Processes
The manufacturing process used to fabricate composites can require more labor, energy, and capital equipment than traditional materials. While an aluminum or steel part can be formed quickly with dies or presses, composites typically need time-consuming lamination by hand or specially-designed molds for compression. Additional steps like trimming, drilling, and finishing add cost.
However, automated composites manufacturing is improving. Automated fiber placement machines can layup parts much faster than by hand. And large batch production runs using compression molding cut down the per-part costs significantly.
Design Flexibility
A key advantage of composites is the ability to tailor the material properties and part shape as needed for optimal structural efficiency. While metals are limited by their isotropic material behavior, composites can be designed with fibers oriented exactly where strength or stiffness is required.
This design flexibility allows composite parts to use less material, be optimized for loads, and integrate functions compared to metals. The result is lower weight and better performance.
Lifetime Cost Savings
While the upfront material and manufacturing costs of composites are often higher than metals, the lifetime costs can offset this premium. For example, a carbon fiber aircraft part may have 5x the upfront cost of aluminum. But carbon fiber is stronger and lighter than aluminum, allowing significant fuel savings over the decades-long operating life of the aircraft. When factoring in these downstream savings, composites can actually be cheaper in total cost.
Applications of Composites
Aerospace
Composite materials are widely used in aircraft and spacecraft because of their high strength-to-weight ratio. Replacing heavy aluminum and steel components with composites improves fuel efficiency and range. Carbon fiber composites comprise 50% or more of the structural weight in many new airliners like the Boeing 787 and Airbus A350. The Airbus A220 and Boeing 777X use over 50% composites by weight.
Military and supersonic aircraft demand performance over cost-savings, so almost all major components like wings and fuselages are made from advanced carbon fiber epoxy composites. The F-35 Lightning II fighter is estimated to contain 42% composites by weight.
Composites are essential for spacecraft too. Almost the entire airframe of the SpaceX Dragon capsule is carbon fiber. The payload fairings for rockets and satellites are commonly made from lightweight composites.
Automotive
While less pervasive than in aerospace, composites are gaining ground in high-end automotive manufacturing. Race cars now contain large amounts of carbon fiber composites to lower weight and improve speed and handling. The BMW i3 uses a carbon fiber reinforced plastic passenger cell for safety and efficiency. High-performance brands like Lamborghini utilize carbon fiber for styling and strength.
More mainstream cars are adopting composites for exterior body panels and interior parts. The latest Corvettes and Cadillacs use sheet molding compound and carbon fiber hoods and roofs. This allows styling freedom while maintaining safety and lowering vehicle weight for fuel economy. Expect to see further adoption of composites materials as automakers respond to emissions and mileage regulations.
Marine
Fiberglass composites have been used for boat hulls and decks since the 1950s. They continue to dominate marine construction today. Composite hulls are lighter, stronger, and more corrosion resistant than traditional wood or metal. Modern naval ships use advanced composites above and below the waterline for stealth and performance. Carbon fiber masts and booms on sailboats take advantage of high strength and stiffness at low weight aloft.
Sports Equipment
Golf clubs, tennis rackets, hockey sticks, bicycles – many types of sports equipment have transitioned from wood and steel materials to composites. For example, carbon fiber tennis rackets offer 50-80% more stiffness than traditional rackets at lighter weight. Composites allow sports gear designers to tailor stiffness, strength, weight and shape for optimum playing performance and ergonomics.
Infrastructure
Civil engineers are adopting fiber-reinforced polymer composite materials for bridges, wind turbines, liquid storage tanks and other infrastructure. Composites have advantages over steel, concrete and wood in terms of strength, lifetime cost and sustainability. For example, composite bridge decks last longer than concrete and have lower lifecycle costs. Composites perform well in corrosive environments common for wastewater treatment and storage. As composite manufacturing scales up and automated processes provide cost reductions, expect broader infrastructure adoption.
Manufacturing Processes for Composites
There are a variety of methods used to manufacture composite parts. The processes range from completely hands-on manual methods to fully automated high-volume production. Here are summaries of the most common manufacturing techniques:
Hand Layup
The hand layup technique is the simplest composite fabrication method. Plies of fiber fabric are impregnated with epoxy resin by hand, layered onto a mold surface, rolled to consolidate, and left to cure. Hand layup allows maximum control and is suited for large, low volume parts. However, it is labor intensive and prone to inconsistencies.
Spray Layup
The spray layup process uses a chopper gun to spray short fiber and resin onto a mold surface. The fiberglass or carbon fiber mat is chopped into short lengths for the spray. This method is fast and low cost, but produces parts weaker than conventional composite layup. Spray layup is common for large, simple fiberglass parts.
Filament Winding
In filament winding, continuous composite fibers are impregnated with resin and tightly wound around a rotating mandrel. The winding pattern and angles can be precisely controlled to optimize mechanical properties. Filament winding is ideal for producing seamless composite tubes, cylinders and drive shafts.
Pultrusion
Pultrusion continuously pulls fiber and resin through a heated steel forming die to produce constant cross-section composite profiles. The process is fast and cost-effective for making composite rods, tubes, beams and other extruded shapes in high volumes.
Compression Molding
Compression molding squeezes a fiber and resin preform inside a heated steel mold cavity to shape and cure the part. Preforms can be pre-impregnated with resin or resin can be injected into the mold. Compression molding is suitable for complex, high performance and high volume composite parts.
Automated Fiber Placement
Automated fiber placement (AFP) uses a CNC machine to lay composites tape onto a mold along precise programmed paths. AFP dramatically reduces labor and improves quality compared to hand layup. It is ideal for producing large, complex and curved composite structures like aircraft wings and fuselages.
Resin Transfer Molding (RTM)
In resin transfer molding, the fiber preform is placed in a mold cavity and resin is injected under pressure to impregnate the preform. RTM produces high fiber volume fraction and low void content parts. It is a popular process for automotive and high performance composites.
| Process | Description | Typical Applications |
|---|---|---|
| Hand Layup | Manual impregnation and ply layers | Large, low volume parts like boats |
| Spray Layup | Chopped fiber and resin spray | Simple fiberglass parts |
| Filament Winding | Continuous fiber winding over mandrel | Tubes, cylinders, drive shafts |
| Pultrusion | Pulling fiber and resin through heated die | Composite rods, beams |
| Compression Molding | Pressing preform in heated mold | High volume automotive parts |
| AFP | Automated fiber tape placement | Aircraft structures |
| RTM | Injecting resin into fiber preform | High performance auto parts |
Cost Factors for Composite Manufacturing
Many variables influence the costs of manufacturing composite parts. Here are some of the key factors:
Material Selection
– Fiber type (carbon, glass, aramid etc.)
– Matrix type (epoxy, polyester, vinyl ester etc.)
– Fiber areal weight/ply thickness
– Number of plies
– Prepreg vs dry fabric
Higher performance fibers like carbon and epoxy matrices are more expensive than lower grade materials. Maximizing fiber volume fraction and optimizing laminate design minimizes material usage.
Process Choice
– Manual vs automated processes
– Mass production vs low volume batches
– Additional steps like trimming, drilling, joining
Automated processes like AFP reduce labor costs but require high capital investment. Large production runs amortize costs over more parts. Each additional manufacturing step adds cost.
Part Size and Complexity
– Surface area
– Number of details and features
– Tolerances and surface finish requirements
– Assembly vs monolithic design
Larger and more complex parts require more materials, time and labor to produce. Tight tolerances demand precision tools and quality control. Parts designed for assembly add cost over a single monolithic design.
Quality Expectations
– Dimensional accuracy and tolerances
– Cosmetic appearance
– Internal defects limits
– Strength and stiffness properties
– Testing and inspection requirements
Higher quality requirements demand more precise tools, controlled processes, inspection testing, and defect rework. This adds cost.
Industry and Application
– Aerospace vs automotive vs marine
– Military vs commercial
– Product service life and duty cycle
The acceptable cost for a composite part depends heavily on the application and industry. For example aerospace demands the highest performance regardless of cost.
Estimating Composite Costs
Estimating composite part costs early in the design process is important but challenging. Here are some methods that can be used:
Similar Part Comparison
Leveraging cost data from existing parts with similar materials, processes and specifications. This analog approach provides a quick estimate.
Detailed Bottom-up Estimation
A detailed build-up of costs starting from material prices, labor rates, equipment depreciation, utility usage and overhead factors. More accurate but time consuming.
Parametric Cost Modeling
Using regression models and algorithms to estimate costs based on key part parameters like surface area, production volume, fiber volume fraction, etc. Fast but dependent on model accuracy.
Supplier Quotes
Getting price quotes for prototyping and production from composite suppliers. Direct input from manufacturers but can reveal proprietary part details.
Costing Software
Specialty software tools are available for estimating composite part costs. Some integrate with CAD models for automated analysis. But software incurs licensing expenses.
Choosing the right strategic approach depends on the design stage, available data, in-house expertise and tolerance for uncertainty.
Strategies for Cost Reduction
Here are some methods designers use to reduce composite part costs:
Design Optimization
– Minimize part size
– Consolidate multiple components into single parts
– Design for common tooling and processing
– Standardize materials and processes across programs
Smarter designs maximize performance while minimizing production costs.
Material Selection
– Use lower cost fibers like glass instead of carbon
– Optimize ply schedule and fiber architecture
– Leverage suppliers to get lower cost materials
Reducing material waste through analysis optimization and buying leverage impact costs.
Process Improvement
– Use automation like AFP for high rate production
– Reuse tools and molds across product generations
– Seek more efficient processing methods
– Qualify multiple suppliers to enable flexibility
Investing in automation, equipment longevity and process R&D reduces long term costs.
Quality Control
– Implement statistical process control to minimize defects
– Tighten tolerances only where required
– Develop rigorous inspection procedures
– Feedback quality data to continually improve
Effective quality systems boost yield, minimize rework and prevent over-engineering.
Aftermarket Support
– Design for ease of maintenance and repair
– Use common wear-out parts across platforms
– Facilitate refurbishment and part reuse
– Offer guaranteed maintenance agreements
Lower aftermarket support cost expands market opportunities.
Conclusion
Composite materials have inherently higher upfront material and manufacturing costs compared to traditional metals. But their lifetime value can offset this premium in many applications. As automated processing improves and new materials are developed, expect composites to become even more cost competitive with steel and aluminum. Already composites represent the best performance and long term value proposition for advanced applications like aircraft. Their role will only grow across transportation, infrastructure, marine and consumer products. While not inexpensive, the value provided by composites’ lightweight and corrosion resistant properties makes them an economically viable choice.