Why Custom Engineering Support Is Essential for Advanced Composite Manufacturing

Home > Why Custom Engineering Support Is Essential for Advanced Composite Manufacturing

Published on November 20, 2024

Materials science classifies an advanced composite material as one that includes fibers and resins with generally more robust characteristics than other materials. The traits typically involve higher strength, greater stiffness, or differing elastic modulus attributes, mutually bound into matrices with weaker materials. Though generally more substantial, those fibers integrated into advanced composites also have comparatively higher volumes but lower densities.  

Advanced composite manufacturing seeks to augment an array of advantageous chemical and physical properties. These may include chemical resistance, dimensional stability, flex performance, manufacturability, and temperature resistance, among other traits. In many cases, an advanced composite can replace metals and alloys. Manufacturing these cutting-edge materials has played an increasingly vital role in the aerospace, automotive, consumer goods, defense, electronics, healthcare, marine, oil and gas, renewable energy, and other industries.

Methods of Advanced Composite Manufacturing 

Various methods are used to perform advanced composite manufacturing. Usually, these are classified first into techniques that utilize closed or open molds, though many “open mold” methods involve tooling rather than actual molds. The closed mold method produces well-regulated surfaces along a component’s faces, while open molds only control the surfaces to which the mold (or tool) contacts. The faces in contact with the mold are called the outer mold line. In contrast, the inner mold lines are those surfaces that don’t contact the mold. Processes used for advanced composite manufacturing are sometimes classified by how resin flows along the preform.  

Advanced composite manufacturing processes all typically involve these processes: 

  • Trimming
  • Infusion of fibers with resin
  • Fiber deposition
  • Debulking
  • Curing (thermosets only) 

The actual order of these steps varies depending on the exact advanced composite manufacturing process, except for curing, which is only necessary with those composites containing thermoset resins. To fabricate an advanced composite, the manufacturing techniques that are commonly used include wet lay-up and autoclave processing, liquid composite molding, filament winding, automated tape layering, and automated fiber placement.

Wet Lay-Up & Autoclave Processing

This open mold technique strengthens fabric fibers pre-impregnated within thermoset resin matrices, a “prepreg” system incorporating curing agents. A release film covers the component in the open mold, with prepreg cut into pieces and confined within the tooling. This method involves placing breather cloth, peel ply, and release fabric on the part’s exterior to provide texture, facilitate curing, and enable the draining of excess resin.

A vacuum bag covers the lay-up in the end stages of this advanced composite manufacturing process. Heat cures the resin within the autoclave, while pressure helps drain any excess resin. Once the mold is removed from the autoclave, the finished part is removed and trimmed of excess material. The downsides of wet lay-up and autoclave processes involve the high cost of prepreg materials and an increase in cycle times due to using the autoclave.

Liquid Composite Molding

These methods are also sometimes defined as resin infusion, which involves placing a preform made from the dry fiber into a molding tool that’s then injected with thermoset resin. This negates the need for expensive prepreg materials. These types of advanced composite manufacturing methods include resin transfer molding (RTM), vacuum-assisted RTM (VARTM), resin transfer infusion (RTI), and Seeman Composites Resin Infusion Molding Process (SCRIMP).

While SCRIMP, RTI and VARTM use open molds with a vacuum bag for enclosing the preform to allow easier infusion of the resin, basic RTM techniques just use a closed mold. Depending on the size of the component that’s being fabricated, RTM cycle cure times usually require the part remain within the mold from about 6 to 20 minutes. Sometimes resins with lower viscosity are used, however, which can reduce the time needed in the mold to as little as a minute.

As an advanced composite manufacturing method, RTM can achieve tight tolerances for components with complex geometries. However, manual labor costs tend to be much higher due to the difficulty of automating dry fiber preform lay-ups. Though research continues to automate this step, a cost-effective method for this function has yet to be developed.

VARTM procedures employ vacuum bags that cover single-sided tools to make lower-cost structures that don’t require an autoclave. Though this means longer cycling time, costs are lower than with the RTM closed-mold process. Additionally, as component size increases, so does tooling cost. Manufacturing manufacturing still requires open-mold processes for any more significant part made with an advanced composite. However, processing with an autoclave is still necessary for the highest-performing components.

Filament Winding

Using a rotating mandrill acting as a single-sided mold, the procedures used in this type of advanced composite manufacturing involve pulling fibers from a spool. These fibers then move along a rotational axis that controls the fiber’s positioning of the fiber. Filament winding can be either dry winding, which uses prepreg tape, or wet winding, which uses impregnated fibers that pass through a resin bath.

Parts continuously convex and hollow are well-suited to this method for fabrication from an advanced composite. Manufacturing items like turbine blades, for example, often involves filament winding. Filament winding can also utilize a reusable mandrill with a structure made from metal, alloys, or advanced composites. Manufacturing parts in this manner can also be done with a tool made from ceramic, plaster, salt, sand, or other soluble materials that act as a binder, which can then be dissolved from the component once curing has been completed.

Before infusing resin into the composite, the process of debulking, which involves compacting the dry fibers to reinforce the structure, is initiated. This involves applying tension to the filaments, which depends on how the fibers are oriented. For example, this technique is effective if perpendicular to the rotational axis. Yet the closer the fibers are to the rotational axis, the more difficult it becomes. Further debulking is sometimes required, for which an autoclave, expanding mandrill, or vacuum bag can be used.

Generally, filament winding is an advanced composite manufacturing method that’s easily repeatable. Its automation reduces material waste while enabling higher fiber content levels within the composite. Wet filament winding methods also lower costs further, though this technique has limits when forming convex components or structures that are symmetrical around the mandrill’s axis.

Automated Tape Laying

Gantry-type robots – also referred to as cartesian coordinate robots – are usually used for this advanced composite manufacturing technique. Manipulating heads with rollers and heating elements, the robot deposits prepreg tape onto flat or somewhat curved surfaces, applying pressure and heat to tack and debulk fabric plies together. Typically, the technique uses thermoplastic tape embedded with continuous fibers between 0.11811 and 0.472441 inches (3 to 12 mm) wide. However, tape widths can reach up to 11.811 inches (300 mm) for certain applications.

To begin this process, the tape is stuck to the tooling, automatically building layers on top of each other, with the cutting device contained in the head trimming off and depositing each ply. The tape’s width often leads to more material waste during the tape-laying process. Automated tape laying normally uses thermoset resins, and although curing with a heated head is feasible, it’s better to cure with an autoclave. For this reason, tape-laying processes tend to be highly automated, accumulating deposits of nearly 100 pounds (about 45 kg) per hour when applied to flat surfaces. Disadvantages of this advanced composite manufacturing method include limitations regarding gently curved and flat surfaces and the expense of prepreg materials.

Automated Fiber Placement

Automated fiber placement provides the benefits of both computerized tape laying and filament winding while mitigating the downsides of these two techniques. Widely used for several innovative aerospace applications, this advanced composite manufacturing method has been used to construct sections of the Boeing 787 and Airbus A380. Automated fiber placement has also been used with military planes like the C-17 Globemaster III, F-18 Hornet, F-22 Raptor, and V-22 Osprey.

By simultaneously depositing numerous narrow prepreg tapes, the machine laying the tape can deposit tape quickly and conform to tighter curves without wrinkling, which helps reduce wastage. However, a rotating mandrill or fixed mold can be used with parts limited to shapes with hollow structures or continuously curved surfaces. This is due to how the machine is configured, with more complicated part geometries that can be created by bonding multiple components.

Engineering Support for Advanced Composite Manufacturing

Support is necessary for any business that offers goods or services, and this is no less so than for companies developing an advanced composite. Manufacturing uniquely engineered composites requires guidance on material selection, layup scheduling, and process optimization. Composite materials must be analyzed in the design stage to ensure low failure rates, simulating their stress resistance to improve the component design before making a prototype or large-scale production. Similarly, environmental exposure and mechanical and non-destructive testing are necessary to ensure the reliability of the designed application, along with determining the properties of a new material.

Engineering support also helps manufacturers scale up production while maintaining consistent quality and performance of any newly designed advanced composite. Manufacturing solutions can also be tailored to a customer’s needs, with engineers giving feedback that aids in improving designs to make them more cost-effective and improve manufacturability. By collaborating with a composite supplier with strong engineering support, manufacturers can reduce costs and the time it takes to bring a new product to market.

Prototypes in Advanced Composite Manufacturing

Often, when developing a new material for a component or product, prototypes are necessary. In advanced composite manufacturing, this process involves four basic steps. First comes the design phase, followed by selecting the best material for the product. After these two steps, the molds or tools should be prepared, after which fabrication methods can be determined.

Design Phase 

Whatever the project, this stage starts with translating ideas into workable prototype designs. Engineers, designers, and other stakeholders use computer-aided design (CAD) software first to simulate how a part or product will perform in the real world, considering factors like manufacturability, functionality, and aesthetics. This phase sometimes includes a finite element analysis that evaluates how the material functions when exposed to various environmental conditions and other stressors.

Selecting Materials 

For companies involved in advanced composite manufacturing, material properties like weight, strength, resistance to extreme temperatures, and elasticity should be regulated. These characteristics determine the type of material needed to make the prototype perform as desired. The cost of these materials can vary widely, so it’s important to factor this in along with various benefits and downsides offered by the composite’s properties.

Making & Preparing Molds or Tools

Before a prototype can begin production, a mold or tool must be designed to shape the advanced composite. The mold or tool’s manufacturing depends on the prototype’s intricacy. A 3D-printed mold should sometimes be used, especially for prototypes with complex geometries.

Choosing an Advanced Composite Manufacturing Method

Advanced composite manufacturing techniques, as defined earlier, can be used to create molds for prototypes and larger-scale production. These methods can be manual or automated, with materials layered according to the project’s specifications and design. An experienced composite company can point a client in the right direction for the best method to use for the application. Whether it’s automated fiber placement, automated tape layering, filament winding, liquid composite molding, wet lay-up, autoclave processing, or another advanced composite manufacturing method, a company with top-notch engineering support can provide a solution.

Once all layers have been placed, controlled pressures and temperatures are applied to the prototype until it solidifies the matrices and forms. As noted earlier, autoclaves and vacuum bags are often used during the curing process, depending on the exact technique applied. Once cured properly, the prototype is removed from the mold or tooling, after which surface finishing, like polishing or painting, is done to improve aesthetics and ensure functionality.

Examples of Advanced Composite Manufacturing & Prototyping 

Advanced composite manufacturing and prototyping are used by many industries and for numerous applications, often in conjunction. These include aerospace, automotive, marine, medical, renewable energy, and other sectors. Advanced composites are also used to fabricate drones and motor sport applications. Below are two examples, one from the aerospace sector and the other from the automotive industry.

Aerospace 

The VX4 is a prototype aircraft first developed in the United Kingdom in 2022 to emit no carbon emissions while also producing very little noise. For this purpose, an ideal solution was to develop components made from a carbon fiber composite. Manufacturing the VX4 prototype involved using composites for the propellers, with a singular curing process made the aircraft more aerodynamically efficient while optimizing its low-noise characteristics.

The advanced composite structure also helped the VX4 balance better when cruising or hovering. The airframe’s lightweight design enables it to reach a desirable power-to-weight ratio for electric propulsion. Advanced composite manufacturing also contributes to durability and energy efficiency while ensuring that structural integrity is safe for passengers.

Automotive 

Another advanced composite manufacturing success story comes from the automotive sector, with the development of the Apache APH-01 for an African hybrid rally race in 2024 that went through Morocco, Mauritania, and Senegal. The two high-performance Apache prototypes competed in the Africa Eco Race’s 15th edition, placing one car first. Both prototypes run on biofuels, with vehicles using various types of composites recycled, bio-based, and advanced. Composite manufacturing aided Apache Automotive in developing an ecologically friendly yet durable body perfectly acclimated to desert rally racing.

The Apache APH-01 prototypes incorporated flax for their exteriors, as the material made them vibration-resistant and lightweight. For interior components, basalt-based composites were used to provide greater mechanical strength. The makers used another advanced composite to augment the structure and offer a more aesthetically pleasing look, manufacturing the dashboard with a recycled carbon mat for reinforcement. The Apache APH-01 demonstrated what sustainable advanced composites can achieve compared to more conventional solutions using carbon and epoxies.  

Best Practices for Advanced Composite Manufacturing & Prototyping 

When partnering with a provider of advanced composites, it’s necessary to ensure best practices are followed when choosing the best composite material to use or even developing a new advanced composite. Manufacturing benefits from prototyping, which helps ascertain which composite materials best suit the application. While collaborating and consulting with composite experts is advantageous, leveraging technologies like finite element analysis (FEA) and computer-aided design (CAD) can help predict the behavior of materials and any potential performance issues.

Technologies like FEA and CAD limit how much physical testing is required. While many choices exist when it comes to advanced composite manufacturing methods, best practices promote careful evaluation of which is most appropriate for the application and design of the product. For example, though more advanced methods like liquid composite molding are often necessary for making more complicated designs, hand lay-ups are often suitable for simpler designs. However, one of the most fundamental best practices in advanced composite manufacturing is ensuring that a team of designers, engineers, material scientists, and other technical experts collaborate to innovate and resolve issues.

Spaulding for Advanced Composite Manufacturing

The engineers at Spaulding Composites Inc. provide support for customers ranging from large Fortune 100 manufacturers to small niche manufacturers who need to develop an advanced composite. Our engineers can tailor advanced composites for specific applications by manufacturing custom thermosets. At Spaulding, we understand the nuances of providing a material with the right properties to perform under certain conditions.

Spaulding can help with:

  • Designing for functionality and manufacturability
  • Developing materials that need to meet specific requirements
  • Engineering support throughout the advanced composite manufacturing process, from prototype to production
  • Evaluating material properties throughout the advanced composite manufacturing cycle
  • Identifying all possible means by which a part can malfunction through the use of failure mode analysis
  • Testing for performance and wear over longer periods

While Spaulding Composites has less than a half-century of experience designing and engineering high-heat thermoplastic components and thermoset-based advanced composites, it has been manufacturing composites since its inception in 1873. To learn more about the products and services we can provide to move your project forward, we invite you to contact Spaulding’s engineering support team today.