Composites Manufacturing
In recent years, the manufacturing industry has witnessed a significant transformation with the emergence of composites. These advanced materials, made by combining two or more constituent materials with significantly different physical or chemical properties, have revolutionized various sectors, including aerospace, automotive, and construction.
Composites manufacturing process
Composites manufacturing is a process that involves combining two or more materials with significantly different physical or chemical properties to produce a new material with enhanced characteristics. This process is widely used in various industries such as aerospace, automotive, marine, and construction due to the ability of composites to offer lightweight, high strength, corrosion resistance, and design flexibility.
Composites manufacturing process passes through several steps: design and material selection, mold preparation, layup, resin infusion or injection, curing, demolding, post processing, and quality control.
The process begins with the design phase where engineers specify the desired properties and requirements of the final composite product, and selection of appropriate reinforcement materials (such as fibers like carbon, glass, or aramid) and matrix materials (such as thermoset resins like epoxy, polyester, or vinylester) based on the desired characteristics of the composite.
2. Mold Preparation
A mold or tool is created based on the desired shape and dimensions of the final product. This mold can be made from various materials like metal, fiberglass, or composite materials. The mold is prepared by cleaning, applying mold release agents, and sometimes adding surface treatments to ensure easy release of the finished composite part.
3. Layup
The layup process involves arranging layers of reinforcement materials (fibers) in the desired orientation within the mold. The reinforcement materials can be in the form of woven fabrics, unidirectional tapes, or chopped fibers depending on the specific application and desired mechanical properties. Layers of reinforcement are often combined with the matrix material, either in the form of pre-impregnated (prepreg) fibers or by applying liquid resin during layup.
4. Resin Infusion or Injection
In this step, the matrix material (resin) is introduced into the reinforcement layers to impregnate the fibers and form the composite.
Resin infusion methods include vacuum infusion, resin transfer molding (RTM), and vacuum-assisted resin transfer molding (VARTM), among others.
In resin injection processes, the liquid resin is injected into the mold under pressure to ensure complete impregnation of the reinforcement materials.
5. Curing
Once the reinforcement materials are impregnated with resin, the composite part is subjected to a curing process to harden the resin and bond the fibers together. Curing can be achieved through various methods such as heat (oven curing), chemical curing (room temperature or elevated temperature), or ultraviolet (UV) radiation for certain types of resins.
The curing process is carefully controlled to ensure proper chemical reactions and to prevent defects such as voids or bubbles within the composite.
6. Demolding
After the curing process is complete and the composite has achieved its final mechanical properties, the part is removed from the mold. Demolding must be done carefully to avoid damaging the newly formed composite structure.
7. Post-processing
Once demolded, the composite part may undergo additional post-processing steps such as trimming, drilling, sanding, or surface finishing to achieve the final dimensions and surface quality required for the application. Some composites may also require additional treatments such as painting, coating, or bonding of additional components.
8. Quality Control
Throughout the manufacturing process, quality control measures are implemented to ensure that the composite parts meet the specified requirements and standards.
Non-destructive testing methods such as ultrasonic testing, X-ray inspection, or visual inspection are often used to detect defects or irregularities in the finished parts.
Composites manufacturing process types
There are many different types of composites manufacturing processes, each with its own advantages and disadvantages. The best process for a particular application will depend on a number of factors, including the type of composite material being used, the size and shape of the part being made, the desired properties of the finished part, and the production volume.
There are three main types of composites manufacturing processes: open molding, closed molding, and cast polymer molding.
Open molding
Open molding is a versatile process that can be used to make a wide variety of parts. In open molding, the composite materials are placed in an open mold, where they cure or harden while exposed to the air. Some common open molding processes include: hand lay-up, spray-up, and filament winding.
- Hand lay-up: This is a simple process in which the composite materials are applied by hand to the mold.
- Spray-up: This process uses a spray gun to apply the composite materials to the mold.
- Filament winding: This process uses a rotating mandrel to wind continuous fibers onto the mold.
Closed molding
This process uses a closed mold to create a more uniform and controlled environment for curing the composite materials. Closed molding processes typically produce parts with better surface finish and mechanical properties than open molding processes. Some common closed molding processes include: resin transfer molding (RTM), vacuum infusion, and compression molding.
- Resin transfer molding (RTM): In RTM, the resin is injected into a closed mold that contains the dry fibers.
- Vacuum infusion: In vacuum infusion, the resin is drawn into a closed mold that contains the dry fibers by using a vacuum.
- Compression molding: In compression molding, the composite materials are placed in a closed mold and then compressed with heat and pressure.
Cast polymer molding
