Composite sandwich core materials are used in the construction of composite panels made up of three layers: a low-density core sandwiched between two thin, high-strength skins. These materials are used in a variety of applications, including boat building, aerospace, and construction, due to their high strength-to-weight ratio, durability, and stiffness. Composite sandwich cores are typically made of lightweight materials such as foam, balsa wood, or honeycomb, which provide the necessary strength and stiffness while minimizing weight. The skins are typically made of high-strength materials such as fiberglass or carbon fiber, which provide the necessary strength and stiffness to the sandwich panel.

By employing sandwich core materials in your part or mold, you can achieve much higher flexural strength and flexural modulus than using skin laminates alone.

Want to learn more about Sandwich Core? Visit the Learning Center and read our white paper, Guidelines for Sandwich Core Materials.

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  • Coosa Board Bluewater 20

    Lightweight, Non-Absorbent, Mildew Resistant Core Material
    5 star rating
    The Bluewater composite panels are made from high-density closed-cell polyurethane foam reinforced with continuous...
  • Coosa Board Bluewater 26

    Strong, Structurally Sound, Cost Effective Core Material
    5 star rating
    The Bluewater composite panels are made from high-density closed-cell polyurethane foam reinforced with continuous...
  • Nomex® Honeycomb

    Lightest Possible Construction
    4.5 star rating
    Fabricators use this sandwich core when high strength-to-weight ratios are required. This honeycomb is an...
  • Divinycell DIVINYMAT

    Resin Flows Easily for Vacuum Bagging
    5 star rating
    Divinymat has been engineered specifically for the resin infusion process and serves as both a sandwich core and a...
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  • End Grain Balsa

    Conforms to Most Curves – Marine Grade
    4.5 star rating
    End Grain Balsa is the most widely used core material, and is best suited for dynamic structures where performance...
  • Vinyl Foam: Divinycell 3 lb. Density

    Superior Mechanical and Insulative Properties
    5 star rating
    DIAB closed cell vinyl foams are valued for their superior structural and mechanical properties. These foams are...
  • Vinyl Foam: Divinycell 4 lb. Density

    Strikes Balance Between Strength and Weight
    4.5 star rating
    DIAB closed cell vinyl foams are valued for their superior structural and mechanical properties. When used as a...
  • Vinyl Foam: Divinycell 5 lb. Density

    Highest-Strength Sandwich Core, Form with Heat
    4.6 star rating
    Looking to make a strong composite part? DIAB closed cell vinyl foam is an ideal sandwich core where ultimate...
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Sandwich Core materials from include:

  • Nomex® Honeycomb--Offers the very best strength-for-weight ratio in this category; flexible, fire retardant, and delivers good impact resistance.
  • End Grain Balsa--Conforms to practically any simple curve and most gradual curves.
  • Foam--Includes sheets of vinyl and polyisocyanurate, as well as mix-and-pour foam; all are closed cell and resist water, gas, and oil.

All the Sandwich Core materials in this category are compatible with epoxy, vinyl ester, and polyester resins, and can be used for most lay-up techniques, including vacuum bagging and infusion.

To see how Sandwich Core is used during the vacuum bagging process, visit the Learning Center and read Vacuum Bagging Equipment & Techniques.

Sandwich cores are widely used in composites as a structural element to enhance stiffness, strength, and lightweight properties. A sandwich structure consists of two outer face sheets, typically a composite made with resin and reinforcement fabrics like fiberglass or carbon fiber, and a core material in between. Here are some key aspects of sandwich core use in composites:

  1. Core Materials: Various materials can be used as sandwich cores, each offering different properties and advantages. Some common core materials include:
    1. Foam Cores: Foam materials are popular choices for sandwich cores. They provide lightweight, high strength-to-weight ratio, insulation properties, and good dimensional stability.
    2. Honeycomb Cores: Honeycomb cores are made of lightweight, hexagonal-shaped cells bonded together. Honeycomb cores offer excellent strength-to-weight ratio, stiffness, and impact resistance.
    3. Balsa Wood Cores: End-Grain Balsa wood is a natural material known for its lightweight and high strength properties. Balsa cores provide good mechanical properties, impact resistance, and can be easily shaped or machined.
    4. Coosa Board Core: Coosa board is made from high-density closed-cell foam reinforced with continuous strand fiberglass and woven roving. Coosa cores are quickly becoming an industry standard for lightweight building applications that previously called for the use of plywood.
  2. Stiffness and Strength: The main purpose of using a sandwich core is to increase the structural stiffness and strength of the composite. The core material adds a significant amount of rigidity and distributes loads across the structure, reducing the likelihood of bending, buckling, or deformation.
  3. Weight Reduction: Sandwich structures are known for their lightweight nature, thanks to the use of low-density core materials. By minimizing the weight, sandwich cores offer improved fuel efficiency, increased payload capacity, and enhanced performance in applications like aerospace, marine, automotive, and wind energy.
  4. Energy Absorption: The core material in a sandwich structure can provide excellent energy absorption properties, making it suitable for impact and crash-resistant applications. The core helps absorb and dissipate energy during impact, protecting the structure and its occupants.
  5. Thermal and Acoustic Insulation: Certain core materials, particularly foam cores, offer thermal and acoustic insulation properties. These cores can help regulate temperature, reduce heat transfer, and minimize noise transmission, making them suitable for applications that require thermal or acoustic control.
  6. Design Flexibility: Sandwich structures offer design flexibility, as the choice of core material and thickness can be tailored to specific requirements. Different core materials can be selected based on the desired properties, such as stiffness, weight, insulation, or environmental considerations.
  7. Fabricating Processes: Sandwich structures can be made using various processes, including vacuum bagging, infusion, and hand layup techniques. The choice of process depends on the specific requirements, scale of production, and complexity of the design.

Sandwich cores play a vital role in composite materials, providing enhanced stiffness, strength, and lightweight properties. The selection of the core material depends on the specific application, performance requirements, budget, and fabricating capabilities. Proper consideration and design optimization are crucial to achieve the desired balance of structural integrity, weight reduction, and other performance characteristics in the final composite product.

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