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Core Materials and Foam FAQs

What is sandwich core construction?

A sandwich core construction technique utilizes a lightweight core that is very strong and resists bending much better than a skin laminate. Composite sandwich core construction results in a composite with a high degree of stiffness.

Building the core is a three-step process. First, the outer skin is laminated. While the skin is still wet, the core material is placed on the laminate. Finally, the inner skin goes atop the core material, effectively sealing it.

For decades, the boatbuilding industry has utilized sandwich core construction techniques to build boat hulls that exhibit the desired stiffness. Aircraft and vehicle manufacturers also utilize sandwich core panels.

What materials are used in composite core construction?

Composite core construction typically utilizes three types of materials. The first component is polyvinyl chloride (or PVC) foam core, a composite with polyvinyl copolymer as the first ingredient.

PVC foam core also incorporates materials such as stabilizers, plasticizers, cross-linking compounds, and blowing agents. Once the formulation is complete, PVC foam exhibits impressive strength.

For a hand lay-up project, A500 foam sheets or panels are the go-to composite core materials. Compared to similar materials, A500 foam has maximum impact strength and stiffness. This foams heat distortion temperature is also the highest among comparable foams. Finally, using A500 has an economic benefit, as it does not require as much resin.

Core cell is a tough, damage tolerant A500 foam core with a 5 lb. / cu. Ft. density. Excellent for hull and deck core replacement and anywhere that a robust non-wood core is desired. Good ductility, especially good for hull bottoms, will contour to curved shapes.

Balsa wood panels are also ideal for composite core construction. End grain balsa is available in sheets for flat-panel build projects. Or, purchase balsa with a block scheme, making it suitable for cutting curves and other complex patterns.

What are the benefits of sandwich composites?

Sandwich composites have numerous usage benefits. First, the composites greater core thickness means improved stiffness with little increase in weight and cost. Composites are also adaptable to many aerodynamic shapes, helping to decrease fuel consumption and environmental impact.

Low-maintenance sandwich core materials are also good acoustic and thermal insulators. Because they contain no metal components, they do not have any magnetic properties and can therefore be used alongside vulnerable electronics gear. Sandwich composites can also be used with radar equipment, as radar signals will pass through them with no degradation.

Sandwich composites also dampen vibration while providing fire-proofing capabilities. These composites are also resistant to weather and corrosion, which considerably increases their life spans.

What is foam core?

Foam cores are composites made from liquid polymers such as polyvinyl chloride (PVC) that are blended with blowing agents. After two molding cycles, the resulting foam block contains closed bubbles that are filled with gas. Foam cores are available in varied densities.

Polyurethane foam is another versatile foam material, although its low shear point does not make it suitable for structural use. It is commonly fabricated in foam core sheets, or it can be blown or poured in place for insulation and buoyancy applications. Foam is available in varied densities to meet users application needs. We offer both PVC foam core and pour-in-place polyurethane foam.

What is the difference between plain and grid or double-cut foam core?

A plain (or un-crosslinked) foam core sheet is tough yet flexible, and is ideal for forming flat areas such as boat decks and hulls. After undergoing a thermoforming process, these foam sheets or panels will conform to curved shapes.

Grid-scored foam core facilitates fabrication of curved components without having to thermoform them first. To do that, the core material is scored with a block-like grid pattern, and is then backed with a fiberglass scrim. With varied types of grid-scored foam available, the builder can select a product that matches the application.

Double-cut foam core also contains a scored grid pattern, but only through 40 percent of the materials thickness. Another grid pattern is made on the materials opposite face, and is an offset to the original score scheme. Double-cut foam core is useful in areas with a smaller curvature radius or a difficult-to-achieve an S curve.

What is Divinycell foam?

Divinycell is a type of semi-rigid sandwich core material that exhibits strength and stiffness while remaining light weight. Its cross linkage and PVC foam core structure make it a good candidate for boat decks and flat hull areas.

In addition, Divinycell foams scrim scored surface let it conform to curved surfaces. The foams closed-cell composition makes it water resistant, and it also possesses top-tier insulation capabilities.

What is Balsa Core?

End grain balsa is a structural core material that has been integral to sailboat construction for at least 50 years. Balsas characteristics lend themselves well to sandwich construction. Balsa wood core is a lower-priced alternative to pricier foam core composites.

For flat panel construction, end grain balsa sheets are the best option. For a project with demanding complex curves, choose balsa with a block scheme and scrim backing.

For marine applications, end grain balsa core is lightweight while exhibiting good stiffness and high shear strength. It is resistant to weather and moisture, and also displays good thermal and sound insulation properties.

Aboard a typical fiberglass boat, balsa core may be used in construction of hatch covers, cockpit and salon tables, fish boxes, and non-structural partitions and bulkheads, among other items, where lightweight, stiffness, good weather-resistance and durability is required.