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Sandwich Construction

 “The whole is more than the sum of its parts.” - Aristoteles

A Sandwich structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core. In general, the core material is a low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. The matrix below shows this exponential increase:

Strength of the sandwich

The strength of the sandwich composite material largely depends on two factors:

1. The outer skins:

If the sandwich is supported on both sides, and then stressed by means of a force in the middle of the beam, then the bending moment will introduce shear forces in the material. The shear forces results in the bottom skin being in tension and the top skin being in compression. The core material spaces these two skins apart. The thicker the core material, the stronger the composite. This principle works in much the same way as an I-beam does.


2. The interface between the core and the skin:

Because the shear stresses in the composite material changes rapidly between the core and the skin, the adhesive layer also sees some degree of shear force. If the adhesive bond between the two layers is too weak, the most probable result will be delamination.

With Parabeam®, the core and decklayers are woven together thus forming an integral sandwich structure that cannot delaminate. When the Parabeam® is impregnated with a thermoset resin, the fabric absorbs the resin and due to the capillary forces of the piles (core), the fabric rises to the preset height. In this one-step process a lightweight and strong sandwich fiberglass panel is formed that offers excellent mechanical properties. This process is also explained in our animated video about how to process Parabeam 3D Glass Fabrics.