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3D Fiberglass Sandwich Construction & FRP Panels

Integrating Composite Materials

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

The Parabeam 3D fiberglass material is woven from E-glass yarn and consists of two deck layers connected by vertical yarns. The z-directional yarns, which are woven through the deck layers, tie them together in an integral sandwich structure, and the deck layer preforms absorb the resin. As the fibers are impregnated, the fabric rises to a preset height, and, in a single step, a complex construction is created with z-axis fibers that pick up the shear and compression/buckling loads much as a foam or honeycomb core would.  This allows significant weight reduction without sacrificing stiffness to weight and strength to weight ratios

Thus a sandwich structured composite material is a special class of composite materials that allows for FRP panels with many advantages. It 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:

Thickness  1x     3x      6x
Stiffness     1,0    7,0     37,0
Strength     1,0    3,5     9,2
Weight       1,0    1,03   1,06


 

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 that form an integral sandwich structure which 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.