Just as concrete derives its strength from a reinforcement of iron braid, polyester and epoxy require a reinforcing mesh to absorb forces. This wickerwork usually consists of fiberglass, but can also be made of carbon (carbon), aramid (kevlar) or other materials. The standard glass mat, also known as a shredding mat, consists of bundles of about 4-5 cm long, very fine glass wires joined together with glue to form a mat. These mats are available in various thicknesses. For small packages, we use a standard glass mat of 300 grams per square meter.
An advantage of shredding mats is that the glue that holds the glass threads together dissolves in polyester resin after a few minutes. This causes the mat to become transparent and “swim,” meaning that the loose threads can be easily shifted. This makes it easier to get rid of creases, such as when covering spherical surfaces.
Disadvantages of chipper mats are the rough surface and the high consumption of resin (a 300 g/m² glass mat requires about 600 g of resin per m²). In addition, they are less suitable for use with epoxy resin, as they will not “swim” in it.
With glass fabrics, the threads lie neatly side by side, which means that much less resin is needed to soak them properly (a 200 g/m² glass fabric can be fully soaked with 200 g of resin per m²). This ensures a high glass content and thus high strength. In addition, fabrics provide a smooth and beautiful surface. In combination with epoxy resin, fabrics are usually used, which become beautifully transparent in the resin.
One disadvantage of fabrics is that they will not “swim” in the resin. On three-dimensionally curved surfaces, they can often be shifted a bit, but it is usually necessary to cut and overlap them. The more densely woven the fabric is, the more difficult this becomes.
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