SIGRAPREG pre-impregnated composite materials

SIGRAPREG is the range of pre-impregnated composite materials, known as prepregs, made by SGL Carbon. They are reinforcing textiles of carbon, glass, aramid or natural fibre that have been impregnated with a controlled amount of resin, ready for lay-up and curing into stiff, strong, light fibre composite parts, such as airframe structures, fairings, housings, brackets and tooling for unmanned aircraft and eVTOL programs.

The reinforcement forms in the range are woven fabrics, non-crimp fabrics and non-wovens, so the engineer can choose between a drapable woven textile, a layered unidirectional or multiaxial build for loaded structures and a non-woven for surfaces and complex shapes. By changing the fibre and the textile, the portfolio covers constructions from very light to heavier, and SGL Carbon adapts the prepreg to the customer's requirement. The maker lists the advantages of the resulting components as high mechanical properties, low density, low thermal expansion, high fatigue resistance and, with carbon fibre, good electrical conductivity.

The resin systems are formulated by SGL Carbon and differ in glass transition temperature, curing temperature and time, viscosity, tack and storage stability. The epoxy systems E500 to E503 are transparent, with a glass transition temperature of 110 degrees Celsius, a cure range of 80 to 160 degrees and a shelf life of 70 days at 20 degrees and 12 months at -18 degrees. E320 to E323 have a glass transition temperature of 120 degrees, cure at 90 to 140 degrees and last 90 days at 20 degrees. E340 reaches 140 degrees, and E420 and E422 are snap-cure and transparent systems at 150 degrees that cure at 120 to 170 degrees. Flame-retardant epoxies are available as E310 and E311 at 120 degrees and as E704 and E753 at 140 degrees. E800 is a tooling epoxy with a glass transition temperature of 220 degrees, and the phenolic systems P320 to P322 and P360 are above 200 degrees. Some systems are impact-modified, and others are available on request.

For the sandwich and bonded structures that are common in aircraft, SGL Carbon also supplies SIGRAPREG adhesive films, thin epoxy or phenolic resin films that bond prepregs to honeycomb, metal and foam cores. The film formulations are matched to the prepreg resin systems for compatibility. A product finder on the maker's site helps select a combination of fibre, textile, resin and process.

SGL Carbon supplies the materials to the aerospace, security and defense, automotive and energy storage markets, which gives buyers of unmanned aircraft structures a route for specifying material for lightweight, high-stress components.