Base materials
The Matrix
The main task of the matrix is to transmit load to the fibres, to secure load to be distributed from fibre to fibre, to hold the fibres in place as well as to maintain the external shape of the mould, and to protect the fibres from environmental impacts.
Furthermore, the matrix helps to define essential component properties like its resistance against heat, weather and hydrolysis, impact strength, and heat-protective behaviour of the material. There are two types of matrices, the thermoset and the thermoplastic.
The thermosetting plastics (unsaturated polyester, epoxy, and vinylester resins) used by Hahlbrock cure by chemical intermeshing what makes them undeformable once the curing process has finished. Their advantageous dynamical strength, durability and heat resistance make them best suited for structural engineering applications. Adhesive joints can be carried out conveniently.
Thermoplastics, on the contrary, liquefy when heated over a certain temperature and become shapeable. With lowering temperatures, thermoplastics solidify. Their tensile modulus and stability are clearly lower than with thermosetting plastics. Under constant, persistent loads thermoplastics tend to creeping, i.e. they deform as a function of temperature and time.
Reinforcing Fibres
Fibres are beam-shaped bodies, mostly of circular cross-section and a very large length-to-diameter ratio.The most important reinforcing fibres are glass fibres, carbon fibres, and aramid fibres. These fibres enhance the weight-specific stability and rigidity of composite materials, and they influence their electrical and thermal properties. Fibre type, fibre concentration, and mainly the fibre arrangement are important parameters that influence
the fibre properties.
The fibres are further processed to form one-dimensional entities (short fibres, long fibres, yarns, twines, rovings, tapes) or panels (chopped strand mats, fabrics, non crimped fabrics, meshworks, interlaces yarns, knitted fabrics, fleeces).
These textile semi-finished products can be distinguished according to their prioritised order:
- non-directional (randomly oriented fibres and continuous mats)
- Uuni-directional (only in one direction)
- bi-directional (in two directions, mostly at an angle of 0°/90° - in fabrics)
- multi-directional (up to 4 directions in layers)