Revision 1. 6
1.10
General
1
A high dynamic strength is particularly needed for components which are subject to frequent
bending cycles (e.g. struts in aircraft construction).
Even after several tens of thousands load reversals, epoxy resins suffer only the smallest decrease in
strength and therefore have the highest dynamic strength.
Matrix
This is a reactive resin which acts as a binder, supporting the fibers and transferring to them the
forces acting on the molded part. This requires that the resin adheres well to the fibers.
Essentially, the reactive resin determines the following properties: chemical resistance, aging
resistance, scratch resistance, electrical properties, and shrinkage during curing.
Density, thermal conductivity, thermal expansion, and specific heat depend on the proportions of
reactive resin, curing agent, fibers, and fillers.
Fibers
The mechanical properties of molded materials, e.g. tensile, bending and impact strength, as well as
the ability to absorb energy, are mainly influenced by the fibers. These properties can be influenced
by the choice of fiber materials, the fiber content, and the orientation of the fibers.
Curing
The properties of the cured and molded reactive resin (i.e. of the molded part) depend not only on
the starting material, but also very much on the control of the curing process. Knowledge of the
processes involved in the curing of reactive resin is therefore crucial.
Curing, i.e. when the liquid compounds of reactive resin solidify into three-dimensionally cross-
linked products, can take place as one of three reaction types:
Polymerization
(e.g. unsaturated polyester resins)
Under the effects of reactive agents, e.g. peroxides and accelerators, the double bonds of the starting
components react with each other, releasing heat in the process. The molecules of the starting
components cross-link to form macromolecular structures called polymers.
When several starting materials, such as unsaturated polyester and styrene, are mode to react as
described above, the process is called copolymerization.