Reinforced plastics -- defined as a reinforcing material, normally a fibre, in a polymer matrix -- can be grouped as those used for:
-structural
applications;
-electronic uses.
The reinforced plastics within each group have very different mechanical and physical properties dictated by the fibre reinforcement (material and form), the reinforcement content and orientation and the polymer matrix used to support the reinforcement fibres.
Applications for reinforced plastics instructural andsemi-structural uses include:
-honeycomb facings,
-antennas, trays,
-structural members,
-fairings,
-spacecraft
skin,
-solar cell substrate.
The substrate materials of electronic printed-circuit boards are made from reinforced plastics; equipment housing can be composite rather than metal.
The reinforcement phase in polymer matrix composites can be grouped as:
-long, continuous fibres, unidirectional or woven,
-short (discontinuous) fibres, sometimes "chopped" to a specific length or asfelts and mats; or
-powders and other forms of fillers;
Other forms of
reinforcement, such as whiskers and metal wires, are normally used in composites with a metal matrix phase (see also aluminium-, magnesium-based alloys in subclause A.8). Natural materials (cotton and paper) - used for some composites for electronic laminates - are unacceptable for space applications.
Common commercial materials for continuous reinforcing fibres used in structural applications are:
-Carbon - grouped by their dominating mechanical properties: ultra-high modulus
(UHM), high modulus (HM), intermediate modulus (IM), high NOTE Some overlap exists between categories, especially for IM grades which are often selected for strength and strain, rather than stiffness.
-Aromatic polyamide fibres (aramid).
-Glass - high-performance grades.
-Boron (to a lesser extent) – these have a larger cross-section than the other fibres (normally known as "filaments"). There are two types: boron deposited onto thin tungsten wires, or onto a carbon fibre
substrate.
These fibre-types offer the high-strength and high-modulus properties necessary for structural applications. Glass fibres are usually used for their electrical characteristics, e.g. dielectric, rather than mechanical performance alone. Carbon fibres are conductive, whereas aramid fibres are not. Other polymer-based fibres were proposed, but were not generally evaluated for space. |
