Lecture 4 Flashcards
Composite materials have a —— which is usually the surrounding/continuous material
matrix
If an additional material is added to increase the mechanical properties, they are referred to as
reinforcements
Particulates consist of —— – ——- dispersed within the ——
particles of material, matrix
Thee types of classification of composites:
- particulate
- fibre
- laminar
Fibre composites consist of
fibres of the reinforcing material dispersed in the matrix
Laminar composites are based on
sheets laminated together such as plywood
Specific properties examples 2
- specific strength
- specific modulus
Specific strength =
tensile strength / density
Specific modulus =
elastic modulus / density
Glass fibre reinforced polymer is simplified to ——- and is AKA ——-
GFRP, fibreglass
Metal matrix composites are
metals strengthened by the addition of ceramic material fibres
Aramid fibre reinforced polymer is made up of
aramid fibres in an epoxy or polyester matrix
Continuous fibres oriented in one direction, in parallel lines, give —— properties
anisotropic
Continuous fibres oriented in two directions, crossing over each other perpendicular to each other, give —— —— properties
more uniform
Discontinuous fibres oriented in one direction, parallel to eachother, give ———
anisotropic
Discontinuous fibres oriented in random directions give ——- properties
isotropic
In a fibre matrix, the matrix is usually the materials which is
- low cost
- poor specific properties
In a fibre matrix, the fibres are often the material which is
- more expensive
- superior specific properties
The matrix material performs the role of (5)
- transfers loads to fibres
- holds the fibres in place
- prevents fibres to —?
- protects the fibres from corrosion and mechanical damage
Mechanical bonding is when the matrix and fibres are joined by
interlocking of component surfaces or frictional resistance
Adhesive bonding is when the matrix is joined to the fibre by
chemical reactions at the interface
Reaction bonding is when the matrix is joined to the fibres by
the components reacted together at the interface creating a new chamical compound
Poor adhesion in a fibre matrix can lead to the fibre
not being joined to the matrix and leading to the matrix taking the stress load applied rather than the fibre taking any of the force
Fibres can be discontinuous but their —— —— depend on their length
reinforcement properties
l c =
critical fibre length =
(σf d) / 2 τi
(fibre strength X diameter of the fibre) / 2 strength of the interface between matrix and fibre surface
