65
3
3.1.2 Mechanism of Load Transfer
Polymeric composites have maximum properties in the direction
of reinforcement. Therefore, unidirectional composites have maximum mechanical properties in the longitudinal direction along
the fibres. Optimum volume fraction of fibres leads to the best
performance of composites. The optimum volume fraction for the
fibres and matrix of composites are 0.5 each. In composites, a load
is transferred from fibre to fibre through the matrix by shear force,
as shown in . Fig. 3.2. The load is transferred through the fibre
ends and small fibre lengths near the fibre ends in short fibre composites.
When the length of the fibre is greater than the length over
which the transfer of stress takes place, the end effect is neglected,
and the stress can be assumed to be over the entire length of continuous fibre.
In the case of the deformation of a composite on the application
of a load, four stages are considered:
(i) Both fibre and matrix deform elastically.
(ii) Fibres deform elastically, but the matrix deforms plastically.
Force
Fibre under stress
Matrix under
deformation due to
shear force
Force
. Fig. 3.2 Fibre-to-fibre load transfer through the matrix
3.1 · Micromechanics of Polymeric Composites
3
3.1.2 Mechanism of Load Transfer
Polymeric composites have maximum properties in the direction
of reinforcement. Therefore, unidirectional composites have maximum mechanical properties in the longitudinal direction along
the fibres. Optimum volume fraction of fibres leads to the best
performance of composites. The optimum volume fraction for the
fibres and matrix of composites are 0.5 each. In composites, a load
is transferred from fibre to fibre through the matrix by shear force,
as shown in . Fig. 3.2. The load is transferred through the fibre
ends and small fibre lengths near the fibre ends in short fibre composites.
When the length of the fibre is greater than the length over
which the transfer of stress takes place, the end effect is neglected,
and the stress can be assumed to be over the entire length of continuous fibre.
In the case of the deformation of a composite on the application
of a load, four stages are considered:
(i) Both fibre and matrix deform elastically.
(ii) Fibres deform elastically, but the matrix deforms plastically.
Force
Fibre under stress
Matrix under
deformation due to
shear force
Force
. Fig. 3.2 Fibre-to-fibre load transfer through the matrix
3.1 · Micromechanics of Polymeric Composites