75
3
for many performances in a single component owing to their discrete
properties and anisotropic behaviour. Lightweight airframes for aircrafts, damage-tolerant lightweight parts for automobiles, etc. have
been made possible with advanced composites. Similarly, high-temperature airborne structures (such as ablative composites) are used in
rocket motor linings, re-entry surfaces of rockets, etc.
Usually, matrix shrinkage is one of the major factors in the performance of polymeric composites. The matrix shrinkage causes
inbuilt stress in polymeric composites. Therefore, the selection of
the matrix, resin, and processing methods is the driving factor for
the assessment and prediction of the performance of polymeric
composites. Even so, there are many methods to monitor the condition of the polymeric composites. One of them uses different
coloured laminae in the composite structure so as the composite
weathers the new and emerging colour of ply indicates the remaining strength. During static or impact loading, the polymeric composite absorbs the energy by two methods: the emergence of new
surfaces and material deformation. The first phenomenon that
occurs is the deformation of the surface, and on the application of
excessive stresses, a crack is initiated that creates new surface [13].
The propagation of cracks causes failure of the composite [14, 15].
While predicting the behaviour of polymeric composites, the following factors are important:
(a) Reduction in the bond strength of the interphase
(b) Loss of strength of reinforcement due to stress corrosion
(c) Loss of matrix strength
(d) Dependence of reinforcement and matrix on temperature,
humidity, and time
(e) Degradation of the reinforcement and matrix from UV
radiation
To Be Remembered
1. Micromechanics is the study of the behaviour of fibres and
filaments, matrices, interfaces, and interphases in a
composite upon the application of stress and strain.
2. Macromechanics is the study of the behaviour of the lamina
or laminate when stresses or strains are applied.
3. Properties of composites are the sum of the product of
volume fraction of the constituents and their properties.
4. Ideal volume fractions of reinforcement and matrix are 0.5.
5. In composites, a fibre-to-fibre load is transferred through
the matrix.
6. Matrix experiences shear force during the load transfer from
fibre to fibre in a composite.
7. Critical volume fraction of fibre is the minimum volume
fraction of the fibre experiencing fibre-to-fibre shear force
through the matrix and having good strength in the
composite.
3.3 · Performance of Polymeric Composites
3
for many performances in a single component owing to their discrete
properties and anisotropic behaviour. Lightweight airframes for aircrafts, damage-tolerant lightweight parts for automobiles, etc. have
been made possible with advanced composites. Similarly, high-temperature airborne structures (such as ablative composites) are used in
rocket motor linings, re-entry surfaces of rockets, etc.
Usually, matrix shrinkage is one of the major factors in the performance of polymeric composites. The matrix shrinkage causes
inbuilt stress in polymeric composites. Therefore, the selection of
the matrix, resin, and processing methods is the driving factor for
the assessment and prediction of the performance of polymeric
composites. Even so, there are many methods to monitor the condition of the polymeric composites. One of them uses different
coloured laminae in the composite structure so as the composite
weathers the new and emerging colour of ply indicates the remaining strength. During static or impact loading, the polymeric composite absorbs the energy by two methods: the emergence of new
surfaces and material deformation. The first phenomenon that
occurs is the deformation of the surface, and on the application of
excessive stresses, a crack is initiated that creates new surface [13].
The propagation of cracks causes failure of the composite [14, 15].
While predicting the behaviour of polymeric composites, the following factors are important:
(a) Reduction in the bond strength of the interphase
(b) Loss of strength of reinforcement due to stress corrosion
(c) Loss of matrix strength
(d) Dependence of reinforcement and matrix on temperature,
humidity, and time
(e) Degradation of the reinforcement and matrix from UV
radiation
To Be Remembered
1. Micromechanics is the study of the behaviour of fibres and
filaments, matrices, interfaces, and interphases in a
composite upon the application of stress and strain.
2. Macromechanics is the study of the behaviour of the lamina
or laminate when stresses or strains are applied.
3. Properties of composites are the sum of the product of
volume fraction of the constituents and their properties.
4. Ideal volume fractions of reinforcement and matrix are 0.5.
5. In composites, a fibre-to-fibre load is transferred through
the matrix.
6. Matrix experiences shear force during the load transfer from
fibre to fibre in a composite.
7. Critical volume fraction of fibre is the minimum volume
fraction of the fibre experiencing fibre-to-fibre shear force
through the matrix and having good strength in the
composite.
3.3 · Performance of Polymeric Composites