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8. Shear force is at the maximum at the ends of fibres and is
zero at the centre of the fibre in short fibre composites.
9. Tensile force is experienced at the maximum at the centre
of the fibre and is zero at the ends of fibres in short fibre
composites.
10. Composite laminae are orthotropic in nature (i.e. has a
symmetrical structure in three principal planes).
Exercises
1. Calculate the density and tensile strength of E-glass-reinforced
epoxy composite having V f and V m of 0.50 each. The density and
tensile strength of E-glass fibres are 2.54 g/cm 3 and 3500 MPa,
respectively. The density and tensile strength of the epoxy resin
are 1.2 g/cm 3 and 80 MPa, respectively. What is the specific tensile strength of this composite?
2. How many layers of glass fibre are required for making a planar
laminate of 3 mm thickness with ideal volume fractions? The
thickness and arial density of glass fibre are 0.33 mm and 425
GSM (g/m 2 ), respectively. Densities of glass and epoxy resin are
2.54 g/cm 3 and 1.2 g/cm 3 , respectively.
3. Calculate the random modulus of an injection- moulded glass
fibre-reinforced nylon composite. Here, V f = 0.3, fibre
length = 2 mm, fibre diameter = 10 microns, E f = 350 GPa, and
E m = 3 GPa.
4. Calculate the longitudinal and transverse modulus in GPa for a
continuous fibre-reinforced composite having a fibre content of
60% by weight, ρ m = 1.0 g/cm 3 , ρ f = 2.5 g/cm 3 , E m = 3 GPa, and
E f = 70 GPa.
5. A glass CSM-reinforced polyester composite has a 40% glass
fibre by weight. The fibre length and diameter of glass CSM are
40 mm and 12 microns, respectively. Find the random modulus
of this composite. The moduli of glass fibre and polyester resin
are 72 GPa and 2.0 GPa, respectively.
6. Find the critical length of the fibre in a glass CSM- reinforced
polyester composite. The ultimate tensile strength and diameter
of the glass fibre are 3000 MPa and 12 microns, respectively. The
yield stress of the matrix is 48 MPa.
7. What are the weaves or pattern of reinforcement to be selected
for fabrication of (a) composite boat hull, (b) composite nose
cone of aircraft, (c) composite water storage tank, and (d) composite pole/mast? Give reasons for your selection.
8. Water absorption of epoxy resin is 4%, and its specific gravity is
1.2 g/cm 3 . What is the maximum water percentage in a carbon
fibre-reinforced epoxy composite that has a specific gravity of
1.6 g/cm 3 and where V f = 0.5.
9. Estimate the tensile modulus of a UD glass/epoxy composite
and carbon/ aluminium composite for V f = 0.4. Also calculate V crit
and V min for the maximum load carried by these composites for a
cross-sectional area of 20 cm 2 .
Chapter 3 · Micromechanics and Macromechanics of Polymeric Composites
3
8. Shear force is at the maximum at the ends of fibres and is
zero at the centre of the fibre in short fibre composites.
9. Tensile force is experienced at the maximum at the centre
of the fibre and is zero at the ends of fibres in short fibre
composites.
10. Composite laminae are orthotropic in nature (i.e. has a
symmetrical structure in three principal planes).
Exercises
1. Calculate the density and tensile strength of E-glass-reinforced
epoxy composite having V f and V m of 0.50 each. The density and
tensile strength of E-glass fibres are 2.54 g/cm 3 and 3500 MPa,
respectively. The density and tensile strength of the epoxy resin
are 1.2 g/cm 3 and 80 MPa, respectively. What is the specific tensile strength of this composite?
2. How many layers of glass fibre are required for making a planar
laminate of 3 mm thickness with ideal volume fractions? The
thickness and arial density of glass fibre are 0.33 mm and 425
GSM (g/m 2 ), respectively. Densities of glass and epoxy resin are
2.54 g/cm 3 and 1.2 g/cm 3 , respectively.
3. Calculate the random modulus of an injection- moulded glass
fibre-reinforced nylon composite. Here, V f = 0.3, fibre
length = 2 mm, fibre diameter = 10 microns, E f = 350 GPa, and
E m = 3 GPa.
4. Calculate the longitudinal and transverse modulus in GPa for a
continuous fibre-reinforced composite having a fibre content of
60% by weight, ρ m = 1.0 g/cm 3 , ρ f = 2.5 g/cm 3 , E m = 3 GPa, and
E f = 70 GPa.
5. A glass CSM-reinforced polyester composite has a 40% glass
fibre by weight. The fibre length and diameter of glass CSM are
40 mm and 12 microns, respectively. Find the random modulus
of this composite. The moduli of glass fibre and polyester resin
are 72 GPa and 2.0 GPa, respectively.
6. Find the critical length of the fibre in a glass CSM- reinforced
polyester composite. The ultimate tensile strength and diameter
of the glass fibre are 3000 MPa and 12 microns, respectively. The
yield stress of the matrix is 48 MPa.
7. What are the weaves or pattern of reinforcement to be selected
for fabrication of (a) composite boat hull, (b) composite nose
cone of aircraft, (c) composite water storage tank, and (d) composite pole/mast? Give reasons for your selection.
8. Water absorption of epoxy resin is 4%, and its specific gravity is
1.2 g/cm 3 . What is the maximum water percentage in a carbon
fibre-reinforced epoxy composite that has a specific gravity of
1.6 g/cm 3 and where V f = 0.5.
9. Estimate the tensile modulus of a UD glass/epoxy composite
and carbon/ aluminium composite for V f = 0.4. Also calculate V crit
and V min for the maximum load carried by these composites for a
cross-sectional area of 20 cm 2 .
Chapter 3 · Micromechanics and Macromechanics of Polymeric Composites