80
4
Processing polymer composites is quite ubiquitous in the domain of
polymer engineers. The true aspects of polymer processing have a
direct correlation with rheological properties of the material concerned. The fundamental concept behind the theory of rheology
dates back to the basic definition of work being done, which is
dependent on two important parameters, notably force and its corresponding displacement.
W F d
= ⋅
The force that is needed to displace a material from its coordinates
and its centre of gravity to a new set of coordinates needs to overcome a resistance against the material to move from its position of
inertia. Relating to Newton’s first law of motion, this resistance is
the principal parameter that governs this entire theory. The work
done corresponds to the energy that is needed to displace the body,
which also goes hand in hand with the parameter known as resistance.
This concept has been developed over time in order to define
the intrinsic properties of a material, known as rheology, defined as
the study of the flow and deformation of a material. The resistance
talked about earlier corresponds to what is needed to make a material flow (for melts) or deform (for solids). Correspondingly, the
work done can be attributed to the power required to accomplish
the desired work. In simpler words, the significance of rheology in
polymer processing is mainly to make a product easily with less
power required [1].
The control of viscosities, kinetics of impregnation, and consolidation of a composite optimize both the processing time and the
quality of composite products. In the processing of composites, the
following phenomena occur:
5 Capillary effects and dynamic wetting phenomena
5 Fluid flow in a porous medium
5 Mechanical equilibrium between the reinforcement and the
fluid flowing through it
5 Occurrence of mass/heat transfer mechanisms arising from
curing or solidification
All of these phenomenon and mechanisms influence the rheology
of resin during the processing and post curing of composites. Inapt
mass/heat transfer, during curing, causes warpage in the composite
product. Liquid resins and molten polymers are non- Newtonian
fluids; therefore, only non-Newtonian flow takes place in the processing of polymeric composites [2, 3].
4.1 Fundamentals of Rheology
The study of flow or/and deformation of material (fluid/solid) is
called rheology. Viscosity is part of rheology. Viscosity is defined as
the resistance to flow of a fluid. Flow can be turbulent or laminar.
Chapter 4 · Rheology in Processing of Polymeric Composites
4
Processing polymer composites is quite ubiquitous in the domain of
polymer engineers. The true aspects of polymer processing have a
direct correlation with rheological properties of the material concerned. The fundamental concept behind the theory of rheology
dates back to the basic definition of work being done, which is
dependent on two important parameters, notably force and its corresponding displacement.
W F d
= ⋅
The force that is needed to displace a material from its coordinates
and its centre of gravity to a new set of coordinates needs to overcome a resistance against the material to move from its position of
inertia. Relating to Newton’s first law of motion, this resistance is
the principal parameter that governs this entire theory. The work
done corresponds to the energy that is needed to displace the body,
which also goes hand in hand with the parameter known as resistance.
This concept has been developed over time in order to define
the intrinsic properties of a material, known as rheology, defined as
the study of the flow and deformation of a material. The resistance
talked about earlier corresponds to what is needed to make a material flow (for melts) or deform (for solids). Correspondingly, the
work done can be attributed to the power required to accomplish
the desired work. In simpler words, the significance of rheology in
polymer processing is mainly to make a product easily with less
power required [1].
The control of viscosities, kinetics of impregnation, and consolidation of a composite optimize both the processing time and the
quality of composite products. In the processing of composites, the
following phenomena occur:
5 Capillary effects and dynamic wetting phenomena
5 Fluid flow in a porous medium
5 Mechanical equilibrium between the reinforcement and the
fluid flowing through it
5 Occurrence of mass/heat transfer mechanisms arising from
curing or solidification
All of these phenomenon and mechanisms influence the rheology
of resin during the processing and post curing of composites. Inapt
mass/heat transfer, during curing, causes warpage in the composite
product. Liquid resins and molten polymers are non- Newtonian
fluids; therefore, only non-Newtonian flow takes place in the processing of polymeric composites [2, 3].
4.1 Fundamentals of Rheology
The study of flow or/and deformation of material (fluid/solid) is
called rheology. Viscosity is part of rheology. Viscosity is defined as
the resistance to flow of a fluid. Flow can be turbulent or laminar.
Chapter 4 · Rheology in Processing of Polymeric Composites