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| Molded Composites
for Metal Alloy Substitution |
The intrinsic merit
of engineered thermoplastics is their specific strength which
makes
them 60 percent lighter than aluminum and 80 percent lighter
than steel. Hence, these
fiber-reinforced thermoplastics are popular in metal substitution.
The choice of
reinforcing fiber and matrix resin is dependent on various factors
and end use. In
addition to mechanical properties such as tensile strength and
stiffness and impact
toughness, these composites can be tailored for thermal and
electrical specifications,
flammability and toxicity, and corrosion resistance.
Table 1 lists the range of nominal properties of high-temperature
composites molded
from carbon fiber reinforced polyethersulfone (PES), polyetherimide
(PEI), and
polyphenylene sulfide (PPS). These composites are highlighted
for their ability in
substituting for metal alloys in engineering applications. |
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| Table 1: Molded Composites
for Metal Alloy Substitution |
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| Property |
Tensile
Sength
(MPa) |
Tensile
Modulus
(GPa) |
Strain to
Failure
(%) |
Flexural
Strength
(MPa) |
Flexural
Modulus
(GPa) |
Impact
(IUN,
J/m) |
Nominal
Range |
195 - 264 |
32 - 42 |
0.5 - 1.1 |
252 - 360 |
25 - 35 |
534 - 775 |
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All of the above compounds
are noted for their V0 flammability rating which is
important in the transportation sector such as the airlines.
The inherent chemical and
moisture resistance of the matrix polymer and the reinforcing
carbon fiber makes these
materials ideal in hot, wet and corrosive applications.
The Technical Development Center (TDC) at PlastiComp has investigated
the
mechanical properties of the above composites as a function
of reinforcement fiber
types, fiber-matrix interaction, fiber lengths, fiber weight-fractions
and matrix resins
characteristics. The key findings of this expanding study help
tailor the mechanical
behavior and response of the PlastiComp composites in various
applications. Figure 1
illustrates the role of fiber weight fractions on the composite
tensile properties. The
scanning electron micrograph (SEM) illustrates the role of fiber-matrix
interface. |
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Figure 1:
Tensile Properties of Composites vs. Fiber Weight Fraction.
Adjacent, Scanning Electron Micrograph of the Fiber-Matrix Interface |
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Unlike continuous
fiber placement, chopped fibers can be easily positioned in
complex
part geometries. In order to optimize and fully utilize the
tensile properties of the fibers,
it is important that the fibers are longer than a critical length
of approximately 500 ?m.
Higher fiber lengths lead to increases in tensile properties
and most significantly to the
impact toughness of these materials. Increasing fiber weight
fractions up to 30 to 50
weight percent leads to proportional increases in tensile properties.
Beyond these fiber
fractions, the fiber ends act as stress concentrators which
leads to reductions in tensile
properties. Thus, fiber length and fiber weight fractions can
be tailored to specific
requirements. Finally, composite performance is predicated by
the fiber – matrix
adhesion at the micromechanical level. PlastiComp has worked
with several fibers and
resins manufacturers in developing a comprehensive understanding
of fiber tow-size
effects and the role of fiber-matrix coupling agents.
The Technical Management team at PlastiComp insists that all
technical advances must
translate into industry-ready manufacturing methods. Together,
our pultrusion Long-
Fiber Thermoplastics (LFT) pellets and our patented Pushtrusion®
in line molding
technologies provide full parametric control on all aspects
of reinforcement fibers and
matrix resins. PlastiComp technologies cover injection and compression
molded
compounds. The engineering staff at PlastiComp utilizes Mold
Flow Analysis and Finite
Element Methods in designing, prototyping and specifying manufacturing
methods for
engineering composite parts. |
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Pushtrusion®
and D-GMT®™ are trademarks and
Complēt® is a registered trademark of Plasticomp LLC |
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questions or comments using the request form. |
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