Stephen Tsai

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Stephen Tsai
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A lamina is a single layer of matrix reinforced
with fibers (tows).
Lamina 1X
12 Ply Layup10X
A laminate is a combination of lamina of the same
or different materials and/or orientation.
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Fiber patterns and/or plies orientation(s) can be
selected to suit the direction of loading.
directional fibers for directional loading
directional
shear
truss
transverse
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When loaded in the direction of the fibers,
composites have approximately three times the
specific strength and stiffness of metals.
Metals
Composites
Metals
Composites
Metals
Composites
Composites
Metals
Composites
Metals
Composites
Metals
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Composites are lighter than metals - but extra
plies may be required to enhance transverse
and/or shear strength.
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Composites are less notch sensitive in fatigue
than metals.
un-notched
notched
KT1.0
open hole
KT3.0
Static
Static
Static
Net Area Tensile Strength - ksi
Static
Fatigue
Fatigue
Fatigue
Fatigue
Aluminum
Gr/Ep
Gr/Ep
Aluminum
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Composite strength is more sensitive to impact
than for metals.
Metals - No Effect
Compression Strength (strain) After Impact
(in./in.)
Small Tools
Hail
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Composites and metals have comparable fracture
strength.
All 45o
Quasi-Isotropic
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Composite (matrix) strength is degraded by
elevated temperature and/or moisture content.
400
200
0
100
300
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The Achilles Heel of composites is the matrix.

Transverse Strength - ksi
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Composites are poor conductors of heat.
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Composites expand less than metals - tool design
can be critical.
Graphite Epoxy
Typical Range
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Poissons ratio is highly dependent on lamina
form and laminate buildup.
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