پاورپوینت مواد آگزتیک 19 اسلاید (pptx) 19 اسلاید
دسته بندی : پاورپوینت
نوع فایل : PowerPoint (.pptx) ( قابل ویرایش و آماده پرینت )
تعداد اسلاید: 19 اسلاید
قسمتی از متن PowerPoint (.pptx) :
Auxetic
Materials
materials
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titles
2
introduction
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Some natural substances would exhibit
auxetic
behavior, such as iron pyrites (Love, 1944),
pyrolytic
graphite (Garber, 1963).
Lakes (1987) discovered that isotropic
auxetic
foams could be easily produced from conventional foam (
polyurethan
foam with NPR = -0.7).
These new types of materials were named
“
auxetics
”
by Evans (1991).
Auxetic
materials expand laterally when stretched longitudinally and contract laterally when compressed.
Currently, a large number of
auxetic
materials have been developed, including :
PU , PTFE , UHMWPE , PP , Nylon …
3
definition
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Poisson’s ratio :
Conventional
vs.
Poisson’s ratio > 0
x
y
Auxetic
Poisson’s ratio < 0
x
y
P
ULL
P
ULL
P
ULL
P
ULL
4
Range of
poisson’s
ratios :
-1
≤
ν
≤
0.5
classification
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5
classification
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Re-entrant structure
Compression
&
heating process
Uniaxial
loading
Conventional :
Uniaxial
loading
Auxetic
:
Other re-entrant structures
6
classification
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Polymeric structure
(
Ⅰ
)
(
Ⅱ
)
(
Ⅲ
)
7
classification
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Chiral
structure
8
classification
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Rotating units
►
Square units
►
Triangle units (Star-shape structure)
9
classification
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Disordered structures
The results of research on
disordered structure
is closer to real material structures.
10