Festigkeit und Schadensanalyse - ETH Zürich
Festigkeit und Schadensanalyse - ETH Zürich
Festigkeit und Schadensanalyse - ETH Zürich
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22�13<br />
2� � � � � � � �<br />
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FASERVERSTÄRKTE KUNSTSTOFFE<br />
2<br />
33 12<br />
. (5.28)<br />
Er verwendet nur die ersten vier Invarianten <strong>und</strong> erstellt daraus als allgemeinste Form für ein <strong>Festigkeit</strong>skriterium:<br />
A<br />
2<br />
2<br />
1I<br />
I � B1I<br />
I � A2I<br />
II � B2I<br />
II � C12I<br />
I III<br />
� A3I<br />
III � A4I<br />
IV<br />
�1<br />
. (5.29)<br />
Hashin's Gedanken zum physikalischen Zusammenhang zwischen Spannungen, Bruchebene <strong>und</strong><br />
Bruch werden hier wegen ihrer Klarheit zitiert:<br />
“It may be argued that in the event that a failure plane can be identified, the failure is produced by<br />
the normal and shear stresses on that plane. For the fiber mode (FF) the failure plane is approximately<br />
the x2x3 plane. Therefore, the stresses producing this failure are �11, �12 and �13; Fig.<br />
5.8(a).”<br />
“The matrix mode (IFF) is a planar fracture in fiber direction; Fig. 5.8(b). The stresses on this plane<br />
are �nn, �nt and �1n. The first two are expressed in terms of the stresses �22, �33 and �23, while the<br />
last is expressed in terms of �12 and �13. Therefore, �11 does not enter into this failure mode.”<br />
� 12<br />
�11 �13 � 1n<br />
Abbildung 5.8: Failure modes and failure planes (after [1])<br />
x 2<br />
x 1<br />
“Matrix mode modeling is more complicated (compared to fiber mode modeling) since the failure<br />
plane is not a priori identified. One possible procedure would be to formulate a surface failure criterion<br />
which would depend on �nn, �nt and �1n.”<br />
“For example, a simple choice is<br />
2<br />
x 3<br />
2<br />
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� � � � �<br />
nn � nt �1n<br />
f ( � , , 1 ) � �<br />
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nn � nt � n<br />
� 1.<br />
(5.30)<br />
�<br />
� �T<br />
� � �T<br />
� � � A �<br />
2<br />
5-13 Version 1.0 (September 2010)