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From:
http://www.isd.uni-hannover.de/188.html?&L=1
This picture shows a finte element simulation of buckling of a cylindrical fiber composite shell under axial loading.
ISD writes:
"Since fiber composite components are usually thin-walled structures, the stability failure plays an important role. In difference to isotropic materials it is not only the variation of the laminate setup, which has to be considered additionally, but also the special cases of failure, which can occur at the same time as stability failure.
One special challenge is the design of axially compressed shells of revolution, like circular cylinders. There, the collapse load heavily depends on imperfections, caused by the manufacturing. Guidelines like the NASA SP-8007 propose knockdown factors to handle this problem. These knockdown factors, which are based on empirical test performed in the 60s, turned out to be very conservative for modern shells and are not intended to be used for anisotropic shells.
At ISD, a fast semi-analytic probabilistic procedure has been developed that enables a fast prediction of the stochastic distribution of buckling load of cylindrical shells caused by the scattering of geometry, wall-thickness, material properties and loading imperfection. Compared to Monte Carlo simulations the semi-analytic method requires significantly fewer buckling load calculations giving equally accurate results. Knowing the distribution function of buckling load, a level of reliability is chosen and a design load is defined, which is lower than all test results and less conservative than NASA SP-8007."
Contact: Dipl.-Ing. Benedikt Kriegesmann
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