Papers by Author: Zhen Shen

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Authors: Zhen Shen, Sheng Chun Yang, Pu Hui Chen
Abstract: In this paper the relationship between CAI and compressive design allowables of composite structures were discussed and it was pointed out that traditional CAI values could not reflect the behavior of composite materials to withstand impact adequately and no relationship between CAI values and compressive design allowables existed. Based on the integrity requirements of composite structures, it was pointed out that the evaluation system of composite materials to withstand impact should include both damage resistance and damage tolerance. Large numbers of test data verified that the knee point phenomenon of composite laminates to withstand impact existed. Based on failure mechanisms, it was proposed that the behavior evaluation system of composite systems to withstand impact was based on the properties at the knee point, that is, the maximum capability to keep integrity of the front plies (the maximum contact force) characterizing damage resistance and the threshold of dent depth(or impact energy)~compressive strength(or failure strain) curves characterizing damage tolerance.
Authors: Qiang Ye, Pu Hui Chen, Zhen Shen
Abstract: A method was developed to predict numerically the dent depth of composite laminates subjected to quasi-static indentation. A progressive damage analysis was conducted for composite laminates under quasi-static transverse compressive loading by using a strain based Hashin and Yeh failure criteria as well as the FEM, and a series of degraded elastic constants of the damaged zone were drawn from the numerical results. The effective elastic constants of the damaged zone of the laminates were reevaluated according to Sun’s explicit expression. Finally, the dent depth vs. indentation force curve was predicted based on Swanson’s contact theory. The numerical simulations on the static indentation tests of T700/BA9912, T700S/5228 and T700/QY9511 laminates were done via this method. The numerical results agree well with the test data in the terms of the contact force and the corresponding dent depth.
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