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RISS 인기검색어
- 검색키워드
- 저자 : Waas Anthony M (검색결과 3 건)
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Dynamic failure of a sandwich structure subjected to an in-plane axial impact
Ji, Wooseok,Waas, Anthony M. ELSEVIER (APPLIED SCIENCE) 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.180 No.-
<P><B>Abstract</B></P> <P>Dynamic response of sandwich structures subjected to in-plane axial impact loading is investigated experimentally and numerically. A comprehensive set of impact test results on sandwich panels with various configurations is presented. Experimental observation is made using high-speed cameras to closely examine the detailed temporal responses of the sandwich columns before the collapse of the entire structures. It is found that the failure mode is significantly affected by the core thickness. Finite-element based simulation is also performed to have a better understanding of the failure mechanism. Discrete cohesive zone model (DCZM) is utilized to model delamination failure at the interface between the skins and core. The interfacial failure is driven by dynamic buckling of the skin, competing against the bonding strength at the interface.</P>
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Lin Shiyao,Post Alex,Waas Anthony M 한국CDE학회 2024 Journal of computational design and engineering Vol.11 No.1
Computational progressive failure analysis of carbon fiber reinforced polymer composite is of vital importance in the verification and validation process of the structural integrity and damage tolerance of modern lightweight aeronautical structures. Enhanced Schapery theory (EST) has been developed and applied to predict the damage pattern and load-bearing capacity of various composite structures. In this paper, EST is enhanced by a deep neural network (DNN) model, which enables fast and accurate predictions of matrix cracking angles under arbitrary stress states of any composite laminate. The DNN model is trained by TensorFlow based on data generated by a damage initiation criterion, which originates from the Mohr–Coulomb failure theory. The EST-DNN model is applied to open-hole tension/compression problems. The results from the EST-DNN model are obtained with no loss in accuracy. The results presented combine the efficient and accurate predicting capabilities brought by machine learning tools and the robustness and user-friendliness of the EST finite element model.
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Yeom, Bongjun,Sain, Trisha,Lacevic, Naida,Bukharina, Daria,Cha, Sang-Ho,Waas, Anthony M.,Arruda, Ellen M.,Kotov, Nicholas A. Nature Publishing Group 2017 Nature Vol. No.
<P>Tooth enamel comprises parallel microscale and nanoscale ceramic columns or prisms interlaced with a soft protein matrix(1-3). This structural motif is unusually consistent across all species from all geological eras(4-6). Such invariability-especially when juxtaposed with the diversity of other tissues-suggests the existence of a functional basis. Here we performed ex vivo replication of enamel-inspired columnar nanocomposites by sequential growth of zinc oxide nanowire carpets followed by layer-by-layer deposition of a polymeric matrix around these. We show that the mechanical properties of these nanocomposites, including hardness, are comparable to those of enamel despite the nanocomposites having a smaller hard-phase content. Our abiotic enamels have viscoelastic figures of merit (VFOM) and weight-adjusted VFOM that are similar to, or higher than, those of natural tooth enamels-we achieve values that exceed the traditional materials limits of 0.6 and 0.8, respectively. VFOM values describe resistance to vibrational damage, and our columnar composites demonstrate that lightweight materials of unusually high resistance to structural damage from shocks, environmental vibrations and oscillatory stress can be made using biomimetic design. The previously inaccessible combinations of high stiffness, damping and light weight that we achieve in these layer-by-layer composites are attributed to efficient energy dissipation in the interfacial portion of the organic phase. The in vivo contribution of this interfacial portion to macroscale deformations along the tooth's normal is maximized when the architecture is columnar, suggesting an evolutionary advantage of the columnar motif in the enamel of living species. We expect our findings to apply to all columnar composites and to lead to the development of high-performance load-bearing materials.</P>
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