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Caltech

GALCIT Colloquium

Friday, October 7, 2016
3:00pm to 4:00pm
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Guggenheim 133 (Lees-Kubota Lecture Hall)
Computational Modeling and Experimental Characterization of the Damage and Fracturing Behavior of Textile Composites for Large Aeronautical Structures
Marco Salviato, University of Washington,

Thanks to their outstanding specific mechanical properties including stiffness, strength and intra-laminar and inter-laminar fracture toughness, textile composites represent a rapidly emerging, cost‐effective technology for the manufacturing of large mechanical and aerospace structures. However, in order to take advantage of the outstanding characteristics of these materials, understanding their damage and fracturing behavior across multiple scales, from micro to macro, is quintessential.

The first part of the talk aims at discussing the main challenges for the extensive application of textile composites in large mechanical and aerospace structures. The main damage mechanisms as well as the main issues regarding the scaling of mechanical properties are analyzed. The limitations of the current design paradigm, which relies on strength-based criteria inherited from plasticity theories, are discussed in detail. Then, the need for robust and efficient computational multi-scale models to capture damage evolution and failure at is clarified.

The second part of the presentation discusses a general constitutive model to simulate the orthotropic stiffness, pre-peak nonlinearity, failure envelopes, and the post-peak softening and fracture of textile composites. In this formulation, the constitutive laws are expressed in terms of stress and strain vectors acting on planes of several orientations within the material meso-structure. The model exploits the spectral decomposition of the orthotropic stiffness tensor to define orthogonal strain modes at the microplane level. These are associated to the various constituents at the mesoscale and to the material response to different types of deformation. Strain-dependent constitutive equations are used to relate the microplane eigenstresses and eigenstrains while a variational principle is applied to relate the microplane stresses at the mesoscale to the continuum tensor at the macroscale. Thanks to these features, it is shown that the resulting spectral stiffness microplane formulation can easily capture various physical inelastic phenomena typical of fiber and textile composites such as: matrix microcracking, micro-delamination, crack bridging, pullout, and debonding. The model closely matches a bulk of experimental results including, among others, the energy absorption caused by axial progressive crushing of composite crush cans for cars, for different lay-up configurations. 

For more information, please contact Mallory Neet by phone at 626-395-8026 or by email at [email protected].