Micromechanical analysis of ceramic composite materials using the Parametric HFGMC

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SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Monday, June 29, 2020 at 14:00 
Wolfson Building of Mechanical Engineering, Room 206
"ZOOM" SEMINAR
Micromechanical analysis of ceramic composite materials using the Parametric HFGMC
Meirav Grimberg
Advisor:  Prof. Rami Haj-Ali

The goal of this research is to develop a new micromechanical modeling framework for a wide range of ceramic composite materials (CMCs).  Towards this goal, the Parametric High Fidelity Generalized Method of Cells (PHFGMC), has been employed.  The method is based on a micromechanical analysis and used to predict the effective thermos-mechanical properties, including the mechanical response of the material subject to external loading.  
In the first part, the PHFGMC method was used to investigate the mechanical behavior of unidirectional (UD) IM7/977-3 carbon-epoxy composite material systems. A UD composite plate was made from this material, and SEM measurements were used to characterize the local microstructure of this composite.  Specialized image processing was developed to depict the local geometry attributes and material imperfections such as voids and fiber packing.  Idealized repeating-unit-cell (RUC) periodic PHFGMC models were generated, analyzed, and compared, such as square and hexagonal arrays. PHFGMC predictions for the equivalent homogenized thermos-mechanical properties, local stress distribution maps under different remote application of loading are presented. The PHFGMC simulations included damage initiation and propagation.
Next, combined 2D and 3D periodic PHFGMC nested models were generated for a more complex material system: Ceramic Matrix Composites (CMC). The first CMC system investigated was made from pyrolyzed 8-harness phenolic carbon-matrix composite followed by Liquid Silicon Infiltration (LSI) manufacturing process to introduce silicon carbide (SiC) matrix phase. The combined CMC contains at least five different phases makes the nested PHFGMC-RUC modeling process very challenging. A CT discretization methodology was proposed and analyzed. The prediction results have been compared to four-point -bending experiments. Next, the effective mechanical and thermomechanical properties prediction of UD and 5-harness CMC material systems was presented and compared to FE analysis and data available in the literature. The PHFGMC is shown to be well-suited for modeling the thermos-mechanical behavior of CMC composites. 

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https://zoom.us/j/96584758181?pwd=WC9PMXdsYzJ3NFdEN2Q5ZUtOZEVjdz09 The meeting will be recorded and made available on the School’s site.

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SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Monday, June 29, 2020 at 14:00 
Wolfson Building of Mechanical Engineering, Room 206
"ZOOM" SEMINAR
Damage models for low-velocity impact and compression after impact analysis of multi-layered laminates

Shlomo Spitzer
MSc Student of Prof. Rami Haj-Ali

Composite materials and structures allow optimizing both material and structural mechanical properties for different needs. The heterogeneous nature of laminated composite materials presents a significant challenge, namely complex damage mechanisms and their accurate modeling. Low-velocity impact (LVI) introduces substantial non-visible damage in layered composite structures, such as delamination, matrix cracking, fiber breakage and fiber buckling.  Thus, there is a strong need to develop an LVI prediction analysis tool for laminate structures capable of both assessing the extend of LVI damage and evaluating the residual strength reduction and limit the serviceability of the structure. The reduction of compression after impact (CAI) strength is of high interest due to its elevated sensitivity to pre-existing damage triggered by LVI. Hence, it is essential to develop predictive mechanical damage models for both LVI and CAI.

 In this study, a through-thickness meso-mechanical sublaminate homogenization model is proposed for the impact analysis of multi-layered plates subjected to LVI followed by CAI. This sublaminate model performs through-thickness homogenization using the smallest repeated stacking sequence of the laminate. The sublaminate includes a thin interface layer with progressive damage degradation that represents the interlaminar delamination damage mode.  The sublaminate model also incorporated intra-ply damage and was compared to layer-by-layer modeling strategies. A framework for saving and transferring the accumulated damage parameters from the LVI to the following CAI analysis was developed and showcased. LVI and CAI analyses of composite plates are performed and compared with test results conducted in collaboration with the University of Michigan.  The proposed sublaminate shows a good overall prediction ability for LVI of multi-layered composite plates.

Join Zoom Meeting
https://zoom.us/j/96584758181?pwd=WC9PMXdsYzJ3NFdEN2Q5ZUtOZEVjdz09 The meeting will be recorded and made available on the School’s site.