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Multiscale Simulation of Fracturing Carbon-epoxy Braided composites

Two-dimensional triaxially braided composites (2DTBCs) can dissipate large amount of energy during fracturing. The biggest challenge remains in engineering this carbon-epoxy composite to optimize energy dissipation and to discover critical and sensitive factors affecting fracturing performance. The simulation started with the definition and dicretization of Repetitive Unit Cell (RUC), see Figure below

Images of 2DTBC and reconstructed RUCs with bias tow angles of 30o, 45o and 60o. Images from University of Michigan, prof. Waas' group.

Since the fracture parameters are best manifested in the scaling properties and are the main parameters in the size effect law, the nominal strengths of three geometrically similar notched beams of three different sizes are simulated in a 3D finite element framework. A collection of RUCs was embeded in a notched beam, which creates a finely disretized region around the notch and a coarse disretization around, see Figure. Python script generated the embedded geometry with the help of hanging nodes and master-slave nodes.

The simulation uses framework of damage mechanics. A fixed orientation of three perpendicular planes, aligned with material orientation axes, defines six damage variables; three for normal stress and three for shear. The material law handles the class CompoDamageMat. The left Figure shows the notched beam with embedded damaged RUCs, the next Figure experimental detail and the right Figures matches with experimental data and fitting to the the size effect law.

?300 ?180 ?90

dsc00519a.jpg

By fitting the size effect law, the fracture energy was found in the range 212 - 464 N/mm. For more information, see our article

  • V. Šmilauer, C. G. Hoover, Z. P. Bažant, F. C. Caner, A. M. Waas, K. W. Shahwan: Multiscale Simulation of Fracture of Braided Composites via Repetitive Unit Cells, Engineering Fracture Mechanics, in press, 2011.

Created 12/2010 by Vít Šmilauer. Acknowledgements belong to C. G. Hoover, B. Patzák, Z. P. Bažant, A. M. Waas and K. W. Shahwan.

gallery/fracture2dtbc.1292192491.txt.gz · Last modified: 2010/12/12 23:21 by smilauer