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Testing of carbon fiber reinforced materials can be difficult due to the complex structure and material behavior of the composite. To tackle this problem, researchers at Shimadzu and Cybernet Systems developed a workflow that compares CAE analysis results with the results of actual measurements of a fabric material.
This case study presents the CAE analysis workflow which starts with a carbon fiber reinforced thermo plastics (CFRTP) fabric material that was scanned using microfocus X-ray CT system to capture its internal structure. The scan data was reconstructed in Simpleware software to carry out multiscale analysis and simulate fracture behavior at the microscopic scale. By comparing the measured results from a testing system with the CAE multiscale analysis, it was possible to demonstrate the value of the technique.
To predict material physical properties values using the homogenization technique, the shape of the microstructure for the analysis model needed to be given as a known quality. The Multiscale.Sim™ add-in tool for Ansys® software was used to generate models based on the shape parameters of the microstructure, with virtual material testing/numerical material testing (NMT) carried out on this default structural data (Model 1), and for structural data (Model 2) generated from a CFRTP fabric material using a microfocus X-ray CT system (inspeXio™ SMX™-225CT FPD HR, Shimadzu).
This image data was imported to Synopsys Simpleware software to identify the cross-sectional shape and the pitch and volume fraction of the fiber bundles. Virtual material testing was carried out in Ansys CAE software and Multiscale.Sim using a unit cell for different deformation modes and other conditions to acquire the elastic modulus of anisotropy in three directions from stress-strain characteristics for each direction. Furthermore, strain distribution at microscopic scale was measured through zooming analysis of the model of the rectangular test specimen.
Uniaxial tensile test (actual measurement) image data synchronized to loading was obtained from the test piece using a Precision Universal Testing Machine (AGX™-V, Shimadzu) and noncontact digital video extensometer (TRViewX (SP.1.0.0), Shimadzu). The modulus of longitudinal elasticity (Young’s modulus) was acquired from the relationship of stress and strain, while the strain distribution of the test piece surface was captured using the digital image correlation (DIC) technique.
The two models from default structural data and image data were used for simulation, with the latter displaying non-uniform fiber bundles. A comparison was made of the elastic modulus identified by CAE/NMT and the uniaxial tensile test (actual measurement). Between the two results, the elastic modulus in the uniaxial tensile test was 55.46 (GPa), but 32.56 (GPa) for the default structural data, showing a large error. By contrast, Model 2 showed 51.75 (GPa), and was therefore closure to the measured value.