PSI - Issue 37

Andrzej Katunin et al. / Procedia Structural Integrity 37 (2022) 195–202 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The predamaged CFRP structures were then subjected to NDT using UT (both in B- and C-Scan modes) and XCT techniques for the evaluation of the accuracy of the identification of internal structural damage. The B-Scans were obtained using the FlawInspecta ® ultrasonic scanning system, while the C-Scans were acquired using the Boeing ® MAUS ® V scanning system. The spatial resolutions of B- and C-Scans were 0.508 mm and 0.254 mm, respectively. The XCT results were used as the reference due to their highest spatial resolution and accuracy resulting from the 3D representation of damage. The tested specimens were cut to the dimensions of 40×70×2.5 mm to increase the resolution of the resulting XCT scans. Note that in all cases the BVID was smaller than the dimensions of the specimen after cutting. The scanning was performed using the Nikon ® XT H 225 ST industrial XCT scanning system within the scanning area of 40×40×2.5 mm and the resulting dimensions of a single voxel of 0.022×0.022×0.01 mm. 2.2. Damage reconstruction, numerical simulations, and parametric modeling In the next step, the reconstruction algorithms, which enable an extraction of the geometry and a location of the damage from NDT results, were developed separately for each type of NDT results. The algorithms were based on advanced methods of signal and image processing and allowed reconstructing 3D shapes of BVID. Next, based on results of a fusion of UT and XCT data, the resulting algorithm was appropriately tuned (Katunin et al., 2020). In parallel, FE dynamical simulations were performed in the LS-DYNA ® commercial FE software to justify the obtained experimental results from NDT studies and provide a statistical validity of these results. The FE models were prepared according to the setups of the experimental impact tests, taking into consideration both the geometry of impactors and specific boundary conditions of the specimens as well as experimentally determined material properties of the tested CFRP structures. The simulations were performed in the failure analysis mode, and the resulting failure modes were extracted from the FE results and adjusted to the reconstructed damage shapes obtained from the experimental studies. Collected data from NDT testing and FE simulations were then processed in order to develop parametric models of BVID for particular impactors. The parametrization was controlled by the impact energy, which was connected with the damage extent. For this purpose, the extents of the resulting damage shapes from all data sources were averaged after introducing certain needed correcting factors, while the generic shapes of BVID were obtained from the averaging of the reconstructed XCT scans, since they were considered as reference data. Finally, the scaling factors were determined for each considered impactor to evaluate the scaling rules in the parametric models of BVID. A flowchart of the developed approach is presented in Fig. 1. The resulting parametric models were implemented in the CATIA V5 commercial CAD system, where the particular delaminated areas were simulated as extrusions in the location of layers interfaces with the thickness of 0.01 mm.

Fig. 1. The flowchart of the developed approach on BVID modeling.