Grażyna Giersz
Composites Engineer — Damage Tolerance · Materials & Process Engineering
Kraków, Poland
Composites Engineer specializing in damage tolerance analysis of CFRP primary structures. Uses Abaqus Explicit for impact simulation and Abaqus Standard with cohesive zone elements for delamination growth prediction. Supports structural certification by providing analysis substantiation and test planning for damage tolerance demonstration. Works closely with nacelle and fan cowl design teams.
Expertise
- composite damage tolerance analysis
- FEM modeling of composite structures (Abaqus)
- impact damage simulation (explicit dynamics)
- cohesive zone modeling for delamination
- structural testing for composite certification
Technologies
Work History
2025-01
Composite structural test plan for damage tolerance certification — defined test articles, inspection intervals, and load cases for a damage arrest demonstration test per CS-23/CS-25 composite structural certification requirements.
Challenge: The certification basis for the composite structure referenced AC 20-107B (Composite Aircraft Structure), but several provisions of AC 20-107B were interpreted differently by our DER and the EASA composite specialist. Required organizing a dedicated technical workshop to align interpretation before the test plan was finalized.
Learned: Composite structural certification test planning must align DER interpretation of AC 20-107B before test articles are manufactured. Interpretation differences discovered after specimen manufacture lead to test plan revisions that waste expensive composite test articles.
2024-04
Delamination growth prediction for CFRP nacelle panel under cyclic pressure loading — simulated fatigue-driven delamination growth using Abaqus VCCT (Virtual Crack Closure Technique) with Paris law crack growth.
Challenge: Paris law delamination growth under cyclic loading in Abaqus requires very small load increments to capture crack growth accurately — the default automatic increment size produced non-physical crack jumps. Required implementing a custom increment size control that limited crack growth to 0.1 element length per cycle increment.
Learned: Fatigue delamination growth simulation in Abaqus VCCT requires explicit crack increment size control. The default automatic stepping is designed for static analysis — for cyclic analysis, limit crack advance to a fraction of element length per increment to get physically meaningful growth predictions.
2023-10
Cohesive zone model (CZM) development for CFRP interply delamination — calibrated cohesive element properties (Knn, Ktt, Kss, GIc, GIIc) from DCB and ENF fracture test data. Validated against MMB mixed-mode test results.
Challenge: CZM cohesive stiffness parameters must be chosen carefully — too stiff causes numerical instability, too soft introduces artificial compliance. An automated viscous regularization parameter study was needed to find the stable range for the specific element size used in the structural model.
Learned: CZM cohesive stiffness must be validated against the specific element size in the structural model. Cohesive parameters validated with a fine-mesh calibration model can produce unstable results in the coarser structural mesh — always re-verify stability with the target element size.
2023-03
Hail impact simulation for composite fan cowl — Abaqus Explicit simulation of 40mm hail ice sphere impact at 200 m/s on a 6-ply CFRP panel. Predicted damage extent (delamination, fiber failure) for BVID threshold calibration.
Challenge: Hail ice material model (elastic-perfectly-plastic with failure) was highly sensitive to failure strain — ±10% change in ice failure strain changed predicted delamination area by 35%. Required sensitivity study and conservative ice model calibration against published drop-weight impact test data.
Learned: Ice material model calibration for hail impact simulation is critical and non-trivial. The failure strain is the most sensitive parameter — calibrate it against controlled experiments (drop-weight tests on representative panels) before using the model for certification analysis.