Patrycja Wieczorek

2025-03

Ply angle optimization of nacelle structure using ANSYS response surface method — optimized 8 ply angles to minimize weight while maintaining failure index < 0.85 under all load cases.

Challenge: Response surface optimization with 8 continuous variables required a large DOE to avoid local optima. The optimum fibre angles were non-intuitive (not 0/±45/90) for the biaxial stress state in this structure.

Learned: Composite optimization results should always be sanity-checked against classical lamination theory. If the optimizer converges to a non-quasi-isotropic layup for a biaxial field, understanding why is as important as the weight saving.

2024-10

Composite repair patch analysis for damaged nacelle panel — FEM of scarf and step-lap repair geometries, adhesive modeled with cohesive elements, load transfer efficiency comparison.

Challenge: Scarf repair requires maintaining the correct ply orientation throughout the taper. ANSYS ACP's element set-based ply definition became unwieldy for 11-ply scarf geometry. Switched to a Python ACP scripting approach to define ply boundaries programmatically.

Learned: Repair analysis is geometrically complex — the model setup time often exceeds the analysis time. Scripted ply definition in ACP via pyACP is significantly faster than GUI-based definition for repair geometries.

2024-04

Low-velocity impact analysis on composite nacelle panel — Hashin progressive damage model in ANSYS, residual strength assessment after impact for damage tolerance qualification.

Challenge: Hashin damage model in ANSYS Mechanical does not support element deletion (element erosion) — damaged elements remain in the model and can cause negative stiffness. Had to monitor energy balance and discard models where hourglass energy exceeded 5% of internal energy.

Learned: Impact simulations with progressive damage require strict energy balance monitoring. Unrealistic energy spikes typically signal numerical instability in damaged elements, not physical behavior.

2023-12

Delamination analysis of CFRP panel using cohesive zone model (CZM) — Mode I and Mode II fracture energy calibrated from DCB and ENF specimens. Predicted delamination onset and propagation.

Challenge: CZM mesh sensitivity is critical — the cohesive zone length must contain at least 3-5 elements. For the material parameters given, this required element sizes below 0.3 mm at the delamination front, creating a very large model.

Learned: CZM analysis requires a careful estimate of the cohesive zone length before meshing. The formula involves fracture toughness, stiffness, and strength — computing it upfront prevents having to remesh after the first attempt.

2023-07

First-ply failure analysis using Tsai-Wu failure criterion — identified critical ply under combined in-plane and out-of-plane loading. Compared Tsai-Wu vs Puck criterion for this UD-CFRP layup.

Challenge: Tsai-Wu and Puck criteria gave significantly different failure indices for the 90° plies under transverse tension — Puck's physically based mode separation (fibre failure vs inter-fibre failure) was more consistent with test data.

Learned: Tsai-Wu is simpler but cannot distinguish fibre failure from matrix cracking. For design allowable work where failure mode matters (residual strength after first ply failure), Puck or Hashin criteria are more informative.

2023-02

Fan blade composite layup model in ANSYS ACP — defined 47-ply CFRP laminate with variable thickness zones, draping simulation to check fibre angle deviation on doubly-curved geometry.

Challenge: Draping simulation showed fibre angle deviation up to 8° in the leading edge region — exceeding the 5° manufacturing tolerance. Had to work with manufacturing to redesign the ply cut pattern to reduce deviation.

Learned: Draping simulation should be part of the design process, not just manufacturing verification. Knowing the achievable fibre angles during design allows trade-offs to be made before tooling is committed.