Auxetic Metamaterial Core Laser Cutting & CAM Strategy

Auxetic structures exhibit a Negative Poisson's Ratio (NPR), meaning they expand laterally when stretched longitudinally and contract laterally when compressed. In aerospace sandwich panels, crash-absorbing automotive crumple zones, and protective biomedical liners, auxetic cores provide superior shear modulus, synclastic dome curvature conformability, and high specific energy absorption (SEA).

1. Re-Entrant Honeycomb Deformation Mechanics

The standard re-entrant honeycomb achieves auxetic behavior through inward-angled diagonal ribs ($ heta < 0$). Under uniaxial tension along the $y$-axis, the diagonal ribs flex outward, pushing the adjacent vertical struts apart laterally and generating negative Poisson's expansion:

2. Prepress Vector Kerf & Stress Relief Filleting

Laser and waterjet cutting of thin-walled metallic and polymeric auxetic sheets introduces critical CAM toolpath considerations:

• Vertex Fillet Radii ($R \ge 1.5 t$): Sharp re-entrant internal corners create severe stress concentration factors ($K_t > 3.5$). Adding smooth tangency fillets to all interior vector vertices mitigates fatigue cracking under cyclic loading.
• Common-Line Cutting (CLC) Optimization: Sharing common cutlines between adjacent unit cells reduces laser cutting time by up to 45% and eliminates thermal distortion from double-heating thin walls.
• Kerf Offset Compensation: Precision kerf offsetting (typically $0.12–0.25 ext{ mm}$ for fiber laser) must be applied symmetrically outward to maintain exact engineered rib thickness ($t$).