Gecko Peel-Front Fracture Kinetics (2D)

Peel Geometry

Peel angle θ 30°

Work of adhesion Γ 0.60 mN/mm

Applied peel force F 5.00 mN/mm

Pad width 8.0 mm

Peel Front

Live Readouts

Energy release rate G0.80 mN/mm

Kendall critical force4.48 mN/mm

Front velocity0.0 mm/s

Setae engaged100%

Total pad force40.0 mN

How it works

This is the 2D counterpart to the 3D setae-array model — same Kendall peel physics, but here the peel front is not just read off Kendall's formula, it is driven by real crack-tip fracture kinetics. You set an applied peel force F directly; the simulation computes the energy release rate at the delamination front and integrates the front's motion from a fracture-mechanics rate law, frame by frame.

G  =  F · (1 − cos θ)                     energy release rate (mN/mm)
Fcrit  =  Γ / (1 − cos θ)                  Kendall's critical peel force
v_front  =  v₀ · max(0, G/Γ − 1)           linear debonding-rate law

If F ≤ Fcrit  →  G ≤ Γ  →  front does not move at all.
If F  > Fcrit  →  front advances, faster the further F sits above Fcrit.

Kendall's classic equation F/b = Γ/(1 − cos θ) is the special, rate-independent case of this: it is exactly the force at which the energy release rate first equals the work of adhesion — the threshold below which nothing peels no matter how long you wait. Push F only slightly over that threshold and the front creeps; push it hard over and it peels fast. This is the same Griffith-type fracture criterion used to model real peel-test crack propagation, and it reduces to Kendall's rate-independent law in the quasi-static limit.

θ slider — the instantaneous angle between the backing film and the surface at the peel front.
Γ slider — work of adhesion per unit width; higher Γ raises both the critical force and (for a given excess force) slows the front.
F slider — the peel force per unit width you are actually applying. Below the critical force line the front is locked — this is the gecko's "shear lock" state made explicit as a real threshold, not just a color change.
Pad width — scales total force by the number of engaged seta columns.

Idle

Bonded seta (shear-locked) Detached (peeled off) Backing film