Cushion Curve Chart Simulator (2D)

Drop Test Setup

Drop height 60 cm

Cushion thickness 30 mm

Product mass 20 kg

Cushion material

Product fragility rating

Impact Readout

Ready to drop

Peak deceleration

— G

Static stress

— kPa

Max compression

— %

Material used

— cm³

How it works

This is the classic packaging-engineering "cushion curve" (per ASTM D1596): peak impact deceleration plotted against the product's static stress (its weight divided by the pad's contact area), for a given drop height. Real cushion labs measure this curve once per material and thickness, then any engineer can read off the safe operating point without dropping a single extra sample.

Static stress:     σ_st = m·g / A
Cushion stress:    σ(ε) = E₀·ε + Ef·ε^n      (ε = compression / thickness)
Energy balance:    σ_st·(h + t·ε_max) = t·∫₀^ε_max σ(ε) dε
Cushion curve:     G_peak = σ(ε_max) / σ_st

The chart on the right is built by solving that energy balance for ε_max at many static-stress values (bisection on the closed-form strain-energy integral) — it never runs a time-step. The live drop on the left is a separate calculation: a real time-stepped nonlinear spring-damper (adds a viscous damping term the energy method omits), so its peak G lands slightly differently from the chart, and if the pad bottoms out its penalty-wall contact spike pushes the live G noticeably above the chart's undamped estimate — the chart is theory, the drop is the messier reality. Both agree that the point counts as "damaged" whenever the cushion runs out of travel before the product stops.

EPE foam — soft, high densification strain (~75%), the industry default for electronics.
Molded fiber pulp — stiffer and greener (recycled paper pulp), less travel before bottoming out.
Recycled cardboard honeycomb — very stiff, thin, low material volume, but a hard "knee" — needs enough thickness or it transmits a spike.
Air pillow — very soft and reusable-air-based, but bulky (large volume for the same protection).

Drag the mass slider and watch the white dot slide along its material's curve, and the pad thickness slider redraw the curve family — the goal is the thinnest, lowest-volume cushion whose curve still sits under the fragility line at your product's static stress.

Product (live drop) Cushion pad Cushion curve (energy method) Fragility limit