CALCULATORS / MATERIAL RESPONSE AND SELECTION

Specific stiffness and strength calculator

Material modulus-to-density ratio; no structural geometry comparison.

materials-specific-stiffness.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	specificm^2/s^2
	25555600
	20444400

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

specific stiffness target25555555.56 m^2/s^2✓ passes

BASELINE INPUTS

modulus69 GPadensity2700 kg/m^3

CALCULATED

specific25556000 m^2/s^2

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Specific stiffness and strength
# Scope: Material modulus-to-density ratio; no structural geometry comparison.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

modulus = 69 GPa
density = 2700 kg/m^3

specific := modulus/density [m^2/s^2]

check specific stiffness target: specific >= 20000000 m^2/s^2

scenario alternative: modulus = 55.2 GPa

Calculated from your source · not saved

Baseline · Baseline

specific stiffness target25555555.56 m^2/s^2 ✓ passes

alternative · alternative

specific stiffness target20444444.44 m^2/s^2 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

specific: specific = modulus/density [m^2/s^2]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

modulus: 69 GPa
density: 2700 kg/m^3

Calculated

specific: 25555600 m^2/s^2

Assumptions and limits

Material modulus-to-density ratio; no structural geometry comparison.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Specific stiffness and strength. Inputs: candidate densities, moduli and strengths. Outputs: mass-normalized material comparison. Model scope: Screening with user-supplied or cited material properties. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: candidate densities, moduli and strengths
Outputs: mass-normalized material comparison
Modes: calculate, compare, sweep
Drawing: Material tradeoff plot

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS