CALCULATORS / MATERIAL RESPONSE AND SELECTION

Composite longitudinal modulus calculator

Unidirectional longitudinal iso-strain rule of mixtures only; not laminate ABD theory.

materials-composite-laminate.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	longitudinalModulusGPa
	139.2
	111.96

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.

fiber fraction physical0.60 ✓ passes

fiber fraction upper bound0.60 ✓ passes

BASELINE INPUTS

fiberFraction0.6 fiberModulus230 GPamatrixModulus3 GPa

CALCULATED

longitudinalModulus139.2 GPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Simple laminate stiffness
# Scope: Unidirectional longitudinal iso-strain rule of mixtures only; not laminate ABD theory.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

fiberFraction = 0.6
fiberModulus = 230 GPa
matrixModulus = 3 GPa

longitudinalModulus := fiberFraction*fiberModulus+(1-fiberFraction)*matrixModulus [GPa]

check fiber fraction physical: fiberFraction >= 0
check fiber fraction upper bound: fiberFraction <= 1

scenario alternative: fiberFraction = 0.48

Calculated from your source · not saved

Baseline · Baseline

fiber fraction physical0.60 ✓ passes

fiber fraction upper bound0.60 ✓ passes

alternative · alternative

fiber fraction physical0.48 ✓ passes

fiber fraction upper bound0.48 ✓ 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.

longitudinal modulus: longitudinalModulus = fiberFraction*fiberModulus+(1-fiberFraction)*matrixModulus [GPa]

Original worked example

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

Given

fiber fraction: 0.6
fiber modulus: 230 GPa
matrix modulus: 3 GPa

Calculated

longitudinal modulus: 139.2 GPa

Assumptions and limits

Unidirectional longitudinal iso-strain rule of mixtures only; not laminate ABD theory.

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: Simple laminate stiffness. Inputs: ply thicknesses; angles; orthotropic properties. Outputs: in-plane stiffness; directional compliance. 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: ply thicknesses, angles, orthotropic properties
Outputs: in-plane stiffness, directional compliance
Modes: calculate, compare, sweep
Drawing: Material tradeoff plot

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