How is fiber volume fraction measured?

Cut a specimen from the cured laminate, then burn off the resin or digest it in acid so only fiber remains. Divide the fiber volume by the specimen volume, both from that same sample.

What fiber volume should a structural laminate target?

Most aerospace laminates sit between 55 and 65 percent, but the value on the drawing or prepreg datasheet governs. Use your design allowables, not a generic number.

Why can fiber volume not exceed the laminate volume?

Both entries describe one sample, so the fiber cannot take up more volume than the whole laminate. The block usually means two different samples or a unit error.

Does the matrix share include voids?

Yes, because only fiber and total volumes are entered, so voids stay in the matrix share. A void content test separates them before you blame resin content.

Composites, Fiberglass & Advanced Materials calculator

Fiber Volume Fraction Calculator

Find fiber volume fraction from the fiber volume and total volume of one cured laminate sample. Matrix share and the gap to target show whether the laminate is resin rich or dry.

What this calculator does

Fiber volume fraction from the two volumes of one cured sample, with matrix share and the gap to the target.

Formula used

Fiber volume fraction = fiber volume ÷ cured laminate volume × 100
Matrix volume = cured laminate volume − fiber volume
Matrix share = matrix volume ÷ cured laminate volume × 100
Gap to target = target fiber volume − fiber volume fraction, in points

Inputs explained

Fiber Volume in Laminate: Fiber volume from burn-off or acid digestion of the cured sample.
Cured Laminate Volume: Total volume of the same cured sample, by immersion or measurement.
Target Fiber Volume: Target from the laminate specification or design allowables.

How to use the result

Best suited to checking a cured laminate against its target, diagnosing a resin-rich or dry laminate, setting a fiber volume target for a part.
Burn-off and acid digestion destroy the sample; cut the specimen from a representative area. A void content test is separate: a high matrix share can mean resin or porosity.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 280.569 (BLS, Aug 2026), up 6.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
Steel mill PPI stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. New factory orders are up 8.5% year over year (Census).

Common questions

How is fiber volume fraction measured? Cut a specimen from the cured laminate, then burn off the resin or digest it in acid so only fiber remains. Divide the fiber volume by the specimen volume, both from that same sample.
What fiber volume should a structural laminate target? Most aerospace laminates sit between 55 and 65 percent, but the value on the drawing or prepreg datasheet governs. Use your design allowables, not a generic number.
Why can fiber volume not exceed the laminate volume? Both entries describe one sample, so the fiber cannot take up more volume than the whole laminate. The block usually means two different samples or a unit error.
Does the matrix share include voids? Yes, because only fiber and total volumes are entered, so voids stay in the matrix share. A void content test separates them before you blame resin content.

Related guides

How to Estimate Composite Part Cost from Fiber to Finished Part

Last reviewed 2026-10-01.