Testing standard

ASTM D828 Tensile Testing of Paper and Paperboard

Standard Test Method for Tensile Properties of Paper and Paperboard Using Constant-Rate-of-Elongation Apparatus

Written and technically reviewed by Dak System Inc. engineeringLast reviewed 27 August 2026

ASTM D828 measures the tensile properties of paper and paperboard. A strip of defined width is pulled at a rate chosen so it breaks in about twenty seconds, and the method reports tensile strength, stretch at break and tensile energy absorption. Results depend heavily on grain direction, so machine and cross directions are always tested and reported separately.

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At a glance

Test type: Tensile — the specimen is pulled apart
Published by: ASTM
Edition: D828 — current edition not confirmed from a publisher source at the time of writing
Material: Paper, board & corrugated
Runs on: Series 7200 and Series 9000

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Explore the DAK machines already listed for ASTM D828, then review the grips, measurement and setup requirements below.

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01Understand the method

What the test does

A strip of paper of defined width — commonly 15 or 25 mm — is clamped across a span of about 180 mm in flat-faced grips. The crosshead separates at a rate chosen so the specimen breaks in roughly twenty seconds, and force is recorded against grip separation to break. Strips are cut and tested in both the machine and the cross direction, and the two sets of results are reported separately. From the force-elongation curve the method derives tensile strength as force per unit width, stretch at break as a percentage of the span, and tensile energy absorption as the area under the curve.

What it measures, and why it matters

The three outputs describe different things a paper has to do. Tensile strength governs whether the web survives the pull of a converting machine, a printing press or a bag-filling line — a break on a fast press is expensive and immediate. Stretch describes how much the sheet gives before it goes, which matters wherever paper is formed, wrapped or drawn. Tensile energy absorption combines both and is the property that predicts how a sack or carrier bag survives being dropped, where the ability to absorb a shock matters more than any peak force. Because all three vary strongly with grain direction, the pair of directions is what actually characterises the sheet.

02Prepare the specimen and test settings

Specimen

Paper is anisotropic, moisture-sensitive and easily nicked. All three show up in this test, and all three are handled by preparation rather than by the machine.

Width: 15 mm or 25 mm, as the specification requiresCut to width precisely — the strength is force divided by this dimension.
Span: 180 mm typical
Grain direction: Machine and cross direction tested separatelyFibres align with the machine direction during forming, so MD strength is commonly one and a half to three times CD.
Edges: Cut cleanly with a sharp precision cutterA nick in the edge is a notch, and paper is notch-sensitive. It is the largest single source of low outliers.
Conditioning: 23 ± 1 °C and 50 ± 2 % RHPaper gains strength as it dries and loses it as it takes up moisture, quickly enough to matter within a working day.
Handle by the ends only: Never across the test spanDakFinger pressure creases the sheet, and a crease across the span is a fold line the specimen will break along.
Cut strips from across the web: Not all from one placeDak

An MD figure and a CD figure describe the same sheet and are not interchangeable. A single tensile strength quoted for a paper without its direction is incomplete to the point of being misleading.

Test speed

Rate: Chosen so the specimen breaks in about 20 ± 5 sA time to break rather than a fixed speed, because papers differ enormously in stretch.
Elongation: From grip separation over the span
Tensile energy absorption: Area under the force-elongation curveOften more informative than strength for sack and bag papers, where the ability to absorb a shock matters more than a peak force.
Reject jaw breaks: Do not average them inDak

03Build the test setup on a DAK machine

What the machine must be capable of

Low forces measured accurately — many papers break between a few newtons and a few hundred — so the load cell must resolve well at the bottom of its range rather than merely tolerate the test. A crosshead whose rate can be set to achieve a twenty-second break across papers of widely differing stretch is needed, which in practice means a range of available speeds rather than one. Grips must clamp evenly across the full strip width: a strip held harder at one side tears from that side, and pneumatic grips hold a more consistent pressure across the width than screw-tightened jaws. The laboratory needs paper-grade humidity control.

Grips and fixtures for this method

Standard 25 mm

Pneumatic Vice Action Grip

Pneumatic vice action grips give a constant clamping force across the full strip width, which is what stops a paper strip tearing from one side of the jaw.

Specifications

Rubber facedTJ-34

25mm Square Vice Action Grip

A 25 mm square vice grip suits the narrower strip widths where a wide jaw is unnecessary.

Specifications

Running ASTM D828 on the Series 7200 and Series 9000

Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.

	The method asks for	Dak supplies
Capacity	Low — commonly 5 N to 500 N on a 15 mm or 25 mm wide strip	Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000
Force accuracy	unknown — ASTM E4 is not among this method's referenced documents, which name no force-verification standard and no accuracy class	ISO 7500-1 Class 0.5 — the method sets no class of its own
Gripping	Flat-faced line-contact or vice grips of the specified width, aligned so the strip is loaded squarely	Our vice-action grips, built to the specimen
Environment	23 ± 1 °C and 50 ± 2 % RH per TAPPI conditioning practice; paper strength is strongly moisture-dependent	3009 series chambers, −150 °C to +400 °C — temperature only

04Run the test

How the test runs

Cut strips to width with a sharp precision cutter, in both machine and cross direction.
Inspect the cut edges for nicks.
Condition at 23 ± 1 °C and 50 ± 2 % RH for the full period.
Fit flat grip faces at least as wide as the strip.
Set the span to the specified value.
Mount the strip square, handling it only by the ends, with no slack and no pre-tension.
Set the rate to give a break in about 20 s.
Pull to break, recording force and grip separation.
Discard specimens breaking at or in the jaws.
Compute strength per unit width, stretch and TEA.
Report machine and cross direction results separately.

05Calculate, report and interpret

Calculations

Tensile strength—

Tensile strength = Fmax / w

Fmax: maximum force, N
w: specimen width, mm

Reported as force per unit width — kN/m — rather than as a stress, because paper thickness is poorly defined and compressible.

Stretch at breakε

ε = ΔL / L₀ × 100

ΔL: increase in span at break, mm
L₀: initial span, mm

Tensile index—

Tensile index = tensile strength / grammage

Normalises for basis weight, so papers of different grammage can be compared on fibre quality and bonding.

Tensile energy absorptionTEA

TEA = area under the force-elongation curve, per unit area of specimen

What the report has to contain

Reference to ASTM D828 and the edition
Paper identification and grammage
Specimen width and span
Grain direction for each set of results
Conditioning atmosphere and duration
Rate used and the time to break achieved
Tensile strength per unit width, stretch and TEA
Tensile index where grammage is known
Number of specimens and number discarded for jaw breaks
Mean and standard deviation for each direction

What goes wrong in practice

Edge nicks produce the low outliers that dominate most data sets, and they are preventable with a sharp cutter and an edge inspection. Jaw breaks are the next problem — they measure the clamping rather than the paper and must be discarded rather than averaged in. Creases from handling the specimen across its span behave exactly like nicks. Away from the bench, the most common reporting failure is quoting a tensile strength without its grain direction, which loses the single largest variable in the measurement. Humidity drift biases results consistently and quietly, which makes it harder to catch than any of these.

06Compare methods and find answers

ASTM D828 or ISO 1924-2

	ASTM D828	ISO 1924-2
Loading	Constant rate of elongation	Constant rate of elongation
Rate basis	Break in about 20 s	20 ± 5 mm/min for the standard span
Span	180 mm typical	180 mm
Outputs	Strength, stretch, TEA	Strength, stretch, TEA, tensile index

The two are close and often produce comparable numbers, but the rate is defined differently — a time to break in one and a fixed elongation rate in the other. On papers with unusual stretch that difference is real, so the certificate should name the method run.

Questions we are asked about this test

What is ASTM D828?

It is the ASTM method for the tensile properties of paper and paperboard using constant-rate-of-elongation apparatus. A strip of defined width is pulled over a defined span at a rate giving break in about twenty seconds, and the method reports tensile strength per unit width, stretch at break and tensile energy absorption.

Why is tensile strength reported per unit width rather than as a stress?

Because paper thickness is poorly defined and compressible — measured caliper depends on the pressure applied to measure it, so a stress calculated from it would inherit that uncertainty. Force per unit width, in kN/m, avoids the problem entirely. Where papers of different basis weight must be compared, tensile index — strength divided by grammage — normalises for weight without invoking thickness at all.

Why must machine and cross direction be tested separately?

Because paper is strongly anisotropic. Fibres align with the direction of travel as the sheet is formed, so machine direction strength is commonly one and a half to three times the cross direction value, while cross direction stretch is higher. A single tensile figure quoted without its direction is incomplete to the point of being misleading, and the ratio between the two is itself a useful process indicator.

What is tensile energy absorption and when does it matter?

It is the area under the force-elongation curve — the work needed to break the strip. It matters most where a paper has to survive a shock rather than a steady pull: sack papers, carrier bags, and any packaging that gets dropped or jerked. A strong but brittle paper and a weaker but stretchier one can have very different TEA values, and the stretchier one often performs better in service.

Why is the rate specified as a time to break?

Because papers vary enormously in stretch — some break below 2 % elongation and others well above 5 %. A single fixed crosshead speed would break the low-stretch papers very quickly and the high-stretch ones slowly, at quite different strain rates. Setting the rate to achieve a break in about twenty seconds puts every paper on a comparable footing.

Why do I get occasional very low results?

Almost always a nick in the cut edge. Paper is notch-sensitive, and a small defect from a blunt cutter or careless handling is a stress raiser that the specimen breaks from at a fraction of its proper strength. Inspecting the edges before testing, and handling strips only by their ends so no crease crosses the span, removes most of these outliers.

How tightly does humidity need to be controlled?

More tightly than for most materials. Paper takes up and gives off moisture quickly, and its strength changes measurably with moisture content — enough that a strip left out of the conditioned atmosphere for a while during preparation will read differently from one tested promptly. The 23 ± 1 °C and 50 ± 2 % RH atmosphere is standard for paper testing, and it applies during the test as well as before it.

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This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.