ISO 7763:2024

Testing of paper and board - Compressive strength of a sample held in S-shape

This document specifies a test method for determining the compressive strength of a sample fixed into an S-shape in the machine direction. This document is applicable to papers with a grammage of 80 g/m2 to 220 g/m2; different grammages can lead to unreliable results.

Essais des papiers et des cartons — Résistance à la compression d'un échantillon tenu en forme de S

General Information

• Status: Published
• Publication Date: 18-Jun-2024
• ICS: 85.060 - Paper and board
• Technical Committee: ISO/TC 6/SC 2 - Test methods and quality specifications for paper and board
• Drafting Committee: ISO/TC 6/SC 2 - Test methods and quality specifications for paper and board
• Current Stage: 6060 - International Standard published
• Start Date: 19-Jun-2024
• Due Date: 15-Jul-2024
• Completion Date: 19-Jun-2024

Overview

ISO 7763:2024 - Testing of paper and board - Compressive strength of a sample held in S-shape specifies an S‑test method for measuring the compressive strength of paper and board strips fixed into an S‑shape in the machine direction. The method is intended for papers with a grammage of 80 g/m² to 220 g/m² and produces an S-test value expressed in kN/m. The test is analogous to the Short‑Span Compression Test (SCT) and shows good correlation with corrugated medium test (CMT) load‑curve behaviour.

Key topics and technical requirements

• Scope and applicability
  • Test applicable to papers with grammage 80–220 g/m²; other grammages can give unreliable results.
• Test principle
  • A 15.0 ± 0.1 mm wide strip is clamped so that it undergoes double bending and assumes an “S” shape; compressive force is applied parallel to the paper plane until buckling/failure.
• Apparatus and dimensions
  • Test piece width: 15.0 ± 0.1 mm; minimum length 90 mm.
  • Free clamping length: 4.0 ± 0.1 mm; lateral offset between clamps: 1.00 ± 0.05 mm.
  • Clamping jaw length: 30 ± 2 mm.
  • Clamping force: (2 300 ± 500) N and jaws must grip full width without burrs.
  • Test speed: 3.0 ± 1.0 mm/min (movable clamp toward fixed clamp).
• Procedure and measurements
  • Follow specified clamp closing sequence to avoid pre‑stressing the strip.
  • Record maximum load F (nearest 1 N) or S directly in kN/m (two decimal places).
  • Calculation: S = F / b (F in newtons, b in millimetres → result in kN/m).
  • Minimum requirement: obtain at least 20 valid measurements for a test series.
• Calibration, inspection and conditioning
  • Force measuring device calibration (load cell) across the application range; clamp spacing and offset checks; sample conditioning per ISO 187; sampling per ISO 186.
• Precision
  • Repeatability and reproducibility evaluated by interlaboratory study (see Annex A).

Applications and users

• Who uses ISO 7763:2024
  • Paper and board manufacturers, quality control laboratories, R&D teams, converters of corrugated board.
• Practical applications
  • Predicting compressive performance of corrugating medium and corrugated board.
  • Quality assurance during production and material selection for packaging.
  • Correlation with SCT and CMT helps troubleshoot corrugator performance and board strength issues.
  • Providing standardized test data for supplier specifications and product comparisons.

Related standards

• ISO 186 - Sampling to determine average quality (normative reference).
• ISO 187 - Standard atmosphere for conditioning and testing (normative reference).
• Related test types: SCT (Short‑Span Compression Test) and CMT (Corrugated Medium Test) - for comparative and correlative evaluations.

Keywords: ISO 7763:2024, S-test, compressive strength, paper testing, paper and board, grammage, clamping jaws, corrugated medium, SCT, CMT, ISO 186, ISO 187.

Standards Content (Sample)

International
Standard
ISO 7763
First edition
Testing of paper and board —
2024-06
Compressive strength of a sample
held in S-shape
Essais des papiers et des cartons — Résistance à la compression
d'un échantillon tenu en forme de S
Reference number
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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or ISO’s member body in the country of the requester.
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
5.1 Cutting device .1
5.2 S-test apparatus.2
5.2.1 General .2
5.2.2 Sequence .2
6 Inspection and maintenance . 3
6.1 General .3
6.2 Force measuring device . .3
6.3 Clamping jaws .3
7 Sampling . 3
8 Conditioning of samples . 3
9 Preparation of test pieces . 3
10 Procedure . 4
11 Calculation and expression of results . 4
12 Precision . 4
13 Test report . 4
Annex A (informative) Precision . 5
Annex B (informative) Closing order of the clamps . 7
Annex C (informative) Evaluation of a uniform clamping effect . 8
Bibliography . 9

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee SC 2,
Test methods and quality specifications for paper and board.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
The compressive strength of a sample fixed into an S-shape is tested analogous to the SCT (short-span
[1]
compression test) where the maximum compressive force which the sample withstands is measured
parallel to the plane of the paper. During this test, the sample strip is subjected to double bending and then
assumes the shape of the letter “S”, which is why the test is referred to as “S-test”. In comparison to the SCT,
the clamps of the “S-test” are positioned with an offset and larger spacing. This is a test method with a good
st [2,3]
correlation to 1 yield of the load curve during a CMT (corrugated medium test) measurement.

v
International Standard ISO 7763:2024(en)
Testing of paper and board — Compressive strength of a
sample held in S-shape
1 Scope
This document specifies a test method for determining the compressive strength of a sample fixed into an
S-shape in the machine direction.
2 2
This document is applicable to papers with a grammage of 80 g/m to 220 g/m ; different grammages can
lead to unreliable results.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for
monitoring the atmosphere and conditioning of samples
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
S-test value
maximum strength of a corrugating medium when subjected to double bending until failure occurs in
relation to the sample width under specified conditions
Note 1 to entry: The results are expressed in kilonewtons per metre (kN/m).
4 Principle
The sample is fixed between two clamping devices as such to create a 1 mm offset to the plane of the sheet.
Subsequently, a compressive force is applied parallel to the plane of the paper. This results in double bending
over a test length of 4 mm. Failure of the structure at the maximum load occurs in the form of buckling.
5 Apparatus
5.1 Cutting device
The cutting device shall be suitable for preparing sample strips with a width of (15,0 ± 0,1) mm and a
minimum sample length of 90 mm. The edges of the sample shall be cleanly cut and free from any damage.

5.2 S-test apparatus
5.2.1 General
The S-test apparatus is provided with two clamping devices for inserting the 15 mm wide test piece
(Figure 1, key 1 + 3 as well as 2 + 4). A clamping jaw pair (Figure 1, key 1 + 3) is movable in the direction of
testing while another clamping j
...