ISO 12815:2025

Fibre-reinforced plastics - Determination of the plain-pin bearing strength

This document specifies a procedure for determining the plain-pin bearing strength of fibre-reinforced plastic composites. The method described in this document is applicable to fibre-reinforced plastic composites with either thermoset or thermoplastic matrices.

Plastiques renforcés de fibres — Détermination de la résistance au matage au moyen d'une goupille ordinaire

General Information

• Status: Published
• Publication Date: 25-Feb-2025
• ICS: 83.120 - Reinforced plastics
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13/WG 2 - Laminates and moulding compounds
• Current Stage: 6060 - International Standard published
• Start Date: 26-Feb-2025
• Due Date: 10-Jan-2027
• Completion Date: 26-Feb-2025

Relations

• Revises: ISO 12815:2013 - Fibre-reinforced plastic composites - Determination of plain-pin bearing strength
• Effective Date: 13-Jan-2024

Overview

ISO 12815:2025 - Fibre-reinforced plastics - Determination of the plain-pin bearing strength - defines a standardized test method to determine the plain-pin bearing strength of fibre‑reinforced plastic (FRP) composites with either thermoset or thermoplastic matrices. The standard specifies specimen geometry, apparatus (including a 6 mm plain pin and loading jig), test procedure, conditioning, data collection and result calculation. The property is reported as the maximum load divided by the projected pin contact area (σp = Pmax / (d × t)) and applies to the specific laminate lay-up tested.

Key topics and requirements

• Scope and principle: Measures plain‑pin bearing strength under tensile loading with a clearance‑fit metallic pin; maximum load defines the property.
• Specimen geometry: Preferred width 36 mm ± 0.5 mm, length 100–180 mm, hole 6 mm diameter (tolerances specified), end distance e typically 36 mm (6 × hole diameter). Alternative sizes must keep specified ratios (width/hole = 6; end distance/hole = 6; pin diameter/specimen thickness = 1.5).
• Apparatus: Test machine per ISO 5893, hardened steel plain pin (6 mm), loading jig with minimum 0.5 mm clearance, accurate load indicator (≤ ±1% full scale).
• Specimen preparation: Panels produced per ISO 1268 series; machining, hole drilling and tabbing guidance included; specimens must be flat and free from damage.
• Test conditions and data: Conditioning per ISO 291; constant test speed (ISO 5893); measure load, failure mode, hole roundness (newly added), and report roundness in test reports.
• Calculation & precision: Defined method to calculate σp and statistical treatment guidance (ISO 2602 referenced).

Practical applications

• Material characterization: quantify bearing resistance of composite laminates for design data.
• Design input for bolted and pinned joints in structural composites (aerospace, automotive, marine, wind energy).
• Quality control and research: compare lay-ups, matrix types (thermoset vs thermoplastic), and processing variations. Note: ISO 12815:2025 measures plain‑pin bearing strength of the laminate, not the full behaviour of a bolted joint under real assembly conditions (torque, washers, relaxation). Additional joint tests (e.g., torqued‑bolt tests) are recommended for specific joint designs.

Who should use it

• Composite materials engineers and test laboratories
• Product designers and structural analysts in aerospace, automotive, marine, wind and sporting goods
• Manufacturers validating laminate lay‑ups and quality control
• Standards bodies and researchers comparing bearing performance across materials

Related standards

• ISO 5893 (test machines), ISO 1268 (test plate manufacture), ISO 527-4 (tensile test conditions), ISO 291 (conditioning), ISO 472, ISO 2602 (statistics).
• Harmonized/related methods: ASTM D5961, prEN 6037 (referenced for alignment and joint testing guidance).

Keywords: ISO 12815:2025, plain-pin bearing strength, fibre-reinforced plastics, FRP bearing test, composite pin bearing, test specimen, pin diameter 6 mm, ISO 5893, ISO 1268.

Standards Content (Sample)

International
Standard
ISO 12815
Second edition
Fibre-reinforced plastics —
2025-02
Determination of the plain-pin
bearing strength
Plastiques renforcés de fibres — Détermination de la résistance
au matage au moyen d'une goupille ordinaire
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test specimens . 4
6.1 Shape and dimensions .4
6.1.1 Preferred specimen size .4
6.1.2 Alternative specimen size .4
6.2 Preparation of specimens .4
6.2.1 General .4
6.2.2 End tab material (if required) .4
6.2.3 Application of end tabs .4
6.2.4 Machining the test specimens .4
6.3 Checking the test specimens .5
7 Number of test specimens . 5
8 Conditioning . 5
9 Procedure . 5
9.1 Test conditions .5
9.2 Specimen and pin dimensions .5
9.3 Testing speed .5
9.4 Data collection .5
9.5 Failure load .5
9.6 Failure mode .6
10 Calculation and expression of results . 7
11 Precision . 7
12 Test report . 8
Annex A (informative) Interlaboratory validation exercise for plain-pin-bearing test method .10
Bibliography .12

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13, Composites
and reinforcement fibres.
This second edition cancels and replaces the first edition (ISO 12815:2013), which has been technically
revised.
The main changes are as follows:
— the measurement of the roundness of the hole has been added;
— the range of testing speed has been expanded;
— the roundness of the hole in the test reports has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
In preparing this harmonized version to other similar methods, such as prEN 6037 and ASTM D 5961,
harmonization with open-hole tests has been achieved where relevant (e.g. specimen and hole size). The
method is applicable to all current and future fibre-reinforced plastic composites meeting the requirements
of this document.
The method described in this document uses the maximum load to define the plain-pin laminate bearing
strength. This point is well-defined and has been shown to be at a similar level to the less easily defined,
initial failure in the similar “torqued bolt” test(s). In the torqued bolt test, the load can increase after the
bearing failure (up to × 2), as the failed material is jammed against the bolt, washers and loading jigs. The
property determined applies only to the laminate lay-up tested.
The strength properties of “bolted” joints are dependent on the actual conditions involved for the joint being
assessed. This includes initial bolt torque (including any load lost in bolt threads), effect of relaxation due to
visco-elastic effects, effect of hot/wet conditioning, washer size/over-size, bolt material/rivet details and
chamfer depth/plate thickness. It is recommended that additional tests to the plain-pin test be conducted
for the actual joint conditions of interest in the applications, as no standardized configuration can represent
all these variations. ASTM D 5961 can be used as guidance on bolted joint tests.

v
International Standard ISO 12815:2025(en)
Fibre-reinforced plastics — Determination of the plain-pin
bearing strength
1 Scope
This document specifies a procedure for determining the plain-pin bearing strength of fibre-reinforced
plastic composites.
The method described in this document is applicable to fibre-reinforced plastic composites with either
thermoset or thermoplastic matrices.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO 472, Plastics — Vocabulary
ISO 527-4:2023, Plastics — Determination of tensile properties — Part 4: Test conditions for isotropic and
orthotropic fibre-reinforced plastic composites
ISO 1268 (all parts), Fibre-reinforced plastics — Methods of producing test plates
ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval
ISO 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of
traverse) — Specification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following 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
plain-pin bearing strength
σ
p
stress obtained by dividing the maximum load by the projected cross-sectional area of the pin contact area
with the specimen (i.e. d x t)
Note 1 to entry: The result is expressed in megapascals, MPa.

Key
t thickness e distance from end of specimen
w specimen width h length of tabbing (if used)
L specimen length d pin/hole diameter
Figure 1 — Test specimen for determination of plain-pin bearing strength
4 Principle
A test specimen consisting of a strip of rectangular cross-section with a plain hole, centrally positioned with
respect to the width, is loaded in tension by a clearance fit metallic plain-pin. The maximum load sustained
by the specimen is used to determine the plain-pin bearing strength, based on the projected area on the pin
in contact with the specimen. The test measures a plain-pin bearing strength under these loading conditions,
rather than a load to fail a bolted joint, for the laminate lay-up tested.
5 Apparatus
5.1 Test machine.
5.1.1 General, test machine conforming to ISO 5893 as appropriate to the requirements given in 5.1.2 to 5.1.3.
5.1.2 Speed of testing, v, shall be kept constant according to ISO 5893.

5.1.3 Indicator for load, such that the error in the indicated force is less than ±1 % of the full scale (see
ISO 5893).
5.2 Micrometer, or equivalent, capable of reading to 0,01 mm, or less, and suitable for measuring the
thickness, t and width, w of the test specimen; and the pin/hole diameter, d and position. The micrometer
shall have faces appropriate to the surface being measured (i.e. flat faces for flat, polished surfaces and
hemispherical faces for irregular surfaces).
5.3 Loading jig and pin, the plain-pin is loaded by a double-shear metal plate assembly, as shown in
Figure 2. The loading jig shall include clearance, c, of at least 0,5 mm on both sides of the specimen and shall
not distort under the applied load. The pin should be manufactured in a hardened steel. The loading pin shall
similarly not distort during the test and should be a clearance fit in the hole in the specimen, unless specified
otherwise. The loading pin shall have a diameter of 6 mm (tolerance 0 to −0,05 mm).
NOTE Hardened plates are acceptable as an alternative to the use of the hardened bushes shown in Figure 1.
Key
1 grip plate 5 specimen
2 side plate 6 machine grips
3 hardened bushes c clearance = 0,5 mm (minimum)
4 hardened loading pin
Figure 2 — Loading plates and test arrangement

6 Test specimens
6.1 Shape and dimensions
6.1.1 Preferred specimen size
The specimen shall have a width, w, of 36 mm ± 0,5 mm and a length, L of 100 to 180 mm. In
...