ISO 12815:2025

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
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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
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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 strengt
...