ISO 12815:2013

INTERNATIONAL ISO
STANDARD 12815
First edition
2013-03-01
Fibre-reinforced plastic
composites — Determination of
plain-pin bearing strength
Composites plastiques renforcés de fibres — Détermination de la
résistance au matage au moyen d’une goupille ordinaire
Reference number
©
ISO 2013
© ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
5.1 Test machine. . 3
6 Test specimens. 4
6.1 Shape and dimensions . 4
6.2 Preparation of specimens . 5
6.3 Checking the test specimens . 5
7 Number of test specimens . 6
8 Conditioning . 6
9 Procedure. 6
9.1 Test conditions . 6
9.2 Specimen and pin dimensions . 6
9.3 Testing speed . 6
9.4 Data collection . 6
9.5 Failure load . 6
9.6 Failure mode . 6
10 Calculation and expression of results . 7
11 Precision . 8
12 Test report . 9
Annex A (informative) Round-Robin validation exercise for plain-pin-bearing test method .10
Bibliography .13
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 ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12815 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13, Composites
and reinforcement fibres.
iv © ISO 2013 – All rights reserved

Introduction
In preparing this harmonized version, reference was made to 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 International Standard.
The method described in this International Standard 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) (see below). In the torqued bolt
test, the load can increase after the bearing failure (up to x 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, Standard test method for
bearing response of polymer matrix composite laminates, can be used as guidance on bolted joint tests.
INTERNATIONAL STANDARD ISO 12815:2013(E)
Fibre-reinforced plastic composites — Determination of
plain-pin bearing strength
1 Scope
This International Standard specifies a procedure for determining the plain-pin bearing strength of
fibre-reinforced plastic composites.
The method described in this International Standard is applicable to fibre-reinforced plastic composites
with either thermoset or thermoplastic matrices.
2 Normative references
The following referenced documents are indispensable for the application 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 527-4, Plastics — Determination of tensile properties — Part 4: Test conditions for isotropic and
orthotropic fibre-reinforced plastic composites
ISO 472, Plastics — Vocabulary
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 2818, Plastics — Preparation of test specimens by machining
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.
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.
3.2
specimen coordinate axes
coordinate axes for the material under test, the direction parallel to the plate longitudinal axis
being defined as the “1” direction, the direction perpendicular to them as the “2” direction
and, the direction “3” being perpendicular to the plate (i.e. the through-thickness direction)
[SOURCE: ISO 527-4:1997, Clause 4.8]
Key
t thickness
w specimen width
L specimen length
e distance from end of specimen
h length of tabbing (if used)
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 of the pin in contact with the specimen. The test measures a material plain-pin bearing strength
under these loading conditions, rather than a load to fail a bolted joint, for the laminate lay-up tested.
2 © ISO 2013 – All rights reserved

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 an 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
2 side plate
3 hardened bushes
4 hardened loading pin
5 specimen
6, 7 machine grips
c clearance = 0.5 mm (minimum)
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 cases of
dispute the specimen length shall be 180 mm. For specimen thickness reference shall be made to the
international standard for the material or the appropriate part of ISO 1268 for test panel manufacture,
otherwise a minimum of 4 mm shall be used for the pin hole size given in 6.1.2. The width of individual
specimens shall be parallel to within 0,2 mm. The configuration of the specimen is shown in Figure 1.
4 © ISO 2013 – All rights reserved

A hole, 6 mm (tolerance 0 to + 0,05 mm), in diameter is machined within 0,1 mm of the specimen centre
line and a distance, e, of 36 mm (i.e. 6 × the hole diameter) from the end of the coupon. Providing that an
acceptable bearing failure (c.f. shear-out) is still obtained, the end distance, e, can be reduced to 18 mm.
6.1.2 Alternative specimen size
Alternative specimens shall maintain a specimen width/hole diameter and an end distance/hole
diameter ratio of 6; and a plain-pin diameter/specimen thickness of 1,5.
NOTE For existing applications, a 6,35 mm (0,25”) hole at 38,1 mm (1,5”) from the end of a 38,1 mm (1
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