ISO 16572:2008

Timber structures — Wood-based panels — Test methods for structural properties

ISO 16572:2008 specifies test methods for determining the structural properties of commercial wood-based and lignocellulosic fibrous panel products for use in load-bearing timber structures. These properties are intended for the calculation of characteristic values. NOTE Bamboo is an example of a lignocellulosic fibrous material.

Structures en bois — Panneaux à base de bois — Méthodes d'essai pour la détermination des propriétés structurelles

General Information

• Status: Published
• Publication Date: 25-May-2008
• ICS: 79.060.01 - Wood-based panels in general
• ICS: 91.080.20 - Timber structures
• Technical Committee: ISO/TC 165 - Timber structures
• Drafting Committee: ISO/TC 165 - Timber structures
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 11-Apr-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16572
First edition
2008-06-01

Timber structures — Wood-based
panels — Test methods for structural
properties
Structures en bois — Panneaux à base de bois — Méthodes d'essai
pour la détermination des propriétés structurelles




Reference number
ISO 16572:2008(E)
©
ISO 2008

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ISO 16572:2008(E)
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©  ISO 2008
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ISO 16572:2008(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviated terms . 2
5 Sampling. 3
5.1 Sampling of panels. 3
5.2 Sampling of specimens. 3
6 Preparation of test pieces. 4
6.1 Conditioning. 4
6.2 Dimensions of test pieces . 4
6.3 Moisture content. 4
6.4 Density . 4
7 Bending properties. 5
7.1 True bending properties flatwise . 5
7.2 Apparent bending properties flatwise . 7
7.3 Bending properties edgewise. 8
8 Compression properties . 10
8.1 General. 10
8.2 Compression test for small test pieces. 10
8.3 Compression test for large-size test pieces . 12
8.4 Expression of results . 14
9 Tension properties. 14
9.1 Test piece . 14
9.2 Loading equipment. 14
9.3 Loading method. 15
9.4 Test procedure . 15
9.5 Expression of results . 15
10 Panel shear. 16
10.1 Panel shear — Method A. 16
10.2 Panel shear — Method B. 17
10.3 Expression of results . 20
11 Planar shear . 20
11.1 Method A — Loaded by plates . 20
11.2 Method B — Five-point bending. 23
12 Test report . 24
12.1 General. 24
12.2 General data . 24
12.3 Data on the material. 24
12.4 Data on individual test pieces . 25
12.5 Data on physical properties. 25
12.6 Additional information. 25
12.7 Sampling data . 25
Annex A (informative) Small-size compression test pieces . 26
Annex B (informative) Example of cutting schedule . 27
Annex C (informative) Panel shear — Method B. 28
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ISO 16572:2008(E)
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 16572 was prepared by Technical Committee ISO/TC 165, Timber structures.
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ISO 16572:2008(E)
Introduction
For each type and grade of panel product, as defined (for example in a wood-based panel standard), it is
necessary to determine characteristic values of structural properties to enable it to be used for structural
purposes. This International Standard details the necessary testing, which may only need to be carried out
once for each type and grade of product unless there is a reason to suspect a significant change has occurred
in its properties.
This International Standard is not intended for quality control testing.

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INTERNATIONAL STANDARD ISO 16572:2008(E)

Timber structures — Wood-based panels — Test methods for
structural properties
1 Scope
This International Standard specifies test methods for determining the structural properties of commercial
wood-based and lignocellulosic fibrous panel products for use in load-bearing timber structures. These
properties are intended for the calculation of characteristic values.
NOTE Bamboo is an example of a lignocellulosic fibrous material.
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 9424, Wood-based panels — Determination of dimensions of test pieces
ISO 9427, Wood-based panels — Determination of density
ISO 16979, Wood-based panels — Determination of moisture content
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
knife check
separation of the fibres which does not extend through the thickness of the veneer
3.2
length
〈wood-based panels〉 long dimension of the test piece in the plane of the panel
3.3
specimen
〈wood-based panels〉 piece of the panel from which a test piece will be fabricated
3.4
test area
〈wood-based panels〉 that portion of the test piece from which the structural property is being evaluated
3.5
test piece
〈wood-based panels〉 specimen or aggregate of parts from a sample fabricated to the size and shape required
for testing
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ISO 16572:2008(E)
3.6
width
〈wood-based panels〉 short dimension of the test piece in the plane of the panel
4 Symbols and abbreviated terms
A cross-sectional area of the test piece within the gauge length, equal to bt, in square millimetres
b measured width of test piece, in millimetres
E modulus of elasticity, in megapascals
F load, in newtons
F maximum load applied to the test piece, in newtons
max
F increment of load on the linear portion of the load-deflection curve, in newtons (see Figure 1)
∆
f strength, in megapascals
G modulus of rigidity, in megapascals
I second moment of area, in millimetres to the fourth power
a
k slope of the linear portion of the load versus deformation or deflection curve, in newtons per
millimetre (see Figure 1)
l length of test piece, in millimetres
l gauge length, in millimetres
1
l distance between an inner load point or line and the nearest support, in millimetres
2
M moment, in newton millimetres
t measured thickness of test piece, in millimetres
t nominal thickness of the panel being tested, in millimetres
1
u deflection or deformation, in millimetres
u increment of deflection corresponding to F , in millimetres (see Figure 1)
∆ ∆
W section modulus, in millimetres to the third power
Subscripts applied to loads, capacities, strengths, stiffnesses, and moduli of elasticity:
app apparent
c compression
edge edgewise
m bending
s planar shear
t tension
true true bending
v panel shear
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ISO 16572:2008(E)

Key
X deflection or deformation
Y load
1 slope = k
NOTE Experience has demonstrated that suitable values of F and F are approximately 10 % and 40 % of F ,
1 2 max
respectively.
Figure 1 — Load-deflection or deformation graph within the linear range
5 Sampling
5.1 Sampling of panels
All panels in a sample shall be of the same type, grade, thickness range and composition and/or lay-up as
defined in a standard or product specification. The sample shall be representative of the product as defined.
5.2 Sampling of specimens
The position of the specimens within the panels shall be selected to ensure the sampling of specimens is
unbiased. The specimens for each type of test in each direction shall be from a different position in different
panels of the same sample.
NOTE An example of a cutting schedule based on a sample of four panels, each with a minimum area of
1 200 mm × 2 400 mm, is given in Annex B.
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ISO 16572:2008(E)
6 Preparation of test pieces
6.1 Conditioning
6.1.1 Standard conditioning
With the exception of 6.1.2, all test pieces shall be conditioned to constant mass in an atmosphere of relative
humidity (65 ± 5) % and temperature (20 ± 2) °C. Constant mass is deemed to be attained when the results of
at least three successive weighings indicate the moisture content has stabilized to within ± 0,5 % for at least a
48 h period.
If the conditions of the testing room are not the same as those in the conditioning chamber, test pieces shall
remain in the conditioning chamber until testing.
6.1.2 Alternative conditionings
Test pieces may be differently conditioned and/or unconditioned.
Unless otherwise noted in the test report, results from Clauses 7 to 11 shall be corrected to reflect
conditioning as specified in 6.1.1. The procedure for correcting structural properties shall be technically sound,
using moisture content results from 6.3, and shall be recorded in the test report.
6.2 Dimensions of test pieces
6.2.1 Method of measurement
The dimensions shall be determined in accordance with ISO 9424.
6.2.2 Measurements to be taken
The thickness of the test pieces shall be measured at the four corners of the test area and averaged. With the
exception of panel shear, methods A and B, the width of the test pieces shall be measured at two points along
each edge of the test area and averaged. The length of the test pieces for panel shear, method A, and planar
shear, method A, tests shall be measured at two points along each edge of the test area and averaged. The
length of the test pieces for panel shear, method B, shall be measured along the centreline of the test area
(including the radius section), as shown in Figure 9.
If the thicknesses of individual plies or layers in plywood or composite panels are required, then each shall be
measured to the nearest 0,1 mm at the four edges of the test piece and averaged.
6.3 Moisture content
6.3.1 Method of measurement
The moisture content shall be determined in accordance with the procedures of ISO 16979.
6.3.2 Measurements to be taken
The moisture content shall be determined from at least one test piece per panel and measured at the time of
testing.
6.4 Density
6.4.1 Method of measurement
The density shall be determined in accordance with the procedures of ISO 9427.
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ISO 16572:2008(E)
6.4.2 Measurements to be taken
The density shall be determined from at least one test piece per panel and measured at the time of testing.
7 Bending properties
7.1 True bending properties flatwise
7.1.1 Test piece
The test piece shall be rectangular in cross-section. The depth of the test piece shall be equal to the thickness
of the panel, and the width shall be not less than 300 mm. The total length of the test piece shall be the span
between the supports plus an overhang sufficiently long to prevent the test piece from slipping off the supports
during testing.
7.1.2 Loading equipment
The loading equipment shall be capable of measuring the load to an accuracy of 1 % of the maximum load.
7.1.3 Loading method
The application of the load shall be as shown in Figure 2, with minimum dimensions as noted. Contact points
for loads and reaction forces shall be continuous across the width of the test piece and (30 ± 1) mm in
diameter. The test hardware shall include appropriate mechanisms, such as rollers or pivots, to minimize the
development of axial forces in the test piece and to allow the test piece to deflect freely under load. The
application of the load shall create a zone of uniform bending moment between the load points, free of shear
stresses.
The recommended distance for l is 16t to preclude shear failures outside the zone of uniform bending
2 1
moment.
NOTE 1 Large deflections may occur when test pieces with small bending stiffness are tested to failure, thus
alternative test arrangements may be required. In general, the test configuration described in this subclause is suitable for
a test piece with a thickness greater than 9 mm (corresponding to a bending stiffness per unit width of about
2
300 kN⋅mm /mm). Smaller thicknesses may be tested by using smaller-diameter supports and proportionally reducing the
distances between them.
NOTE 2 Thick and/or wide test pieces may require larger-diameter supports.
Dimensions in millimetres

Key
1 test piece
Figure 2 — True bending modulus of elasticity and stiffness test configuration
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ISO 16572:2008(E)
7.1.4 Test procedure
7.1.4.1 Rate of application of load
The load, F, shall be applied at a constant rate so that the maximum load is reached within (300 ± 120) s.
7.1.4.2 Measurement of length and deformation
The lengths l and l shall be measured to the nearest 1 mm. The deflection of the test piece shall be
1 2
measured between two parallel lines, perpendicular to the span, located in the zone of uniform moment, as
shown in Figure 2. This distance (the gauge length) shall be not less than 250 mm. Deflection measurements
may be referenced relative to the top or bottom of the test piece. Test pieces exhibiting excessive twist/warp
may require two points of deflection measurement, in which case the average of the two readings shall be
used in the calculations. The deflection over the gauge length shall be measured to the nearest 0,01 mm.
For t less than 9 mm thick, the minimum 250 mm gauge length may be proportionally reduced, but should be
1
as large as possible while maintaining adequate clearance between the gauges and the loading equipment.
7.1.5 Expression of results
7.1.5.1 True modulus of elasticity and bending stiffness
The true bending modulus of elasticity of the test piece shall be calculated from the linear portion of the load
versus deflection graph, as given in Equation (1) or (2):
2
Fll
∆12
E = (1)
m,true
16uI
∆ a
or
2
kl l
12
E = (2)
m,true
16I
a
The true bending stiffness, E I , of the test piece shall be calculated from the linear portion of the load
m,true a
versus deflection graph, as given in Equation (3) or (4):
2
Fll
∆12
EI = (3)
m,true a
16u
∆
or
2
kl l
12
EI = (4)
m,true a
16
7.1.5.2 Bending strength and moment capacity
The bending strength of the test piece shall be calculated as given in Equation (5):
F l
max 2
f = (5)
m,true
2W
The moment capacity of the test piece shall be calculated as given in Equation (6):
F l
max 2
M = (6)
max,true
2
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ISO 16572:2008(E)
7.2 Apparent bending properties flatwise
7.2.1 Test piece
The test piece shall be rectangular in cross-section. The depth of the test piece shall be equal to the thickness
of the panel, and the width shall be 300 mm. The total length of the test piece shall be 48 times t plus an
1
overhang sufficiently long to prevent the test piece from slipping off the supports during testing.
7.2.2 Loading equipment
The loading equipment shall be capable of measuring the load to an accuracy of 1 % of the maximum load.
7.2.3 Loading method
The application of the loads shall be as shown in Figure 3 and accurate to the nearest 1 mm. Contact points
for loads and reaction forces shall be continuous across the width of the test piece and (30 ± 1) mm in
diameter. The test hardware shall include appropriate mechanisms, such as rollers or pivots, to minimize the
development of axial forces in the test piece and to allow the test piece to freely deflect under load.
NOTE Thick test pieces may require larger-diameter supports.

Key
1 test piece
2 support
Figure 3 — Apparent bending modulus of elasticity and stiffness test configuration
7.2.4 Test procedure
7.2.4.1 Rate of application of load
The load, F, shall be applied at a constant rate so that the maximum load is reached within 300 ± 120 s.
7.2.4.2 Measurement of length and deformation
The effective gauge length, l , shall be measured to the nearest 1 mm. The deflection of the test piece shall
1
be measured at mid-width and mid-span. Test pieces exhibiting excessive twist/warp may require two points
of deflection measurement near the outer edges of the test piece at mid-span, in which case the average of
the two readings shall be used in the calculations.
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ISO 16572:2008(E)
Deflection measurement may be from the top or bottom of the test piece and shall be referenced relative to
the top of the test piece, above the outside supports. If referencing deflection measurements from test
hardware, steps shall be taken to reduce error due to crushing at contact points and hardware
settling/movement.
The deflection over the gauge length shall be measured to the nearest 0,01 mm.
7.2.5 Expression of results
7.2.5.1 Apparent modulus of elasticity and bending stiffness
The apparent bending modulus of elasticity of the test piece shall be calculated from the linear portion of the
load versus deflection graph, as given in Equation (7) or (8):
3
23Fl
∆ 1
E = (7)
m,app
1296uI
∆ a
or
3
23kl
1
E = (8)
m,app
1296I
a
The apparent bending stiffness, E I , of the test piece shall be calculated from the linear portion of the
m,app a
load versus deflection graph, as given in Equation (9) or (10):
3
23F l
∆ 1
EI = (9)
m,app a
1296u
∆
or
3
23kl
1
EI = (10)
m,app a
1296
7.2.5.2 Bending strength and moment capacity
The bending strength of the test piece shall be calculated as given in Equation (11):
F l
max 2
f = (11)
m,app
2W
The moment capacity of the test piece shall be calculated as given in Equation (12):
F l
max 2
M = (12)
max,app
2
7.3 Bending properties edgewise
7.3.1 Test piece
The test piece shall be rectangular in cross-section and shall have a width, b, of 50 mm, a length, l, of 915 mm
and a thickness, t, equal to the thickness of the panel, as shown in Figure 4.
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ISO 16572:2008(E)
7.3.2 Loading equipment
The loading equipment shall be capable of measuring the load to an accuracy of 1 %.
7.3.3 Loading method
The load and reaction forces shall be applied to the nearest 1 mm, as shown in Figure 4. The test piece shall
be oriented on edge, with the plane of the panel parallel to the load, F. The load, F, shall be applied mid-span.
The contact points for the load and the reaction forces shall be continuous across the width of the test piece
and shall be sufficient in area to prevent crushing of the test piece. The test hardware shall include
appropriate mechanisms, such as rollers or pivots, to minimize the development of axial forces in the test
piece and to allow the test piece to freely deflect under load.
Test pieces having a b/t ratio of three or greater are subject to lateral instability during loading. Lateral
supports, if used, shall allow movement of the test piece in the direction of load application and have minimal
frictional restraint.
Bearing plates at least 25 mm in length are recommended to preclude crushing of the test piece.
Dimensions in millimetres

Key
1 test piece
2 support
Figure 4 — Edgewise bending test configuration
7.3.4 Test procedure
7.3.4.1 Rate of application of load
The load, F, shall be applied at a constant rate so that the maximum load is reached in not less than 10 s and
not more than 300 s.
7.3.4.2 Measurement of deformation and ultimate load
Deformation shall be measured as the deflection at the load point with respect to the end reaction plates, to
the nearest 0,01 mm.
If, because of the design of the apparatus, the deflection measurement includes extraneous components, the
deflection data may be adjusted for such extraneous components. Any such adjustments shall be detailed in
the test report.
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ISO 16572:2008(E)
7.3.5 Expression of results
7.3.5.1 Bending modulus of elasticity and stiffness capacity
The edgewise bending modulus of elasticity of the test piece shall be calculated from the linear portion of the
load versus deflection graph, as given in Equation (13) or (14):
3
F l
∆ 1
E = (13)
m,edge
48uI
∆ a
or
3
kl
1
E = (14)
m,edge
48I
a
The edgewise bending stiffness capacity, E I , of the test piece shall be calculated from the linear portion
m,edge a
of the load versus deflection graph, as given in Equation (15) or (16):
3
F l
∆ 1
EI = (15)
m,edge a
48u
∆
or
3
kl
1
EI = (16)
m,edge a
48
7.3.5.2 Bending strength and moment capacity
The bending strength of the test piece shall be calculated as given in Equation (17):
F l
max 1
f = (17)
m,edge
4W
The moment capacity of the test piece shall be calculated as given in Equation (18):
F l
max 1
M = (18)
max,edge
4
8 Compression properties
8.1 General
Compression tests shall be in accordance with 8.2 for small-size test pieces or 8.3 for large-size test pieces.
8.2 Compression test for small test pieces
8.2.1 Test piece
8.2.1.1 General
The preparation of the test pieces will depend on the nominal thickness, t , of the panel to be tested. If t is
1 1
40 mm or greater, the test piece shall consist of one piece of the panel being tested, and be as described in
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ISO 16572:2008(E)
8.2.1.2. If t is less than 40 mm, the test piece shall consist of several pieces of the panel being tested and be

1
fabricated as per 8.2.1.3.
8.2.1.2 Panels having a thickness of 40 mm or greater
For panels with a t of 40 mm or greater, the test piece shall have a width, b, of 200 mm, a length, l, of
1
between five and six times t and a thickness, t, equal to the thickness of the panel.
1
8.2.1.3 Panels having a thickness of less than 40 mm
For panels with a t of less than 40 mm, the test piece shall be formed from the bonding together of
1
specimens of adjacent positions within the panel until the thickness, t, of the test piece is not less than 40 mm.
The specimens shall be oriented to make the test piece as symmetrical as possib
...