SIST EN 17418:2021
(Main)Two-component epoxy and polyurethane adhesives for on-site repair of cracked timber structures - Testing, requirements and repair strength verification
Two-component epoxy and polyurethane adhesives for on-site repair of cracked timber structures - Testing, requirements and repair strength verification
This document specifies test methods and requirements for two-component epoxy and polyurethane adhesives for on-site repair of cracks in timber structures made of strength graded structural timber with rectangular cross-section, structural finger-jointed timber, glued solid timber and glued laminated timber made of softwood species by injection of the repair adhesive with glue line thicknesses up to 8 mm. The adhesive can also be used to rehabilitate cracks in the area of joints made by nails, screws, dowel-type fasteners and dowels with threads. The adhesive can also be used to fill gaps between the faces of structural components. This document addresses exclusively adhesives which fulfil the requirements according to Clause 8.
NOTE There is no sufficient experience with adhesives which do not fulfil the requirements in 8.4.4.
This document also covers the repair of surface treated wood. It does not cover the repair of preservative treated wood, modified and stabilized wood with considerably reduced swelling and shrinkage properties, e.g. acetylated wood, heat treated wood and polymer impregnated wood.
The adhesive is intended for the repair of load bearing timber structures not subjected to temperatures more than 60 °C over a longer time in service classes 1 and 2 according to EN 1995-1-1 which are loaded predominantly static or non-fatigue quasi static, see EN 1990 and EN 1991-1-1. A verification of quality and bond line integrity of the on-site repair bonding is given in an informative Annex A.
Zwei-Komponenten-Epoxid und Zwei-Komponenten-Polyurethan-Klebstoffe zur Reparatur von beschädigten Holzbauteilen auf der Baustelle - Prüfung, Anforderungen und Nachweis der Reparatur-Festigkeit
Dieses Dokument legt Prüfverfahren und Anforderungen für Zweikomponenten-Epoxid- und Zweikomponenten-Polyurethanklebstoffe für die Reparatur von Rissen in Holzkonstruktionen aus nach Festigkeit sortiertem Bauholz mit rechteckigem Querschnitt, keilgezinktem Bauholz, Balkenschichtholz und Brettschichtholz aus Nadelholz auf der Baustelle durch Injektion des Reparaturklebstoffs mit einer Klebstofffugendicke von bis zu 8 mm fest. Der Klebstoff kann auch zum Reparieren von Rissen im Bereich von Verbindungen, die durch Nägel, Schrauben, stiftförmige Verbindungen und Gewindestifte entstanden sind, verwendet werden. Der Klebstoff kann auch verwendet werden, um Fugen zwischen den Flächen von tragenden Bauteilen zu füllen. Dieses Dokument behandelt ausschließlich Klebstoffe, die die Anforderungen nach Abschnitt 8 erfüllen.
ANMERKUNG Es gibt keine ausreichende Erfahrung mit Klebstoffen, die die Anforderungen aus 8.4.4 nicht erfüllen.
Dieses Dokument ist außerdem anwendbar für die Reparatur von oberflächenbehandeltem Holz. Es ist nicht anwendbar für die Reparatur von mit Holzschutzmitteln behandeltem Holz, modifiziertem und vergütetem Holz mit deutlich verringerten Quell- und Schwindungseigenschaften, wie z. B. acetyliertes Holz, wärmebehandeltes Holz und polymerimprägniertes Holz.
Der Klebstoff ist für die Reparatur von tragenden Holzkonstruktionen vorgesehen, die in den Nutzungsklassen 1 und 2 nach EN 1995 1 1 nicht über eine längere Zeitspanne Temperaturen von mehr als 60 °C ausgesetzt sind und die überwiegend statisch oder ermüdungsfrei quasistatisch (siehe EN 1990 und EN 1991 1 1) belastet werden. Eine Überprüfung der Qualität und der Unversehrtheit der Klebfuge der Reparaturverklebung auf der Baustelle ist im informativen Anhang A enthalten.
Adhésifs bicomposants polyuréthanes et époxydiques pour la réparation sur site de structures en bois fissurées - Essais, exigences et vérification de la résistance des réparations
Le présent document spécifie des méthodes d’essai et des exigences relatives aux adhésifs polyuréthanes et époxydiques bicomposants destinés à la réparation sur site de fissures dans des structures en bois constituées de bois de structure à section rectangulaire classé pour sa résistance, de bois de structure abouté à entures multiples, de bois massif reconstitué et de bois lamellé collé à base de résineux, par injection de l’adhésif de réparation, avec des épaisseurs de joint de colle jusqu’à 8 mm. L’adhésif peut également être utilisé pour réhabiliter des fissures situées au niveau d’assemblages réalisés à l’aide de pointes, de tire-fonds, d’organes d’assemblage de type tige et de broches à filetage. L’adhésif peut aussi servir de joint épais entre les faces des composants structuraux. Le présent document traite exclusivement des adhésifs qui répondent aux exigences de l’Article 8.
NOTE L’expérience acquise jusqu’ici avec les adhésifs ne satisfaisant pas aux exigences de 8.4.4 n’est pas suffisante.
Le présent document traite également de la réparation des bois ayant reçu un traitement de surface. Il ne couvre pas la réparation des bois traités avec un produit de préservation, des bois modifiés et stabilisés ayant des propriétés de retrait et de gonflement fortement réduites, par exemple les bois acétylés, les bois traités thermiquement et les bois imprégnés de polymère.
L’adhésif est destiné à la réparation des structures portantes en bois non exposées à des températures supérieures à 60 °C sur une durée prolongée dans les classes de service 1 et 2 selon l’EN 1995 1 1, qui sont soumises à des charges essentiellement statiques ou quasi statiques ne mettant pas en jeu des phénomènes de fatigue, voir l’EN 1990 et l’EN 1991 1 1. L’Annexe A, informative, présente une vérification de la qualité et de l’intégrité du joint de collage d’un collage réalisé lors d’une réparation sur site.
Dvokomponentna epoksi in poliuretanska lepila za popravilo nalomljenih lesenih konstrukcij na kraju samem - Preskušanje, zahteve in preverjanje trdnosti popravljenih delov
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-maj-2021
Dvokomponentna epoksi in poliuretanska lepila za popravilo nalomljenih lesenih
konstrukcij na kraju samem - Preskušanje, zahteve in preverjanje trdnosti
popravljenih delov
Two-component epoxy and polyurethane adhesives for on-site repair of cracked timber
structures - Testing, requirements and repair strength verification
Zwei-Komponenten-Epoxid und Zwei-Komponenten-Polyurethan-Klebstoffe zur
Reparatur von beschädigten Holzbauteilen auf der Baustelle - Prüfung, Anforderungen
und Nachweis der Reparatur-Festigkeit
Adhésifs bicomposants polyuréthanes et époxydiques pour la réparation sur site de
structures en bois fissurées - Essais, exigences et vérification de la résistance des
réparations
Ta slovenski standard je istoveten z: EN 17418:2021
ICS:
83.180 Lepila Adhesives
91.080.20 Lesene konstrukcije Timber structures
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 17418
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2021
EUROPÄISCHE NORM
ICS 83.180
English Version
Two-component epoxy and polyurethane adhesives for
on-site repair of cracked timber structures - Testing,
requirements and repair strength verification
Adhésifs bicomposants polyuréthanes et époxydiques Zwei-Komponenten-Epoxid- und Zwei-Komponenten-
pour la réparation sur site de structures en bois Polyurethan-Klebstoffe zur Reparatur von
fissurées - Essais, exigences et vérification de la beschädigten Holzbauteilen auf der Baustelle -
résistance des réparations Prüfung, Anforderungen und Nachweis der Reparatur-
Festigkeit
This European Standard was approved by CEN on 8 February 2021.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17418:2021 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Symbols . 8
5 General requirements . 8
6 Classification . 8
7 Bond strength of adhesive-wood interface . 9
7.1 General . 9
7.2 Requirements . 9
7.2.1 Bond strength in longitudinal tensile shear tests . 9
7.2.2 Resistance to delamination . 9
7.2.3 Effect of wood shrinkage on the shear strength. 9
7.2.4 Effect of compression shear stress and climatic changes . 10
7.3 Test methods . 10
7.3.1 Determination of bond strength in longitudinal tensile shear test . 10
7.3.2 Determination of resistance to delamination . 10
7.3.3 Determination of the effect of wood shrinkage on the shear strength . 10
7.3.4 Determination of the effect of compression shear stress and climatic changes . 10
8 Tests on cohesive strength of monolithic adhesive specimens . 11
8.1 General . 11
8.2 Tensile tests . 11
8.2.1 Specimen . 11
8.2.2 Procedure. 12
8.2.3 Expression of results . 13
8.2.4 Requirements . 13
8.3 Compression tests . 13
8.3.1 Specimen . 13
8.3.2 Procedure. 13
8.3.3 Expression of results . 14
8.3.4 Requirements . 14
8.4 Block shear tests . 14
8.4.1 Specimen . 14
8.4.2 Procedure. 14
8.4.3 Expression of results . 14
8.4.4 Requirements . 15
9 Large scale component tests including drill core tests . 16
9.1 Straight beams with predefined glue lines . 16
9.1.1 Specimen . 16
9.1.2 Conditioning of the specimens . 17
9.1.3 Test procedure . 18
9.1.4 Expression of results . 18
9.1.5 Evaluation and requirements . 18
9.2 Large scale specimens with repaired glue lines . 19
9.2.1 General . 19
9.2.2 Straight beams with repaired glue lines . 19
9.2.3 Curved beams with repaired glue lines . 19
9.3 Block shear tests with water treated drill cores . 22
9.3.1 General . 22
9.3.2 Sampling . 22
9.3.3 Specimens . 22
9.3.4 Conditioning of specimens . 22
9.3.5 Test procedure . 23
9.3.6 Requirements . 23
9.4 Long term loading and residual strength tests . 23
9.4.1 General . 23
9.4.2 Specimens . 23
9.4.3 Test procedure . 24
9.4.4 Requirements . 24
10 Repair of cracks in dowel type fasteners connections . 25
10.1 General . 25
10.2 Specimen . 26
10.3 Procedure . 27
10.4 Expression of the test results . 28
10.5 Requirements . 28
11 Working properties of the adhesive . 29
11.1 General . 29
11.2 Determination of working life under reference conditions . 29
11.3 Determination of curing time under reference conditions . 29
11.4 Determination of time to fully cured state . 29
11.4.1 General . 29
11.4.2 Tensile tests . 29
11.4.3 Block shear tests . 29
11.4.4 Declared time to fully cured state . 30
12 Test report . 31
12.1 General . 31
12.2 Adhesive . 31
12.3 Preparation of specimens and testing procedure . 31
12.4 Test results . 31
Annex A (informative) On-site repair control test . 32
Bibliography . 33
European foreword
This document (EN 17418:2021) has been prepared by Technical Committee CEN/TC 193 “Adhesives”,
the secretariat of which is held by UNE.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2021, and conflicting national standards shall
be withdrawn at the latest by September 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
1 Scope
This document specifies test methods and requirements for two-component epoxy and polyurethane
adhesives for on-site repair of cracks in timber structures made of strength graded structural timber with
rectangular cross-section, structural finger-jointed timber, glued solid timber and glued laminated timber
made of softwood species by injection of the repair adhesive with glue line thicknesses up to 8 mm. The
adhesive can also be used to rehabilitate cracks in the area of joints made by nails, screws, dowel-type
fasteners and dowels with threads. The adhesive can also be used to fill gaps between the faces of
structural components. This document addresses exclusively adhesives which fulfil the requirements
according to Clause 8.
NOTE There is no sufficient experience with adhesives which do not fulfil the requirements in 8.4.4.
This document also covers the repair of surface treated wood. It does not cover the repair of preservative
treated wood, modified and stabilized wood with considerably reduced swelling and shrinkage
properties, e.g. acetylated wood, heat treated wood and polymer impregnated wood.
The adhesive is intended for the repair of load bearing timber structures not subjected to temperatures
more than 60 °C over a longer time in service classes 1 and 2 according to EN 1995-1-1 which are loaded
predominantly static or non-fatigue quasi static, see EN 1990 and EN 1991-1-1. A verification of quality
and bond line integrity of the on-site repair bonding is given in an informative Annex A.
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.
EN 302-1, Adhesives for load-bearing timber structures — Test methods — Part 1: Determination of
longitudinal tensile shear strength
EN 302-2, Adhesives for load-bearing timber structures — Test methods — Part 2: Determination of
resistance to delamination
EN 302-4, Adhesives for load-bearing timber structures — Test methods — Part 4: Determination of the
effects of wood shrinkage on the shear strength
EN 302-6, Adhesives for load-bearing timber structures — Test methods — Part 6: Determination of the
minimum pressing time under referenced conditions
EN 302-7, Adhesives for load-bearing timber structures — Test methods — Part 7: Determination of the
working life under referenced conditions
EN 302-8, Adhesives for load-bearing timber structures — Test methods — Part 8: Static load test of
multiple bond line specimens in compression shear
EN 383, Timber Structures — Test methods — Determination of embedment strength and foundation
values for dowel type fasteners
EN 408, Timber structures — Structural timber and glued laminated timber — Determination of some
physical and mechanical properties
EN 923, Adhesives — Terms and definitions
EN 13183-2, Moisture content of a piece of sawn timber — Part 2: Estimation by electrical resistance
method
EN 14080:2013, Timber structures — Glued laminated timber and glued solid timber — Requirements
EN 14358, Timber structures — Calculation and verification of characteristic values
EN 17334:2021, Glued-in rods in glued structural timber products — Testing, requirements and bond shear
strength classification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 923 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
two component epoxy adhesive
thermosetting synthetic resin derived from an exothermic polymerization reaction of an epoxide group
with amines, acid anhydrides, phenols, alcohols or thiols
3.2
two component polyurethane adhesive
2C-PUR
urethane polymers which are cross-linked by the reaction between polyol or polyamine with isocyanate
3.3
service class 1
climatic conditions characterized by a moisture content in the materials corresponding to a temperature
of 20 °C and the relative humidity of the surrounding air only exceeding 65 % for a few weeks per year
Note 1 to entry: In service class 1, which comprises typical indoor conditions, the average moisture content in
most soft-woods will not exceed 12 %.
[SOURCE: EN 1995-1-1:2004, 2.3.1.3, modified – Indoor conditions added in Note 1 to entry]
3.4
service class 2
climatic conditions characterized by a moisture content in the materials corresponding to a temperature
of 20 °C and the relative humidity of the surrounding air only exceeding 85 % for a few weeks per year
Note 1 to entry: In service class 2, to which most covered exterior conditions belong, the average moisture
content in most softwoods will not exceed 20 %.
[SOURCE: EN 1995-1-1:2004, 2.3.1.3, modified – Covered exterior conditions added in Note 1 to entry]
3.5
service class 3
climatic conditions leading to a higher moisture contents than in service class 2
[SOURCE: EN 1995-1-1:2004, 2.3.1.3]
3.6
glue line
adhesive layer between the wood members
[SOURCE: EN 301:2017, 3.7]
3.7
thick glue line
glue line of nominal thickness in the range of 0,3 mm up to the maximum tested thickness but not more
than 8,0 mm at the time of bonding
Note 1 to entry: This definition of a thick glue line is different from that in EN 301. Thick glue lines are achieved
by using spacers, grooves or similar devices with a thickness of 0,3 mm to 8,0 mm when two plain members are
glued together.
3.8
close contact glue line
glue line thickness of maximum 0,1 mm
Note 1 to entry: Close contact glue line is achieved by pressing together two plane wood members with a
clamping pressure of (0,8 ± 0,1) N/mm without grooves, spacers or similar device.
[SOURCE: EN 301:2017, 3.9]
3.9
bond line
glue line including the two intermediate zones between adhesive and wood
[SOURCE: EN 15425:2017, 3.6]
4 Symbols
a distance between loading and support, in millimetres (mm)
b specimen width of the net cross-section, in millimetres (mm)
f apparent compression strength, in newtons per square millimetre (N/mm )
c,app
f apparent embedment strength, in newtons per square millimetre (N/mm )
h,app
f embedment strength, in newtons per square millimetre (N/mm )
h,k
f apparent tensile strength, in newtons per square millimetre (N/mm )
t,app
f apparent shear strength, in newtons per square millimetre (N/mm )
v,app
F compression test failure load, in newtons (N)
c,max
F load in long term tests, in newtons (N)
perm
F tensile test failure load, in newtons (N)
t,max
Fu ultimate load, in newtons (N)
F shear test failure load, in newtons (N)
v,max
h specimen height, in millimetres (mm)
h component height, in millimetres (mm)
w
t specimen thickness of the net cross-section, in millimetres (mm)
t glue line thickness, in millimetres (mm)
b
σ ultimate bending stress, in newtons per square millimetre (N/mm )
m,u
σ ultimate tensile stress perpendicular to grain, in newtons per square millimetre (N/mm )
t,90,u
τ ultimate shear stress, in newtons per square millimetre (N/mm )
u
5 General requirements
Adhesives for structural purpose shall produce joints of such strength and durability that the integrity of
the bond in the rehabilitated element is maintained throughout the intended service life of the structure.
6 Classification
If the adhesive meets the requirements of Clauses 7 to 9, the adhesive shall be classified as type I. The
classification of adhesive consists of:
— number of this document;
— type of adhesive (I);
— temperature in bond creep rupture test in °C;
— working properties (Adhesives tested for all working properties according to Clause 11 are specified
by the letter “w” at the end of the designation code.).
EXAMPLE EN 17418-I-60-w.
NOTE Presently, exclusively a temperature testing/classification for 60 °C is covered by the standard.
The wood species for which the tested adhesive can be used shall be given in the adhesive manufacturer’s
declaration.
7 Bond strength of adhesive-wood interface
7.1 General
Adhesives complying with this document shall meet the performance requirements specified in 7.2.1 to
7.2.4 when tested in accordance with the following test methods:
a) longitudinal tensile shear test (see 7.3.1) using bonded specimens made from beech (Fagus sylvatica
L.);
b) delamination test (see 7.3.2) on bonded specimens made from Norway spruce (Picea abies L.
H.KARST). The test with Norway spruce also covers silver fir (Abies alba MILL.) and Scots pine (Pinus
sylvestris L.). If the adhesive is to be used on wood from other conifers species or treated wood, also
prepare four laminated members using representative samples from those species or wood treated
that way and perform the delamination test according to 7.3.2;
c) shrinkage stress test (see 7.3.3) on bonded specimens made from Norway spruce (Picea abies
L. H.KARST);
d) multiple compression shear test (see 7.3.4) on bonded specimens made from beech (Fagus sylvatica
L.).
The adhesives shall be applied according to the manufacturer`s instructions.
7.2 Requirements
7.2.1 Bond strength in longitudinal tensile shear tests
The tensile shear strength values of close contact glue lines, 1,0 mm and 4,0 mm thick glue lines
determined according to 7.3.1 shall meet the requirements given in Table 1.
Table 1 — Minimum mean tensile shear strengths for close contact and gap joints on beech
)
specimens (in N/mm
Close contact Thick glue line Thick glue line
Treatment
glue line 1,0 mm 4,0 mm
Serial No
EN 302-1
Type Ι Type Ι Type Ι
A1 10,0 8,0 6,0
A2 6,0 4,0 3,0
A3 8,0 6,4 4,8
A4 6,0 4,0 3,0
A5 8,0 6,4 4,8
A7 8,0 5,5 4,5
7.2.2 Resistance to delamination
The limits on delamination for specimens of any glue line thickness determined according to 7.3.2 shall
be less or equal than 5 % in any specimen.
7.2.3 Effect of wood shrinkage on the shear strength
The mean shear strength after climatic treatment determined according to 7.3.3 shall not be lower than
1,5 N/mm .
7.2.4 Effect of compression shear stress and climatic changes
When tested in accordance with 7.3.4, not more than one of the six specimens may fail during the test
period. The mean creep deformation of all the bond lines in each of the remaining test specimens shall
not exceed 0,05 mm after the test.
If a failure within a specimen occurs as a solid wood failure without any interference with the bond line,
the specimen shall not be counted and four of the five remaining specimens shall fulfil the requirements.
In the case that more than two specimens in a test series collapse due to solid wood failure (low wood
quality), the whole test shall be repeated.
7.3 Test methods
7.3.1 Determination of bond strength in longitudinal tensile shear test
The tests shall be made in accordance with EN 302-1, but with glue line thicknesses close contact, 1,0 mm
and 4,0 mm. The specimens with glue line thickness 4 mm shall be prepared with a pressureless
preparation.
NOTE Applying a narrow slot (width about 2 mm, depth about 2 mm) between the end of the groove and the
wide side of the adherent has shown to be a suitable method for ensuring pressureless bonding of the specimens.
The method of preparation of the specimens is described in EN 302-1. Following this method, the
specimens are built-up with the adhesive layer covered by two adherents of the same thickness (on top
and below the adhesive layer).
7.3.2 Determination of resistance to delamination
The tests shall be made in accordance with EN 302-2, but with glue line thicknesses close contact and
4 mm. The close contact glue line may be replaced by a test with a defined (spacers) glue line thickness
of 0,2 mm. The specimens with glue line thickness 4 mm shall be prepared with a pressureless
preparation. Different from EN 302-2 the tests with bonded members with close contact or 0,2 mm glue
line shall be performed exclusively with two specimens with long assembly time.
7.3.3 Determination of the effect of wood shrinkage on the shear strength
The tests shall be made in accordance with EN 302-4, but with a glue line thickness of 2 mm.
7.3.4 Determination of the effect of compression shear stress and climatic changes
The tests shall be made in accordance with EN 302-8 but with a temperature of 60 °C to 62 °C in the first
cycle and a glue line thickness of 2 mm.
The test may be replaced by the tests according to EN 17334:2021, 7.3.4 and EN 17334:2021, Clause 9.
8 Tests on cohesive strength of monolithic adhesive specimens
8.1 General
Monolithic adhesive specimens for tensile tests, compression tests and shear test are manufactured. The
tests are used for evaluating tensile strength, and shear strength of the bulk adhesive.
NOTE As the adhesive layer acts as separate component/layer subject to any combined stress state the bulk
adhesive strength properties are equally important as the bond/interface performance versus the timber.
8.2 Tensile tests
8.2.1 Specimen
Figure 1 shows the geometry and dimensions of the monolithic compact shoulder shaped tension
specimen.
Dimensions in millimetres
a) isometric projection and loading scheme b) dimensions of the specimen
Key
1 clamping area
b width of the smallest cross-section in millimetres (mm) = 10 mm
t depth in millimetres (mm) = 15 mm to 20 mm
F tensile force
t
Figure 1 — Shape, dimensions and loading scheme of the tensile specimens
The specimens shall either be manufactured by pouring the mixed adhesive in specifically shaped
negative forms made of material (e.g. polytetrafluoroethylene (PTFE)) which does not exhibit any bond
with the adhesive, see Figure 2. Alternatively, the specimens can be manufactured by cutting or milling
to the required size and shape from rectangular monolithic adhesive bars produced in a first step by
pouring the mixed adhesive in a bar shaped form, see Figure 3. Specimens shall be manufactured at
(20 ± 2) °C.
Figure 2 — Specimen manufacture by means of specifically shaped negative forms
a) Preparation b) Finished bar
Figure 3 — Prefabrication of adhesive bars for manufacturing of specimens
8.2.2 Procedure
The tensile tests are performed in two different test series I and II. In test series I the specimens are tested
after conditioning at an ambient temperature of (20 ± 2) °C for at least four weeks. The specimens of test
series II are first conditioned at an ambient temperature as for test series I and are then additionally
conditioned at 60 °C to 62 °C for 6 h immediately preceding testing. The specimens of this test series are
tested directly after the conditioning at 60 °C to 62 °C at ambient room temperature. In each test series I
and II, three specimens shall be tested.
The specimen is mounted in the test machine with a clamping length of the grips of 8 mm and a width
being at least the width of the specimen (34 mm). The axial tensile load is applied until failure. The load
shall be increased with a constant rate of movement of the loading head. The time to failure shall be not
less than 30 s but not more than 120 s.
8.2.3 Expression of results
The apparent tensile strength of the specimen is calculated as:
F
t, max
f =
(1)
t,app
bt⋅
where
F is the tensile load at failure, in newtons (N);
t,max
b and t are the edge lengths of the net cross-section in the necked region, in millimetres (mm).
8.2.4 Requirements
The requirements for the tensile strength values of test series I and II are specified in Table 2 for epoxy
and polyurethane adhesives. No individual value in either series I or II shall be less than 0,85 times of the
respective mean value.
8.3 Compression tests
8.3.1 Specimen
Figure 4 shows the geometry and dimensions of the monolithic compact, cubic compression test
specimen. The manufacture of the specimen is analogous to 8.2.1.
8.3.2 Procedure
The compression tests are performed in two different test series I and II, see 8.2.2.
The specimen is mounted in the test machine according to Figure 4. The axial compression load is applied
with a constant rate of displacement of the cross head until failure.
Key
t = 20 mm h = 40 mm
b = 35 mm Fc compression force
Figure 4 — Test scheme and dimensions of the compression specimens
8.3.3 Expression of results
The apparent compressive strength of the specimen is calculated as:
F
c, max
f = (2)
c,app
bt⋅
where
F is the compression load at failure, in newtons (N);
c,max
b and t are the edge lengths of the net cross-section, in millimetres (mm).
8.3.4 Requirements
The requirements for the compressive strength values of test series I and II are specified in Table 2 for
epoxy and polyurethane adhesives. No individual value in either series I or II shall be less than 0,85 times
of the respective mean value.
8.4 Block shear tests
8.4.1 Specimen
Figure 5 shows the geometry and dimensions of the monolithic compact, cubic block shear test specimen.
The manufacture of the specimens is analogous to 8.2.1.
8.4.2 Procedure
The shear tests are performed in two different test series I and II, see 8.2.2. The specimen is mounted in
the test machine according to Figure 5. The load is applied with a constant rate of displacement of the
cross head until failure.
8.4.3 Expression of results
The apparent shear strength of the specimen is calculated as:
F
v, max
f =
(3)
v,app
bl⋅
v
where
F is the shear load at failure, in newtons (N);
v,max
l and b are the edge lengths of the net cross-section, in millimetres (mm).
v
Dimensions in millimetres
Key
l = 20 mm
v
b = 35 mm
h = 40 mm
Fv shear load
Figure 5 — Test scheme and dimensions of the shear specimens
8.4.4 Requirements
The requirements for the shear strength values of test series I and II are specified in Table 2 for epoxy
and polyurethane adhesives. No individual value in either series I or II shall be less than 0,85 times of the
respective mean value.
Table 2 — Requirements for the tensile, compression and shear strength values of test series I
and II
Mean strength in N/mm
Type of loading Adhesive Test series I (20 °C) Test series II (60 °C)
f f
mean mean
2C-EP 55 49,5
Tensile test
2C-PUR 25 22,5
2C-EP 85 55
Compression test
2C-PUR 25 16
2C-EP 40 28
Shear test
2C-PUR 25 17,5
9 Large scale component tests including drill core tests
9.1 Straight beams with predefined glue lines
9.1.1 Specimen
9.1.1.1 Build-up and components
Each specimen shall be produced by bonding two straight glulam beams (here components) along the
narrow faces whereby the secondary i.e. repair glue lines shall have different nominal thicknesses which
are constant along the beam length. The dimensions of the components and of the specimen are shown
in Figure 6. The glulam components shall conform to EN 14080 and the strength class shall be either
GL 28h or GL 30h.
In order to avoid premature bending failures instead of the intended shear failures the specimen shown
in Figure 6 may be reinforced symmetrically at the bending tension edge e. g, by (screw-)glued-on solid
wood boards or LVL. The reinforcement has to be considered appropriately in the evaluation of the test
results.
The wood species shall be spruce/fir (Picea abies/Abies alba). The surfaces of the bonded narrow faces
of the components shall not be specifically prepared by planing or sanding and shall be aged after delivery
for at least 3 months at sheltered climate conditions. The moisture content of the components shall be
minimally 8 % and maximally 15 % at the time of manufacture of the specimens. The moisture content of
each component shall be determined by a total of 10 measurements using a calibrated moisture meter
and following the method described in EN 13183-2. The accuracy of the moisture meter shall be
within ± 2 % moisture content. Five moisture measurements shall be performed at a penetration depth
of the electrodes of 1 cm, the other five measurements shall be performed at 2 cm depth. The moisture
content of the component shall be calculated as the mean value of all moisture measurements.
The nominal glue line thicknesses t to be manufactured are 0,1 mm (close contact), 2 mm, 4 mm, and
b
8 mm. For each glue line thickness 3 specimens shall be produced.
Dimensions in millimetres
Key
F load
a distance between loading and support
1 loading and support plates, length 240 mm to 280 mm
Figure 6 — Test scheme and dimensions of a straight beam
9.1.1.2 Manufacture
The manufacture shall be performed in sheltered environment at a temperature of minimally 18 °C and
maximally 25 °C. The two components of each specimen with nominal thicknesses of the secondary glue
line of 2 mm, 4 mm and 8 mm shall be positioned vs. each other with a distance according to the nominal
secondary glue line thickness. Dust may be removed prior to bonding by oil-free pressurized air.
NOTE The correct distances can be achieved by small wooden distance pieces inserted at both beam ends and
in the centre part.
Then the narrow edges of the gap between the components are sealed with a suitable tape or similar
provisions (e.g. spattling compound) and the adhesive is injected through openings of the sealing. It shall
be ensured, that the complete gap with a thickness of 2 mm to 8 mm is filled with adhesive. This is
achieved by drilling holes through the sealing in rather regular distances of about 10 cm to 30 cm. The
adhesive infill by pneumatic pressure pump is started at hole i = 1 at one beam end. When adhesive pours
out from the next adjacent hole i + 1, the first hole is permanently closed by a wooden pin. Then a new
infill is started in hole i + 1 until pour out at hole i + 2 occurs and so on.
The specimens with close contact secondary glue line shall be manufactured by applying the adhesive by
roller or comb to one of the narrow faces of both components. Then the components are cramped
together with an applied pressure of maximally 0,2 N/mm . The pressure application can be performed
by several methods, e.g. hydraulic press-bed or single-pressing frames. The cramping pressure shall be
maintained for the time specified by the adhesive manufacturer.
The curing time of the adhesive shall conform to the provisions of the adhesive manufacturer and shall
take into consideration the effect of the glue line thickness.
After curing of the adhesive, the wide sides of the specimen shall be planed in order to provide a clearly
visible secondary glue line and hereby especially a clearly visible wood and secondary glue line transition
zone/interface to enable a detection of possible crack propagation close to or in the secondary glue line
in the bending tests.
9.1.2 Conditioning of the specimens
Two different climate conditionings (test series I and II) shall be applied to the specimens equally for all
secondary glue line thicknesses.
Two specimens of each secondary glue line thickness sample shall be conditioned in sheltered climate
conditions, labelled test series I, at 18 °C to 25 °C and a relative humidity of the surrounding air not below
20 % and not above 75 %, respectively. The conditioning time shall conform to the specifications of the
adhesive manufacturer and shall ensure a fully (>90 %) cured state of the adhesive.
In test series II, one specimen of each secondary glue line thickness sample shall be stored in full
weathered unsheltered conditions (service class 3 according to EN 1995-1-1) in Central European
geographical location between latitude 45° and 60°, or equivalent, for a time period of 12 months. During
the storage time, the temperature and relative humidity shall be recorded.
After storage in full weathered conditions the specimens of test series II shall be conditioned until a wood
moisture content of (12 ± 3) % is reached. The wood moisture content shall be determined by a calibrated
electrical moisture meter with ten measurements (five measurements at 1 cm and 2 cm penetration
depth within a distance of between 2 cm and 4 cm from the secondary glue line on the long side of the
beam) at equally spaced locations distributed along the total specimen length. The moisture content of
the specimen shall be evaluated as the average value of all measurements.
9.1.3 Test procedure
The specimens shall be tested in bending shear in a 4-point bending test according to the
dimensions/specifications given in Figure 6. The loading procedure shall be as specified in EN 408 with
a constant rate of load piston movement; ultimate load shall be achieved in a timespan of (300 ± 120) s.
The beam deflection shall be measured at midspan at either the bending compression edge (then one
transducer at mid-width) or at mid-depth at both wide faces. The load-midspan deflection curve shall be
recorded. The fracture initiations and the failure progression shall be monitored and recorded at both
wide sides by at least one person per side. Hereby special consideration shall be given to the eventual
crack initiation and propagation in the vicinity of or in the secondary glue line.
9.1.4 Expression of results
Based on the ultimate load F the ultimate shear and bending stresses are calculated from:
u
3 F
u
τ = (4)
u
4h⋅⋅b
and
3Fa⋅
u
σ =
(5)
mu, 2
bh⋅
where
h 2 ht+ (6)
wb
NOTE The maximum stresses τu and σm,u are not called strength values as the failure can occur either as a pure
bending or a pure shear failure or as a combined bending and shear failure.
9.1.5 Evaluation and requirements
The evaluation shall be done on each of the two test series (I and II).
In case of a shear failure in the bulk glue line area (fracture surface in the bond l
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