EN 16613:2025

SLOVENSKI STANDARD
01-september-2025
Steklo v gradbeništvu - Lepljeno steklo in lepljeno varnostno steklo - Določevanje
mehanskih lastnosti vmesnih slojev
Glass in building - Laminated glass and laminated safety glass - Determination of
interlayer viscoelastic properties
Glas im Bauwesen - Verbundglas und Verbundsicherheitsglas - Bestimmung der
viskoelastischen Eigenschaften von Zwischenschichten
Verre dans la construction - Verre feuilleté et verre feuilleté de sécurité - Détermination
des propriétés viscoélastiques des intercalaires
Ta slovenski standard je istoveten z: EN 16613:2025
ICS:
81.040.20 Steklo v gradbeništvu Glass in building
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 16613
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2025
EUROPÄISCHE NORM
ICS 81.040.20 Supersedes EN 16613:2019
English Version
Glass in building - Laminated glass and laminated safety
glass - Determination of interlayer viscoelastic properties
Verre dans la construction - Verre feuilleté et verre Glas im Bauwesen - Verbundglas und
feuilleté de sécurité - Détermination des propriétés Verbundsicherheitsglas - Bestimmung der
viscoélastiques des intercalaires viskoelastischen Eigenschaften von Zwischenschichten
This European Standard was approved by CEN on 7 April 2025.

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, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16613:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 7
5 Test procedure . 9
5.1 General. 9
5.2 Test specimens . 11
5.3 Test method . 11
5.3.1 Glass transition temperature T (Step 1) . 11
g
5.3.2 Determination of the temperature and time dependent shear modulus G (T,t) . 11
int
6 Evaluation of the shear transfer characteristics . 15
6.1 Determination of the temperature and time dependent shear modulus G (T,t) . 15
int
6.2 Load durations and temperature ranges . 15
7 Test report . 16
Annex A (normative) Bending creep method for the determination of the interlayer
properties . 17
Annex B (normative) Preparation of test specimens . 26
Annex C (informative) Time-temperature-superposition principle and Prony series . 27
Annex D (informative) Interlayer mechanical properties at different frequencies for a
chosen temperature . 30
Annex E (informative) Determination of the displacement of the point of contact between
the support rollers and the plate . 31
Bibliography . 33

European foreword
This document (EN 16613:2025) has been prepared by Technical Committee CEN/TC 129 “Glass in
building”, the secretariat of which is held by NBN.
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 November 2025, and conflicting national standards
shall be withdrawn at the latest by November 2025.
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.
This document supersedes EN 16613:2019.
a) The test procedure has been changed from tensile vibration to parallel-plate oscillation.
b) A more detailed description of the test procedure is provided comprising four subsequent steps.
c) Annex A has been reviewed and is used for non-isotropic and multilayer interlayer materials as well
as Step 4 in the main test procedure. It provides the methods to calculate the effective thickness,
shear transfer coefficient 𝜔𝜔, the coupling factor 𝜂𝜂 and the interlayer shear modulus G .
int
d) Annex C details the procedure to obtain the master curve and the Prony parameters.
e) The new Annex D will help determine mechanical properties used for calculation of noise reduction.
f) Annex E provides guidance for a precise geometrical assessment of a deflected specimen.
g) Interlayer stiffness family classification criteria have been removed.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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, Türkiye and the
United Kingdom.
Introduction
The purpose of this document is to provide viscoelastic properties of interlayer materials for structural
design of laminated glass.
In addition, it provides a method to calculate interlayer mechanical properties at different frequencies
that can be used for calculation of sound reduction indices.
1 Scope
This document specifies a test method for determining the mechanical viscoelastic properties of
interlayer materials. The interlayers under examination are those used in the production of laminated
glass or laminated safety glass. The shear characteristics of interlayers are needed to design laminated
glass in accordance with EN 16612:2019 and EN 19100 (all parts).
Parameters of the Prony series, widely used in numerical simulation, can be derived from the
measurements in Annex C.
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 1288-3, Glass in building — Determination of the bending strength of glass — Part 3: Test with
specimen supported at two points (four point bending)
EN ISO 6721-1:2019, Plastics — Determination of dynamic mechanical properties — Part 1: General
principles (ISO 6721-1:2019)
ISO 6721-10, Plastics — Determination of dynamic mechanical properties — Part 10: Complex shear
viscosity using a parallel-plate oscillatory rheometer
ISO 6721-11, Plastics — Determination of dynamic mechanical properties — Part 11: Glass transition
temperature
EN 16612:2019, Glass in building — Determination of the lateral load resistance of glass panes by
calculation
ISO 18437-6, Mechanical vibration and shock — Characterization of the dynamic mechanical properties
of visco-elastic materials — Part 6: Time-temperature superposition
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 6721-1:2019 and
ISO 18437-6 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
glass transition temperature
interval of temperature in which a material changes from a rubbery state to a solid state or vice versa
3.2
interlayer shear transfer coefficient
coefficient between 0 and 1 describing the ability of an interlayer material to transfer shear forces
between the glass plies of a laminated glass pane when submitted to bending
3.3
relaxation modulus
ratio of the time-dependent stress to an imposed constant strain of the interlayer
3.4
complex modulus
ratio of dynamic stress and dynamic strain of a viscoelastic material that is subjected to a sinusoidal
vibration
3.5
storage modulus
real part of the complex modulus
3.6
loss modulus
imaginary part of the complex modulus
3.7
phase angle
phase difference between the dynamic stress and the dynamic strain in a viscoelastic material subjected
to a sinusoidal oscillation (δ)
Note 1 to entry: See Figure 2.
Note 2 to entry: The phase angle is expressed in radians (rad).
Note 3 to entry: In a dynamic experiment, it is the angle between the complex modulus G* and the projection of its
elastic part, the storage modulus part G’.
3.8
loss factor
tangent of the phase angle, also expressed as the ratio of the dynamic loss modulus G” over the dynamic
storage modulus G’
Note 1 to entry: See Figure 1.
Note 2 to entry: The loss factor is expressed as a dimensionless number.
3.9
shift factor
value (positive or negative) of the horizontal displacement of each DMTA curve along the frequency axis
to form the master curve
3.10
master curve
curve obtained by shifting isothermal DMTA curves measured at different frequencies and at a selected
reference temperature
3.11
time-temperature superposition
principle which enables prediction of material behaviour outside the testable range
3.12
Prony series
formula that allows calculation of the shear modulus based on Prony parameters
3.13
Prony parameters
parameters to evaluate the shear relaxation modulus from the Prony series, including the normalized
moduli g , relaxation times τ and the initial shear modulus G
i i 0
4 Symbols and abbreviations
a(Τ) Temperature dependent, horizontal shift factor in the time-temperature
superposition principle
b Width of the test specimen
b Average width of the plate
ave
lcor Corrected distance between supporting rollers in case of bent glass plate
l Reduction of the span per each supporting roller
red
C , C Empirical constants of the WLF-TTS visco-elastic formula
1 2
d Distance of the mid-plane of the glass plies from the mid-plane of the laminated glass
composed of two plies of the same thickness
d Distance of the mid-plane of the glass ply 1 from the mid-plane of the laminated glass
d Distance of the mid-plane of the glass ply 2 from the mid-plane of the laminated glass
d Distance of the mid-plane of the glass ply 3 from the mid-plane of the laminated glass
D Flexural stiffness at “no shear” condition
abs
D Flexural limit at “full shear” condition
full
Di Flexural stiffness of the glass ply i
DMTA Dynamic Mechanical Thermal Analysis (-TS: temperature sweep, -AS: amplitude
sweep, -TFS: temperature-frequency sweep)
DSC Differential Scanning Calorimetry
e Deflection under self weight
dl
e Deflection under applied load
f
EET Enhanced Effective Thickness method
E Young’s modulus of glass
E Activation energy
a
E Young's modulus of the interlayer material
int
f Frequency
F Four point bend test load
g Normalized shear moduli
i
G*, |G*| Shear complex modulus
G' Shear storage modulus
G” Shear loss modulus
G Initial shear modulus (at a time 0)
G Equilibrium modulus (at infinite time)
∞
G Shear relaxation modulus of the interlayer material
int
h Thickness of glass pane of laminated glass composed of n plies of the same thickness
h Nominal thickness of pane 1 of an insulating glass unit or ply 1 of a laminated glass
h Nominal thickness of pane 2 of an insulating glass unit or ply 2 of a laminated glass
h Nominal thickness of pane 3 of an insulating glass unit or ply 3 of a laminated glass
h Effective thickness of laminated glass for calculation of stress
ef,σ
h Effective thickness of laminated glass for calculation of deflection
ef,w
h Effective thickness of laminated glass deflecting under load
ef,wt
h Nominal thickness of pane i of an insulating glass unit or ply i of a laminated glass
i
h , h , h Thickness of the interlayer
int int,1 int,2
l Distance between centre lines of bending rollers
b
l Distance between centre lines of supporting rollers
l Distance between two original points of contact of the supporting rollers and the
cor
glass after deformation of the glass
l Reduction of the span per each supporting roller
red
n Number of plies (only in Annex A) and number of spring-damper elements (only in
Annex C)
p Self weight of the plate
P is the polynomial coefficient of the shear storage modulus of degree j, with j ranging
r,j
from 0 to 7;
P is the polynomial coefficient of the shear loss modulus of degree j, with j ranging
s,j
from 0 to 7;
r Radius of the curved glass deflected under self weight
r Radius of the roller
r
R Universal gas constant
t Load duration
Time needed to apply load
tr
T Temperature in °C
T Crystallization temperature
c
T Glass transition temperature
g
T Temperature in Kelvin
k
T Melting temperature
m
T Reference temperature
r
T Reference temperature
ref
T Reference temperature in Kelvin
k,r
TTS Time-temperature superposition
Poisson’s number of the interlayer material
νint
ν Poisson’s number of glass material
WLF-TTS Williams-Landel-Ferry TTS
x Axis x illustrating the horizontal position of the test specimen
x Distance between the first supporting roller and the first bending roller
F1
x Distance between the first supporting roller and the second bending roller
F2
y Axis y illustrating vertical displacement
y Deflection under self weight
c,g
y' Angular deformation under self weight
dl
y'p Angular deformation under two punctual loads
y' Formula of the curvature of the support roller
r
y' Total angular deformation under self weight and punctual loads
t
y Total deflection under self weight and applied load
tot
y Total measured deflection under self weight and applied load
tot,m
β Scaling factor
δ Phase angle
η Coupling coefficient used in Annex A (EET)
η Coefficient of viscosity used in Annex C (Maxwell model)
v
η Coupling coefficient for laminated glass composed of two plies
η3 Coupling coefficient for laminated glass composed of three plies
η Coupling coefficient for laminated glass composed of n plies with the same thickness
n
Ψ Boundary coefficient for beam made of n plies
b
σ Calculated stress
τ Relaxation times
i
ω Interlayer shear transfer coefficient
ω Angular frequency (only in Annex C)
f
5 Test procedure
5.1 General
The general methodology of the test used is provided in EN ISO 6721-1. DMTA measurement is
performed preferably following ISO 6721-10, parallel plate oscillation.
Alternatively, the non-resonance methods ISO 6721-6 (shear vibration), ISO 6721-4 (tensile vibration),
ISO 6721-7 (torsional vibration) can be used.
NOTE 1 The commonly used interlayers are generally isotropic materials. Depending of the choice of
measurement method, the interlayer shear or Young’s modulus can be converted into each other using
Formula (1).
E
int
(1)
G =
int
21+ v
( )
int
Where ν is the Poisson’s number of the interlayer. ν can be approximated with 0,49, which leads to
int int
the approximation:
EG≈ 3 (2)
int int
Scientifically, Poisson’s number depends on the temperature, but for the purpose of structural design of
laminated glass, this effect can be ignored.
There are some interlayers which cannot be formed into test pieces or which are not stable with
exposed edges in such small sizes. For these interlayer materials, the relevant interlayer properties can
be determined by calculation from the results of bending tests. Depending on the method of calculation
used for design of laminated glass, the relevant shear characteristics may be determined according to
Annex A.
DMTA measurements devices are limited in frequency range, with guidance provided in each part of the
ISO 6721 series as cited above. In order to obtain modulus values at higher or lower frequencies, time-
temperature superposition (TTS) analysis is applied. From a set of temperature-frequency curves, the
time dependence of viscoelastic properties is calculated.
The here presented TTS is valid for thermo-rheologically simple materials. The material shall be linear
viscoelastic under the deformations of interest, i.e. the deformation shall be expressed as a linear
function of the stress by applying very small strains.
When applying WLF-TTS, shift factors should be used within the glass-transition temperature range. At
a temperature below the glass-transition temperature, other TTS such as the Arrhenius model may be
used.
The determination of the viscoelastic properties of interlayer materials implies generally the following
steps:
— Step 1: DSC should be performed to determine thermomechanical phases (crystalline, amorphous)
and characteristic temperatures (glass transition T , crystallization T and melting temperature T );
g c m
additionally DMTA-TS to determine thermomechanical phases (crystalline, amorphous) and
characteristic temperatures (glass transition T , crystallization T and melting temperature T ).
g c m
— Step 2: DMTA-AS to check for linear viscoelasticity (linearity in stress-strain and time)
— Step 3: DMTA-TFS to acquire a set of curves depending on temperature and frequency. A
subsequent TTS treatment with master curving is applied to deduce the time-temperature
superposition law(s) and Prony series (if needed), see Annex C.
NOTE 2 The shear relaxation modulus values G used for finite-element calculations, or other advanced
int
calculation methods, can be derived from the Prony series.
— Step 4: Conduction of large scale validation tests (bending creep).
For non-isotropic materials a direct measurement of the shear modulus shall be performed. This can be
performed with DMTA or according to Annex A.
NOTE 3 For materials from which no small specimens can be produced, Step 4 can be considered as sufficient
(see Annex A).
5.2 Test specimens
The test specimens shall be manufactured from samples representative of normal interlayer material
production. The test specimens shall be processed under normal laminating conditions according to
Annex B.
The thickness, h , of the test specimens should be not less than 0,50 mm thick and not more than
int
2,0 mm thick. The layering and stacking of the interlayer material to achieve an appropriate thickness
shall be representative of normal production processes.
The test specimen size and tolerances on dimensions shall be determined according to the
requirements of ISO 6721-10.
Two sets of test specimens are required. One set of three test specimens is used for determining the
glass transition temperature, T , (see 5.3.1). The other set of one test specimens is used for the
g
evaluation of the G (T ,t) curve (see 5.3.2).
int r
Prior to testing, adequate hygrothermal conditioning of test samples is essential for a reproducible
experimental examination. Important aspects for the conditioning are the level of cure and cross linking
of the polymer and the polymer moisture content at the intended level. The manufacturer's storage
instructions shall be followed.
The sample shall be first processed, stored for stabilization during a period according to the interlayer
manufacturer and conditioned for a period of one week for all interlayer types in the laboratory.
5.3 Test method
5.3.1 Glass transition temperature T (Step 1)
g
Initial tests shall be conducted on at least three test specimens according to ISO 6721-11 to determine
the glass transition temperature of the interlayer material. This is used to refine the temperatures
assessed in 5.3.2. Alternatively, the DSC measurement performed following EN ISO 11357-2 can be
used. Following the results of the measurement, the heating rate and temperature range of the DMTA-
TFS (Step 3) can be decided.
NOTE 1 If the interlayer material is in a non-vitreous state, it might not be possible to determine a glass
transition temperature.
NOTE 2 A rigorous TTS procedure is only valid for thermo-rheological simple material. Only one phase
transition of the first order might be present, like vitreous transition or fusion.
NOTE 3 In the case of polymeric blends (mixture), block copolymers or other copolymers with specific
monomer distributions, each polymeric component will have their specific rheological behaviour as a function of
temperature. TTS does not apply to such blends or materials.
The temperature program is generally set between −40 °C and +100 °C with a heating rate of 3 K/min.
The frequency should be set to 1 Hz and the amplitude should be in the linear-viscoelastic range. The
temperature sweep experiment should typically be executed from the upper temperature to the lower
temperature of the tested range. Following the results of the measurement, the heating rate and
temperature range of the DMTA-TFS (Step 3) can be decided.
5.3.2 Determination of the temperature and time dependent shear modulus G (T,t)
int
5.3.2.1 General
A series of tests should be conducted according to ISO 6721-10 in combination with bending creep test
to eventually evaluate G (T,t) for a range of load durations t (or frequencies f), and a range of
int
temperatures, T.
5.3.2.2 Amplitude sweeps measurement using DMTA-AS method (Step 2)
DMTA-AS measurement is performed to ensure that the testing regime (temperature, frequency) is
within the linear viscoelastic region of mechanical behaviour.
Amplitude sweeps with testing frequency of 𝑓𝑓 = 1 Hz are undertaken at different temperatures (𝑇𝑇𝑔𝑔 –
40 °C; 𝑇𝑇 ; 𝑇𝑇 + 40 °C). These temperatures are between −40 °C and +80 °C. The amplitude may be set for
g g
most testing modes and interlayer materials in the region of 0,01 % to 0,3 %.
5.3.2.3 Temperature-frequency sweeps measurement using DMTA-TFS method (Step 3)
DMTA-TFS measurement is performed to determine the time and temperature dependent material
behaviour. The test temperatures for the temperature-frequency sweeps shall be selected according to
the thermo-mechanical regions of the polymer as found via Step 1.
The testing should start at high temperatures and go to low temperatures to minimize effects of
physical ageing of the polymer below T . A holding phase of 5 min to 10 min will be applied before to
g
decrease the temperature.
The frequency range evaluated should at least range from 0,1 Hz to 10 Hz (or the corresponding
angular frequencies) and comprise 10-15 frequencies per temperature evaluated. Eigenfrequencies
should be checked beforehand.
In the case of PVB material, general conditions are 𝑇𝑇 between 𝑇𝑇 − 40 °C and 𝑇𝑇 + 40 °C. 𝑇𝑇 is usually
g g g
around 20 °C but depends on the plasticizer content. It is advised to conduct a temperature test
program with temperature steps of 2 °C to 5 °C and a maximum cooling rate of 2 K/min.
In the case of EVA material, general conditions are between 𝑇𝑇 + 20 °C and 𝑇𝑇 + 100 °C. 𝑇𝑇 is usually
g g g
around −40 °C but depends on the ratios of the compounds. It is advised to conduct a temperature test
program with temperature steps of 2 °C to 5 °C and a maximum cooling rate of 2 K/min.
In the case of ionomer material, general conditions are 𝑇𝑇 between 𝑇𝑇 - 50 °C and 𝑇𝑇 + 40 °C. It is advised
g g
to conduct a temperature test program with temperature steps of 2 °C to 5 °C and a maximum cooling
rate of 2 K/min. For this material the testing may start from low temperatures and go to high
temperatures.
The measurement procedure gives access to the storage modulus (G', elastic material component) and
the loss modulus (G”, viscous material component). The ratio G”/G' gives the loss factor tanδ (δ, phase
angle or mechanical damping factor).
NOTE 1 Loss factor is illustrated in Figure 1. Phase angle is illustrated in Figure 2.
NOTE 2 A shift of the series is often observed near the T . It is due to an entropic contribution to the polymeric
g
chain retraction force which adds to the free energy.

Key
δ phase angle, rad
G’ shear storage modulus, MPa
G” shear loss modulus, MPa
|G*| shear complex modulus, MPa
Figure 1 — Loss factor
Key
t time, s
1 dynamic stress, MPa
2 dynamic strain, dimensionless
δ phase angle, rad
f frequency, Hz
Figure 2 — Phase angle
From the temperature-frequency measurement sets, master curves for G’ and G” at the reference
temperature T may be generated by only horizontally shifting the individual modulus curves. This is
r
graphically illustrated in Figure 3 for G’ and can also be applied to G”. If an angular frequency was
specified or used for the measurements, it should be converted to a regular frequency for the test report
and used with Annex D. Annex C describes the TTS models, which may be used to mathematically
approximate the shift factors a(T).
NOTE 3 The sections of shifted measured G’(ω ) and G”(ω ) data that constitute the respective master curves
f f
can be used for the determination of the Prony parameters according to Clause C.2. The master curves for G’ and
G” are part of the test report.
Key
1 results at different test temperatures
2 transformations to the reference temperature (T ) give the master curve
G' shear storage modulus, MPa
T to T temperatures during the test, °C
1 4
a(T) temperature dependent, horizontal shift factor
f frequency, Hz
Figure 3 — Determination of the master curve
The reference temperature, Tr (labelled Tref in Figure 3), shall be chosen.
NOTE 4 The reference temperature is typically chosen in relation to the glass transition of the interlayer, see
Clause C.1 for further guidance.
The master curve can also be used to determine the shear modulus used in acoustic software (see
Annex D).
5.3.2.4 Bending creep tests (Step 4)
Bending creep tests on the laminates shall be conducted according to Annex A to validate the DMTA-
based Prony-series and TTS. The objective is to measure deflection for a range of temperatures T and a
range of load durations t sufficient to define the interlayer shear modulus.
With respect to the evaluation of the creep and relaxation tests, the interlayer shear modulus can be
computed for times t > 10 t (where t is the time needed to apply the load). This method is applicable
r r
for a Gint value between 0,5 and 10 MPa.
6 Evaluation of the shear transfer characteristics
6.1 Determination of the temperature and time dependent shear modulus Gint(T,t)
The determination of the interlayer shear relaxation modulus G (t) from the G’ and G” master curves is
int
described in C.1. For any given temperature T, a graph plotting G (t) can be generated. An example of
int
this is shown in Figure 4.
Key
Gint(t) time dependent shear relaxation modulus o
...