ISO 4410:2023

Test methods for the experimental characterization of in-plane permeability of fibrous reinforcements for liquid composite moulding

This document specifies test methods for the experimental characterization of in-plane permeability of fibrous reinforcements for liquid composite moulding. Requirements for test equipment, test methods and data analysis are detailed, to ensure optimal accuracy and reproducibility of the results.

Méthodes d'essais pour la caractérisation expérimentale de la perméabilité dans le plan des renforts fibreux pour le moulage de composites liquides

General Information

• Status: Published
• Publication Date: 18-Jul-2023
• ICS: 83.120 - Reinforced plastics
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13/WG 1 - Reinforcements and reinforcement products
• Current Stage: 6060 - International Standard published
• Start Date: 19-Jul-2023
• Due Date: 18-Dec-2023
• Completion Date: 19-Jul-2023

Overview

ISO 4410:2023 - Test methods for the experimental characterization of in‑plane permeability of fibrous reinforcements for liquid composite moulding - defines standardized procedures to measure and report the unsaturated in‑plane permeability of fibrous reinforcements used in liquid composite moulding (LCM). The standard prescribes requirements for test equipment, specimen and mould preparation, fluid and injection systems, measurement of pressure/temperature/flow, and data analysis to ensure accuracy, repeatability and reproducibility of permeability results.

Keywords: ISO 4410:2023, in‑plane permeability, fibrous reinforcements, liquid composite moulding, LCM, permeability measurement.

Key topics and technical requirements

• Principle and background
  • Permeability is characterized in the context of Darcy’s law and expressed as a symmetric second‑order tensor; ISO 4410 focuses on the two principal in‑plane permeabilities.
• Design of experiments
  • Guidance on selection of injection method, number of repeat tests, setting fibre volume fraction, injection pressure, temperature control and plausibility checks.
• Specimen and mould preparation
  • Requirements for specimen cutting, stacking, mass measurement, mould height, surface roughness, alignment and thickness control.
• Test fluids and injection systems
  • Specifications for preparing test fluids and conditioning the injection system to minimize experimental bias.
• Measurement and instrumentation
  • Procedures for measuring fluid pressure, temperature and flow rate and for flow‑front monitoring.
• Two primary experimental methods
  • Method A - Linear flow experiments: apparatus design, injection/vent geometry, data segmentation and algorithm for permeability tensor calculation.
  • Method B - Radial flow experiments: apparatus specifics, inlet/vent geometry, radial flow monitoring and data processing.
• Data processing and validity
  • Data acquisition sampling, segmentation, evaluation procedures, tensor calculation and validity checks to quantify uncertainty.
• Documentation
  • Mandatory reporting content for single experiments and options for documenting repeat tests and model approximations.

Practical applications

• Designing and optimizing LCM processes for fast, complete impregnation (short cycle times and high part quality).
• Material selection and qualification for automotive, aerospace, marine and wind‑energy composite components.
• Process simulation and modelling where accurate permeability inputs are required for flow front prediction and tooling design.
• Quality control and R&D in material suppliers’ and test laboratories.

Who should use ISO 4410:2023

• Composite process engineers and production planners working with LCM (RTM, infusion).
• R&D teams and materials scientists characterizing reinforcement architectures.
• Test laboratories that provide permeability measurements for part design or supplier qualification.
• Simulation specialists needing validated permeability data for flow modelling.

Related standards

• Prepared by ISO/TC 61 (Plastics) SC 13 (Composites and reinforcement fibres); users may cross‑reference complementary ISO standards on composite testing and material characterization for broader test and conformity frameworks.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 4410
First edition
2023-07
Test methods for the experimental
characterization of in-plane
permeability of fibrous
reinforcements for liquid composite
moulding
Méthodes d'essais pour la caractérisation expérimentale de la
perméabilité dans le plan des renforts fibreux pour le moulage de
composites liquides
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviated terms . 2
4 Principle . 5
5 Design of experiments . 5
5.1 Selection of injection method . 5
5.2 Number of repeat tests . 5
5.3 Setting the fibre volume fraction . 6
5.4 Selecting the fluid injection pressure . 6
5.5 Temperature conditions . 6
5.6 Plausibility checks . 6
6 Test specimen and specimen preparation . 7
6.1 General information. 7
6.2 Specimen cutting . 7
6.3 Specimen stacking . 7
6.4 Specimen mass measurement . 8
7 Test fluid and fluid injection system preparation . 9
7.1 Test fluid . 9
7.2 Preparing the fluid and the injection system . 9
8 Mould preparation .9
8.1 Specimen thickness control . 9
8.2 Mould height . 9
8.3 Surface roughness of mould . 11
8.4 Alignment of top and bottom part of mould . 11
9 Measurement of fluid pressure, temperature and flow rate .11
9.1 Fluid pressure measurement . 11
9.2 Fluid temperature measurement . 11
9.3 Fluid flow rate measurement . 11
10 Method A: Linear flow experiments .11
10.1 Apparatus design . 11
10.2 Specimen planar dimensions .12
10.3 Injection gate geometry .12
10.4 Vent geometry . 13
10.5 Fluid injection system .13
10.6 Test preparation . 13
10.6.1 Edge sealing .13
10.6.2 Placing the specimen in the mould . 13
10.7 Sensor equipment/Data acquisition . 14
10.7.1 Fluid flow front measurement . 14
10.7.2 Sampling of measurement data . 15
10.8 Data processing. 15
10.8.1 Data segmentation .15
10.8.2 Data evaluation procedure . 15
10.8.3 Calculating the permeability tensor . 17
10.8.4 Validity checks . 18
11 Method B: Radial flow experiments .20
iii
11.1 Apparatus design . 20
11.2 Specimen planar dimensions .20
11.3 Injection gate geometry . 21
11.4 Vent geometry . 21
11.5 Fluid injection system . 21
11.6 Test preparation . 22
11.6.1 Inserting the inlet hole in the specimen . 22
11.6.2 Placing the specimen in the mould . 22
11.7 Sensor equipment/Data acquisition . 23
11.7.1 Fluid flow front monitoring . 23
11.7.2 Sampling of measurement data . 23
11.8 Data processing. 23
11.8.1 Data evaluation range . 23
11.8.2 Data segmentation .23
11.8.3 Data processing algorithm . 24
11.8.4 Validity checks .29
12 Result documentation .29
12.1 Single experiment documentation (Mandatory) .29
12.2 Documentation of repeat experiments (Optional) .30
12.3 Documentation of model approximation (Optional) . 31
Bibliography .32
iv
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13,
Composites and reinforcement fibres.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
Liquid composite moulding (LCM) processes are employed for the manufacture of fibre reinforced
polymer composites (FRPC). In all LCM processes, dry fibrous reinforcements are impregnated with a
liquid resin system, which is cured following reinforcement impregnation to form the matrix in which
the fibres are embedded. Impregnation is driven by positive applied pressure and/or vacuum. LCM is
widely applied for the manufacture of lightweight components in the automotive, aerospace, marine,
and energy (e.g. blades for wind turbines) industries.
To obtain short cycle times and high component quality in LCM, i.e. fast and complete saturation of the
reinforcement with liquid resin, a suitable process design is required, based on knowledge of material
properties. Darcy’s law relates the phase-averaged flow velocity to the applied pressure gradient,
the dynamic resin viscosity, and the reinforcement permeability for fluid flow. The permeability of
fibrous structures, such as reinforcements, is generally direction-dependent and is described by a
symmetric second-order tensor. Diagonalisation of the tensor leads to three principal permeabilities,
which correspond to the flow oriented along three orthogonal axes, two of which describe the in-plane
permeability.
This document focuses on the experimental characterization of unsaturated in-plane permeability
of reinforcing materials for LCM. As with any kind of experiment, methodological, systematic
and statistical errors may arise. In order to minimize methodological errors caused by different
experimental methods, this document covers the two most common approaches, linear and radial flow
experiments. Systematic errors inherent to these methods are minimized by distinct procedures for
preparing and executing the flow experiments as well as for post-processing the acquired measurement
data as prescribed in this document. Statistical errors are dominated by variations in material
properties, particularly inhomogeneous areal weight and thus, fibre volume fraction of the reinforcing
materials. This document covers well known statistical methods, such as multiple experiments at
repetitive conditions, in order to estimate the uncertainty associated with the results.
vi
INTERNATIONAL STANDARD ISO 4410:2023(E)
Test methods for the experimental characterization of in-
plane permeability of fibrous reinforcements for liquid
composite moulding
1 Scope
This document specifies test methods for the experimental characterization of in-plane permeability of
fibrous reinforcements for liquid composite moulding. Requirements for test equipment, test methods
and data analysis are detailed, to ensure optimal accuracy and reproducibility of the results.
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 cited edition applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 286-1:2010+Cor1: 2013, Geometrical product specifications (GPS) — ISO code system for tolerances on
linear sizes — Part 1: Basis of tolerances, deviations and fits
ISO 2555, Plastics — Resins in the liquid state or as emulsions or dispersions — Determination of apparent
viscosity using a single cylinder type rotational viscometer method
ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms,
definitions and surface texture parameters
ISO 21920-3, Geometrical product specifications (GPS) — Surface texture: Profile — Part 3: Specification
operators
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1.1
in-plane permeability
quantitative material parameter of a fibrous reinforcement (a porous medium), relating the phase-
averaged flow velocity of a liquid in the reinforcement to the applied pressure gradient and the dynamic
viscosity of the fluid.
Note 1 to entry: During impregnation of a fibrous reinforcement with a fluid, the permeability of the fibrous
reinforcement, the permeability tensor, K , relates the phase-averaged flow velocity, v , to the applied pressure
gradient, ∇p , and the dynamic resin viscosity, μ , as stated in Darcy’s law.
K
 
v =− ⋅∇p
 
μ
 
As per this definition, the permeability is given in units of square metres (m ). Importantly, the permeability of a
reinforcement depends on the fibre volume fraction and the geometrical fibre arrangement. Because of the
directionality of the fibre arrangement in a reinforcement, the permeability is generally anisotropic. The
principal components of the tensor K , in its diagonal form are referred to as k and k , representing the highest
1 2
and lowest values of the in-plane permeability, respectively.
Note 2 to entry: Permeability is an equivalent parameter defined at the level of an equivalent homogeneous
medium representing an intrinsically heterogeneous material. Darcy’s law has been extended to unsaturated
flow or transient flow, neglecting the effect of dynamic wetting.
3.1.2
unsaturated flow
dynamic flow of a fluid in a porous medium where initially empty (vacuum) pore spaces are filled or an
initially present fluid (e.g. air) is displaced
3.1.3
in-plane anisotropy ratio
characteristic of a material showing different properties in different directions
Note 1 to entry: The in-plane anisotropy ratio, α , is defined here as the ratio of lowest to highest in-plane
k
permeability, i.e. α = .
k
3.1.4
linear injection
injection of fluid into a porous medium along one short edge of a rectangular geometry, resulting in a
flow along the long edge, with velocity vectors oriented primarily in one direction
3.1.5
radial injection
injection of fluid into a porous medium through a central injection gate, resulting in a flow with velocity
vectors extending radially outward from the gate, in all in-plane directions
3.1.6
race-tracking
locally increased flow velocity in gaps between specimen and mould
3.1.7
slowtracking
locally decreased flow velocity caused by over-compaction of the specimen along the mould edges
3.1.8
orientation angle
angle, β, between the direction of highest flow velocity, k , and a reference direction, which is commonly
the production direction of the material
Note 1 to entry: See Figure 2.
3.2 Symbols and abbreviated terms
Symbol Unit Meaning
m
A Specimen area (i.e. l multiplied with w for rectangular specimens)
s s s
m Constants for the calculation of the principal permeabilities
C
14…
% Coefficient of variation
CV
D
Matrix containing the ()xy,,z data sets of an experiment
e
Eigenvector
Auxiliary functional terms
ff,
FS Full scale
Symbol Unit Meaning
h m Height of the reinforcement specimen
i Counting variable indicating the time step
J Counting variable for experimental configurations of mould height and number
of layers
k Counting variable indicating the measurement data set
m Kozeny constants
k and k
C,1 C,2
m Average of experimentally measured permeability
k
e
m Experimentally determined permeability
k
e
0 m Experimentally determined permeability in the defined reference direction
k
e
45 m Experimentally determined permeability orientated at an angle of 45° to the
k
e
defined reference direction
90 m Experimentally determined permeability perpendicular to the defined refer-
k
e
ence direction
−45 m Experimentally determined permeability orientated at an angle of -45° to the
k
e
defined reference direction
m Permeability in flow direction
k
x
m Permeability perpendicular (in-plane) to flow direction
k
y
m Highest in-plane permeability
k
m Lowest in-plane permeability
k
m Out-of-plane permeability
k
m Highest in-plane permeability, adjusted according to the actual fibre volume
k
1,a
fraction
m Lowest in-plane permeability, adjusted according to the actual fibre volume
k
2, a
fraction
m Permeability tensor
K
m Specimen length
l
s
LCM Liquid composite moulding
m
Slope of the trend line correlating x and t
mid
kg Specimen mass (dry)
M
s
n Number of measurement data sets in an experiment
Number of layers of a fibrous reinforcement in a specimen
n
L
Number of sampled data sets in a linear injection experiment
n
T
Number of experiments in a set
N
p
Pa Array of experimental pressure values
∇p Pa Pressure gradient applied across the specimen, i.e. the gauge pressure applied
Pa Pressure drop
ΔP
Pa Time-averaged pressure drop
ΔP
eff
q
Coefficient in paraboloid matrix
q
Array of coefficients from paraboloid matrix
 Coefficient in rotated matrix
q
Q m /s Volume flow rate
Q Matrix of paraboloid coefficients
Symbol Unit Meaning
3x3 Submatrix of paraboloid coefficients
Q
 Matrix of rotated paraboloid coefficients
Q
m Specimen radius
r
s
m Major radial extension of flow ellipse
r
m Minor radial extension of flow ellipse
r
m Root mean square error of fitting the elliptic paraboloid
E
RMS
f
Pa Root mean square error of the pressure
E
RMS
p
m Permeability standard deviation
s
N−1
S Scatter matrix
SVD Singular value decomposition
t
s Time
t
s Array of experimental timestamp values
°C Time-averaged temperature
T
eff
v
m/s Darcy velocity vector
V Coefficient of variation
% Fibre volume fraction
V
f
m Specimen width
w
s
x
m Spatial coordinate in the reference direction of the coordinate frame of the test
rig
m Shortest distance between the inlet region and the flow front position at the
x
mid
midpoint along the specimen width
m Shortest distance between the inlet region and the flow front position along
x
M1
the upper edge of the specimen in linear injection
m Shortest distance between the inlet region and the flow front position along
x
M2
the bottom edge of the specimen in linear injection
y
m Spatial coordinate perpendicular (in-plane) to the reference direction of the
coordinate frame of the test rig
z
s Experimental time
α
Anisotropy ratio ( kk/ )
β degrees Angle indicating orientation of K with respect to the defined reference direc-
tion of the considered fibrous reinforcement
° Relative angle between the long cutting edge of a specimen for linear flow ex-
δ
periments reinforcement and the defined reference direction of the considered
fibrous reinforcement
ε
m Root mean square error of the flow front location x
Critical threshold for the race-tracking error
ε
crit
m Measurement error
ε
K
Race-tracking error
ε
R
μ
Pa∙s Dynamic viscosity of fluid
Eigenvalue
λ
Auxiliary quantities
ξ
02…
kg/m Material density
ρ
f
φ % Porosity of reinforcement
Symbol Unit Meaning
kg/m Areal density of a fibrous reinforcement layer (grammage)
w
A
ω
°
Smallest of the three relative angles δ selected for testing
4 Principle
A specimen of the fibrous reinforcement is compressed between two impermeable, parallel plates
at a defined and uniform thickness. Then, a test fluid with known viscosity is injected at constant
injection pressure through a defined inlet region, either a linear injection gate along one specimen edge
or a radial injection gate in the centre of the specimen. This results in a one- or two-dimensional (i.e.
linear or elliptical) flow pattern. While the reinforcement is impregnated, the flow front propagation
is tracked to determine the directional flow front velocity. Data reduction schemes based on Darcy’s
law are applied to calculate in-plane permeability from the flow front velocity, the applied pressure
gradient, the fluid viscosity, and the reinforcement porosity.
5 Design of experiments
5.1 Selection of injection method
The linear and radial test methods are equally applicable to the majority of reinforcements.
NOTE In special cases, each of the methods provides relevant specific advantages and disadvantages
resulting from the different injection strategies:
— In the linear flow method, resin flows along the specimen edges. Gaps between the specimen and the mould
walls can induce race-tracking, causing locally increased flow velocity compared to the bulk material. In the
radial flow method, flow takes place within the specimen. However, if k >> k , the flow front in the k
1 2 1
-direction may reach the specimen edges before the minimum distance to the inlet (to obtain a stabilised
flow front shape) is reached in the k -direction. This would cause a calculation error as the resulting change
in the pressure distribution is not considered during data processing.
— Radial injection methods allow for determination of the full in-plane permeability tensor in a single test,
whereas it requires three tests in the linear injection method.
— Radial injection methods typically employ more expensive tooling than linear injection, due to the greater
propensity for mould deflection owing to the larger specimen surface area.
Details on specific sources of scatter are described in detail in the publications on the results of
international benchmark studies (see References [1] to [3]).
5.2 Number of repeat tests
The flow experiments defined in this document for characterization of unsaturated in-plane
permeability are destructive by nature as the reinforcement specimen is irreversibly saturated with
the test fluid. Therefore, repeat tests shall not be performed on a previously tested specimen. In repeat
tests, new specimens with identical specifications, preferably from the same material roll/sheet, are
tested at identical target conditions.
For statistical evaluation, at least five repeats shall be performed for each test condition.
NOTE Depending on the material, five repeats might still not be enough to reach a confidence interval
required for certain statistical evaluations, e.g. calculation of standard deviation (see Reference [4]).
5.3 Setting the fibre volume fraction
The dependence of the in-plane permeability values on the fibre volume fraction is often of major
interest. Varying the fibre volume fraction for a given reinforcement may either be done by adapting the
mould cavity height, the number of layers present in the mould, or both, according to Formula (1):
nw⋅
LA
V = (1)
f
ρ ⋅h
f
All tests at a particular value of V shall be performed with the same number of layers, n . To minimize
f L
the differences in flow conditions near the mould bottom or top, and in the middle of the specimen, all
tests shall be performed with the minimum values n =4 and h =2 mm, respectively.
Lm, in min
The uncompressed thickness of a specimen shall be greater than the anticipated mould height for the
test, to ensure tight packing of the specimen against the top mould surface.
Formula (1) assumes that the reinforcement consists of one type of fibre. If more than one fibre
material is used, or if additional materials are present in the reinforcement, such as polymeric powder
binder or stitching yarns, this shall be considered by calculating separate volume fractions for each
material component, from their respective areal densities and material densities, and then adding up
the component volume fractions. In this case, one should use the term “solid volume fraction” (the sum
of volume fractions of all components) to point out that the solid volume consists of more than one type
of reinforcing fibres or other solids.
5.4 Selecting the fluid injection pressure
The injection pressure shall not exceed 0,3 MPa.
This document does not define a minimum pressure. Yet, it is emphasized that, with decreasing injection
pressure, the measurement error caused by neglecting the capillary pressure and wetting effects
increases. This capillary pressure depends on the fluid/reinforcement interaction and can reach a
sufficient value to have an influence on the calculated permeability. It is thus recommended to estimate
the capillary pressure for the combination of test fluid and reinforcement, and to use a pressure
gradient significantly higher than the estimated value (at least two times higher). A corresponding test
method is, for example, described in Reference [5]. In any case, it is important to consider the wetting
properties of the test fluid to evaluate the validity of the permeability value calculated. For common
test fluids and fibre structures, depending on their fibre volume fraction and orientation, capillary
pressures from 1 kPa to 40 kPa have been found.
NOTE The injection pressure can influence the permeability measurement. Darcy’s law assumes a rigid
porous media. However, reinforcements and the mould can both deform under high fluid pressure.
5.5 Temperature conditions
The test shall be performed under isothermal conditions.
5.6 Plausibility checks
After initial set-up of a new test apparatus, a basic plausibility check on the results should be performed.
This can be done by performing measurements on a reference porous media such as the one described
in Reference [6]. The geometrical data of this structure (including a CAD-model), as well as information
on its permeability characteristics can be downloaded from: https:// standards .iso .org/ iso/ 4410/ ed -1/
en.
6 Test specimen and specimen preparation
6.1 General information
The types of reinforcement tested by the methods described in this document may be woven fabrics,
non-crimp fabrics, braids, knits or non-wovens, but can also include fibre structures prepared by dry
fibre placement, tailored fibre placement or similar processes. In general, this document is applicable to
characterization of specimens with a quasi-homogeneous structure. Figure 1 shows examples of typical
reinforcements.
a) Non-crimp fabric b) Woven fabric c) Non-woven
Figure 1 — Examples of reinforcement types
In the context of composite manufacturing, reinforcements are frequently made from carbon, glass or
aramid fibres. Other fibre types, e.g. synthetic fibres such as polyethylene-based fibres or natural fibres
such as hemp or flax, may be used. In general, this document is not restrictive in terms of the fibre
material to be investigated nor its sizing, as long as there is no interaction with the fluid, such as fibre
swelling due to moisture absorption or sizing dissolution.
6.2 Specimen cutting
Methods, which allow high cutting accuracy to be obtained and minimize specimen deformation shall
be applied. The use of computerized numerical controlled (CNC) machines is recommended. Other
cutting methods can be applied if a high degree of geometrical accuracy can be obtained.
NOTE Dimensional inaccuracies and unwanted deformation induced by cutting and handling, cause errors
in the calculation of the fibre volume fraction, and can contribute to unwanted race-tracking, uneven nesting and
local slowtracking effects.
6.3 Specimen stacking
A reference direction and reference side shall be defined for every fibrous reinforcement to be tested.
For roll materials, the production direction and top side, as illustrated in Figure 2, shall be used as the
reference direction and side, respectively. When intending to measure the permeability of one specific
fibrous reinforcement, all layers stacked to form the specimen shall have aligned reference directions
and the reference side on top (see Figure 2).
Key
A top side
B bottom side
C production direction
D layer
Figure 2 — Schematic illustration of production direction and top side of specimen
The reference direction and side should be marked on the specimen to ensure correct allocation of the
permeability values and proper reporting.
When obtaining permeability values intended as input for numerical simulation of LCM processes, this
document can generally be applied to:
— a specific multi-layer specimen comprising of one specific fibrous reinforcement, where the layers
have the same or differing orientation angles or
— a specific multi-layer specimen comprising of more than one fibrous reinforcement,
as long as the validity criteria defined in 10.8.4 and 11.8.4 are fulfilled. The lay-up should then be
identical to the lay-up used in the process and should be measured at the same cavity height as intended
for the process. A reference direction and side of the (multi-)material should be clearly recorded.
The values measured may need to be further modified when 3D flow or placement around complex
curvatures (sheared permeability) is expected in numerical simulations.
NOTE Lay-ups where the layers have the same or differing orientation angles or comprise more than one
fibrous reinforcement are prone to the occurrence of significant flow front distortions through the thickness,
which can cause measurement error.
6.4 Specimen mass measurement
Before permeability characterization, but after cutting and stacking, the following procedure for mass
(M ) measurement shall be followed for each specimen.
s
— Use a scale which has an accuracy of at least ±0,1 g.
— Weigh the complete specimen directly after preparation with minimum handling in between.
Specimen handling shall be careful at any time, to minimize fraying at the edges. Fraying can lead to
unwanted race-tracking effects or a reduced specimen mass and a corresponding reduction of the
calculated fibre volume fraction.
7 Test fluid and fluid injection system preparation
7.1 Test fluid
The test fluid shall be a quasi-Newtonian, incompressible fluid having a viscosity between 70 mPa·s
and 200 mPa·s at the test temperature (usually ambient). The temperature-dependent viscosity, μ()T ,
shall be tested in a relevant temperature range using a rheometer or viscometer, to be able to calculate
the actual viscosity for a known test temperature. Independent of the applied test method, the accuracy
concerning the fluid temperature setting and measurement shall adhere to the requirements defined in
ISO 2555.
NOTE Typical fluids used for permeability characterization for fibrous reinforcements are silicone oil,
rapeseed oil, motor oil, corn syrup, polyethylene glycol or fructose solutions.
7.2 Preparing the fluid and the injection system
Before adding the test fluid to the reservoir, the reservoir shall be cleaned of any residual from
previously used fluid (if this was of a different kind). Information on proper cleaning agents for specific
test fluids are usually available from the supplier of the test fluid.
Before starting an experiment, the pressure vessel around the fluid reservoir shall be checked for air
leaks.
The complete fluid injection arrangement, including the fluid, the reservoir and the actual test
apparatus, shall be placed in the room where the test is to be performed, at ambient temperature, for at
least 24 h before testing.
8 Mould preparation
8.1 Specimen thickness control
The mould consists of two halves, top and bottom, arranged in a way such that the cavity is horizontally
oriented, in order to avoid asymmetric gravitational forces. To ensure that the specimen thickness is
uniform, the top and bottom parts of the mould shall be flat and parallel. Adjustment of the mould
height shall be possible at high accuracy. Methods used for adjustment of the mould height shall not
interfere with the test method. In general, all measures of the test rig shall at least correspond to
tolerance class IT10 according to ISO 286-1:2010+Cor1: 2013. The maximum deflection shall be <2 % of
the target mould height, when the inner surfaces of the mould are pressurized to the pressures expected
during testing. To obtain the required properties a metallic mould should be used. Alternatively, glass
or another transparent material may be used for parts of the mould if visual flow front tracking is
employed.
NOTE To adjust the mould height, often spacers, i.e. shims, are inserted between the bottom and top parts
of the injection mould. Alternatively, the mould height is set using a press where the displacement is controlled
through the use of linear variable differential transformers (LVDT) or laser distance sensors.
8.2 Mould height
During a permeability test, the difference between the mould height at centre and any other point in the
mould shall be <2 %.
As it is generally impractical to monitor the mould height during a test, the mould height should be
characterised once before the start of a test series and again at the end of a test series. A test series is
a number of subsequent repeat tests (see 5.2). The mould height should be measured at five positions,
as indicated in Figure 3 for specimen tested according to Method A (see Clause 10) and Figure 4 for
specimen tested according to Method B (see Clause 11). For this, a specimen of the type to be tested is
to be prepared, including edge sealing measures if applicable (see 10.6.1). Holes are cut in the specimen
at the appropriate positions, and the specimen is placed in the mould. Small blocks of a deformable
material (e.g. plasticine) are placed in the cut-out holes. The mould is closed as for permeability testing,
but no test fluid is injected. The mould is re-opened, the deformable material is removed (without
inducing any further deformation), and the thickness of the compressed material blocks is measured.
The thickness corresponds to the (local) mould height. For the repetition of this procedure at the end of
the test series, the same cut-out specimen as before can be used. To assess the cavity repeatability, it is
recommended to repeat the test multiple times at each measured location.
Figure 3 — Locations (five dots) for measurement of mould height for linear injection
Figure 4 — Locations (five dots) for measurement of mould height for radial injection
To increase efficiency, the procedure may be performed before and after a number of test series, if
these solely differ with respect to the target fibre volume fraction. In this case, the procedure should
be performed with the highest intended fibre volume fraction. As the pressure on the mould surface
is highest at the highest fibre volume fraction, and the risk for mould deflection is highest, it can be
assumed that the requirement for the mould height (in terms of uniformity of the height) will be met for
lower fibre volume fractions.
This procedure only considers errors in the mould geometry and mould deformations resulting from
the mould closing load. Additional deformation induced by the injection pressure is neglected. This
additional mould deformation can be evaluated by distance sen
...