ISO 19927:2018

Fibre-reinforced plastic composites — Determination of interlaminar strength and modulus by double beam shear test

This document specifies a procedure for determining the interlaminar strength, and modulus, by double beam shear (DBS) tests of fibre-reinforced plastic composites. The method is suitable for use with glass or carbon fibre-reinforced plastic composites with thermoset matrices, providing an acceptable interlaminar failure is obtained. This document only applies to laminate with a symmetrical and balanced lay‐up as it avoids bending/twisting or bending/extension coupling deformations (see 6.2). The preferred lay-up is unidirectional, with fibres aligned along the specimen (axial) length. The suitability of the test for specific lay-ups, matrices and fibres (e.g. natural) are assessed by trial tests to ensure the correct delamination failures are obtained.

Composites plastiques renforcés de fibres — Détermination de la résistance interlaminaire et du module par un double essai de cisaillement de faisceau

General Information

• Status: Published
• Publication Date: 12-Aug-2018
• ICS: 83.120 - Reinforced plastics
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Current Stage: 9092 - International Standard to be revised
• Due Date: 21-Nov-2024
• Completion Date: 21-Nov-2024

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 19927
First edition
2018-08
Fibre-reinforced plastic composites —
Determination of interlaminar
strength and modulus by double beam
shear test
Composites plastiques renforcés de fibres — Détermination de
la résistance interlaminaire et du module par un double essai de
cisaillement de faisceau
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 4
6 Test specimens. 6
6.1 Shape and dimensions . 6
6.1.1 Preferred specimen size . 6
6.1.2 Alternative specimen size . 7
6.2 Preparation of specimens . 7
6.2.1 General. 7
6.2.2 Machining the test specimens . 7
6.3 Checking the test specimens . 7
7 Number of test specimens . 7
8 Conditioning . 7
9 Procedure. 7
9.1 Test conditions . 7
9.2 Specimen dimensions . 8
9.3 Testing speed . 8
9.4 Data collection . 8
9.5 Failure mode acceptance . 8
9.6 Critical load . 8
9.7 Slope of load-displacement curve . 8
10 Calculation and expression of results . 9
10.1 Interlaminar shear strength . 9
10.2 Interlaminar shear modulus .10
11 Precision .11
12 Test report .13
Annex A (informative) Additional details relating to calculation of shear modulus, G .14
Annex B (informative) Interlaboratory study .17
Bibliography .21
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13,
Composites and reinforcement fibres.
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iv © ISO 2018 – All rights reserved

Introduction
Interlaminar shear (ILS) properties of load-bearing composite laminates are important for structural
design, stress analysis and numerical modelling, material development and selection, component
manufacture as well as for repair of delaminated structural components. A number of test methods have
been developed for the determination of shear properties of composite laminates and several have been
1) 1)
standardized, including short beam strength (SBS) [ASTM D2344, ISO 14130, EN 2377 and EN 2563 ],
V-notched beam (known also as Iosipescu shear), ASTM D5379, V-notched rail (ASTM D7078) and
notched tension (ASTM D3846, BS 4994) or notched compression (BS 6464).
SBS methods are very popular due to their simplicity in specimen preparation, test operation and
cost-effectiveness, though they are used to determine only an apparent ILS strength for QA purposes
rather than for use in design. However, a loaded SBS specimen does not have a pure ILS region within its
gauge section so it often fails in a number of modes, dependent on, amongst others, type of composite
materials, lay-up and specimen thickness. Unacceptable SBS failure modes include flexural failure, local
crushing (under central loading roller) and plastic deformation and roller-induced through-thickness
shear band.
The DBS method is based on loading a composite beam on double support spans (i.e. between 5 loading
points), which generates a stress state that minimises axial bending stresses while promoting
interlaminar shear stresses. In DBS tests delamination occurred consistently within one of the pure ILS
regions in the specimens, for a range of laminated composite materials or lay-ups.
Comparisons with the SBS ILS strength results indicated that the DBS ILS strengths were 20 % to >30 %
higher. In addition, a value of the interlaminar shear modulus can be obtained, providing values of E ,
E , G and ν are known or measured separately for the material under test.
22 12 12
1) CEN Aerospace series.
INTERNATIONAL STANDARD ISO 19927:2018(E)
Fibre-reinforced plastic composites — Determination
of interlaminar strength and modulus by double beam
shear test
1 Scope
This document specifies a procedure for determining the interlaminar strength, and modulus, by
double beam shear (DBS) tests of fibre-reinforced plastic composites.
The method is suitable for use with glass or carbon fibre-reinforced plastic composites with thermoset
matrices, providing an acceptable interlaminar failure is obtained.
This document only applies to laminate with a symmetrical and balanced lay-up as it avoids bending/
twisting or bending/extension coupling deformations (see 6.2). The preferred lay-up is unidirectional,
with fibres aligned along the specimen (axial) length.
The suitability of the test for specific lay-ups, matrices and fibres (e.g. natural) are assessed by trial
tests to ensure the correct delamination failures are obtained.
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.
ISO 291, Plastics — Standard atmospheres for conditioning and testing
ISO 472, Plastics — Vocabulary
ISO 1268 (all parts), Fibre-reinforced plastics — Methods of producing test plates
ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval
ISO 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of
traverse) — Specification
ISO 16012, Plastics — Determination of linear dimensions of test specimens
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 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
critical load
F
crit
load at delamination, as defined in 9.5 for acceptable failure modes
Note 1 to entry: See Cases 1-3.
Note 2 to entry: It is expressed in newtons (N).
3.2
interlaminar shear strength
τ
13 max
shear strength calculated from the critical load
No
...