ISO 19350:2025
(Main)Recycled carbon fibre — Determination of tensile strength distribution and interfacial shear strength of single filament embedded in matrix polymer
Recycled carbon fibre — Determination of tensile strength distribution and interfacial shear strength of single filament embedded in matrix polymer
This document specifies methods for the simultaneous measurement of the fibre tensile strength distribution, and the fibre resin interfacial shear strength of recycled carbon fibres using the modified fragmentation test.
Fibre de carbone recyclée — Détermination de la distribution de la résistance à la traction et de la résistance au cisaillement interfacial d'un filament unique noyé dans une matrice polymère
General Information
Standards Content (Sample)
International
Standard
ISO 19350
First edition
Recycled carbon fibre —
2025-01
Determination of tensile strength
distribution and interfacial
shear strength of single filament
embedded in matrix polymer
Fibre de carbone recyclée — Détermination de la distribution
de la résistance à la traction et de la résistance au cisaillement
interfacial d'un filament unique noyé dans une matrice polymère
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols. 1
3.1 Terms and definitions .1
3.2 Symbols .1
4 Principle . 2
5 Tensile test machine and specimen . 2
5.1 Tensile test machine .2
5.2 Grip.2
5.3 Microscope .2
5.4 Test specimens.2
5.5 Number of tests .4
6 Testing technique. 4
6.1 Test procedure .4
6.2 Validity of the test .6
7 Calculation of results . 6
7.1 Summary of measurement data .6
7.2 Calculation of tensile strength distribution .7
7.3 Calculation of interfacial shear strength .8
7.4 Validity of the test result .8
8 Reporting of test results . 9
Bibliography .10
iii
Foreword
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iv
Introduction
The properties of recycled carbon fibres are potentially different from those of the original virgin carbon fibres.
Therefore, it is very important to evaluate the properties of recycled carbon fibres in order to reuse them as
reinforcing fibres. The tensile strength distribution and interfacial shear strength of recycled carbon fibres are
essential for the production of composite materials using recycled carbon fibres. This document describes how
to measure the tensile strength distribution and interfacial shear strength of recycled carbon fibres.
v
International Standard ISO 19350:2025(en)
Recycled carbon fibre — Determination of tensile strength
distribution and interfacial shear strength of single filament
embedded in matrix polymer
1 Scope
This document specifies methods for the simultaneous measurement of the fibre tensile strength
distribution, and the fibre resin interfacial shear strength of recycled carbon fibres using the modified
[1]
fragmentation test .
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 10618, Carbon fibre — Determination of tensile properties of resin-impregnated yarn
ISO 11566, Carbon fibre — Determination of the tensile properties of single-filament specimens
ISO 11567, Carbon fibre — Determination of filament diameter and cross-sectional area
3 Terms, definitions and symbols
3.1 Terms and definitions
No terms and definitions are listed in this document.
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/
3.2 Symbols
Symbol Definition
E
fibre tensile modulus, GPa Tensile modulus of the recycled carbon fibres
D
average fibre diameter, μm Average fibre diameter of the recycled carbon fibres
L Gauge length, mm Initial distance between grips
Total fibre length, mm Total length of a fibre within the observed area of all speci-
l
mens
Length of a fibre within the observed area of each specimen i
l Fibre length, mm
i
m
Weibull shape parameter Shape parameter of the 2-parameters’ Weibull distribution
Total number of break points
N()ε Total number of fibre break points in all specimens at ε
fibre fibre
Δ Displacement, mm Displacement given between gauges
Incremental film strain The magnitude of the strain on the film in each step
Δε
film
Symbol Definition
Δn ε Incremental number of fibre break Incremental number of fibre break points within each specimen
()
i film
points i at ε .
film
ΔN ε Total incremental number of fibre Total incremental number of fibre break points within each
()
fibre
break points specimen i at ε
fibre
Film strain Strain applied to the specimen film. Displacement divided by
ε
film
gauge length
Thermal shrinkage In-plane film shrinkage strain during specimen moulding. In this
ε
document, the shrinkage direction is positive direction, and the
expansion direction is negative direction
Fibre strain Film strain minus thermal shrinkage during moulding
ε
fibre
-1
Density of break points, m Total break point number divided by fibre length
λε()
fibre
-1
Saturated density of break points, m Break point density at the end of tests
λλ
∞
ττ
Interfacial shear strength, MPa Interfacial shear strength between recycled carbon fibre and
matrix polymer
σ Weibull scale parameter, MPa Scale parameter of the 2-parameters’ Weibull distribution
4 Principle
The tensile strength distribution (Weibull parameters) and interfacial shear strength of recycled carbon
[1]
fibres are evaluated using a modified fragmentation test . In this test, a single fibre embedded in a polymer
film is pulled in steps and the number of fibre breaks at each step is counted. From the double logarithm
graph of the fibre break point density and fibre strain, the fibre tensile strength distribution and interfacial
shear strength are evaluated simultaneously, assuming that the strength of the recycled carbon fibre follows
a two-parameter Weibull distribution.
5 Tensile test machine and specimen
5.1 Tensile test machine
The tensile test machine shall be able to measure the displacement applied to the specimen. In addition, the
displacement of the crosshead of the machine shall be accurate to less than 1 µm. To observe fibre breaks, the
specimen should be observed at high magnification observation during the fragmentation test. Therefore,
for example, the test machine should be placed under a microscope, or a microscope should be attached to
the test machine.
5.2 Grip
For accurate measurement of displacement, the grips should be free of slippage. The gripping surfaces
should be parallel in order to suppress local deformation of the film.
5.3 Microscope
A microscope capable of observing the break points of a single recycled carbon fibre should be used. Video
or photographic documentation is preferred.
5.4 Test specimens
The specimen is a polymer sheet with a single recycled carbon fibre embedded at the centre.
The Young's modulus and fibre diameter of the fibre to which this document applies shall already be known
using ISO 11567, and ISO 10618 or ISO 11566, respectively. The thermal shrinkage of the polymer shall also
be known.
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