Notched Impact Test
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Notched impact test
Conventional notched impact test
Notched Charpy impact test
Russel first introduced a pendulum hammer as a testing device for impact testing in 1898. However, this type of test is not associated with the name Russel today, but with that of Charpy, G. A. A., due to the way in which Charpy applied this method to impact bending tests on metallic Material & Werkstoff materials from 1901 onwards. In 1904, Charpy proposed integral impact energy as a toughness value, which he had determined using his well-known arrangement. Although more than 125 years have passed since the introduction of the Charpy test, the determination of notch impact strength according to Charpy is still one of the most widely used methods in industrial testing practice. However, due to numerous formal shortcomings, this method is strictly speaking only justified for use in quality assurance.
The conventional Charpy impact test is standardised according to ISO 179-1 and is used to assess the toughness behaviour of plastics under impact loading using notched test specimens. In the Charpy impact test setup, the test specimen is positioned on two supports and subjected to an impact in the middle by a pendulum hammer of a pendulum impact tester (see: impact loading pendulum impact tester) (see Fig. 1).
The prismatic test specimens must be manufactured in accordance with the relevant moulding compound standard and can be produced directly by injection moulding or by machining pressed or cast plates. Type 1 test specimens (see Table) are mainly used for thermoplastics and can be taken from multipurpose test specimens in accordance with ISO 3167 Type A. Type 2 and 3 test specimens are only used for composite materials with interlaminar shear fracture, e.g. long fibre-reinforced plastics.
| Fig. 1: | Schematic representation of the Charpy arrangement for performing notched impact tests |
The fracture energy required to destroy the test specimens with defined dimensions (see Table) is determined using a pendulum impact tester. Gravity acts as the driving force. The measuring principle of a pendulum impact tester is based on determining the difference between the angle of fall and the angle of rise, which is determined by the energy loss of the pendulum hammer due to the fracture energy on the test specimens.
| length l (mm) | with b (mm) | thickness h (mm) | span L (mm) | |
|---|---|---|---|---|
| type 1 | 80 ± 2 | 10.0 ± 0.2 | 4.0 ± 0.2 | 62 (-0.0/+0.5) |
| type 2 | 25 h | 10 or 15 | 3 | 20 h |
| type 3 | (11 or 13) h | (6 or 8) h |
The notch impact strength (Charpy) is calculated using the following equation.
with
| Wc | absorbed impact energy |
A summary of literature results on impact strength acN is contained in Landolt-Börnstein Volume VII/6A3 [1], which is listed in the references [2–6].
Dynstat notched impact test
The determination of toughness properties using the DYNSTAT arrangement is preferred when only small quantities of material are available (e.g. in component testing). In DIN 53435, the notched impact strength ak of notched test specimens in the impact bending arrangement (DS – K) is determined according to the following equation:
Dynstat notched impact strength:
with
| An | the impact energy absorbed by the test specimen | |
| hk | ≈ | 2/3 of the original thickness h |
Figure 2 shows a schematic representation of the impact test arrangement for an unnotched specimen.
| Fig. 2: | Impact test arrangement DS – K for determining toughness using the Dynstat configuration |
The pendulum hammer energies possible for the test are 0.2 J, 0.5 J, 1.0 J and 2.0 J at an impact velocity of the pendulum hammer of 2.2 m/s. The test specimens are machined from the moulded part (finished part). All surfaces and edges must be free of damage and defects when viewed with the naked eye. If necessary, any grooves caused by grinding (220 grit or finer) and subsequent polishing must be removed in the longitudinal direction.
The dimensions of the rectangular cross-section of the notched test specimens are:
| length l | = | (15 ± 1) mm |
| with b | = | (10 ± 0,5) mm |
| thickness h | = | 1.2 – 4.5 mm |
A U-notch of (0.8 ± 0.1) mm in width is sawn, planed or milled into the test specimens transversely, i.e. perpendicular to the axis of the bar. Thereby the depth of the notch must be selected such that the residual cross-sectional area is 2/3 of the original cross-sectional area. The test specimen is inserted vertically in a force-fit manner, with an insertion length lE of (5.5 ± 0.1) mm [1, 7].
Izod notched impact test
The determination of IZOD impact strength in accordance with ISO 180 is carried out for rigid thermoplastic moulding and extrusion compounds, including filled and reinforced compounds, as well as sheets made of rigid thermoplastics, fibre-reinforced thermosetting and thermoplastic composites with unidirectional or non-unidirectional reinforcement, such as mats, fabrics, rovings, chopped fibres, composite and hybrid reinforcement; rovings and chopped fibres, as well as sheets made of pre-impregnated materials (prepregs) and rigid thermosetting moulding compounds, including filled and reinforced composites, sheets made of rigid thermosetting plastics, including those made of layered materials. The impact energy EC absorbed during fracture of a notched test specimen is related to the initial cross-sectional area of the test specimen at the notch according to the following equation:
IZOD impact strength:
with
| Wc | absorbed impact energy | |
| h | thickness | |
| bN | remaining width (ligament) at the base of the notch |
Unlike the testing of notched test specimens in the Charpy arrangement, where the impact is applied to the side opposite the notch, in the IZOD arrangement the pendulum hammer strikes the side on which the notch is located. A schematic representation of the toughness test in the IZOD arrangement is shown in Fig. 3.
| Fig. 3: | Impact loading with IZOD arrangement |
The test specimens can be produced in accordance with the relevant moulding compound standard or by pressing and injection moulding, or they can be taken from multipurpose test specimens. The dimensions of the different test specimens are listed in the Table [1, 8].
Table: Test specimen types and dimensions for the impact test according to ISO 180
| method/designation | specimen (mm) | notch type | notch base radius rN (mm) | ligament bN (mm) |
|---|---|---|---|---|
| DIN EN ISO 180/A | length l = 80 ± 2 width b = 10.0 ± 0.2 thickness h = 4.0 ± 0.2 | A | 0.25 ± 0.05 | 8.0 ± 0.2 |
| DIN EN ISO 180/B | B | 1.0 ± 0.05 |
Instrumented Charpy impact test (ICIT)
……to the wiki overview article: Instrumented Charpy impact test
The instrumented Charpy impact test is a method of mechanical materials testing or experimental fracture mechanics testing (see: fracture mechanical testing) that is increasingly used in materials development and optimisation.
The Figure shows the importance of instrumented testing (see: electronic instrumentation) when performing the Charpy impact test. While the notch impact energy K, which is the same for both materials in conventional toughness assessment due to its integral character, the result of the instrumented test shows clear differences in terms of load and deformation components. In addition, the instrumented Charpy impact test allows fracture mechanics parameters to be determined for the assessment of toughness.
| Fig. 4: | Schematic representation of a load–deflection diagram for two materials with different deformation behaviour |
The instrumented Charpy impact test can therefore be used either to determine the impact strength or notch impact strength acU or acN, or to evaluate the load–deflection behaviour (see: conventional impact test). In this case, the ISO 179-2 [9] standard applies. In addition, the instrumented Charpy impact test also serves as an experimental basis for fracture mechanical toughness characterisation [10–12].
See also
References
| [1] | Grellmann, W., Seidler, S.: Mechanical and Thermomechanical Properties of Polymers. Landolt-Börnstein. Volume VIII/6A3, Springer, Berlin (2014) 192–218, (ISBN 978-3-642-55165-9; see AMK-Library under A 16) |
| [2] | Russel, S. B. (1898): Experiments with a New Machine for Testing Materials by Impact. American Society of Civil Engineers 39/826, 237–250 [Reprint: Siewert, T. A., Manahan S. (Eds.) (2000): The Pendulum Impact Testing: A Century of Progress. ASTM STP 1380, 17–45] |
| [3] | Charpy, G. A. A. (1901): Essay on the Metals Impact Bend Test of Notched Bars. [Reprint: Siewert, T. A., Manahan, S. (Eds.) (2000): The Pendulum Impact Testing: A Century of Progress. ASTM STP 1380; https://doi.org/10.1520/STP14386S; Charpy, G. A. A. (1901): Note sur L’essai des metaux a la flexion par choc de barreaux entailles. Association internationale pour l’essai des materiaux. Congres de Budapest 1901 [also published in: Soc. Ing. Civ. de Francis. Juni 1901, 848–877] |
| [4] | Charpy, G. A. A. (1904): Report on Impact Test of Metals. Proc. Intern. Association for Testing Materials, Vol. I, Report III |
| [5] | Grellmann, W., Seidler, S. (Eds.): Kunststoffprüfung. Carl Hanser, Munich (2025) 4th Edition, pp. 151–163 (ISBN 978-3-446-44718-9; E-Book: ISBN 978-3-446-48105-3; see AMK-Library under A 23) |
| [6] | ISO 179-1 (2026-03): Plastics – Determination of Charpy Impact Properties – Part 1: Non-instrumented Impact Test |
| [7] | DIN 53435 (2024-10): Testing of Plastics – Bending Test and Impact Test on Dynstat Test Specimens |
| [8] | ISO 180 (2023-06): Plastics – Determination of Izod Impact Strength |
| [9] | ISO 179-2 (2020-05): Plastics – Determination of Charpy Impact Properties – Part 2: Instrumented Impact Test |
| [10] | ESIS P2-92 (1992): Procedure for Determining the Fracture Behaviour of Materials |
| [11] | ESIS TC 4 (2001): A Testing Protocol for Conducting J-Crack Growth Resistance Curve Test on Plastics |
| [12] | MPK-Procedure_MPK-ICIT (2016-08): Testing of Plastics – Instrumented Charpy Impact Test (ICIT): Procedure for Determination the Crack Resistance Behaviour using the Instrumented Impact Test |