ISO 178:2010
Plastics - Determination of flexural properties

Standard No.

ISO 178:2010

Release Date

2010

Published By

International Organization for Standardization (ISO)

Status

Withdraw

Replace By

ISO 178:2010/Amd 1:2013

Latest

ISO 178:2019

Scope

1.1 This International Standard specifies a method for determining the flexural properties of rigid (see 3.12) and semi-rigid plastics under defined conditions. A standard test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of test speeds is included. 1.2 The method is used to investigate the flexural behaviour of the test specimens and to determine the flexural strength, flexural modulus and other aspects of the flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test). 1.3 The method is suitable for use with the following range of materials: ⎯ thermoplastic moulding, extrusion and casting materials, including filled and reinforced compounds in addition to unfilled types; rigid thermoplastics sheets; ⎯ thermosetting moulding materials, including filled and reinforced compounds; thermosetting sheets. In agreement with ISO 10350-1[5] and ISO 10350-2[6], this International Standard applies to fibre-reinforced compounds with fibre lengths u 7,5 mm prior to processing. For long-fibre-reinforced materials (laminates) with fibre lengths > 7,5 mm, see ISO 14125[7]. The method is not normally suitable for use with rigid cellular materials or sandwich structures containing cellular material. In such cases, ISO 1209-1[3] and/or ISO 1209-2[4] can be used. NOTE For certain types of textile-fibre-reinforced plastic, a four-point bending test is preferred. This is described in ISO 14125. 1.4 The method is performed using specimens which may be either moulded to the specified dimensions, machined from the central section of a standard multipurpose test specimen (see ISO 20753) or machined from finished or semi-finished products, such as mouldings, laminates, or extruded or cast sheet. 1.5 The method specifies the preferred dimensions for the test specimen. Tests which are carried out on specimens of different dimensions, or on specimens which are prepared under different conditions, can produce results which are not comparable. Other factors, such as the test speed and the conditioning of the specimens, can also influence the results. NOTE Especially for semi-crystalline polymers, the thickness of the oriented skin layer, which is dependent on the moulding conditions, also affects the flexural properties. 1.6 The method is not suitable for the determination of design parameters but can be used in materials testing and as a quality control test. 1.7 For materials exhibiting non-linear stress/strain behaviour, the flexural properties are only nominal. The equations given have been derived assuming linear elastic behaviour and are valid for deflections of the specimen that are small compared to its thickness. With the preferred specimen (which measures 80 mm × 10 mm × 4 mm) at the conventional flexural strain of 3,5 % and a span-to-thickness ratio, L/h, of 16, the deflection is 1,5h. Flexural tests are more appropriate for stiff and brittle materials showing small deflections at break than for very soft and ductile ones. 1.8 Contrary to the previous editions of this International Standard, this edition specifies two methods, method A and method B. Method A is identical to the method in previous editions of this International Standard, i.e. it uses a strain rate of 1 %/min throughout the test. Method B uses two different strain rates: 1 %/min for the determination of the flexural modulus and 5 %/min or 50 %/min, depending on the ductility of the material, for the determination of the remainder of the flexural stress-strain curve.

ISO 178:2010 Referenced Document

• ISO 10724-1 Plastics - Injection moulding of test specimens of thermosetting powder moulding compounds (PMCs) - Part 1: General principles and moulding of multipurpose test specimens
• ISO 16012 Plastics - Determination of linear dimensions of test specimens*， 2015-03-01 Update
• ISO 20753 Plastics*， 2023-11-01 Update
• ISO 23529 Rubber - General procedures for preparing and conditioning test pieces for physical test methods*， 2016-11-01 Update
• ISO 2602 Statistical interpretation of test results; estimation of the mean; confidence interval
• ISO 2818 Plastics — Preparation of test specimens by machining*， 2018-12-13 Update
• ISO 291 Plastics - Standard atmospheres for conditioning and testing
• ISO 293 Plastics — Compression moulding of test specimens of thermoplastic materials*， 2023-02-21 Update
• ISO 294-1:1996 Plastics - Injection moulding of test specimens of thermoplastic materials - Part 1: General principles, and moulding of multipurpose and bar test specimens
• ISO 295 Plastics - Compression moulding of test specimens of thermosetting materials
• ISO 7500-1 Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Calibration and verification of the force-measuring system*， 2018-02-01 Update
• ISO 9513 Metallic materials.Calibration of extensometer systems used in uniaxial testing; Technical Corrigendum 1*， 2013-05-01 Update

ISO 178:2010 history

• 2019 ISO 178:2019 Surface chemical analysis — Secondary ion mass spectrometry — Linearity of intensity scale in single ion counting time-of-flight mass analysers
• 2013 ISO 178:2010/Amd 1:2013 Plastics - Determination of flexural properties; Amendment 1
• 2010 ISO 178:2010 Plastics - Determination of flexural properties
• 2004 ISO 178:2001/Amd 1:2004 Plastics - Determination of flexural properties; Amendment 1: Precision statement
• 2001 ISO 178:2001 Plastics - Determination of flexural properties
• 1993 ISO 178:1993 Plastics; determination of flexural properties
• 1975 ISO 178:1975 Surface chemical analysis — Secondary ion mass spectrometry — Linearity of intensity scale in single ion counting time-of-flight mass analysers
• 1972 ISO 178:1972 Title missing - Legacy paper document