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| ISO 178 | |
|---|---|
| Title | ISO 178 |
| Status | Published |
| Year | 2019 |
| Organization | International Organization for Standardization |
| Scope | Determination of flexural properties of plastics |
| Pages | 10 |
ISO 178
ISO 178 specifies a standardized method for determining the flexural properties of rigid and semi-rigid plastics. The standard establishes procedures for three-point and four-point bending tests to obtain modulus of elasticity in bending, flexural stress, and flexural strain. It is used by manufacturers, testing laboratories, regulatory agencies, and research institutions to ensure comparability of mechanical property data across materials, specimens, and studies.
ISO 178 defines the method for measuring flexural behavior of plastics under controlled conditions to produce repeatable data for engineering design, quality control, and material comparison. It is intended for use by organizations such as the International Organization for Standardization, national standards bodies, testing laboratories, and manufacturers involved with polymers like polyethylene, polycarbonate, and fiber-reinforced composites. The results support applications including product certification, material selection by designers at firms like Airbus, Ford, and Toyota, and compliance testing referenced by agencies such as the European Committee for Standardization and the United States National Institute of Standards and Technology.
The standard describes both three-point and four-point bending configurations to derive flexural modulus, flexural stress at a specified strain, and flexural strain at a specified stress. It prescribes test speeds, support spans, and specimen dimensions that harmonize with related standards from ASTM and DIN. Typical outcomes inform engineers and researchers at institutions like MIT, ETH Zurich, and Fraunhofer about stiffness and strength for components used in contexts such as aerospace structures at NASA, automotive parts at BMW, and consumer products by Procter & Gamble.
Apparatus requirements include a bending test machine with calibrated load and deflection measurement systems, supports and loading noses of defined radii, and temperature-controlled enclosures when required. Relevant instruments are used by laboratories at SGS, TÜV, and Intertek to ensure conformity. Specimen preparation details cover molding, machining, cutting, and conditioning to specified temperatures and humidity levels in accordance with practices at laboratories associated with universities such as Imperial College London and Stanford. Materials tested often include examples from suppliers like BASF, DuPont, and SABIC.
The procedure mandates alignment, support span setting, and selection of loading noses for three-point or four-point tests, with load applied at a constant speed tied to specimen thickness and span. Measurement focuses on load and deflection to calculate flexural stress and modulus, using equations and calibration practices consistent with metrology standards upheld by organizations such as the International Electrotechnical Commission and national metrology institutes like PTB and NPL. Tests may be performed at different temperatures to simulate service conditions encountered by companies like Rolls-Royce and Siemens.
Reported values typically include flexural modulus, flexural stress at specified strain or at fracture, flexural strain, test speed, support span, specimen dimensions, conditioning, and test temperature. Laboratories report uncertainty and repeatability data in line with guidance from the International Laboratory Accreditation Cooperation and accreditation bodies such as UKAS and ANAB. Data are used by engineers in design offices at Boeing, Renault, and Honda to compare materials, validate finite element models developed at research centers like Lawrence Livermore National Laboratory, and support regulatory submissions to agencies such as the European Chemicals Agency.
Safety provisions address guarding against specimen failure fragments and ensuring operator protection consistent with standards from OSHA, ISO 45001, and local occupational safety agencies. Quality assurance emphasizes calibration of load cells and displacement transducers, traceability to national measurement institutes, regular interlaboratory comparisons coordinated by bodies like ASTM International, and adherence to laboratory management systems such as ISO/IEC 17025. Proficiency testing and round-robin studies among industrial labs at companies like Honeywell, 3M, and Philips help maintain data integrity.
The method originated from earlier national standards and was consolidated into an international framework to harmonize practices across Europe, North America, and Asia. Revisions have incorporated advances in instrumentation, metrology, and materials science, reflecting input from standards committees and stakeholders including polymer manufacturers, testing laboratories, and academic researchers from institutions such as Caltech, the University of Cambridge, and Kyoto University. Periodic updates ensure alignment with companion standards covering tensile testing, impact resistance, and composite characterization used by organizations like SAE International and the European Polymer Federation.
Category:Standards