ASTM D638 : 22 New ASTM DRM Policy

Significance and Use

4.1 This test method is designed to produce tensile property data for the control and specification of plastic materials. These data are also useful for qualitative characterization and for research and development.

4.2 Some material specifications that require the use of this test method, but with some procedural modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 in Classification D4000 lists the ASTM materials standards that currently exist.

4.3 Tensile properties are known to vary with specimen preparation and with speed and environment of testing. Consequently, where precise comparative results are desired, these factors must be carefully controlled.

4.4 It is realized that a material cannot be tested without also testing the method of preparation of that material. Hence, when comparative tests of materials per se are desired, exercise great care to ensure that all samples are prepared in exactly the same way, unless the test is to include the effects of sample preparation. Similarly, for referee purposes or comparisons within any given series of specimens, care shall be taken to secure the maximum degree of uniformity in details of preparation, treatment, and handling.

4.5 Tensile properties provide useful data for plastics engineering design purposes. However, because of the high degree of sensitivity exhibited by many plastics to rate of straining and environmental conditions, data obtained by this test method cannot be considered valid for applications involving load-time scales or environments widely different from those of this test method. In cases of such dissimilarity, no reliable estimation of the limit of usefulness can be made for most plastics. This sensitivity to rate of straining and environment necessitates testing over a broad load-time scale (including impact and creep) and range of environmental conditions if tensile properties are to suffice for engineering design purposes.

Note 5: Since the existence of a true elastic limit in plastics (as in many other organic materials and in many metals) is debatable, the propriety of applying the term “elastic modulus” in its quoted, generally accepted definition to describe the “stiffness” or “rigidity” of a plastic has been seriously questioned. The exact stress-strain characteristics of plastic materials are highly dependent on such factors as rate of application of stress, temperature, previous history of specimen, etc. However, stress-strain curves for plastics, determined as described in this test method, almost always show a linear region at low stresses, and a straight line drawn tangent to this portion of the curve permits calculation of an elastic modulus of the usually defined type. Such a constant is useful if its arbitrary nature and dependence on time, temperature, and similar factors are realized.

Scope

1.1 This test method covers the determination of the tensile properties of unreinforced and reinforced plastics in the form of standard dumbbell-shaped test specimens when tested under defined conditions of pretreatment, temperature, humidity, and testing machine speed.

1.2 This test method is applicable for testing materials of any thickness up to 14 mm (0.55 in.). However, for testing specimens in the form of thin sheeting, including film less than 1.0 mm (0.04 in.) in thickness, ASTM standard D882 is the preferred test method. Materials with a thickness greater than 14 mm (0.55 in.) shall be reduced by machining.

1.3 This test method includes the option of determining Poisson's ratio at room temperature.

Note 1: This standard and ISO 527-1 address the same subject matter, but differ in technical content.

Note 2: This test method is not intended to cover precise physical procedures. It is recognized that the constant rate of crosshead movement type of test leaves much to be desired from a theoretical standpoint, that wide differences may exist between rate of crosshead movement and rate of strain between gage marks on the specimen, and that the testing speeds specified disguise important effects characteristic of materials in the plastic state. Further, it is realized that variations in the thicknesses of test specimens, which are permitted by these procedures, produce variations in the surface-volume ratios of such specimens, and that these variations may influence the test results. Hence, where directly comparable results are desired, all samples should be of equal thickness. Special additional tests should be used where more precise physical data are needed.

Note 3: This test method may be used for testing phenolic molded resin or laminated materials. However, where these materials are used as electrical insulation, such materials should be tested in accordance with Test Methods D229 and Test Method D651.

Note 4: For tensile properties of resin-matrix composites reinforced with oriented continuous or discontinuous high modulus >20-GPa (>3.0 × 106-psi) fibers, tests shall be made in accordance with Test Method D3039/D3039M.

1.4 Test data obtained by this test method have been found to be useful in engineering design. However, it is important to consider the precautions and limitations of this method found in Note 2 and Section 4 before considering these data for engineering design.

1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

What ASTM D638 means for plastics testing

ASTM D638 provides the framework for tensile testing of plastics using standardized specimens and methods.

It ensures consistency in results across laboratories.

It supports material selection and quality control in manufacturing.

It provides reliable data for regulatory compliance and product design.

Standardized approach vs inconsistent lab methods

1. Before ASTM D638: labs used varied specimen shapes and speeds, making results incomparable.
2. With ASTM D638-22: specimen types I–V, defined test speeds, and reporting rules deliver globally consistent results.

Core building blocks of ASTM D638 test method

1. Specimen types: five standardized geometries (Type I–V) for different material forms and thicknesses.
2. Testing speed: crosshead speeds/strain rates defined per material category.
3. Measured properties: tensile strength, elongation at break, and modulus of elasticity.
4. Equipment: universal testing machine with appropriate grips; extensometers for strain measurement.
5. Reporting: stress–strain curves, failure mode, specimen type, speed, and conditioning.

High-value use cases of ASTM D638

1. Plastics manufacturing: validate new formulations and batches.
2. Composites: ensure performance for aerospace/automotive applications.
3. Quality assurance labs: maintain compliance and supplier consistency.
4. R&D: compare materials for product development and optimization.
5. Education: teach tensile behavior of polymers and testing best practices.

Integration of ASTM D638 with other standards

1. Pairs with ISO 527 (international equivalent) for global reporting.
2. Used alongside ASTM D882 (thin films) and ASTM D790 (flexural) for complete profiling.
3. Supports cross-lab reproducibility and supplier qualification programs.

How to choose the right ASTM D638 edition

1. ASTM D638-22: current revision with the latest clarifications.
2. ISO 527: use when customers require ISO reporting or for EU programs.
3. Older versions: keep only if legacy contracts or historical data comparisons demand it.

Deployment timeline and cost benchmarks

1. Week 1: obtain ASTM D638-22 PDF; review specimen requirements and speed tables.
2. Weeks 2–3: calibrate machines/extensometers; train staff on updated strain-rate procedures.
3. Weeks 4–6: run validation studies; update QA SOPs, templates, and data reporting.
4. Budget guidance: get ASTM D638 and related standards via BSB Edge subscription to reduce per-document spend.

Common pitfalls and how to avoid them

1. Incorrect specimen prep: follow exact Type I–V dimensions and edge quality.
2. Improper speeds: set crosshead speed per material category to avoid skewed results.
3. Missing failure mode: record brittle vs. ductile behavior; include gauge length and strain data.
4. Mixing standards: don’t swap ISO 527 for D638 unless agreed in the contract.

Case study: labs reduced testing errors by 35 percent

A plastics lab upgraded to ASTM D638-22 with improved extensometry and SOPs.

Results: cross-lab consistency improved, operator errors decreased, and testing errors dropped by 35 percent.

Bonus: customers trusted reports more for regulatory submissions and supplier audits.

Next steps and additional resources

1. Get ASTM D638-22 PDF for your lab.
2. Train technicians on correct specimen types and strain-rate selection.
3. Update QA protocols with D638 reporting requirements and data retention.
4. Link out to resources: ASTM Book of Standards, ISO 527 reference, and plastics testing guides.

Frequently Asked Questions

1. What is ASTM D638
It is the standard test method for determining tensile properties of plastics.

2. What does ASTM D638-22 cover
Specimen geometry (Types I–V), test speeds, equipment, data reporting, and accuracy requirements.

3. What are the ASTM D638 specimen types
Five geometries designed for different material forms and thickness ranges.

4. How is tensile strength measured to ASTM D638
By pulling a standardized specimen to failure in a universal testing machine and analyzing stress–strain data.

5. Which industries use ASTM D638 testing
Plastics, composites, automotive, aerospace, research labs, and QA labs.

6. How can I access ASTM D638 PDF or the latest revision
Through BSB Edge or ASTM International.

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