ASTM D638
ASTM D638 is a standard test method for determining the tensile properties of reinforced and unreinforced plastics. It includes tensile testing and other procedures using a standard dumbbell shaped specimen of plastic materials. It is a common practice in the plastic industry for purposes of determining the quality and performance of the materials.
Home » Services » CNC Machining Service » Acrylic CNC Machining » ASTM D638
Rigid plastics, including both reinforced and non-reinforced types.
The standard covers all types of plastics. However, specific names of material can vary according to the type of plastic testing (for example, commercially, polyethylene or polypropylene, and so forth).
The examination can be used with plastics that are usually strained into custom shapes by injection molding, die-cutting or machining. It cannot be applied for thicknesses of films or sheets lower than 1.00 mm, which are better tested according to ASTM D882.


Kingsun's senior machining engineer
ASTM D638 Properties
Mechanical Properties
- Tensile Strength: The quantity of stress necessary to rupture a plastic material.
- Tensile Modulus: Defines the rigidity characteristics of the substance.
- Elongation: The ability of the material to extend before rupturing.
- Poisson’s Ratio: This is also the transverse strain that is produced by axial strain in the longitudinal direction.
Physical Properties
Includes various types like Type I, IV, and V, which differ in size and are typically molded or machined into specific shapes.
Thermal Properties
ASTM D638 tests can be conducted in temperature-controlled environments to simulate end-use conditions.
Electrical Properties
Not specifically covered under ASTM D638, as it focuses on mechanical properties.
Post Treatments
Specimens may be conditioned in specific environments to simulate real-world conditions before testing.
Common Applications
This testing method is commonly employed in the industries that seek to comprehend the tensile properties of plastics such as automotive, aerospace, and consumer goods.
Recommended Reading


Frequently Asked Questions (FAQs)
Q: What is ASTM D638?
A: ASTM D638 is the standard test method for the determination of tensile properties of plastics, which details how tensile testing of plastic materials, such as tensile strength and its elongation, is done.
Q: What are the specimen types used in ASTM D638 testing?
A: In the process of testing for ASTM D638, there are a number of test specimen types employed, notably Type I, Type II, Type III, Type IV, and Type V, as the circumstances may require, each fitting a specific purpose.
Q: How is the tensile strength test performed according to ASTM D638?
A: To carry out D638, a test sample is mounted in a universal testing instrument where a tensile load is applied on the sample until all of the materials fail. Subsequently, the results obtained from this are scrutinized to get information pertaining to tensile strength and other properties.
Q: What is the importance of the tensile properties of plastics?
A: The tensile properties of plastics are relevant so as to know how the plastics can be utilized in real situations. These properties enable manufacturers to choose materials according to their strength, stiffness, purpose and other operational parameters.
Q: In tensile properties, what does ASTM D638 measure?
A: ASTM D638 is used to measure several tensile properties such as tensile strength, elongation at break, and tensile modulus, among others, which are essential in many mechanical assessments of plastics.
Q: Is it possible to do ASTM D638 on both reinforced and unreinforced plastics?
A: Yes, ASTM D638 can be employed on unreinforced and reinforced plastics, giving room for comprehensive tensile strength tests of the constituents and other properties.
Q: What test equipment is applied for ASTM D638?
A: A universal testing machine is normally employed for carrying out ASTM D638 since it allows relative precision when controlling the test speed and measuring the tensile strength and others.
Q: What is the importance of the test speed during ASTM D638?
A: The importance of the test speed in ASTM D638 is that it can affect the tensile properties that are measured. Different materials may need different speed of tests for accuracy.
Q: In what ways are ASTM D638 standards similar or different from other ISO standards?
A: ASTM D638 and ISO standards may be aimed at testing tensile properties of plastics; considering they may not be identical, particulars of the test procedures and specimen types will likely vary. It is necessary to check the respective standard in order to contain essential operations.