ASTM D638 Standard Test Method for Tensile Properties of Plastics
ASTM D638 measures the tensile characteristics of unreinforced and reinforced plastics. The test measures the strength, hardness, and expansion of plastic products used in industry for production, packaging, automotive, electrical, and consumer goods. The method relies on standardized dumbbell-shaped specimens tested in a universal testing machine under standard conditions. The test results are tensile strength, tensile modulus, elongation, and Poisson's ratio. ASTM D638 helps manufacturers maintain control over material quality, compare formulations, and carry out engineering designs.
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ASTM D638 Introduction
ASTM D638 (Standard Test Method for Tensile Properties of Plastics) establishes a standard for assessing the tensile properties of plastic material. The tensile test simply pulls on a plastic specimen until it deforms or breaks. It is suitable for all unreinforced and reinforced plastics and provides good information about the mechanical properties of a particular material for quality control, material improvement, and design purposes. Since plastics are sensitive to strain rate, temperature, humidity, and specimen preparation details, testing conditions require stringent control in the laboratory.
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ASTM D638 Testing
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Testing Procedures and Requirements
Technicians cut the standard specimen (dumbbell-shaped) and condition it in a designated temperature- and humidity-controlled environment. Subsequently, it will be secured to a universal testing machine. This machine elongates the specimen at a constant crosshead speed until it breaks or fractures. Measure the load and extension data and use them to compute tensile characteristics.
Yield Point Determination
For materials that exhibit yielding, operators record the yield point using methods such as offset yield (0.2%) or observable yield behavior from the stress-strain curve.
Ultimate Tensile Strength Measurement
Technicians keep loading the specimen until the maximum load is reached. They use this maximum load and the initial cross-sectional area to determine the tensile strength.
Elongation and Failure Analysis
Test terminated when specimens broke. For material characterization, operators measure elongation at break, examine the location of the failure (gauge or grip section), and assess the failure mode.
ASTM D638 Grips and Fixtures
Scope of ASTM D638
Calculates tensile characteristics of plastics.
It is suitable for unreinforced and reinforced plastics.
Measures strength, stiffness, and elongation.
Assesses and contributes to quality control and development of plastic materials.
Gives data for engineering design uses.
ASTM D638 Equipment and Sample Preparation
Specimen Details
Technicians test rigid and semi-rigid plastics, including thermoplastics, thermosets, polymer blends, and reinforced plastics. Specimens are typically dog-bone-shaped tensile specimens and molded or machined from sheets, plaques, or finished parts. Their voids, bubbles, cracks, sink marks, or surface defects must not affect tensile properties.
Specimen Preparation
The operators carefully condition the specimens to a stable moisture and temperature equilibrium and measure all dimensions before testing. Provide rounded edges and uniform-gauge sections to avoid stress concentrations during loading.
Specimen Dimensions
The laboratory makes standard dog bone specimens. The specimen includes a narrow-gauge strip and broad grip areas to provide uniform stress distribution and good specimen grip during tensile loading.
Use of ASTM D638
Tests the mechanical properties of plastics.
Compares and selects plastic materials.
Implements suggestions for plastic product development and research.
Indicates the effects of engineering design decisions on plastic manufacturing.
What is Tensile Strength, And Why Does It Matter?
The tensile strength is the highest stress that a plastic can withstand before breaking. Tensile strength is a measure of resistance to mechanical loads and deformation; the higher the tensile strength, the greater the resistance.
How Do Testing Conditions Affect Results?
Plastic materials are very sensitive to temperature, humidity, pressure, charges, and sample training. Variations in those conditions can substantially affect tensile strength, modulus, and elongation. In this respect, laboratories maintain test conditions to ensure a reliable effect.
Common Challenges and Troubleshooting
Technicians face specimen slippage, misalignment, specimen-size variability, or environmental changes. These problems affect tensile properties and repeatability. The correct preparation of samples, calibration of equipment, and control of environmental conditions contribute to reliable results.
ASTM D638 Testing Technique, Process, and Data Collection
First, technicians prepare and condition plastic specimens. Then place the specimen in the testing machine and connect the extensometer. The machine is used to apply a tensile force at a given speed until failure. The test records loads and system elongation continuously during the test. Lastly, technicians create a stress-strain curve and work out tensile properties.
Analysis Results and Interpretation
ASTM D638 evaluates several important tensile properties of plastics, such as tensile strength (MPa), tensile modulus (GPa or MPa), and elongation at break. A higher tensile strength means the material is more resistant to pulling forces before it breaks, and a higher tensile modulus means the material is more resistant to deformation under a pulling force. This allows engineers to choose a variety of plastics to suit the required material accommodations.
Rohit Dhembare is an Operations Associate at MaTestLab Inc. and holds a postgraduate degree in Organic Chemistry.
FAQ's
Where can I get the astm d638 tested?
You can share your astm d638 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d638 test to various testing techniques.
How much do I need to pay for the astm d638 test?
Please contact us for a detailed quote for your astm d638 testing needs. Cost incurred to carry out different astm d638 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
How many samples are required for astm d638?
The required number of samples or specimens should comply with the procedure given in the astm d638 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
How much discount can I get on the astm d638 test?
MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
How many days will it take to complete the astm d638 test?
The turnaround time for astm d638 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
Where can I get the astm d638 tested?
You can share your astm d638 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d638 test to various testing techniques.
MaTestLab Inc. offers accessible, quick, and affordable material testing, product testing, and failure analysis services. We support your on-demand testing and expert consultation needs with the help of our extensive network of material testing laboratories situated in the US and other parts of the world.
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