ASTM E831 / D696 Linear Thermal Expansion (CTE) Testing
The coefficient of Linear Thermal Expansion (CLTE) is determined by TMA or Dilatometer ASTM E831, ASTM D696, ISO 11359. CLTE measures the rate at which a given material expands as a function of temperature. This test is important to select thermally stable material for designing parts of different equipment and machines.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
Coefficient of linear thermal expansion tests involve measuring the rate at which the length of materials changes with a given change in temperature. This is an important test for assessing the dimensional stability requirements for material selection programs and for thermal compatibility assessment programs. ASTM E831 defines the thermomechanical analysis method for linear thermal expansion tests for solid materials. Similarly, ASTM D696 defines the dilatometer method for linear thermal expansion tests for plastic and electrical insulation materials.
Scope, Applications, and Benefits
Scope
The ASTM E831 standard test method is used to determine the coefficient of linear thermal expansion via thermomechanical analysis, measuring the dimensional change of specified specimens with respect to temperature. The ASTM D 696 standard test method measures the thermal expansion of plastic materials using a vitreous silica dilatometer over a specified low-to-ambient temperature range.
Coefficient of linear thermal expansion testing evaluates:
- Linear thermal expansion coefficient of metallic, polymeric, ceramic, and composite materials
- Dimensional change behavior of solid materials across defined temperature ranges
- Thermal compatibility assessment of dissimilar material combinations in assembly applications
- Effect of material composition, orientation, and processing on thermal expansion behavior
- Compliance with the defined thermal expansion coefficient requirements for material specifications
Applications
- Metallic, ceramic, and composite materials requiring thermal expansion characterization
- Plastic and electrical insulating materials requiring ASTM D 696 dilatometer expansion data
- Electronic packaging, PCB substrate, and semiconductor materials require CTE matching data
- Automotive, aerospace, and industrial components requiring thermal dimensional stability data
- Material suppliers and processors requiring ASTM E 831 and ASTM D 696 thermal expansion data
Benefits
- Provides reliable CTE data for material thermal compatibility and dimensional stability assessment
- Supports material specification compliance and supplier assessment programs
- Identifies thermal expansion mismatches in material combinations before assembly
- Delivers traceable thermal expansion test records for engineering and research submissions
- Reduces thermal stress risk by verifying material CTE early in the design approval cycle
Test Process
Sample Preparation
Specimens prepared to defined dimensions and conditioned per applicable ASTM requirements.
1Thermal Analysis Setup
Specimen loaded into TMA or dilatometer and configured for defined temperature scan conditions.
2Thermal Expansion Measurement
Dimensional change measured as function of temperature across defined test temperature range.
3Data Analysis & Reporting
CTE calculated from dimensional change data and assessed against criteria for test compliance result.
4Technical Specifications
| Parameter | Details |
|---|---|
| Applicable Materials | Metals, ceramics, composites, plastics, and electrical insulating materials |
| ASTM E 831 Technique | Thermomechanical analysis for solid material linear thermal expansion measurement |
| ASTM D 696 Technique | Vitreous silica dilatometer for plastic and electrical insulating material expansion measurement |
| Measured Parameters | Linear dimensional change, temperature, and calculated thermal expansion coefficient |
| Measured Outputs | Dimensional change data, CTE values, thermal expansion curves, and test compliance result |
Instrumentation Used for Testing
- Calibrated thermomechanical analyzer for ASTM E 831 solid material CTE measurement
- Vitreous silica dilatometer for ASTM D 696 plastic material thermal expansion measurement
- Certified temperature and dimensional reference standards for instrument calibration
- Specimen conditioning chamber with temperature and humidity control
- Specialist thermal expansion data acquisition and CTE calculation software
- Data reporting and thermal expansion curve visualization system
Results and Deliverables
- Dimensional change versus temperature data across defined test range for all specimens
- Calculated coefficient of linear thermal expansion values per ASTM E 831 and ASTM D 696
- Statistical summary of CTE results across the test specimen set
- Test compliance result assessed against defined material thermal expansion requirements
- Combined ASTM E 831 and ASTM D 696 thermal expansion test report
Frequently Asked Questions
ASTM E831 and ASTM D696 measure the coefficient of linear thermal expansion. They determine how materials expand or contract with temperature changes. This gives important information for dimensional stability and design considerations.
ASTM E831 is usually used for solid materials with thermomechanical analysis. ASTM D696 is often applied to plastics through dilatometry. Both methods measure linear thermal expansion behavior.
Thermal expansion impacts the dimensional stability of components that experience temperature changes. ASTM E831 and ASTM D696 assist engineers in choosing compatible materials to avoid warping, stress buildup, or failure in assemblies.
ASTM E831 and ASTM D696 are commonly used for metals, plastics, ceramics, composites, and polymers used in electronics, automotive, aerospace, and construction applications.
ASTM E831 and ASTM D696 assess thermal expansion in controlled lab settings. These tests may not reflect how materials behave in actual service conditions with complex thermal cycles, mechanical loads, or environmental factors.
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