Fraunhofer Institute for Ceramic Technologies and Systems IKTS
Fraunhofer Institute for Ceramic Technologies and Systems IKTS

Determination of the coefficient of thermal expansion (CTE)

Topic

Another important material property is the coefficient of thermal expansion (CTE). The behavior of this value in terms of expansion when the temperature changes play an important role in the design of materials combination and composition. Strong differences in the coefficients of two bonded structures and weak cohesive and adhesive forces of the joining partners, can lead to damage in the form of cracks and delamination, even if small temperature increases.

Thermo-mechanical analysis (TMA) is used to measure the thermal expansion of polymeric, metallic or ceramic materials under temperature changes and allows to calculate the resulting CTE over a temperature range.

Thermo mechanical analyzer "TMA Q400EM" from TA Instruments.
© Fraunhofer IKTS
Thermo mechanical analyzer "TMA Q400EM" from TA Instruments.
Measurement of CTE on metals or polymers.
© Fraunhofer IKTS
Measurement of CTE on metals or polymers.
Measurement of the CTE on composite systems in the stack structure.
© Fraunhofer IKTS
Measurement of the CTE on composite systems in the stack structure.
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Characterization of the coefficient of thermal expansion (CTE) of polymer materials

  • Identification of materials for the specific operating temperature range and with high resistance to ageing effects
    • Characterization of aging effects due to e.g. temperature changes, moisture/heat, salt spray or media exposure
    • Measurement of temperature-dependent sample expansion and calculation of the CTE 
© Fraunhofer IKTS
With ideal materials, the glass transition is outside the operating temperature range.
Measurement of sample expansion and example of a stabilized material or fully cross-linked polymer.
© Fraunhofer IKTS
Measurement of sample expansion and example of a stabilized material or fully cross-linked polymer.
Example of high post-crosslinking (usually unfavorable for reliability).
© Fraunhofer IKTS
Example of high post-crosslinking (usually unfavorable for reliability).

Characterization process for modeling for FEM simulation

  • Sample production
    • Production of a negative mold
    • Mixing and casting the molds
  • Turning for high plane parallelism
  • Measurement using TMA and calculation of the CTE
  • Data preparation for FEM simulation
CTE measurement.
© Fraunhofer IKTS
CTE measurement.
Extraction for FEM.
© Fraunhofer IKTS
Extraction for FEM.
© Fraunhofer IKTS
3. FEM simulation.

System specification for thermal-mechanical analysis (TMA)

Thermal-Mechanical
Device:  Q400EM from TA Instruments Force resolution: 0,001 N Temperature range: -80 to 1000 °C**
Maximum force: 2 N Displacement resolution: < 0,5 nm Heating and cooling rate: 2 to 50 K/min***
Minimum force: 0,001 N Frequency range: 0,01 to 2 Hz* Temperature stability: 0,1 K
*for DTMA and MTMA measurements; **usable temperature ranges -70 to 400 °C and 25 to 1000 °C; ***dependent on the target temperature.

 

Load possibilities
Measurement of CTE of solid-state materials and very soft materials
Characterization of the melting behavior of coatings on their substrates
Characterization of the deformation temperature of rigid materials