High Temperature Thin Film Strain Sensor Calibration and Mounting
High temperature thin film strain sensor accuracy depends on rigorous apparent strain polynomial correction, dielectric barrier integrity, and drift mitigation.
Ceramic Matrix Composite Strain Measurement
Metrological Method
Surface deformation tracking on non-homogeneous refractory materials quantifies mechanical response under extreme thermal loads. Accurate ceramic matrix composite strain measurement requires sensor integration techniques that accommodate matrix microcracking and anisotropic thermal expansion. Optical extensometry and direct-deposited thin film gauges track local strain fields without reinforcing the composite surface.
Woven silicon carbide fibres create local strain variations that differ from bulk structural response. Gage selection depends on reinforcement weave architecture and operational temperature limits.
Substrate Interaction
Porous surface topologies and ceramic cloth weaves generate local strain concentrations across individual yarn bundles. Direct bonding of resistance strain gauges requires planarisation layers to prevent uneven load transfer and premature cement failure. High surface roughness accelerates bondline peeling under shear loading.
Thermal expansion mismatch between oxide coatings and silicon carbide matrices introduces parasitic thermal strain during heat up. Gauge active lengths must span several weave repeat units to average microscopic matrix cracks into macroscale strain values.
Thermal Compensation
High thermal gradients induce significant apparent strain in bonded metallic gauges above eight hundred degrees Celsius. Thermocouple arrays positioned adjacent to the strain gauge provide real-time temperature data for numerical compensation algorithms. Optical tracking systems utilize blue illumination and bandpass filters to isolate surface features from thermal incandescence.
Calibration bars made from identical composite batches provide empirical thermal output curves. Dynamic strain measurement requires high-bandwidth amplifiers to capture microcrack propagation events.
Measurement Limit
Severe matrix oxidation at high temperatures degrades the gauge installation bondline and causes signal loss. Fiber weave orientation alters transverse sensitivity and complicates planar strain tensor calculations. Capacitive strain gauges offer low drift alternative solutions for long-term static testing up to one thousand degrees Celsius.
Acoustic emission sensors operate alongside strain instrumentation to detect internal fiber pullout.