Advantages of SMA strain gauges

High elasticity due to strain-induced phase transformation

  • max. reversible strain: 8 % (80,000 µm/m)
  • proof for 106 cycles at 1 % (10,000 µm/m) strain
  • min. gauge factor: 5
  • transverse sensitivity (GFRP): -0.09

Simple sensor integration into polymers and composites

  • embedment of sensor structures via injection molding, laminating and infiltration

Minimum thermal drift compared to carbon fibre sensors

Simple data acquisition by means of electric resistance changes

Extremely long lifetime

Schematic of strain sensor structure made of SMA wires
Electrical resistivity change of SMA when strained
Fatigue properties of SMA sensor compared to conventional strain gauges

State-of-the-art of conventional strain sensors

Strain gauges, textile + thin film sensors

  • elastic up to 0.2 % strain (2,000 µm/m)
  • limited fatigue strength in plastic components
  • fatigue break for higher strain amplitudes

Faser-Bragg-grating sensors

  • expansive and huge measurement instrumentation
  • not useful for small and mobile applications

Carbon fibre sensors

  • low gauge factor
  • strong temperature dependence