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Module 7: Advanced Topics in Vibration Control

Lecture 37: Active Constrained Layer

Table below describes the damping performances of viscoelastic materials, hard-damping alloys and active materials.

Table 37.1: Damping performance of VEM

Damping Material		Advantages	Disadvantages
Passive Damping Materials	Viscoelastic	High Damping Low weight Penalty No external effort needed	Unsuitable for very low and high temperatures and at low frequencies No controllability
Passive Damping Materials	Hard Damping Alloys	High temperature, high frequency operating range No external effort needed	Relatively low damping High weight penalty High strain dependency No controllability
Active vibration suppression Materials	Piezoelectric, Magnetostrictive alloys or composites	Controlled blocking force generation High or Moderate temperature, high frequency operating range	Low inherent damping in most operating range External energy supply Instability issues in control
Active vibration suppression Materials	Shape Memory alloys	Large strain applications	Lower controllability Low frequency bandwidth Needs either stress or temperature induced phase Transformation

The ACLD or hybrid system could be considered to be a fusion of purely active and purely passive damping. It retains the advantage of passive damping in terms of robustness and reliability while reducing the overall weight of the system and increasing the efficiency to attain high damping over a large frequency band.