Page 173 - Template Tesis UTM v2.0

4.10.1 Mechanical Impedance

Mechanical impedance is one of the crucial aspects that should be considered

when analysing the dynamic properties of composite materials. In general, mechanical

impedance presents the ratio of the force on a system which is undergoing simple
harmonic motion to the velocity of the particle, indicating the capability of the

structures in resisting harmonic force. Thus, it is compulsory to obtain the mechanical

impedance in SHPB testing of the tested specimens as well as the Hopkinson bars,
especially when dealing with low impedance materials. This is due to most of the

incident waves would be reflected at the interface. Mechanical impedance, and wave
velocity, of the Hopkinson bars and the specimens can be determined using

Equation 4.3 [167–168] ;

= x x (4.3)

Where ;

- Cross-sectional area of the specimen
- Density of the specimen

- Wave velocity of specimen

wave velocity, can be determined using Equation 4.4;

= √ (4.4)

Where;

- Young’s modulus of specimen

- Density of specimen

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