Measurements of the Elastic Modulus

One of the applications of the UMT-series Micro-Tribometer is the precision measurement of the elastic modulus of video, audio and magnetic tapes. This paper describes a test procedure for this type of measurement. 

Experimental procedure: Figure 1 shows a schematic of the test set-up for measurement of the elastic modulus of a recording tape. 

Fig. 1. Schematic of Elasticity Modulus Test Setup

Magnetic tape is clamped between two holders, one of which is attached to the normal force sensor installed on the base of the Micro-Tribometer. The other clamp is attached to the vertical (Z) carriage of the tribometer. The Z-carriage moves up and down at preset distances at a vertical speed of 1 mm/s; thus, providing a series of tensile deformations of the magnetic tape. The corresponding force sensor output data and Z-carriage position data are recorded to a test file for further analysis and calculation.
The graph of the tensile stresses induced in the tape vs. the tape strain are plotted and the slope of this graph provides the value of the elastic modulus of the tape.

After the elastic modulus of the trilayer tape is obtained, the front (magnetic) and back layers are sequentially removed, and the elastic modulus of each combination of two layers is obtained as described above. This technique of selective stripping provides a measure of the contribution of each layer of the trilayer tape to the combined tape modulus. 

Figure 2 presents the typical data for a trilayer magnetic recording tape with front and back coating layers (FMB) in place, with the back coating removed (FM) and with both coating layers removed (M), leaving only the Mylar substrate.

Fig.2. Force/Strain Plot for Magnetic Tape

Table 1 shows the values of the elastic modulus for different tape layers.

Table 1.