JANAF specimen

Figure 2. Schematic of the extrusion behavior of the JANAF specimen. The extended sample ( = 1.57) on the right shows a displacement of the oval markings through the jaw area (11)...

Other techniques for measuring strain more satisfactorily in the gage section of the JANAF specimen have been developed. One inexpensive and simple method is the use of a clear plastic film extensometer which is attached to the gage section of the specimen. A mark on the face of the specimen is pulled past evenly spaced lines on the clear film, and the... 

Figure 3. JANAF specimen with plastic film extensometer in place...

Figure 4. JANAF specimen with Farris (27) extensometer...

Figure 7. Plot of effective gage length (EGL) vs. strain comparing the Saylak cylindrical specimen with the JANAF specimen. Three propellant formulations were tested (83)...

Standard JANAF tensile specimens. Strain rate, 0.74 in./in./min. 

The results of one study to determine the maximum allowable time between casts are shown in Table XI. These data show that a change in the point of failure in the JANAF Instron tensile specimens occurred when the time between casts was changed from 48 to 72 hours. When the time between casts was increased to 96 hours, a marked change in the mechanical properties also occurred. Based on these data, the time between casts would be limited to 48 hours for this propellant. 

Standard JANAF tensile specimens. Interface approximately the midpoint of the gage section. 

Standard JANAF tensile specimens tested at a strain rate of 0.74 in./in./min. Batch interface at approximately the midpoint of the gage section. 

Figure 1. JANAF uniaxial solid propellant tensile specimen with typical gripping jaws. Dimensions are in inches...

The uniaxial test is widely used for quality control and formulation testing for obvious reasons. The JANAF configuration is not likely to be replaced for these purposes, especially since the backlog of information relative to the formulation art is composed primarily of data from this specimen. Grain structural analysts require more precise information, however, and when uniaxial data are obtained for their purposes, more elaborate and time-consuming tests may be conducted. 

Figure 5. Several uniaxial specimen configurations (a) Thiokol end-bonded, (b) cylindrical, (c) Stanford Research Institute configuration, (d) JANAF/Tab end hybrid, (e) rectangular tab end (f) flow reservoir...

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