Izod Pendulum Test

Polymeric materials for structural application sometimes undergo impact loads or rapid stress loading. There are a couple of test methods that can assess the ability of material to withstand such loads. Most common methods among them are Charpy and Izod impact tests in which Charpy test is generally used for metals whereas Izod test is very popular methods for polymeric materials [18]. The Izod pendulum test by which impact toughness is measured is described in the standard ASTM D 256. Average of four or five readings is taken and average of these gives the impact strength of the material. Comparison of materials can be done by taking a standard test specimen for all the cases because total impact energy depends on notch shape, length and also

Pointing (1909) conducted the first experiment to measure the elasticity of a material. He applied oscillatory deformations to the material and measured the mechanical response at different temperatures. Thus solidus and liquidous phase behaviour of polymers could be modelled mechanically with the combinations of springs and dashpots [20]. Main principle of working of the instrument is that a sample is subjected to a sinusoidal oscillating stress, its response will be sinusoidal oscillation with similar frequency provided the material remains within its elastic limits. In case of a viscous material response will be an out-of-phase strain wave. This phase difference in the applied and measured response frequency at extremes will be such that for a Newtonian liquid the phase angle will be 90 degrees and that for a perfectly elastic solid will be 0 degrees. Phase angle thus for a viscoelastic material will be in between 0 and 90 degrees

Tensile test instrument and test specimen [24]

Polymers can be easily characterised with respect to their mechanical properties by analysing their stress-strain curve. As described in the Table.6, relative mechanical behaviour of the polymers can be studied by tensile test.

Table.3. Characteristic features of polymer properties as related to stress-strain curve

Modulus Yield stress Ultimate strength Elongation at break Description of polymers

Low Low Low moderate Soft & weak
Low Low High High Soft & tough
High None Moderate Low Hard & brittle
High High High High Hard & tough

4. Polymeric Materials for Army Stores
Polymeric material for development of various army stores are selected according to their application, qualitative requirement and service conditions. Some frequently used materials are described below:
4.1. Polycarbonates (PC): These are a group of thermoplastic polymers having carbonate groups in their structures. Polycarbonates are used in engineering as well as in commodity items. They are strong, tough and optically transparent. Polycarbonates find many applications as they can be easily worked, moulded and thermoformed. It has high impact-resistance but has low scratch-resistance therefore; a hard silicon based coating is applied to polycarbonate eyewear lenses and exterior automotive components. Polycarbonate is highly transparent to visible light and may have better light transmission than