Impact Strength

• Impact Strengths the capability of the material to withstand a suddenly applied load and is expressed in terms of energy.• it expressed in j/m or kg cm/cm of notch. • Its a mechanical property of any material.

Significance: impact strength of material determines the toughness of material it means resistance to high speed loading

Factors affecting the impact strength

• Rate of loading• Temperature• Orientation• Processing condition and types• Degree of crystallinity , molecular weight

Impact test for plastics can be categorized in three major types: 1.pendulum impact test : charpy, izod ,tensile impact test2.Drop weight impact :

3.Instrumented impact test :

Test specimen and conditioning

For Izod test : 64.5mm × 12.7 mm × 3.2mmFor charpy test : 127mm × 12.7mm × 3.2mm

Notch : the angel of notch is 45°± 1° with a radius of 0.25 mm.

Laboratory atmosphere is 23 ± 2°C and 50 ± 5 % RH

Notched Izod Impact Strength Specimen is held as a vertical cantilevered beam and is broken by a pendulum. Impact occurs on the notched side of the specimen.

The test was developed in “1905” by the French scientist Georges Charpy. Charpy Impact Strength Specimen is held as a simply supported beam and is impacted on the side opposite the notch. This method is no longer covered under ASTM D256 but is still reported as such.

Izod / charpy impact test

Equipment :

Izod impact

Charpy Impact

What we know form impact strength test :

• Shock loading characteristics of material• Test result used for comparison of material, manufacturing condition, material texture design and treatment .

Factors Affecting Test Result

• Notch

• Specimen thickness

• Specimen preparation

• Temperature

• Filler and other additives

• Limitations

References

• Handbook of Plastics Testing and Failure Analysis by Vishu Shah• Google books ,Google scholar• Fundamentals of plastics testing by S.K. Nayak• www.polymer-filler.blogspot.com