ISO 179 Plastics - Standard Test Method for Determination of Charpy Impact Properties

The Charpy effect is a single point test that measures the resistance of materials to impact from a swinging pendulum. The Charpy effect is defined as the kinetic energy required to initiate fracture and continue to fracture until the specimen breaks.

ISO 179 specifies a method for determining the Charpy impact strength of plastics under defined conditions. A number of different samples and test configurations have been described. Different test parameters are specified according to the type of material, the type of test specimen and the type of notch.

The method can be used to investigate the behavior of certain types of specimens under defined impact conditions and to predict the brittleness or toughness of specimens within the limitations inherent in the test conditions. It can also be used to determine comparative data from similar material types.

The method has a wider applicability range than that given in ISO 180 (Izod impact testing) and is more suitable for testing materials that show interlayer shear fracture or materials that exhibit surface effects due to environmental factors.

The method is suitable for use with the following range of materials:

• Rigid thermoplastic molding and extrusion materials (including filled and reinforced compounds in addition to unfilled types) and rigid thermoplastic sheets;
• Rigid thermoset molding materials (including filled and reinforced compounds) and rigid thermoset sheets (including laminates);
• Fiber-reinforced thermoset and thermoplastic composites containing unidirectional or multidirectional reinforcements (such as mats, woven fabrics, woven rovings, chopped strands, combination and hybrid reinforcements, rovings and milled fibers) or containing sheets made of pre-impregnated materials (prepregs), including filled compounds ;
• Thermotropic liquid crystal polymers.

Impact tests using the Charpy method are used to characterize a plastic at high expansion rates. Stress occurs suddenly and in a 3-point bending structure. In the classical method, the result is presented as the energy uptake of the sample. In addition, instrument measurement methods allow the display of force-displacement diagrams, provide additional material information, and allow automatic assignment of the fracture type.

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