Question

name and describe the two impact fracture testing techniques

Answer 1

CHARPY IMPACT TEST

The Charpy impact test was invented in 1900 by Georges Augustin Albert Charpy and it is regarded as one of the most commonly used test to evaluate the relative toughness of a material in a fast and economic way. The Charpy impact test measures the energy absorbed by a standard notched specimen while breaking under an impact load. This test continues to be used as an economical quality control method to determine the notch sensitivity and impact toughness of engineering materials such as metals, composites, ceramics, and polymers.

The standard Charpy impact test specimen is of dimension 55 mm × 10 mm × 10 mm, having a notch machined across one of the larger dimensions. The Charpy impact test measures the energy absorbed by a standard notched specimen while breaking under an impact load. This test consists of striking a suitable specimen with a hammer on a pendulum arm while the specimen is held securely at each end. The hammer strikes opposite the notch. The energy absorbed by the specimen is determined precisely by measuring the decrease in motion of the pendulum arm.

The important factors that affect the toughness of a material include low temperatures, high strain rates (by impact or pressurization), and stress concentrators such as notches, cracks, and voids

IZOD IMPACT TEST

The Izod impact test was named after English engineer Edwin Gilbert Izod. The Izod impact test is like the Charpy impact test and is used to test materials at low temperature. In this test, a specimen is machined to a square or round section, with either one, two, or three notches that have a dimension of 70 mm × 15 mm × 3 mm.

The Izod impact test consists of a pendulum with a determined weight at the end of its arm swinging down and striking the specimen while it is held securely in a vertical position. The impact strength is determined by the loss of energy of the pendulum as determined by precisely measuring the loss of height in the pendulum's swing.

Researchers also defined impact strength as the tendency of polymer composites to endure high-energy impact without breaking or fracturing. They also reported that in fiber-reinforced polymer composites and hybrid composites the impact properties are governed by the properties of the individual fibers used for hybridization, interlaminar, and interfacial adhesion between the fiber and the matrix.