Notched rectangular specimen

ASTM D-3763) (20). The notched Izod test is familiar to most workers in the plastics field. A standard notch is cut in a rectangular specimen. The specimen is broken by a dropping pendulum. The impact strength of the material is computed from loss of momentum of the pendulum. 

Impact is a catastrophic event that has become very important for plastics. While measurements of impact performance have always been made in the past, new applications in the automotive, electronic, and consumer appli-cance industries have placed considerable importance on the quantification of this behavior. Historically, the Izod test has been used routinely to characterize impact. A notched rectangular bar is clamped in a vise and broken by a sharp impact from a hammer attached to a moving pendulum. The test has been widely criticized for being unsuitable for plastics, but it remains the most common test for impact and failure characterization. The Charpy test, widely used in Europe, has seen better acceptance by the scientific community. Here the test specimen, similarly notched, is held in a flexural mode while it is subjected to the impact. 

In the Izod Impact Test, a rectangular specimen is clamped securely at one end, then struck by a weight at the end of a pendulum. As the pendulum continues its swing, it moves a pointer which records the amount of force used up in breaking the specimen. Impact strength is reported as force per imit of specimen width (e.g., N/m or Ibfrin). The specimen is usually notched in the center, but unnotched specimens can also be tested. 

Mechanical property and self-healing ability of shFRC were investigated form three-point bending using 3 mm x 4 mm x 50 mm rectangular specimens with a V-shaped notch whose depth is 1 mm. 

Double torsion test specimens take the form of rectangular plates with a sharp groove cut down the centre to eliminate crack shape corrections. An initiating notch is cut into one end of each specimen (Hill Wilson, 1988) and the specimen is then tested on two parallel rollers. A load is applied at a constant rate across the slot by two small balls. In essence the test piece is subjected to a four-point bend test and the crack is propagated along the groove. The crack front is found to be curved. 

In this test a failing weighted pendulum strikes a rectangular bar specimen, mounted vertically by being clamped at the lower end the specimen is usually notched, the notch dimensions being specified. Commonly used standard conditions are ... 

A rectangular bar of polymer of thickness B = S mm and width = 20 mm has a central notch of length a = 10 mm. The bar is loaded in a three-point bending test with an 80 mm span, S, at room temperature. The bar fractures when the force applied is 300 N. Calculate (a) Kjc for the polymer and (b) the force needed to fracture in a compact tension test a specimen of dimensions IT = 50 mm, J = 10 mm, having a single-edge sharp crack of = 25 mm. 

Test specimens were cut from compression moulded sheet in the form of rectangular bars with the following dimensions (a) 10 x 10 x 110 mm, (b) 16 xl6 x 110 mm and (c) 20 x 20 X 110 mm (Figure 1). A lathe was used to produce the symmetrical notch using a single point cutting tool of tip radius < 20 im. 

The test may be carried out on plain rectangular bars, but most often a carefully defined notch is molded or machined into the face to be struck (Figure 12.8). The impact tests are often regarded as a means of assessing the resistance of a material to shock where notches or stress raisers generally are present. The ratio of impact strength of unnotched to that of notched specimen is sometimes regarded as a measure of the notch sensitivity of a material. 

This is a well-known original ESC test developed by Bell Labs in the late 1940s. Ten rectangular-shaped specimens are cut from a molded plaque prepared using standard methods. A controlled notch is cut horizontally across each specimen, which serves as a crack initiation point. The specimens are bent and inserted into a C -shaped bracket, creating a stress in the specimen. A diagram of this test method is shown in Fig. 10.73. The specimens and bracket are inserted into a tube filled with Igepal solution. The tube is then placed into a heated environment... 

Two methods are used for bend testing—three- and four-point bending tests. Here, the specimens are rectangular, without notches. It is obvious from Fig. 1.48 that the applied force (downward arrows) is compressive by nature, resisted by the tensional force (upward arrows). Thus, the longitudinal stresses at the lower surfaces (convex) in the specimens are tensile and compressive at their upper surfaces (concave). As a consequence, a calculable bending moment develops. The modulus of rupture is the stress of the specimen at its failure and represents the flexural strength of the specimen. 

Beam bending 10 to 10 Rectangular beam about 10 X 0.8 X 2.5 mm Specimen supported across top of a notched holder made from silica glass tubing about 8 mm internal diameter and 10 mm deep. Short, 1 -mm-diameter silica glass rod (ground flat) as knife edge between silica probe and the beam [31]... 

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