Izod impact test specimens

Figure 3-87. During injection molding, a double gate can cause weld lines, when two melt fronts meet in a cavity, and reduce impact strengths, as well as other properties. Single-gated and double-gated Izod impact-test specimens were molded using different plastics to provide impact-strength comparisons.

Figure 5.21 The SEM photographs of the fracture surface for the Izod impact test specimen. (a) Under 88urn and (b) 125-210 tm.

Figure 2-40. Diagram illustrating izod impact test specimen properly positioned in text fixture. (Courtesy of CEAST U.S.A. Inc.)...

IZOD impact test—method for determining the behavior of materials subjected to shock loading. Specimen supported as a cantilever beam is strack by a weight at the end of a pendulum. Impact strength is determined from the amount of energy required to fracture the specimen. The specimen may be notched or unnotched. 

In the notched Izod impact test, with the exception of some rubber modified plastics, the fracture surface of a specimen that has failed ductilely exhibits significant inward collapsing on the sides of the impact bar near the notch, indicating that a large amount of plastic flow has... 

Mechanical tests were carried out in a laboratory where the temperature was maintained at 25°C using a Universal Testing Machine, LR-50 K (LLOYD Instrument, England) at a crosshead speed of 50 mm/min and 98 mm as gauge length. Stress at break, strain at break, work of rupture, and initial modulus were determined as per ASTM standards. Izod notched impact test specimens were... 

PS blends with EPDM were compatibilized by addition of either SB (polystyrene/polybutadiene di-block copolymer) or SEP (polystyrene/ethylene propylene di-block copolymer) and were blended in a corotating twin-screw extruder T = 200°C (Table 11.9). The strands were quenched and pelletized. Some of the pellets were injection-molded (200°C) into 4 mm-thick specimens and irradiated to 50 kGy (3-MeV electron accelerator). Another part of the pellets was similarly irradiated and then injection-molded. The samples for notched Izod impact testing (ASTM D256) were annealed for 24 h at 80°C, or were left at RT for 3 weeks, before testing [van Gisbergen et al., 1990,1991b]. 

Izod impact tests at room temperature were performed on compression molded samples (50x13.0x3.0 mm ), having a notch of 0.5 mm deep and a tip radius of 0.25 mm. The fractured surfaces of the broken specimens were examined in a scanning electron microscope (SEM) after coating with Au-Pd by means of an evaporator. 

Izod Impact Test Izod impact is a test designed to determine the resistance of a plastic to the impaet of a suddenly applied force. It is a measure of impaet strength determined by the difference in energy of a swinging pendulum before and after it breaks a notched specimen held vertically as a cantilever beam. 

The Izod impact test is performed on notched and unnotched single edge clamped specimens and serves to evaluate the toughness behaviour of plastics under impact loading. It is standardized in ASTM D 256 and... 

The impact strength of the pure ENR and its hybrid composites was measured with a standard Izod impact testing machine (model IT 1.4, Fuel Research Instruments, Maharashtra, India) according to ASTM D 256. The measurements were done on unnotched samples (70x10x4 mm) with an impact speed of 1 m/s and energy of 1.4 joules. For each specimen, six measurements were recorded. 

Tensile-impact test n. An impact test that uses a pendulum striker to break a dog-bone-shaped test specimen, described in ASTM D 1822 and 1822M. It differs from the Izod impact test in two important aspects (1) the specimen is not notched and (2) it is broken in simple tension rather than bending. For these reasons, its interpretation is more straightforward. 

The tensile impact strength—ASTM D1822. The tensile impact test eliminates the notch-sensitivity aspect of the IZOD impact test and is a more reliable indicator of impact strength for many applications. This test uses an apparatus very similar to that used for the IZOD tests except that, in this case, the specimen is attached to the pendulum on one end and has a T bar attached to the other end. When the pendulum drops, the T bar catches on the apparatus at its base causing the specimen to undergo tensile impact. For this test, the specimen is 2.50 in long and necks to 0.125 in at the center. The thickness can vary. The gripping surfaces at the ends are 0.50 in wide. This test is typically performed on materials which are too elastic to fail in the IZOD test and is normally found on data sheets. It can be performed on request if it best represents the product s performance requirements. 

In Section 6.8, a detailed analysis of the most frequently used impact tests (i.e., Charpy and Izod impact tests) is used to characterize fracture toughness. Temperature, strain rate, crack tip curvature, specimen thickness, annealing, aging, irradiation, and environmental effects are discussed as test variables using the Iramework of fracture mechanics. 

The Izod impact test is based on an old, established test originally designed for metals in which a notched-bar specimen is tested in cantilever fashion with an excess energy pendulum machine. Izod (ASTM D256), Charpy (ASTM D6110 and Research Report D20-1034, to become a new standard), and the tensile-impact (ASTM D1822) tests can be performed with pendulum machines. 

Charpy impact ASTM D6110 (also. Research Report D20-1034) Similar to Izod impact test. Notched specimen is supported on two ends and struck by a pendulum in the middle, a three-point-bend setting. 

The distinction between brittle and ductile failure is also manifested in two other ways (1) the energy dissipated in fracture and (2) the nature of the fracture surface. The energy dissipated is an important consideration for practical applications and forms the basis of the Charpy and Izod impact tests (discussed in Section 12.8 below). At the testing speeds under which the practical impact tests are conducted it is difficult to determine the stress-strain curve, so impact strengths are customarily quoted in terms of the fracture energy for a standard specimen. 

Freitag and Reinking reported on the property profile of Bayer s commercial polyarylate [31], They observed that polyarylate was less sensitive to specimen thickness than polycarbonate in the notched izod impact test. They stated that polyarylate is quite similar to polycarbonate in hydrolytic degradation by alkalis, dilute acids, and hot water. The injection moldability... 

Stress-strain behavior was examined at room temperature, according to ASTM test D638-68, with a crosshead speed of 0.085 mm/sec. Young s modulus (3), ultimate tensile strength (TS), and ultimate elongation to break (e ) were determined. Notched Izod impact tests were made following ASTM test D256-73 usually 4 to 5 specimens were tested. 

Figure 9.16 Izod impact test arrangement of specimen. View from the front of the apparatus...

Scheme 8.1 Dilational stress concentration effects at the notch tip under the plane strain conditions of notched Izod impact tests on a thick polyamide specimen...

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