Impact tensile

Small and long specimens of tensile bar shape specimens have their major change in dimensions in the necked-down section. The specimen is mounted between a pendulum head and crosshead clamp on the pendulum of an impact tester. The pendulum is released and it swings past a fixed anvil that halts the crosshead clamp. The pendulum head continues forward, carrying the forward portion of the ruptured specimen. The energy loss (tensile impact energy) is recorded, as well as whether the failure appeared to be of a brittle or ductile type. 

This test has possible advantages over the notched Izod test. The notch sensitivity factor is eliminated, and energy is not used in pushing aside the broken portion of the specimen. The test results are recorded in ft-lb/in.2 (kJ/m2). This allows for minor variations in dimensions of the minimum in cross-section area. 

If one is to consider the application of these data to a design, the size of the force and its rate of application would have to be obtained and compared with the design requirement. The breakdown of energy into components 

The term impact implies a very high speed of the acting force, whereas toughness is not related to any specific speed. Since the two terms are used in conjunction with each other in describing resistance to impact, it appears desirable to correlate those readily obtainable properties that would reflect on speed of impact and toughness. 

When use conditions differ from those applied to data sheet tests, certain comparative evaluation can be made. Selecting an established high impact plastic such as polycarbonate as the standard, a tensile test would be made on this material at use speeds of strik- 

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Mechanical with impact —by measuring tensile impact strength. 

Impact tests are, however, used to try to compare the impact strength of different materials. Of these tests four require specific mention. These are the Izod test, the Charpy test, the falling weight tests and the tensile impact test. 

Other impact tests widely used are the falling weight tests where a weight is allowed to fall onto a supported flat or domed surface and tensile impact tests in which a sample is subjected to a sudden shock in tension. Whilst the... 

Although the Izod and Charpy tests are widely used for plastics, other types of test are also popular. These include tensile impact tests and flexural plate (falling weight) tests. The latter is particularly useful in situations where the effects of flow anisotropy are being assessed. In addition, arbitrary end-product tests are widely used to provide reassurance that unforseen factors have not emerged to reduce the impact performance of the product. 

Tensile impact strength (Kg-cm/cm) Blown film properties 1132 2930 780... 

Wt%of graft polymer Stress at 15% elongation (MPa) Stress at 30% elongation (MPa) Stress at 50% elongation (MPa) Tensile strength (MPa) Elongation at break (%) Tensile impact strength (J/m2)... 

The SEM investigation shows that the particle size of the dispersed domain size decreased from 3.3 to 1.1 fxm with the incorporation of 6 wt%, EMA, and this indicates the increased surface area of the dispersed phase morphology. The increase in surface area led to effective compatibilization and is responsible for the increased adhesion strength and tensile impact strength of compatibilized blends. 

Methods employed to determine the impact resistance of plastics include pendulum methods (Izod, Charpy, tensile impact, falling dart, Gardner, Dynatup, etc.) and instrumented techniques. In the case of the Izod test, what is measured is the energy required to break a test specimen transversely struck (the test can be done either with the specimen notched or unnotched). The tensile impact test has a bar loaded in tension and the striking force tends to elongate the bar (Chapter 5, Impact Strength). 

Generic Material Type Trademark Grade Izod Impact Energy for 0.318 cm (0.125 in.) thick, Notched Specimens, J/m Tensile-impact Short Specimens, kJ/m2 Energy Long Specimens, kJ/m2... 

The determination of tensile stress-strain properties is conducted in accordance with ISO 527 [4] and the values that can be obtained are illustrated in Figure 7.1. For weathering tests where cabinet space is restricted some workers have used a tensile impact dumbbell from ISO 8256 [5] with a square central section which allows test pieces to be exposed edge on. The considerable disadvantage is that modulus cannot be measured as there is no parallel gauge length. 

Blends of butadiene-styrene block polymers with polyolefins, particularly polypropylene are mentioned in literature to improve the impact strength of the latter. Since similar improvements can be realized from the use of polyolefin block polymers, the blends have not gained much recognition. However, butadiene-styrene radial teleblock polymers are blended into polyethylene film, to increase the tear resistance and tensile impact. ... 

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