Falling dart

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). 

There are other types of impact tests for shock loading where energy is required to cause complete failure is reported. Each has their specific behaviors that can be related to specific product performance requirements. Tests include ball burst, ball or falling dart using different weights and heights, bag drop, bullet-type instantaneous impact, Charpy, dart drop, Mullen burst, tear resistance, and tub (2). 

ISO 7765-1, Plastics film and sheeting - Determination of impact resistance by the free-falling dart method - Part 1 Staircase methods, 1988. 

In practice, however, the multiaxial stress applied in a falling dart test without a preferred direction, has to be expected. This is addressed by the Gardner test of ASTM, in which a falling dart strikes centrally on a flat surface (e.g. a circular disk). The results of both test methods are important polymer design considerations. 

Impact Falling Dart Falling Ball ft-lbs ft-lbs 4-30 8->45 4-65 ll->45 Monsanto Monsanto... 

Cold impact was measured by the falling dart test in which a 3" x 6" x 0.125" sample is positioned in an inverted U shape, conditioned four hours at -30°C., and impacted at the highest point of the specimen by a weighted two-inch diameter rod-shaped plunger rounded on the end to a one-inch radius. The plunger is dropped from a predetermined height to give 5 mph impact velocity. 

The growth of fracture mechanics has placed greater emphasis on tests that use sharply notched specimens. These results were found to provide more fundamental information. Instrumented impact testing is a recent development that provides information on force-deflection curves. In addition to these notched bar tests, extensive use of falling dart tests is also being made. However, interpretation of the data from the latter is far from straight... 

ASTM D 5628-96 Standard Test Method for Impact Resistance of Flat, Rigid Plastic Specimens by Means of a Falling Dart Tup or Falling Mass), pp. 1-10, American Society for Testing and Materials, Philadelphia, 1996. 

ISO 7765-2 1994. Plastics Film and Sheeting - Determination of Impact Resistance by the Free-Falling Dart Method - Part 2 Instrumented Puncture Test. 

BS 2782, Method 353A, Determination of multiaxial impact behaviour by the falling dart... 

ASTM D5628, Impact resistance of flat, rigid plastic specimens by means of a striker impacted by a falling dart (tup or falling mass), 1995. 

Charpy impact test r 1 Izod impact test 1 falling dart impact test... 

In the falling-dart test a circular sample of polymer is supported horizontally and a pointed steel dart is allowed to fall so that it strikes the centre of the disc. The standard dimensions for this test are radius of test disc 6 cm, thickness of disc 2 mm and radius of dart tip 1 mm. The disc is supported horizontally by an annulus of 4 cm aperture to which it is clamped by a second annulus. The behaviour of the sample can be studied under a variety of dilferent degrees of severity of impact simply by varying the height from which the dart is allowed to fall. 

Impact Resistance of Plastic Film by the Free-Falling Dart Method. Primary Film Test Method ASTM D1709 Additional Test Method ISO 7765-1. A weighted dart is dropped from a standard height onto a taut sample. Depending upon the expected impact strength of the test sample, either method A or method B is chosen. The method defines the dart size and the drop height for the dart. Test method A specifies a dart with a 38 mm diameter dropped from 0.66 m. Test method B specifies a dart with a 51 mm diameter dropped from 1.5 m. 

Impact Resistance, Dart Drop The impact resistance is derived from the mass of the dart and the drop height that cause the specimen to crack or rupture. The total energy impact measures the kinetic energy lost by the free-falling dart that passes through the film. 

Impact resistance Particularly relevant for PO packaging are Gardner (falling dart) impact, drop Impact strength for containers, and tear strength for films. 

Resin Izod Inpact (ASIM D256-56) Notched, Ibinotched, Fb-Lbs Ft-Lbs Falling Dart Inpact, In-Lbs Falling Ball Inpact, Fb-Lbs... 

Plastic—Determination of mnlti-axial impact behaviour of rigid plastics—Part 1 Falling dart method... 

Other impact strength tests that use gravity are the Gardner impact and Falling Dart tests. These are described in the following standards ... 

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