Falling Dart Impact Test

Reproduced with permission from Shell, Shell, website www.basell.com 

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

Falling Dart Impact Test (Fall-O-Scope ATS FAAR)... 

Types of brittle failure, in falling dart impact test (courtesy ICI). 

Falling-Dart Impact Test n In addition to the ASTM tests mentioned at Free-Falling-Dart Test, several similar tests exist for products such as pipe and bottles as well as sheeting. One procedure is the staircase... 

Dart impact test See free-falling-dart test. 

Widely used impact tests are for rigid materials, hod (ASTM D256) and Charpy (ASTM D256) and for flexible structures, falling dart impact (ASTM D3029) and pendulum impact resistance (ASTM D3420). 

Instrumented falling weight impact test were conducted on a home build machine. Details of which have already been given elsewhere (6). Test panels were circular clamped between metal plates with a circular opening of 80 mm. The mass of the falling weight was 0.9 kg. A hemispherical dart with a diameter of 10 mm was used in all cases. 

In the falling-weight impact test a circular disc of material (typically 6 cm diameter and 2 mm thickness, freely supported on an annulus of 4 cm diameter) is impacted by a metal dart with a hemispherical tip (t3q5ically of radius 1 cm). The tests are carried out either under conditions where the impact energy is far in excess of that required to break the specimen or at low levels of impact energy so that damage tolerance and the possible initiation of a crack can be observed. 

ATS FAAR supplies the Fall-O-Scope Universal apparatus for free-falling dart impact resistance tests. The apparatus can be set to obtain the rate of energy absorption dnring the impact. The apparatus can be used to conduct tests to different specifications with computerized operation in the range 70°C-200°C. 

Dart Impact Test See Free-Falling-Dart Test. 

A problem associated with impact strength determination is that standard methods in use (notched Izod, falling weight, and dart impact tests) often have poor correlation. It would be of interest to develop DMA procedures to simulate field service impact situations. 

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). 

We test the impact resistance of polymer plaques using the configuration shown in Fig. 8.8. We subject circular injection molded plaques to the shock of a falling weight with a hemispherical impacter. This test is also known as the Dart Drop Test . Samples can fail in a brittle or a ductile manner. Brittle samples often shatter. Ductile samples can split or a small disk may be punched out of their center. This test provides results that are analogous to those obtained from un-notched impact beam testing. 

ISO 7765-2, Plastics film and sheeting - Determination of impact resistance by the free-falling dart method - Part 2 Instrumented puncture test, 1994. 

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. 

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. 

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