Dart drop impact test

The flaw spectrum approach may be capable also of correlating failure data obtained under conditions which appear to give different material behavior. For example, tensile, Izod, and dart drop impact tests all give different impact energies or toughness measures. In part, this may be explained by the simple idea that a different fraction of flaws is active in each test. Equal biaxial loading (as in dart drop) and uniaxial tension (as in tensile impact) give rise to different flaw activities thus it is to be expected that the number of crazes produced in each test will be different. 

The dart drop impact test, ASTM D1709 and ASTM D4272, is often used for film samples. In D1709, a sample of the film is subjected to an impact by a round-... 

Impact tests were performed using a dart-drop impact tester (DDI/TE, Model DDL 120, Qnalitest Ine., Ft. Lauderdale, Florida, USA) as per ASTM D 4272 standard testing conditions and procedures using a 38.1 mm dart. Ten specimens were tested for eaeh N and average impaet energy was calculated. Barrier property measurements are in progress and will be reported in the ftiture. 

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. 

Polymers which yield extensively under stress exhibit nonlinear stress-strain behavior. This invalidates the application of linear elastic fracture mechanics. It is usually assumed that the LEFM approach can be used if the size of the plastic zone is small compared to the dimensions of the object. Alternative concepts have been proposed for rating the fracture resistance of tougher polymers, like polyolelins, but empirical pendulum impact or dart drop tests are deeply entrenched forjudging such behavior. 

ASTM D 4272 Standard test method for total energy impact of plastic films by dart drop... 

Out of plane impact testing onto a thin shell structure (e.g. to simulate dropping a tool, or the impact of stones, onto an aircraft structure).There are many variants of this test—the specimen can be simply supported or clamped, the projectile can be dropped or fired (1-10 m s ) and may take the form of a sphere, a cylinder with a hemispherical end or a dart. The energy and/or the test speed can be varied by adjusting the mass or drop height. The test can be instrumented to record the force, energy absorbed and the deflection. 

A free-falling dart method for polyethylene films is described in ASTM D1709. Unlike low-speed uniaxial tensile tests, the pendulum impact test measures the resistance of film to impact puncture, simulating high-speed end use application. Dart drop measures the energy lost by a moderate velocity blunt impact passing through... 

The falling weight or dart drop test method simulates actual day-to-day abuse and can be carried out either on standard laboratory specimens or on the articles themselves. Failure may occur in various ways ranging from brittle to ductile failure (Figure 14). Particular care must be taken to avoid the brittle failure by proper selection of grade. At temperatures below -20 °C, elastomer-modified PP is more impact resistant than PP copolymer and homopolymer. 

Driers Drop-Weight Test n (falling-weight test) Any test of impact resistance in which known weights are dropped once or repeatedly on the test specimen. Examples are ASTM D 4272 (plastic films), D 3029, D 4226, and D 4495 (rigid PVC sheet and parts), and F 736, Section 15, (polycarbonate sheet). Also see Free-Falling-Dart Test. 

Impact Resistance n (1) Ability of a coating to resist a sudden blow. Ability to resist deformation from impact. (2) The relative durability of plastics article to fracture under stresses applied at high speeds. A widely used ASTM impact test, www.astm.org, employs the Izod pendulum striker swung from a fixed height to strike a specimen in the form of a notched bar mounted vertically as a cantilever beam. The Charpy tester, an alternative in D 256, uses a specimen in the form of a horizontal beam supported at both ends. ASTM lists some several different impact tests for plastics and plastics products. See also Brittleness Temperature, Drop-Weight Test, Free-Falling-Dart Test, and... 

As far as the mechanical properties are concerned, the tear (test name Elmendorf tear), impact (test name dart drop), and tensile strengths give an indication of the mechanical strength of the tubular film. Some of these properties and the effect the processing parameters have on them were discussed in Section 1.2. The amorphous as well as the crystalline orientation developments during the blowing process depend on... 

Tables 4—6 Ust ASTM methods used for the characterization of PB and PMP. A number of specialized methods were developed for testing particular articles manufactured from polyolefins several of these determine the performance of PB and PMP film, including the measurement of the film s dart impact strength and tear strength. Dart impact strength is measured by dropping a heavy dart with a round tip on a stretched film. Tear resistance, which reflects the film s resistance to tear propagation, is measured with the Ehnendorf tear tester. Two values for the tear strength are usually reported, one in the machine dkection of the film and the other in the transverse dkection. Pipes manufactured from PB are tested by pressurizing them internally with water the time-to-burst failure is determined at various temperatures (46). The standard test method for haze and luminous transmittance (ASTM D1003) is used for the measurement of PMP optical characteristics.

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