Compact tension test

Fig. 7.1. Compact tension test-piece [77], W = 20 mm, B = 4 mm the crack (length a) was introduced by tapping with a razor blade after cooling of the polymer with liquid nitrogen, if necessary...

A rectangular bar of polymer of thickness B = S mm and width = 20 mm has a central notch of length a = 10 mm. The bar is loaded in a three-point bending test with an 80 mm span, S, at room temperature. The bar fractures when the force applied is 300 N. Calculate (a) Kjc for the polymer and (b) the force needed to fracture in a compact tension test a specimen of dimensions IT = 50 mm, J = 10 mm, having a single-edge sharp crack of = 25 mm. 

In mode I compact tension tests, there is a considerable increase in fracture toughness of (3-PP over that of a-PP in certain ranges of temperature and test speed. Figure 11.26(a)-(d) show the variations of Kiq with the crack-tip loading rate, dKIdt, for the a-PP and (3-PP CT specimens tested at various temperatures. The dK/dt is defined as... 

Fig. 1. Compact tension test specimen. All dimensions are in millimeters.

Alternative geometries and test methods to determine the fracture toughness of ceramics and hard materials have been developed over the last decades Herzian indentation [88], the double torsion test [89], and compact tension tests [90 92]. 

Compact tension tests on PMMA specimens give a value of 325 J m" for Gic at 23°C, for a crosshead speed of 5 mm min". The critical crack tip opening displacement 8, determined using an optical interferometry technique, is 4.2 m. Calculate the surface stress acting on the craze formed ahead of the crack tip. 

In treating adhesives as polymeric materials, it is possible to use Fracture-mechanics test specimens to determine material properties independent of geometry. A typical sample would be the compact tension test-piece, where a sheet of material, typically 6-mm thick and 100-mm square, has a sharp crack inserted in one edge. The sample is then loaded perpendicular to the plane of the crack and the load at which crack propagation... 

Eight compact tension It test specimens and four l/2t compact tension test specimens each of base metal (transverse) and weld metal material are provided to augment the fracture toughness data determined from the precracked Charpy tests. This guantity of specimens is sufficient to determine fracture toughness properties over the range extending from linear elastic to elastic-plastic fracture behavior. 

Tensile test, standard and precracked Charpy impact and l/2t compact tension test specimens are used for determining changes in the strength and static and dynamic toughness properties of the materials due to neutron irradiation. A total of 333 standard Charpy impact, 81 precracked Charpy impact, 60 l/2t compact tension and 36 tensile test specimens are provided. The type and quantity of tests specimens provided for establishing the properties of irradiated materials over the lifetime of the vessel are presented in Table 5.3-3. Compact tension specimens provided for capsule irradiation are precracked prior to insertion to reduce the time required for post irradiation testing. The types and quantity of specimens provided exceed the minimum requirements of ASTM E-185-82. 

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