Single-edged notched three point

The critical stress intensity factor, Kc, at fracture initiation was measured by single-edge notched three-point bending tests carried out at low (lOmm/min) and high (Im/s) load point displacement rate under different environmental conditions (temperature and moisture). 

Fig. 12. Testing geometries (a) single-edge notch tension (SENT), (b) single-edge notch three-point bending (SEND), and (c) compact tension (CT).

Single-edge notch three point bending (SENB), Fig. 12... 

Although it is not the intention to provide a comprehensive thesis on the origins of LEFM, it is useful to review the test method that is so often used to characterize the fracture toughness of epoxy polymers. The most common geometry to characterize the fracture toughness of epoxy polymers is the single edge notched, three-point bend test... 

Figure 1 - Typical force/tim curves rec

Fig. 6. Fracture toughness test specimens (a) single-edge notch (b) center notch (c) compact tension and (d) three-point bend. Terms are defined in text.

Figure 19.4 Schematic diagrams showing common fracture test geometries. Single edge-notched (a) three-point-bend, (b) tensile and (c) compact tensiem tests, each using specimens with razor-sharpened notches, are employed for fracture mechanics measurements of fracture toughness and fracture energy. The Izod (d) arxl Chatpy (e) tests are widely practised in industry to evaluate toughness, but use bluntly notched (or un tched) specimens and do not give fracture mechanics data...

Figure 8.19 Single edge-notched beam geometry. Loading is usually either three- (shown here) or four-point bending.

The most common test specimen configurations for performing plane-strain fracture toughness test are the single edge notch bend (SENB or three-point bend) and the compact tension specimens. Hence, for an accurate determination of the plane-strain fracture toughness, a specimen whose thickness exceeds a critical size is required. 

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. 

This appeared as Eq. (1.12a) in Chap. 1). Next, the fracture toughness, Kj, was measured on single-edge crack-Uke specimens with notches of one-half the specimen thickness. The specimen was tested in three-point flexure over a 6-in. span on a commercial testing machine at a crosshead speed of 0.05 in./min. The Kic s were calculated from Brown and Strawley s [14] equation ... 

Fracture tougnness was determined with the single-edge-precracked-beam (SERB) and chevron-notch° methods in three-point bending. 

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