Compact tension specimens

Prompted by the success, TOFD measurements were conducted on a fatigue crack in a stainless steel compact tension specimen. Test and system parameters were optimised following the same procedure used for carbon steel specimens. A clear diffracted signal was observed with relatively good SNR and its depth as measured from the time-of-flight measurements matched exactly with the actual depth. 

For comparison, the following relationship has been found for an X70 pipeline steel (slow strain rate test using compact tension specimens with the precrack located in the heat-affected zone of a weld) ... 

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

In the study of crack growth in epoxy polymers the double-torsion and compact-tension specimens have been the most widely used. The values of KIc may be obtained from 1,2)... 

Fig. 15 Craze-like defect formed in the stress-whitened zone in front of the crack in a POM compact tension specimen loaded at 100 °C (from [65])...

Fig. 12.11 Schematic of a compact tension specimen and in situ observation apparatus.

Fig. 12.12 Results of compact tension specimen showing increase in toughness as crack goes past fiber, and crack opening displacement from which closure stresses can be determined.

Fig. 20 Deformation maps of a a non-nucleated iPP and b its -nucleated homologue (MFR 12dgmin ) for different temperatures and crack tip loading rates as deduced from the fracture surfaces of compact tension specimens. A rough indication of the test speed is provided by the upper scale. Same grades as in Fig. 19...

Fig. 29 Evolution at room temperature of the whitening of the fracture surfaces of compact tension specimens plotted versus the logarithm of the test speed for the non-nucleated and /i-nuclealed grades described in Sect. 5.4. a Height of the intense whitened zone (ZI) b height of the diffuse whitened zone (ZC) measured with a magnifying glass. The average standard deviation of these measurements is 10%...

Fig. 32 SEM/BSE images of microdeformation of /f-nucleated PP tested at room temperature and 0.001 m s-1 at the crack tip of a compact tension specimen a overview of the crack tip damage zone, b and c details from the periphery of the damage zone. The arrows indicate the direction of the applied load...

The amplitude of the stress intensity factor AK for mode I loading of a compact tension specimen is given as... 

Abstract The effects of the amount of rubber, the concentration of fibres and the state of the fibre/matrix interface upon the mechanical behaviour of short glass fibre-reinforced rubber-toughened nylon 6 ternary blends are described. First, tensile tests were carried out on different intermediate materials and then on the ternary blends to derive the stress-strain curves and document the damage mechanisms. Fracture toughness tests were implemented on compact tension specimens and the results were correlated to fractographic observations and acoustic emission analysis to assess the role of the different constituents. 

Fig. 9 Load-loadline displacement curve (a) and SEM micrograph of the surface of rupture (b) of a nylon 6 compact tension specimen.

Figure 7, Compact tension specimen showing the plastic zone around the crack tip.

Bulk samples were cured at 125 °C for 1 h, followed by 177 °C for 2 h, and finally 220 °C for 1 h. Fracture-toughness tests on bulk samples were performed according to the ASTM E399-83 procedure using compact-tension specimens with a thickness of 6.35 mm. Tensile tests were performed following ASTM D638-86. Both tests were run at a 50-mm/min jaw speed. Adhesive formulations were blend-... 

Figure 15. (a) Variation of plane strain fracture toughness with rubber content for samples with an epoxy-to-polyester ratio of 1 2. Compact tension specimens were tested at 0.2 in./min. using ASTM E-399. (b) Variation of strain-energy release rate, GJc, with rubber content for samples with an epoxy-to-polyester ratio of 1 2. 

The plane strain fracture toughness was determined using ASTM E-399 with compact tension specimens. Specimens were precracked using a razor blade. The ratio of the precrack length to the total length of the sample was kept within the specified limits. Only samples with straight precracks were used for testing, which was done at a rate of 0.2 in./min. 

Figure 2. Compact tension specimen used in fracture tests.

Fracture Energy. The fracture energy of cured phthalonitrile samples was measured by using standard compact tension specimens (8). A precrack was always introduced at the end of the saw-cut with a razor blade. Specimens were fractured in an INSTRON at a crosshead speed of 0.125 cm/min. The critical failure load was... 

Fatigue crack propagation tests were performed on 73-nmi x 73-mm (2.9 in. x 2.9 in.) compact-tension specimens that had been machined from the plaques and then precracked. An electrohydrau-lic closed-loop test machine was used to produce a constant-amplitude, 10-Hz sinusoidal load. Host of the tests were performed in duplicate at room temperature in laboratory air at an average ambient RH of A0%. In view of the slow rate of moisture equilibration in air at room temperature (15), the difference between the ambient RH and that of the nylon being tested was presumed to be unimportant within the time period of the test (3-5 hr). 

Tests are conducted, in normal practice, on compact tension specimens rather than wide center-notched plates. Some allowance must be made for geometrical effects, including the finite width of the specimen, the difference between edge and center notches, and any rotations occurring at the grips. 

Figure 11.24 Force-displacement curves of (a) ct-PP and (b) (3-PP compact tension specimens tested at various speeds at 25°C. (From Reference 31 with permission from Elsevier.)...

Crack growth studies were conducted using compact tension specimens machined from cast A356 and compared with friction stir processed regions (Ref 99). Figure 14.39 shows a comparison between the crack growth rates (da/d of different samples. To achieve similar crack... 

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