Double cantilever beam test specimen

Fig. 2. Illustrations of forces to which adhesive bonds are subjected, (a) A standard lap shear specimen where the black area shows the adhesive. The adherends are usually 25 mm wide and the lap area is 312.5 mm. The arrows show the direction of the normal apphcation of load, (b) A peel test where the loading configuration, shown by the arrows, is for a 180° peel test, (c) A double cantilever beam test specimen used in the evaluation of the resistance to crack propagation of an adhesive. The normal application of load is shown by the arrows. This load is appHed by a tensile testing machine or other...

FIG. 18—Change of stress-intensity with time of constant load cantilever beam compared to a contoured double-cantilever beam test specimen and a constant displacement bolt-load compact specimen [20]. 

FIG. 20—Dimensions and configurations for double-cantilever beam test specimen. Specimen contoured to 3 llf + Mh + C, where C is a constant [28]. Ali vslues given in inches. (Note 1 in. = 25.4 mm.)... 

The contoured double-cantilever beam test specimen is a modification that is used to measure crack growth rate at a constant applied stress intensity. This test simplifies the calculation of stress intensity by using a contoured specimen, as its stress intensity is proportional to the applied load and independent of the crack length. Under a constant load, the stress intensity for this specimen remains constant with crack extension. For the test geometry shown in Fig. 20, the magnitude of the stress-intensity factor K is observed to equal 20 times the load. 

Blackman, B.R.K., Dear, J.P., Kinloch, A.J. and Osiyemi, S., The calculation of adhesive fracture energies from double-cantilever beam test specimens. J. Mater. Sci. Lett., 10, 253-256(1991). 

DCB double cantilever beam (test specimen ) PIP pin-in-paste... 

ISO, Standard test method for mode I interlaminar fracture toughness, G/c, of unidirectional fibre-reinforced polymer matrix Composites. ISO 15024 2001. Blackman, B.R.K., H. Hadavinia, A.J. Kinloch, M. Paraschi and J.G, Williams, The calculation of adhesive fracture energies in mode I revisiting the tapered double cantilever beam (TDCB) test. Engineering Fracture Mechanics 2003. 70 p. 233-248. BSI, Determination of the mode I adhesive fracture energy, Gic, of structural adhesives using the double cantilever beam (DCB) and tapered double cantilever beam (TDCB) specimens. 2001. BS 7991. 

With the initial aim of evaluating the applicability of the ISO 15024 standard for fracture toughness testing for non-unidirectional composite laminates, ESIS TC4 has conducted a number of round robin studies on cross-ply laminates with different stacking sequences. We report here the results of two test laboratories from the 3 round robin activity in which double cantilever beam (DCB) specimens made from unidirectional (0°/0°-interface) composite laminates were compared to DCB-specimens with 0°/90°- and 90790° interfaces. In the analysis, correlation with observations from the delamination growth (e.g., deviation from the mid-plane) and post-test (e.g., fracture surface) inspection was attempted. The results are compared with some results in the literature. 

Static Double-Cantilever Beam—Static double-cantilever beam testing was conducted using ASTM D 3433. An Instron 4500 series test frame (Canton, MA) with a 5 kN load cell was used for this testing. All data were collected using custom software written with the National Instruments Lab VIEW software (Austin, TX). Specimens were loaded into the test frame, and a constant opening displacement rate of 1 mm/min was applied. 

Once the performance of the interface bond was established by the previous delamination (durability) tests, contoured double cantilever beam (CDCB) specimens were designed to conduct mode-I fracture tests. In this study, bilayer CDCB specimens (see Fig. 6) were designed by the Rayleigh-Ritz method [8] and used for fracture toughness tests on bonded FRP wood interfaces under both dry and wet conditions. The critical strain energy release rate, G/c, which is a measure of the fracture toughness, is given as ... 

Several testing techniques are possible which use different specimen configurations, different loading modes, and various loading frequencies. Marceau et al. have described results for thick adherend lap shear and double cantilever beam (DCB) specimens exposed to 140 F/100%... 

The double-cantilever beam (DCB) specimen has been used in oil field and other applications [77] and is described in NACE Standard Test Method, Laboratoiy Testing of Metals for Resistance to Sulfide Stress Cracking in H2S Environments (TM0177) (Fig. 7). Thickness of DCB samples used in the oil field has often been restricted by the size of the product form under evaluation. In many applications, thicker samples are preferred as described in ASTM G168, Standard Practice for Making and Using Pre-Cracked Double-Beam Specimen. 

The tapered-double-cantilever-beam(TDCB) specimen [11,12] shown in Fig. 2 is a standard linear-elastic fracture-mechanics (LEFM) test specimen and the value of the adhesive fracture energy, Gg, may be deduced from ... 

Different locus of failure and crack trajectories observed in mode-1 testing of adhesively bonded double cantilever beam (DCB) specimens using aiuminum adherends and an epoxy adhesive (Chen and Dillard 2001)... 

The mode I delamination fracture toughness is measured on flat coupons using the Double Cantilever Beam (DCB) test method. The test method utilizes a unidirectional rectangular composite specimen of uniform thickness with nonadhesive insert (as a delamination initiator) at the midplane. This test method is currently in the process of standardization by ASTM. 

Zehnder, A.T. and Rosakis, A.J. (1990). Dynamic Fracture Initiation and Propagation in 4340 Steel under Impact Loading, International Journal of Fracture, 43, pp. 271-285. Kalthoff, J.F., Beinert, J. and Winkler, S. (1977). Measurements of Dynamic Stress Intensity Factors for Fast Running and Arresting Cracks in Double-Cantilever-Beam Specimens. n Fast Fracture and Crack Arrest, ASTMSTP 627, pp. 161-176, Hahn, G.T. and Kanninen, M.F. (Eds.). American Society for Testing and Materials. 

Substrates. Two commercial aluminium alloys (see Table 1), received as hot-rolled sheets (from ALCAN), were the main body-panel materials used in the current work. The thickness of the sheets varied from 1 to 3 mm for the 5754-0 alloy and from 1 to 2 mm for the 6111-T6 alloy. For the tapered double-cantilever beam (TDCB) tests, where the substrates should remain within the elastic region, a high yield strength alloy, 2014, was used throughout. The specimens were prepared and pre-treated prior to bonding using the procedures proposed by Blackman et. al. [2], The chemical compositions of the alloys employed are given in Table 1. 

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