Double cantilever beam specimen

I ig. X.ll. Residual stillness a.s a funetion crack length as measured from double cantilever beam specimens after impact damage carbon fiber composites containing (O) unmodified epoxy ( ) rubber-... 

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. 

Standard Mode I Double Cantilever Beam specimens for delamination testing of a unidirectional (UD) IM7/977-2 composite were Z-pinned with two separate blocks of Z-Fiber reinforcement. The reinforced beam configuration was such as to provoke an unstable delamination, propagating between the two Z-pin blocks. Crack resistance curves for these specific geometry specimens of IM7/977-2 indicate that the unstable delamination cracks are arrested by the second Z-pin block, with the crack propagation resistance being dictated primarily by the Z-pinning density within a block. Acoustic emission analysis is used to interpret visual observations and other test data. 

The crack initiation energy can readily be determined from a mode I cleavage test using a double cantilever beam specimen [1,2]. This method has been applied to wood-adhesive joints by many researchers [3 17]. The test requires the beam compliance (C), load at crack initiation (P ), crack length at initiation (a), specimen thickness (/), and change in beam compliance = change in displacement of load points/change in... 

In this chapter, an overview of performance characterization of FRP-wood bonded interfaces by conventional and fracture mechanics tests [4- 7] is presented. Modified ASTM standard tests (ASTM D2559 and D905) are first used to study the service performance and shear strength of the bond under moisture and/or mechanical loads, and then a contoured or tapered double cantilever beam specimen [8] is used to evaluate the fracture toughness of bonded interfaces under dry and wet conditions and cyclic loading. 

Finally, the tapered double cantilever beam specimen [8] described in this study can be effectively used to obtain interface mode-I fracture toughness values under various environmental loadings (e.g., under dry and wet conditions [5,14,15]) and cyclic load conditions (fatigue fracture [7]) these data can be implemented in practical applications to assess the potential growth of a delamination crack at the FRP wood interface. 

Hojo M, Aoki T. Thickness effect of double cantilever beam specimen on interlaminar fracture toughness of AS4/PEEK and T800/epoxy laminates. In Stinchcomb WW, Ashbaugh NE, editors. Composite materials fatigue and fracture, vol. 1156. ASTM Special Technical Publication 1993. pp. 281—98. http //dx.doi.org/10.1520/ STP24736S. 

ADCB asymmetric double cantilever beam (specimen)... 

TDCB (tapered double-cantilever beam) specimens were used to determine the healing efficiency and repeatability of the healing. The specific geometry of the TDCB can be seen in Figure 7.27(a). The healing efficiency was evaluated by a tensile test using the Q-TEST 150... 

FIGURE 27.3. Diagram of an ASTM D3433 double cantilever beam specimen. The load is usually applied by attaching a fixture to holes located near the front of the specimen. In general, the initial portion of the specimen is not bonded in order to provide an initial crack. 

The optimal adhesive layer thickness depends on a number of factors. Some bonds, notably Tensile test specimens, are stronger when the adhesive layer thickness is redn-ced. For fracture specimens, including double cantilever beam specimens bonded with structural adhesives (see Fracture mechanics test specimens), optimal bond thicknesses have been identified, although the optimal thickness depends on the loading rate and test temperature. " Enhanced ductility plays a role in this process, and a sufficient quantity of adhesive is desired to dissipate energy (see Peel tests). This latter mechanism is also important in the peel energy of Pressure-sensitive adhesives and other systems. 

To characterize the cyclic crack growth resistance of both neat resins and laminates, fatigue crack propagation (FCP) experiments under Mode I conditions were performed in laboratory air (23 C/50%r.h.) using a computer controlled servohydraulic fatigue testing machine. In the case of neat resins, compact-type (CT) specimens with a width of 50 mm, a hight-to-width ratio of 0.6, and a nominal thickness of 4 mm were used. For composite laminates double cantilever beam specimens (125 x 20 x 8 inm ) were employed. FCP tests were conducted at 10 Hz. The applied waveform was sinusoidal with a constant load amplitude and a minimum-to-maximum load ratio, R, of 0.1. 

F ure 11.14 Pre-cracked probe shapes for stress corrosion cracking tests (a) compact tension specimen (CT) and (b) double cantilever beam specimen (DCB). 

Double cantilever beam specimens are widely applied for constant strain testing. If their width w is at least 10 times greater than their height h, the stress intensity depends only on h, and not on w. In addition, when 2 < alh < 5, K is given by the following simple relation [3] ... 

Figure 14. Idealized force-displacement curve resulting from a fracture experiment using a uniform double cantilever beam specimen. Load is applied to a certain displacement until the crack propagates, at which point the load and crack length are measured. The diagram shows the results of an experiment in which the sample is unloaded prior to reloading. The change in slope with each reloading is due to the change in compliance of the specimen which is a function of crack length.

The use of phenolic resins for wood bonding has been reviewed by Pizzi, Dinwoodie, Kollmann and coworkers, " the U.S. Department of Agriculture, and Barth. Tapered double cantilever beam specimens have been recently used to test the effect of bondline thickness and cure time on the fracture energy of phenolic-wood adhesive joints. ... 

Figure 26. The tapered double cantilever beam specimen.

Conventional fracture mechanics testing specimens, such as the compact, cantilever beam, modified bolt-load compact previously referred to as wedge-opening load (WOL), and contoured double-cantilever beam specimens, have been adapted for testing in both aqueous environments and in a high-pressure gaseous hydrogen environment. 

Category 2 tests are fracture mechanics tests that use notched and precracked specimens that are statically or dynamically loaded, such as cantilever beam, compact tension, and double cantilever beam specimens, and are conducted per ASTM E 399, Test Method for Plane-Strain Fracture Toughness of Metallic Materials. 

FIG. 7—Double-cantilever beam specimen with side groove. 

Figure 12.4). Alternatively, test pieces of standard geometry can be used, for which the compliance is known as a function of crack length. For example, the relationship between the extension A (usually termed the deflection in this case) and the load P for a double cantilever beam specimen of thickness B (see Figure 12.5) is given by...

Show how the Irwin-Kies relationship can be derived by considering the load-extension curve for a specimen with a central crack. Use this relationship to calculate the load that must be applied to a double cantilever beam specimen of half-width 1 cm and thickness 3 mm to cause a crack of initial length 8 cm to begin to propagate, given that the fracture toughness. Sqc is 2 MN... 

Consider stable crack growth conditions such as a double cantilever beam specimen loaded by forcing a wedge along the crack growth direction. Initially the... 

Mill annealed double cantilever beam specimens, 10MHCI, open circuit. 

Crack velocity vs stress-intensity relationships for three heat treatments of double cantilever beam specimens tested in pure (Spec-trograde) methanol and methanol-KI solutions at24 °C. Open symbols tested in Spectrograde. Closed symbols tested in Spectrograde+O M Kl/imelhanol -500 mV (SCE) double canti-l erbeam. 

---