Evaluating fracture toughness

These effects have been found by Creton et al. [79] who laminated sheets of incompatible polymers, PMMA and PPO, and studied the adhesion using a double cantilever beam test to evaluate fracture toughness Fc. For the original laminate Fc was only 2 J/m, but when interface reinforced with increasing amounts of a symmetrical P.M.M.A.-P.S. diblock copolymer of high degree of polymerisation (A > A e), the fracture toughness increased to around 170 J/m, and then fell to a steady value of 70 J/m (Fig. 9). 

The TDCB specimen (Fig. 20) was used for evaluating fracture toughness of bonded FRP-wood interfaces under mode-1 loading [5], and the strain energy release rate G is given in Eq. (1). For one complete cycle, the maximum and minimum strain energy release rates are... 

G.D. Quinn, R.J. Gettings, and J.J. Kubler, Fractography and the Surface Crack in Flexure (SCF) Method for Evaluating Fracture Toughness of Ceramics, Fractography of Glasses and Ceramics, Ceramic Transactions, Vol. 64, American Ceramic Society, Westerville, OH, 1996, pp. 107 144. G.D. Quinn and J.A. Salem, Effect of Lateral Cracks on Fracture Toughness Determined by the Surface Crack in Flexure Method, J. Am. Ceram. Soc., 85 [4] 873 880 (2002). 

G. D. Quinn, R. J. Gettings, and J. J. Kubler, Fractography and the Surface Crack in Flexure (SCF) Method for Evaluating Fracture Toughness of Ceramics, Fractography of Glasses and Ceramics,... 

EWF is based on the theory that total fracture work W, to breakage is partitioned into essential work of fracture that takes place in process zone where fracture process takes place and plastic work of fracture that takes place in plastic zone where gross ductility occurs (Eq. 1), and then evaluates fracture toughness considering those corresponding elements of and (Eq. 2, Eq. 3). 

Heyer, R. H., Fracture toughness evaluation by R-curve methods. ASTM, STP 527... 

Stress Intensity Factor K,5cc a fracture toughness parameter used for evaluating susceptibility to stress-corrosion cracking (the subscript I signifies a tensile mode of stressing). 

Fig 3.8 shows the interface shear bond strength, tb, determined from Eq. (3.7), which is not a material constant but varies substantially with embedded fiber length, L. However, to evaluate all the relevant interface properties properly, which include the interface fracture toughness, Gic, the coefficient of friction, p, and the residual clamping stress, qo, it is necessary to obtain experimental results for a full range of L and plot these characteristic fiber stresses as a function of L. More details of the... 

Anstis, G.R., etal. (1981), Acritical evaluation of indentation techniques for measuring fracture toughness I, Direct crack measurements , J. Am. Ceram. Soc., 64(9), 533-8. AS 1774.5 (1979), The determination of density, porosity and water absorption , Standards... 

T. Nose and T. Fujii, Evaluation of Fracture Toughness for Ceramic Materials by a Single-Edge-Precracked-Beam Method, Journal of the American Ceramic Society, 71[5], 328-333 (1988). 

In the present work, a novel experimental method was proposed to evaluate the modes I-fll fracture toughness of the adhesive interface between concrete and carbon fiber sheets. The validity of the evaluation formula was studied on the basis of the results of finite element analysis. The mixed mode fracture toughness and fracture criterion of the adhesive interface were also studied on the basis of the results of fracture toughness test using the proposed method. 

Strictly speaking, the oscillation terms arising near the interface of different materials should be considered in the above discussion [16]. However, the purpose of the present work is to macroscopically characterize the fracture behavior of the adhesive interface for the design of civil structures. Hence, the inhomogenity of the specimen was neglected for the evaluation of the macroscopic fracture toughness. 

Centre cracked panels as shown in Fig.2(aj are used for evaluating the fracture toughness of the laminated composite and components of it. Pre-fabricated cracks are manually cut, using a razor blade, to a total slit length of 2a = 45 mm. The width and gauge length of the specimens was 2W = 95 mm and 2h = 230 mm, respectively. 

Macheret, J. and Bucci, R.J. (1993) A crack Growth Resistance Curve Approach to Fiber/Metal Laminate Fracture Toughness Evaluation , Eng. Frac. Mech. Vol.45, N0.6, pp.729-739. 

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