Effect of joint geometry

A major feature of the continuum fracture mechanics approach is that the plane strain values of the fracture energy or the stress intensity factor for a given mode of loading should be independent of the geometry of the specimen employed for their evaluation. This is obviously required if the values of Gc and 

Rubber-modified = toughened with dispersed phase of rubbery inclusions. 

Kc are to be evaluated from laboratory specimens, such as those shown in Figs in and 7.8, and then used to design and predict the service life of bonded structures on the principle that the values are material properties. (Allowing of course for the values to be dependent upon test rate, temperature, environment, etc.) Also, even for possibly the less rigorous application of adhesives selection and development it is a distinct advantage if the values of Gc and A cfor the joint are material properties. 

In the case of a rubbery adhesive the work of Gent and Kinloch [11] has shown that the adhesive fracture energy, Gc, is independent of the type of specimen. They used several of the joint geometries illustrated in Fig. 7.7 and confirmed that the value of Gc, when measured for a given value of temperature and crack velocity, is independent of the details of the test specimen. 

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Colhngs TA. On the hearing strength of CFRP laminates. Composites 1982 13 241-52. Cooper C, Turvey GJ. Effects of joint geometry and holt torque on the stmctural Performance of single holt tension joints in Pultmded GRP Sheet material. Compos Stmct 1995 32 217-26. 

Table 4.4. Effect of joint geometry on the apparent shear strengths of two epoxy adhesives cured at 20 C... 

Cooper C and Turvey G J (1995), Effects of joint geometry and bolt torque on the structural performance of single bolt tension joints in pultruded GRP sheet material. Composite Structures, Vol. 32, Nos. 1, pp. 217-226. 

S. Mostovoy and E. J. Ripling, Effect of joint geometry on the toughness of epoxy adhesives, J. Appl. Polym. Sci. 15, 661 (1971). 

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