Analysis of Strength Criteria as Applied to Adhesive Joints

2 Analysis of Strength Criteria as Applied to Adhesive Joints 

These contradictions can to a considerable degree be resolved by a successfully chosen or properly developed theory of limiting stressed states, with the help of which it should be possible to find an explanation of the discrepancies between design, laboratory, and operating values of breaking stresses in adhesive joints. 

Investigation of strength imder the action of normal or tangential stresses only is common to all the existing theories of adhesion and the majority of experimental developments. At the same time, the increase of the areas and volumes of adhesive joints is interrelated with the need to develop engineering methods of calculation of their strength taking account of various kinds of stressed state. 

Equations for the layered mediiun for investigation of the interlaminar fracture and shear stresses in glass-reinforced plastic with fabric reinforcement are given in [379]. The mediiun considered is a set of orthotropic glass-reinforced plastic plates each of them includes one layer of reinforcing fabric and is joined without intermediate layers, and mechanical characteristics of separate plates and the whole set are assumed equal. Experimental validation of the equations is not produced. 

The work reported in [381] deals with interlaminar fracture and shear stresses imder compression in the plane of the layers, which occurs due to natural bending of reinforcing fibers as a result of 

On the basis of the equations [379], it is possible to determine [380] critical stresses of the reinforcing layer of a plate made of orthotropic glass-reinforced plastic under uniaxial and biaxial compression. Compression failure is considered as the result of violation of the operational compatibility of reinforcing material layers under the action of interlaminar fracture and shear stresses, occurring due to loss of separate layer stability. Since compression strength is equal to or less than the critical stress calculated by the formulas obtained, only the maximum possible strength value for the glass-reinforced plastic is determined. Experimental validation of the analytical dependences was not done. 

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