Fatigue crack deflection

Kumar et al. [18] have reported on the fatigue performance of concrete slabs containing reinforced plastic (GRP) rebars. They concluded that cast in situ slabs performed better than precast slabs with respect to fatigue cracking and deflections. The bending response of similar beams has been studied by Faza [19]. 

For the determination of the concrete slab thickness, two distress modes have been considered (a) the flexural fatigue cracking of the slab and (b) the subgrade/sub-base erosion arising from repeated deflections at joints and planned cracks. 

Incorporation of short glass or carbon fibers into many engineering thermoplastics improves their strength, stiffness and heat deflection. The strength and fatigue crack resistance depend on the volume fraction of fiber in the composite, the mechanical properties of the fiber and pol)m[ier and particularly the adhesion between the two components. Nonfibrous fillers find application in low cost composites where they may enhance physical properties or simply replace the more expensive polymer with minimal loss of mechanical integrity. 

Incorporation of short or long glass or carbon fibers into many engineering materials improves their strength, stiffness, and heat deflection. The strength and fatigue crack resistance... 

The fatigue behavior of a material is normally measured in a flexural but also in a tensile mode. Specimens may be deliberately cracked or notched prior to testing, to localize fatigue damage and permit measuring the crack-propagation rate. In constant-deflection amplitude testing a specimen is... 

Constant deflection or strain testers have a disadvantage in that once a large crack develops, the stress level drops below the fatigue endurance limit and the specimen does not fail for quite some time. However, this test allows one to observe crack propagation in the specimen due to slow rate of failure. In contrast, in the constant stress tester, once the crack develops, the amplitude of deformation increases and failure occurs very rapidly (54). 

LOVEGROVE, J.M., SALAH EL DIN, Deflection and cracking of reinforced concrete under repeated loading and fatigue. In Fatigue Of concrete structures, Amer. Concr. Inst., 1982, SP75, pp. 133-52. 

Deflection temperature Environmental stress cracking Fatigue strength Equilibrium elastic line Shear bands Failure envelope Crazing... 

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