Longitudinal reinforcement effects

The received experimental data allow us to conclude that application of a longitudinal reinforcement Ra = 6400 kg/cm2 has a favorable effect on the resistance of the shear beam zones at bend and promotes an increase of crack resistance and a reduction in the general deflection of a beam. 

George et al. [27] studied stress relaxation behaviour of pineapple fibre-reinforced polyethylene composites. They found stress relaxation to be decreased with an increase of fibre content due to better reinforcing effect It is also reported by George et al. [28] that properties of fibre-reinforced composites depend on many factors like fibre-matrix adhesion, volume fraction of fibre, fibre aspect ratio, fibre orientation as well as stress transfer efficiency of the interface. Luo and Netravah [29] found an increase in the mechanical properties of green composites prepared from PALFs and poly(hydroxybutyrate-co-valerate) resin (a biodegradable polymer) with the fibres in the longitudinal direction. However, the researchers reported a negative effect of the fibres on the properties in the transverse direction. 

Longitudinal reinforcements, as stretches arranged along generatrices, show a reduced effectiveness, since they only perform a stitching function between the ideal arches forming the barrel vault. Such an action is particularly important in the presence of horizontal actions. 

Carbon/Aramid Fiber Sheet Jacketing Method. The application of carbon/aramid fiber sheet for the reinforcement of concrete pier is adopted when restricted conditions are present on site, such as no permit of sectional increase due to clearance limit or weight increase on the foundation. The sheet in longitudinal direction is effective to increase the flexural strength and the sheet in transverse direction acts as lateral reinforcement to raise the shear strength. Particularly the fiber sheet is concentrically bonded at the termination of longitudinal rebar at the mid-height. 

Schapery [100] has obtained bonds for the effective for both isotropic and anisotropic composites consisting of isotropic phases by employing extremum principles of thermoplasticity. The exact solutions were derived in particular cases. For a unidirectional composite, the following expressions are obtained. The a (ay) for a fiber-reinforced composite in the longitudinal direction is given by the following equation... 

A composite with equal amounts of fibre in the longitudinal and transverse directions has equal strength and stiffness in the two directions. However, neither would be as high as in the uni-directional case. In theory, if that same amount of fibre was randomly laid in-plane (isotropically), then the resulting composite would have equal strength and stiffness in all in-plane directions but less than in the bi-directional case (in the axes of the fibres). The directionality of the reinforcement has a significant effect on the amount of reinforcement which can be packed into a composite. 

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