Transfer length

It is evident from Fig. 3.29 that there is a minimum fibre length which will permit the fibre to achieve its full load-carrying potential. The minimum fibre length in which the maximum fibre stress, ((rf)maxt be achieved is called the load transfer length, The value of may be determined from a simple force balance... 

Example 3.17 Short carbon fibres with a diameter of 10 fim are to be used to reinforce nylon 66. If the design stress for the composite is 300 MN/m and the following data is available on the fibres and nylon, calculate the load transfer length for the fibres and also the critical fibre length. The volume fraction of the fibres is to be 0.3. 

When the concentration profile is fully developed, the mass-transfer rate becomes independent of the transfer length. Spalding (S20a) has given a theory of turbulent convective transfer based on the hypothesis that profiles of velocity, total (molecular plus eddy) viscosity, and total diffusivity possess a universal character. In that case the transfer rate k + can be written in terms of a single universal function of the transfer length L and fluid properties (expressed as a molecular and a turbulent Schmidt number) ... 

Since fiber pull-out length, p , is difficult to measure with any accuracy from the fracture surface of composite specimens containing high V(, Rpo is often expressed in terms of the inherent properties of the composite constituents. There are three cases considered here depending on the fiber length relative to the critical transfer length. 

In Eq. (6.8) an upper bound estimate of tf is made by the apparent bond strength Tj for the critical transfer length, i.e., 4 fffd/2Tf, based on the early work of Kelly and Tyson (1965). Therefore, Rpo is shown directly proportional to the critieal transfer length. 

The failure processes in thermoplastics composites with aligned glass fibers of sub-critical transfer length have been characterized (Lauke and Schultrich, 1983, 1986a, b Lauke et al., 1985 Lauke and Pompe, 1988) in terms of matrix fracture mode which is determined mainly by the ductility of the matrix material, loading rate and temperature. The total specific work of fracture, / t, is expressed as the sum... 

Figure 9 Voltage vs current and onset of resistance above the critical current for (A) "ideal case", (B) premature thermal runaway, (C) damaged sample, and (D) inadequate current transfer length between voltage and current taps as discussed for low temperature superconductors. Ref. 26.

Fig. 6.19 The basis of the mesoscale model of Rouby and Reynaud. The axial stress, oy in the fiber decreases linearly over the slip length, from a peak value of oy° at the edge of the matrix crack, to a value of o(Ef/Ec) at the end of the slip-zone (z = ls). It is assumed that the crack spacing / is larger than twice the load transfer length /,. It is assumed that the fiber stress decreases linearly to zero over the load transfer length l,. After Rouby and Reynaud.46...

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