FIBRE SPACING

A condition of negative capillary action is achieved. The pressure required to force water through the fabric depends on the surface tension and inversely on the fibre spacing, so that a moderately tight weave is desirable. The passage of air through the fabric is not hindered. 

Swelling of finish to reduce inter-fibre spacing. 

LONG FIBRE SPACINGS IN POLYHEXAMETHYLENE ADIPAMIDES OF VARYING AVERAGE CHAIN LENGTH... 

One of the most important factors affecting composite properties is the volume percentage of fibres in a composite. Two composites made of the same resin and volume of fibres but different fibre densities will have identical mechanical properties. Also, closely packed fibres decrease fibre spacing, resulting in higher local stress concentrations in the material, and reduce complete penetration of resin into the interstices. 

This method does not explicitly contain terms associated with the degree of bonding, fibre spacing, fibre shape, packing geometry and other influential factors which can significantly affect the shear moduli and transverse properties of the lamina. However, as this method is conservative, the actual properties will always be higher than those predicted. 

Romualdi and Batson (1963) have shown that the tensile strength of FRC at the proportional limit is higher than that of the unreinforced matrix. Closely spaced fibres act as crack arrestors and reduce the stress intensity. In other words, the strength is related to the spacing between the fibres, as shown in Fig. 15.2. The average fibre spacing is calculated from Eq. [15.1] ... 

Theoretical and experimental strength ratio as a function of fibre spacing (adapted from Romuaidi and Batson, 1963). 

So-called effective fibre spacing has been proposed by Swamy and Mangat... 

Figure 10.10 Calculated and experimental results of relation between fibre spacings and matrix reinforcement for modulus of rupture and tensile strength in splitting, after Romualdi and Mandel (1964).

Different parameters are responsible for this cracking behaviour, the dominant ones being, as far as we can see today, the fibre spacing, the specific fibre surface [SFS], the degree of fibre dispersion in the material and the fibre matrix bond. 

Krenchel, H., Fibre spacing and specific fibre surface. 

To illustrate the relationship between fibre diameter and fibre spacing, Figure 2.5... 

Figure 4.14 Effect of fibre spacing on first crack stress ratio (after Romualdi and Mandel [23]).

H. Krenchei, Fibre spacing and specific fibre surface , in A. Neviiie (ed.) Eibre Reinforced Cement and Concrete, Proc. RiLEM Symp., The Construction Press, Lancaster, Engiand, 1976, pp. 69 79. 

Flughes and Flannant [52] examined the effects of moisture on the first crack stress, by considering the reduction in the modulus of elasticity of the wet fibre, and using the concepts of crack arrest when the fibre spacing is less than the critical flaw size [52], Their results, assuming a fibre modulus of elasticity of 4 and 40 GPa for wet and dry conditions, respectively, are presented in Table 11.7. If the bond is assumed to remain constant, at about 0.5 MPa (as suggested by Andonian etal. [27]), the matrix failure strain should increase in the wet state. If the bond increases... 

Glass microfibres in the 0.5-0.75 pm diameter range usually yield the best results as a coalescing filter medium. The depth of the fibre bed and the void space to fibre space ratio, are of paramount importance to the proper operation of a coalescing filter. 

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