![]() The warp, bias and binder yarns are fed to the weaving zone, shown in Figure 5, from bobbins mounted on braider bobbin carriers which are equipped with a tension compensation device serving to maintain the yarn tension constant while weaving process (Figure 6(a)). A scheme of these weaving systems on the GEMTEX loom is presented in Figure 4. The basic weaving operations realized on the loom to wave a multiaxis 3D woven structure are: warp, bias and binder yarn feeding, bias yarn positioning in the weaving zone, binder yarn insertion (shedding), filler yarn insertion, beating-up and take-up. Also, the conventional weaving operations, such as shedding (binder yarn insertion), beating-up and take-up, are adapted for this particular movement of the bias yarns. On this loom, a new apparatus using guide blocks technique has been elaborated to accomplish this requirement. An experimental and manual driven prototype of multiaxis 3D weaving loom has been designed and manufactured in the GEMTEX laboratory. ![]() Where, the bias yarns have to be moved one step for each weaving cycle transversely with respect to the loom main axis, which corresponds to the warp yarns feeding direction. As was mentioned earlier, the basic weaving operation required on the loom to produce multiaxis 3D woven structure is the transversal displacement of bias yarns in the weaving zone. That is because of high bending curvature accomplished on binder yarns during weaving process when they pass throughout the weaving zone to alternate their position and to create an appropriate shed to insert the filler yarns. 25 In the present produced preform, Kevlar fibre is used for the binder yarn unlike the in-plane yarns where glass fibre is used. 23,24 Therefore, the manufacturing and weaving parameters of these preforms are also presented in Table 1, as reported by Bilisik. The geometrical and architecture properties of the manufactured preform will be compared with those of preforms produced by means of the tube rapier weaving technique 22 and the tube carrier weaving technique. The unit cell of this structure is defined as the repeated smallest unit of the structure on the mesoscale having the same geometrical and architectural properties across the preform ( Figure 2). Also, the weaving parameters, consisting of the number of each yarn type per one unit cell of the structure, the number of yarns per layer and number and order of in-plane yarn layers, are also listed in Table 1. For the produced preform on the present prototype loom, the manufacturing parameters, involving density and linear density of the used yarns, which are listed in Table 1. the present multiaxis 3D woven preform, the formed bias yarn layers are uniform with an edge-to- edge pattern. The optimized fabrication conditions reduced the unstructured fiber loss by almost one order to <0.3 dB/m at 1.55 μm. Finally, using this advance in knowledge, we successfully fabricated low-loss lead-germanate glass fibers with no presence of reduced metallic Pb particles by optimizing dehydration agent, glass melting, preform extrusion and fiber drawing conditions. Here, the second part of this study reports the investigation of the process conditions to fabricate low-loss lead-germanate glass fiber through further understanding of the co-effects of glass melting and heat treatment atmospheres on the formation of nano- and micron-scale metallic Pb species in both the as-produced and heat treated lead-germanate glasses. The first part of this study reported the optimization of the glass melting procedure to obtain low amount of OH while preventing formation of metallic Pb species in lead-germanate glass. For lead-germanate glass fibers, reducing the content of hydroxyl (OH) groups and the formation of metallic Pb species is essential to pave the way for their applications as low-loss mid-IR fiber optics since OH and metallic Pb species cause intense absorption and scattering loss, respectively, in the mid-IR spectral range.
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