3D-Weaving and Noobing: Characterization of Interlaced and Non-interlaced 3D Fabric Forming Principles
Doctoral thesis, 1997
TEXTILE-based composite materials are the rapidly developing light-weight engineering materials. Fabrics constitute the reinforcement component of the composite material. The fabrics used in composites manufacture are referred to as preforms and are especially engineered as a single-fabric system to impart reliability and performance. Preforms constituting continuous-fibres are producible through fabric manufacturing methods of weaving, knitting, braiding and certain nonwoven techniques. A number of novel techniques have evolved, particularly in the last three decades, to engineer 3D fabrics. However, these new indispensable 3D fabric manufacturing methods, which have been primarily devised to organize and assemble essentially three orthogonal sets of yarn (in the fabric-length, -width and thickness directions), have not been a matter of examination from the point of textile technology. A consequence of this has been the misrepresentation of a unique nonwoven 3D fabric-forming principle and process as 3D-weaving. The lack of proper technical information, terms and definitions have led to the mistaken classification of the patents of the various nonwoven 3D fabric manufacturing developments in the weaving category over the years.
To represent the nonwoven 3D fabric-forming processes as 3D-weaving is technically not correct even if they bear certain similarities with the weaving process design. This is because in these new processes, the foremost operation of shedding, which is central to the weaving principle and without which the weaving process cannot technically progress, is totally dispensed with. Consequently the obtaining process ceases to comply with the principle of weaving and the resulting 3D fabric is a non-interlaced construction. Clearly this non-interlacing process happens to be fundamentally different from the firmly established interlacing characteristics of the weaving process.
The nonwoven 3D fabric-forming process is now recognized by the term 'noobing' and it is designed essentially to assemble three orthogonal sets of yarn, without interlacing them, into a 3D fabric. With this, the constituent yarns of the fabric are free of any crimp. In the absence of any interlacement, the fabric integrity has to be realized through a compulsory binding operation. Because the fabric integrity results from the outermost opposite `interconnected yarns', there is the risk of the fabric splitting up if cut at the surface or internally. The development of an experimental noobing device has upheld these integral characteristics. The noobing process can be classified into uniaxial and multiaxial types, of which the former is comprehensively analysed here as this process type has been mistaken for the 3D-weaving process. The newly gained understanding shows this process could be utilized in the production of certain technical textiles other than preforms as it has a limited near-net shaping capability to produce few `simple' solid cross-sectional profiles. This process can also be employed to produce thick-walled tubular fabrics. The multiaxial noobing process, which has been regarded as multiaxial warp `knitting' process, does not figure in the main focus of the present study.
To characterize the practically unknown 3D-weaving process, the concept of 'dual-directional shedding' operation is introduced. The shedding operation of the conventional 2D-weaving process is limited in its design to form a shed in only the fabric-width direction to enable interlacement of two orthogonal sets of yarn (a weft and either a single or a multiple layer warp). In the 3D-weaving process, the dual-directional shedding operation forms multiple sheds in the fabric-width and also the fabric-thickness direction to effect interlacement of three orthogonal sets of yarn (two orthogonal sets of weft and a multilayer warp). Two distinct dual-directional shedding methods have been developed to demonstrate the practicability of the new concept. These methods have been specifically developed to provide `yarn-to-yarn interconnectivity' for producing a network-like 3D woven 3D fabric block. From such a block, preforms of any desired shape, not only cross-sectional profile, could be cut without the risk of its splitting. Such a course of preform manufacture, referred to as universal preforming, could be a new approach to produce preforms for certain composite material applications.