Band 2, Heft 1

Shape memory alloys (SMAs) are a unique class of alloys which are able both to 'remember' their shape at high temperature during their modification at lower temperature under their transition domain, and able to recover that initial shape when heated. This ability is known as the one-way shape memory effect. Moreover, SMAs present two other interesting properties, superelasticity and damping capabilities, which can be more or less combined with the first one. An SMA wire of Nitinol mesh was manufactured into technical fabric, in order to examine its weaving adaptability in comparison with a stainless wire and to investigate the different possibilities of use of the material inside composite structures. Several tests have been or will be carried out in order to check the effect of the weaving operation, and later to measure the efficiencies of damping and shape modification.

Advanced composite manufacturing processes demand the use of fully fashioned near-net shape preforms. Flat knitting technology is especially suited for the production of such products. Research work which has been carried out at the ITB proved the possibility to obtain biaxial reinforced multilayer weft knitted fabrics with fixed fabric edges, by varying the number of stitches in wale direction. The capability of this method is shown for an open cuboid and a spherical shell.

A procedure based upon image analysis has been adopted to study the influence of several physical parameters on bubble size in foam. A procedure has been described to account for the distribution of bubble size. Foam was generated in a rotor-stator mixer. In the present research, the nature of the surfactant, liquid viscosity, solid phase content, and rotational speed of the mixer were varied. All parameters were found to influence the bubble size and its distribution to a certain extent. These effects were qualified experimentally.

Measuring the thickness of a wire using a micrometer is simple, but textile workers cannot use the same technique. The current report describes a possible method of measuring yarn thickness under lateral force using a range of loads. The effect of twist on thickness and compressibility of yarns is studied.

The shedding without dynamic warp loading is presented by a loom structure with the use of assembles of multi-angle shedding disks, e.g. quadrangular shedding disks and disks for increasing weft density. Several sets of these assembles form the rotating weaving drum, which is electronically controlled. The new machine loom, the multi-layer rotational weaving machine, allows the manufacture of completely new woven fabric structures, which until now was impossible to achieve with the use of conventional weaving machines. Woven fabrics can be manufactured with the use of warp and weft threads of extremely low tenacity, loose structure and strong developed surface, as can grid structures and woven structures with pile loop. The possibility to utilise unspinnable yarn, roving and selvedges was demonstrated on a model weaving machine specially constructed for the tests.

This paper presents an investigation of the dynamic behaviour of a yarn in an interaction with a high-speed object, for the lower warp sheet during the weaving process. The yarn movement on the object can be described in four stages from non-contact, contact, drop-off and withdrawal. A model is developed to predict this interaction, taking into account several factors such as yarn length, yarn tension, object speed, object orientation and object profile. A comparison of theoretical predictions and experimental measurements for different yarns indicates a good agreement. The theoretical model can be used to optimise the object profile in order to reduce the interactive yarn tension and to avoid any yarn damage.