Determination of Poisson's ratio and shear module of complex, nonlinear elastic material, such as woven fabric, is a challenge for researchers in the field of textile mechanics. In the standard method of determining the Poisson's ratio, the transverse fabric strain is measured by a 1% tensile extension. In this way, there is no information about changing the Poisson's ratio at higher tensile extensions, and the methodology itself is unsuitable for larger extensions because of woven fabric buckling. In this research, a device has been designed, which can be built on a dynamometer and which has the ability to measure transverse forces in fabric during tensile test. A mechanical model is developed from which it is possible to calculate Poisson's ratio throughout the fabric stress-strain curve.

Unlike many other engineering materials, deformational behaviour of fabrics is marked by specific nonlinearities. For the purpose of certain engineering analyses, nonlinearity can be approximately described by means of appropriate models. A number of possibilities in approximation of tensile nonlinearity are statistically analysed and compared for the representative selection of woven fabrics. Second-order parabolic approximation is estimated to combine simplicity and good accuracy for a selected woven fabric. It is then included into deformational analysis of specimen in asymmetric tensile loading, as the case representative for structural application of textile, where geometric conditions combined with material properties define the mechanical behaviour of the body. The results indicate the factors of stress concentration due to load eccentricity. Simulation of tensile test gives the theoretical prediction of apparent reduction in stiffness and strength of the specimen in terms of the load eccentricity.

A non‐linear numerical simulation of a standard procedure for textile flexibility testing is performed using discretised beam bending model. Geometric non‐linearity due to large deflections is traced using incremental method. Linear moment‐curvature response is assumed, as well as constant curvature of a finite element of the beam. Numerical procedure is incorporated into a PC programme producing graphical results for the deformed shape of the specimen, non‐linear load‐deflection diagrams and internal force distributions in deformed state. Finally, the method is applied to compute the flexural stiffness of textile materials from the data produced by the standard procedure for flexibility testing.

Purpose -The purpose of this paper is to investigate and illustrate the possibilities of a systematic engineering approach in the design of mechanical reinforcements in garments. A mechanical reinforcement can be designed using optimisation strategies. Design/methodology/approach -In this work, an iterative algorithm for minimum search based on parabolic approximations is proposed and applied in the optimisation of mechanical reinforcement in a selected model problem of a buttonhole type. Findings -Optimisation algorithm based on parabolic approximations, in conjunction with the finite element analysis, offers some promising possibilities as support for the decision-making process in the design of mechanical reinforcements. The selection of optimisation criteria -influence parameters and corresponding weight factors -remains of course to be studied and implemented by the clothing engineering experts.Research limitations/implications -The intention in future work should be to optimise two or more geometric parameters simultaneously (multidimensional optimisation), and to produce a computer program for an automated optimum search. Practical implications -The contents of the paper could be useful for the experts in clothing engineering in the process of design or selection of the reinforcements of weak spots in textiles and garments. Originality/value -This paper provides optimisation routes to the weak sports of mechanical reinforcements in textiles and garments.

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