Mechanical Modeling And Simulation For Woven Fabrics Based On The Dynamics Of Multibody Systems

Woven fabrics have a wide application in real life, such as apparel, fabric rein-forced composites, and body armor for ballistic protection. Because of the complex coupling between the yarns of fabrics, even relatively simple woven plain weave fab-ric, the mechanical properties are very complex. Therefore, in order to better guide the practical application of woven fabrics, it is urgent to to establish the mechanical model, which can reflect their performance effectively. The study on the woven fabric mechanics modeling and dynamic simulation is one of the interests and difficulties in textile research.Woven fabrics is a complex multi-body system, and the dynamics of multi-body systems has obvious advantages to deal with complex engineering problems and has been widely used in many respects, for example, the aerospace engineering systems, the vehicle engineering systems and the biomedical systems, etc. Therefore, in this paper, based on the theory of the computational dynamics of multi-body systems, plain weave woven fabrics as typical study objects, after the study of the mechanical properties of yarns and the special mechanical properties of fabrics due to their weave structures, the study on woven fabric mechanics modeling and simulation and corresponding experiments are carried out.The contributions of this paper are mainly to propose three mechanical model of woven fabric, that is, a model of non-linear particles system for woven fabric (MNPF), a model of rigid bodies for plain-weave fabrics (MRBF) and an improved model of rigid bodies for plain-weave fabrics (IMRBF). In order to verify the innovation, accuracy and efficiency of MNPF, MRBF and IMRBF model, the curtain drape simulation based on MNPF, the simulation of fabric under the KES uniaxial tensile based MRBF, the simulation of fabric under the KES uniaxial tensile and shear, respectively, based on IMRBF are carried out. Taking into account the strong nonlinear characteristics expressed by the yarns under tensile, based on the particle system proposed by Breen, we apply the theory of nonlinear dynamics, and analyze the nonlinear mechanical properties of yarn, and in-troduce a nonlinear factor into the expression of the stretching force elements, propose a model of non-linear particles system for woven fabric (MNPF). Numerical simulation results show that:comparing with the existing particle model, MNPF has better abil-ity to inhibit the super-elastic phenomenon of fabric, more realistic simulation results are obtained, and it can better reflect the fabric's mechanical properties.This paper considers the complex mechanical properties of woven fabric due to its weave structure and applies the computational dynamics of multi-body systems to propose a model of rigid bodies for plain-weave fabrics (MRBF). For the KES uniaxial tensile test, the kinetic qualitative and quantitative analysis are carried out. The qualitative analysis reveals the strong coupling between yarns and the mechanism of the crimp interchange, and also provides a guidance for the quantitative analysis. Through the quantitative analysis, the simulation results of fabric KES uniaxial tensile deformation are obtained. The correctness and validity of MRBF are justified by the comparison of the numerical results and the qualitative analysis and experimental results.MRBF has the following deficiencies:1) the application of Euler parameters to describe the rotation of bodies made the generalized coordinates of system redundant and thus the computation efficiency lowered.2) the two modeling steps, one of which disposed of the interaction of interlacing yarns in a same unit cell by the compressing force element and the other located the application points of the bending force element on the centers of mass of the corresponding bodies, caused the difference between the mechanical performances of the MRBF and the actual fabrics.To these deficiencies, considering that the rigid bodies in MRBF are straight linear threads, this paper adopt the simplified Kardan angular coordinates to describe the rotation of each body, by which the dimension of system is reduced greatly and thus the computation efficiency is boosted. On the other hand, considering that, when fabric under shearing deformation, the contact between yarns leads to the lateral compressing action to prevent the unit cell from rotating, we model this lateral compressing action as contact force element, which makes the proposed model reflect fabric mechanical performance better. Based on the two improvements mentioned above, this paper proposed an im-proved model of rigid bodies for plain-weave fabrics (IMRBF). The simulation of fabric under the KES uniaxial tension and the corresponding comparison and anal-ysis justify the effectivity of IMRBF and the improvement of computation efficiency of IMRBF relative to MRBF. Moreover, the comparison and analysis between the simulation results of fabric under the KES shear and the experiment results show the validity, effectivity and broad applicability of IMRBF.The proposed three models,a model of non-linear particles system for woven fab-ric (MNPF), a model of rigid bodies for plain-weave fabrics (MRBF) and an improved model of rigid bodies for plain-weave fabrics (IMRBF), belong to the discrete fab-ric mechanical model. The main advantage is that, comparing with the continuum mechanics models, they are excellent for their modeling flexibility and their computa-tion efficiency. And comparing with existing discrete mechanical models, the dynamic systems based on MNPF, MRBF and IMRBF, respectively, have less dimensions of the equations of motion and less rigid. Thus, the difficulty of numerical computation is reduced and computation efficiency is improved. The numerical dynamic simu-lations based on the three models have the performances of accuracy, stability and efficiency. MNPF can better suppress the super-elastic effect, the numerical simula-tion results are more realistic than the existing particle models, the dimensions of the equations of motion are smallest. MRBF considers the mechanical properties due to fabric structures, so MRBF is superior than MNPF in the respect of the effectivity of model. In IMRBF, the generalized coordinates of bodies and the force elements are improved, and, thus, its effectivity is further improved. Comparing with MRBF, the IMRBF reflects the mechanical performance of actual fabrics more effectively and higher computation efficiency and has wider application areas.As a result, the work of this paper not only enriches the dynamic model of fab-rics and provides an effective approach to the real-time simulation of fabrics but also further enlarges the application range of the computational dynamics of multi-body systems, has important theoretical and practical significance.