旗袍的造型演变与结构设计变化研究

通过对不同时期的旗袍造型特点变化和不同时期的结构设计特点变化的比较和分析,论述了中国旗袍经历了从平面造型、直线裁剪到立体造型、曲线裁剪和以强调女性形体美为主流的演变过程.在此基础上论述了其长盛不衰和永保旺盛生命力的原因以及预测未来旗袍结构设计的发展趋势.     

棉织物悬垂性能与织物结构参数的灰色关联性

通过测试8种棉织物的结构参数及悬垂性能,应用灰色系统理论,得出了棉织物结构参数与悬垂系数的关联度,对其进行了排序,认为影响棉织物悬垂性能的最主要三个结构参数依次是紧度、平方米重量及厚度.通过用线性回归模型对棉织物悬垂系数与其主要影响因素进行定量分析,认为棉织物的总紧度及平方米重量与悬垂系数呈正线性相关.     

Mass production technologies for textile reinforcement structures

Abstract

This paper reports recent work on the optimisation of preform manufacture. Producing tailored textile semifinished parts, such as non-crimp fabrics (NCFs) with locally adjusted properties, and processing these in a sequence of automated cutting, handling and joining operations are a promising approach to significantly reduce costs and cycle times within preform production. Additionally, along with the enhancement of machinery, the development of simulation tools for designing efficient process chains and understanding the behaviour of reinforcement textiles along the entire production process is essential. The Institut fuer Textiltechnik (ITA) of RWTH Aachen follows this holistic approach, aiming at preforming processes suitable for mass production. In this paper, enhanced production technologies for tailored NCFs are described. Furthermore, an overview of automated technologies for converting these tailored NCFs to near net shape preforms is given. Methodical process chain development is shown in a case study, proving the possibility to significantly increase the operating efficiency of preform production by means of the introduced approach.     

Process and cost modelling applied to manufacture of complex aerospace composite part

Abstract

Novel methods for process simulation and cost analysis have been applied during manufacturing process development of a rotor blade pitch horn. The aim is to reduce costs and lead time on the one hand and to enhance part quality on the other hand. Fabric draping has been simulated using the kinematic draping code PAM-QUIKFORM incorporating new processing strategies. Draping strategies were optimised using a genetic algorithm taking into account manufacturing constraints, which led to a fabric shear reduction by up to 10° with the optimised strategy implemented in manufacturing. A novel material generation of prebindered carbon fibre tows has been used to enhance rigidity and dimensional accuracy of the preform and to minimise processing time. State-of-the-art preforming technology has been incorporated in the process significantly increasing the degree of automation. The process had been analysed based on the activity based costs methodology deriving product costs as sum of costs of all activities involved. Development efforts have been concentrated based on the analysis in order to optimise cycle times with a nearly even duration of the subprocesses. In comparison to a manual prepreg manufacturing process, cost savings with the novel, semiautomated preforming process could be quantified to ～20%.     

Characterisation of material properties for draping of dry woven composite material

Three test methods, uniaxial bias extension, biaxial and picture frame tests are used to characterise the shear behaviour of dry woven fabric during draping. The deformation of the bias extension and biaxial specimens is measured from images of a central gauge section. The forces applied to the material are resolved into forces along and parallel to the tow directions. The deformation of the material in the bias extension and biaxial tests is found to behave in a manner which is reasonably well described by a pin-jointed net analysis. There is negligible change in the shear resistance of the material during biaxial loading, while a slight increase in shear resistance is observed in the picture frame tests. Microscopic examination of the tow architecture [Compos Sci Technol 63 (2003) 99], which shows a significantly smaller crimp amplitude for picture frame tests than for the bias extension and biaxial tests, supports the suggestion raised by Harrison et al. [Proceedings of the 10th European Conference on Composite Materials, 2002], that the increase in resistance in the picture frame tests is associated with an increase in tow cross-over force generated by large loads along the tows.     

Draping the two pieces of pencil pants by woven fabric北大核心

This paper attempts to combine side seam of pants by draping and blocking, produce no lateral seam and fitted pants. The pencil pants although produced by bombs or less elastic woven cloth, but can still do a snug fit, as a result of the merger the outside seam. The whole pair of trousers is composed of only two main cut pieces, which maximum retention fabric patterns and integrity and avoid machining process on the articles, of lattice, the flowers produce fabric loss and reduce processing cost, in the visual produced special beauty of technology. The study adds a new category for woven fabric pants.     

Finite element analysis of textile composite preform stamping

The forming or draping of a textile composite preform may result in large changes in the fibrous microstructure of the preform. This change in the local fiber orientation leads to significant changes in the fabric permeability as well as the mechanical properties of the ensuing composite structure. Therefore, this change in orientation of the tows of the preform needs to be known accurately to calculate the various effective properties of the composite. A new finite element approach for stamping analysis of a plain-weave textile composite preform has been developed. This model is simple, efficient and can be used in the existing finite element codes. The model represents the preform as a mesh of 3-D truss elements and 3-D shell elements. The truss elements model the tows, which are allowed to both scissor and slide relative to one another. The shell elements represent a fictitious material that accounts for inter-tow friction and fiber angle jamming. The model takes into account large strains and large deformations. In-plane uniaxial tension tests have been performed on plain-weave specimens for determining the constitutive law of the transforming medium and to show the inter-tow sliding. Application of the model is demonstrated by simulating the stamping of a preform by a spherical punch. The results from the simulation show good correlation with results from the experiments.     

Simulating Resin Infusion through Textile Reinforcement Materials for the Manufacture of Complex Composite Structures

Increasing demand for weight reduction and greater fuel efficiency continues to spur the use of composite materials in commercial aircraft structures. Subsequently, as composite aerostructures become larger and more complex, traditional autoclave manufacturing methods are becoming prohibitively expensive. This has prompted renewed interest in out-of-autoclave processing techniques in which resins are introduced into a reinforcing preform. However, the success of these resin infusion methods is highly dependent upon operator skill and experience, particularly in the development of new manufacturing strategies for complex parts. Process modeling, as a predictive computational tool, aims to address the issues of reliability and waste that result from traditional trial-and-error approaches. Basic modeling attempts, many of which are still used in industry, generally focus on simulating fluid flow through an isotropic porous reinforcement material. However, recent efforts are beginning to account for the multiscale and multidisciplinary complexity of woven materials, in simulations that can provide greater fidelity. In particular, new multi-physics process models are able to better predict the infusion behavior through textiles by considering the effect of fabric deformation on permeability and porosity properties within the reinforcing material. In addition to reviewing previous research related to process modeling and the current state of the art, this paper highlights the recent validation of a multi-physics process model against the experimental infusion of a complex double dome component. By accounting for deformation-dependent flow behavior, the multi-physics process model was able to predict realistic flow behavior, demonstrating considerable improvement over basic isotropic permeability models.     

Experimental studies and analysis of the draping of woven fabrics

This study investigates and compares the draping and forming of four types of woven fabrics, namely a loose plain weave (basket weave), a tight plain weave, a satin and a twill weave. The fabrics were draped over a hat mould consisting of a hemispherical dome surrounded by a flat base. The draping of each fabric was examined in terms of wrinkle formation, boundary profile of the draped fabric, distribution of fibre orientation and local shear angles. A theoretical analysis of the experimental results involved the calculation of the distributions of the fibre volume fraction and mechanical properties, in terms of components of the reduced stiffness matrix, from the experimental data of local shear angles.