Our early model for predicting nonwoven fabric stress-strain behavior by the finite element method is generalized to include the effects of fiber curl, which is shown to have a great effect on the tensile behavior of the fabric. A numerical method to characterize the lateral contraction of nonwovens during tensile deformation is presented. The effects of fiber arrangement characteristics on the mechanical properties of nonwovens are studied through laboratory experiments and theoretical analysis. The effects of varying thick nesses within the nonwovens on fabric strength, modulus, and stress-strain distribution are also examined. Tensile testing of several nonwoven fabrics verifies the theoretical results.
A new computer model is developed to predict the tensile behavior of nonwoven fabrics from the stress-strain behavior of their constituent fibers and distributions of fiber orientation angles. The finite element method is used to calculate the numerical solution of stress and strain distribution in different regions of the samples during tensile deformation. Stress-strain curves of fabrics are simulated. Tensile testing is done on several nonwoven fabrics to verify the simulated results, which are in a good agreement with those obtained from tensile experiments.
This paper attempts the geometric modeling of woven and braided fabric structures in three dimensions using a computer aided geometric design (CAGD) technique. A new symbolic approach to fabric structure representation, which is useful to the textile CAD/CAM process and fabric design, is presented, and a basic model is proposed that treats a yarn as a three-dimensional solid object. Some traditional 2D fabric models are extended into 3D models and demonstrated in 3D form. The structures of various fabrics are demonstrated in graphic forms, including elementary weaves such as plain weave, twill, and satin; two layer fabrics; braided fabrics; and three-dimensional fabrics as reinforcements for composite materials.
The mechanical behavior of nonwoven geotextiles in soil-fabric interaction is investigated through laboratory experiments and theoretical analysis. A computer model is presented to simulate geotextile performance in pullout tests. The model parameters are based on single fiber properties and the fiber orientation distribution function. A new finite element method is used to calculate numeral solutions of stress and strain distribution in different regions developed in the fabric during the pullout test. The pullout load versus displacement curves of the samples verify the simulated results, which are in good agreement with those obtained from pullout experiments.Geotextiles are widely used with soil structures in the field of geotechnical engineering. In these applications, the geotextile compensates for the obvious weakness of soil in withstanding tensile stress through the geotextile's strength and soil-geotextile interaction. The necessity of testing each geotextile's suitability for a particular application is becoming more and more important as their variety in the international market and their use in geotechnical works increase.The pullout test is a common one for determining the strength and deformation parameters between the reinforcement and the soil in the design of reinforced earth structures [2, 3, 5, 6]. The large scattering of published pullout test results comes from using different testing equipment associated with distinct boundary effects, different testing procedures, and different schemes of placement and compaction of the soil. Numerous studies have also used the finite element method in analyzing reinforced soils [ 1,4,12 ) . In most finite element analysis, the soil is modeled using conventional solid elements, while the reinforcement is generally modeled using extensible beam elements that cannot be bent or compressed.Testing for soil reinforcement interaction coefficients with extensible beams is straightforward, since the tension applied to the reinforcement is readily transferred throughout the length of the reinforcement at very low strains, and changes in the contact area between the soil and reinforcement are limited. This is not the case for geotextiles, which exhibit relatively large strains and lateral contractions-called &dquo;necking&dquo; -within the reinforcement during a pullout test. These strains and contractions, which vary over the length of the sample, can affect the data from the test results. For exarr~le, necking behavior reduces the surface area of the geotextile, which in turn reduces the contact area between geotextiles and sand, resulting in lower pullout resistance.In this study, we establish a new finite element model. Our objective is to obtain information about deformation and stress and strain distribution within the sample during pullout tests, and the influences on those parameters of the constituent fiber properties and structure-related parameters of geotextiles. First, we describe the finite element's constitutive and stiffness matrices from a knowledge...
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