Volume 1, Issue 4, Summer 2001

LINKS BETWEEN , DEVELOPMENT AND FABRIC BEHAVIOR FOR CLOTHING AND TECHNICAL TEXTILES

Sybille Krzywinski, Hartmut Rödel, Andrea Schenk Dresden University of Technology, Dresden, Germany

ABSTRACT

In this paper is shown the necessity for the development powerful 3D CAD-systems for the textile and clothing industry. The connection between 2D CAD-systems with 3D CAD-systems enables the user to prepare a collection more quickly and accurately. Applications could be the drape behavior of fabrics, the deformational behavior of fabrics when covering defined surfaces and also technical textiles.

Keywords: CAD-system, simulation, material behavior, close-fitting garments, technical textiles

1. INTRODUCTION • the systems work only in two- dimensions For garments the phases of product development and preparation of production • the material behavior and the material require approximately triple the time of the parameters are not taken into account. actual garment life span. In order to compensate for the resulting greater efforts Both these aspects are required for the three- in the product preparation and to react more dimensional display of a model with regard quickly and flexibly to the latest , the to the draping in order to give the use of complex CAD - CAM solutions is and model maker a realistic impression of essential. Today there are many existing the model. Optimal possibilities to examine design programs with various software tools the correct fitting and the form of a model and a wide choice of designing functions. In would be the three-dimensional display of a connection with sketching-systems so called two-dimensional pattern construction on a two and a half dimensional presentation dummy or a development of a three- programs can give an optical impression dimensionally constructed model onto the how the colors, motifs and materials look on two-dimensional plane, when the specific a scanned model. Steps of product material parameters are taken into account. preparation such as pattern construction, Therefore, the more detailed treatment of grading, pattern planning and pattern physical and mechanical properties and their optimization and the automated cutting are correct mathematical and physical realized with computer assistance. However, formulation is of interest [1, 2]. commonly used CAD-systems available on the market show the following weak points:

Article Designation: Scholarly Works 1 JTATM Volume 1, Issue 4, Summer 2001

2. THREE-DIMENSIONAL DISPLAY OF the weight per unit are considered in the TWO-DIMENSIONAL PATTERN draping module (Figure 2; Table1). The scale of the property curves depends on The current procedure to create patterns is a the measurement devices. multi-step approach which involves much personnel, time and costs due to the trial and error phase. The fabric properties enter the design process only via expertise of . It is absolutely necessary for CAD-systems to be extended to material parameters and further search for possibilities to connect design and pattern construction more closely in the future [3, 4, 5].

The objective of the research is to create a Figure 1: Comparison: Designer Sketch complete CAD-system for garment and Simulation of Skirt manufacturers including 3D of garments on virtual human beings. An excellent CAD-system for the clothing industry should be comprised of the following modules: • a fabric library correlating easily determined fabric properties to fabric drape configurations; search and sorting routines should be integrated in the library for efficient retrieval of information; • a model for the human body, which can be adapted for persons of different sizes; • routines to simulate garment patterns from specific fabrics on the human body using data from the fabric library. The following figures, which were made using DesignConcept 3D [8] by CDI Technologies Ltd. (recently acquired by Lectra Systemes, France), give an of such a CAD-system. The Figure 2: Fabric Properties software DesignConcept 3D is based on the polygon computation of NURBS (Non- Uniform-Rational-B-Splines). It is Properties Parameters [Unit] Tensile Warp LT considered the state-of-the-art computation 2 method for designing complex polygon Weft WT [ gf cm / cm ] surfaces. Figure 1 shows a comparison Warp 45° RT [ % ] between a sketch by a designer and a Warp 135 ° 2 simulation of a skirt. Bending Warp B [ gf cm / cm ]

Weft 2HB [ gf cm / cm ] In this software program the bending Weight W [mg / cm2 ] properties in warp and weft direction, the Thickness T [ mm] tensile properties in warp, weft , 45 degree warp and 135 degree warp direction and also Table 1: Used Properties

Article Designation: Scholarly Works 2 JTATM Volume 1, Issue 4, Summer 2001

A prerequisite for the simulation process is the two dimensional pattern piece (Figure 3). They can be prepared with conventional 2D CAD-systems.

Figure 5: 2D Pattern with Guidelines and Seams

The next step is to position the 2D mesh into the 3D near the 3D body, from which the draping process starts (Figure 6).

Figure 3: Two Dimensional Pattern

Companies have developed 3D body- scanners where the three dimensional perception of the human body can be realized with a sensor system in a quick and objective way (Figure 4).

Figure 6: Start Position

After this, the user has to generate a surface from the draped mesh. The surface can covered with different colors and/or . Figure 7 shows different examples.

Figure 4: Human Body

The DesignConcept 3D enable the user to seam 2D pattern pieces together and drape them over a 3D model. Therefore, it is necessary to prepare the 2D pattern piece. Guidelines are used to anchor special lines (for example the neckline or waistline) to Figure 7: Examples of Draped Surfaces the 3D body and seam points match different pattern pieces (Figure 5).

Article Designation: Scholarly Works 3 JTATM Volume 1, Issue 4, Summer 2001

Disadvantages include the high and direction from 1.5 to 2 N per 5 cm fabric expensive hardware demands and long width (for underwear, for instance) but it is calculation times (in some cases, up to some also possible to use other tensile force hours). values (for example, for clothes with a high pressure effect) [6]. 3. FIT OPTIMIZATION FOR CLOSE FITTING GARMENTS With the help of powerful software the In the mechanical consideration of designer is in the position to create an deformability of fabrics, two directions are accurate 2D pattern from 3D model surfaces distinguished. The first one deals with drape for close fitting body shapes. behavior of the fabric and the second one is the deformational behavior of fabrics when Problems which are characterized by large covering defined surfaces. This application deformations may be described by requires a nearly wrinkle-free draping of the incremental formulations to determine the fabric, such as close-fitting garments. state of deformation and tension stress. For this purpose, a mesh is generated on the For close-fitting garments like underwear, component surface to be shaped. The mesh sportswear and swimwear, there are high may be generated automatically or demands towards fit and pattern interactively. The accuracy of computation construction. The garment size has to be depends on the triangle size. Material adjusted exactly to the human body, while behavior is attributed to the mesh to ensuring optimal comfort and freedom of simulate the development in the two- movement. In pattern construction for close- dimensional plane, depending on the used fitting elastic clothing, usually the girth material. First, UV-curves have to be drawn measurements of the garment are configured directly on surfaces (Figure 9). Each point to be smaller than the body measurements so on a UV curve has a U and V coordinate, that the material stretches when worn. just like each surface point. When the Consequently, not only body measurements, surface is modified, any UV-curves on the but also mechanical properties of the fabric surface also change. crucially influence the garments fit. The extensibility, i.e. the force - extension relation in case of tensional strain with the corresponding modules, is a significant material parameters. (Figure 8).

5,0

4,0

3,0 warp

weft Force N 2,0

1,0

0,0 0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0 45,0 50,0 55,0 60,0 Extension %

Figure 8: Force-Extension Relation Figure 9: Curves on 3D Surfaces Investigations into wearing strain on knit clothing show that wearing comfort is optimal when stretching the material in girth Article Designation: Scholarly Works 4 JTATM Volume 1, Issue 4, Summer 2001

With the region function, it is possible to create accurate 2D pattern pieces from 3D model surfaces. Regions in 3D grow over model surfaces, conforming to surface contours and crossing the boundaries of adjacent surfaces as directed (Figure 10). Once a 3D region is created on a surface model, it may be “flattened” to produce a 2D region counterpart.

Figure 11: Flattening Process

Figure 10: Regions on Surfaces

The next step is to apply the mechanical properties of the knit fabric to a 3D region mesh. The simulation process is an advanced flattening technique that determines deformation strain, stress and develops a mesh from 3D to 2D based on the mechanical properties applicable to the grain and cross directions. The stress or strain analyses colors show the 3D mesh stress or strain based on the development Figure 12: Visualization of the Realistic Appearance status of the 2D mesh (Figure 11).

In terms of visualization, one can apply 4. TECHNICAL TEXTILES material properties and map to regions in order to enhance the realistic appearance of Textile reinforced light weight structure offer a model (Figure 12). For example, if you significant advantages among others in apply a patterning fabric image to a 2D automobile and aircraft construction, pattern, the “stripes” appear on the especially for the design of curved associated 3D surface just like they appear components. This is achieved when textile on the pattern, regardless of the orientation reinforcing structures, which can be arranged of the 3D surface. and combined very flexibly, are specifically draped. Owing to insufficient design experience and the high cost of material, the potential fields for application in particular in Article Designation: Scholarly Works 5 JTATM Volume 1, Issue 4, Summer 2001

mechanical and the auto industry shape according to the required load and have not been explored. thus avoiding rework (Figure 13).

At present, after the structural element has Three-dimensional CAD programs are been designed, the desired design variant is mainly applied to design complex implemented in several iterations. As a components (AUTOCAD 2000, result, the development of the structural CATIA.)[9,10]. The data obtained by the element most frequently takes a rather long above remarks programs may be transferred time and involves considerable costs. In to the simulation program via suitable order to guarantee the required variety of interfaces (IGES- Initial Graphics Exchange models and to make the structural Specification, VDAFS – interface suited for component adequate for loading, without at the exchange of free forms and curves) [8, the same time increasing the involved time 9]. for industrial engineering, the development of efficient tools for product simulation is of predominant importance.

Since 1997 a research team supported by the German Research Foundation (DFG) has been working at Dresden University of Technology under the headline Textile Reinforcements for High-Performance Rotors Figure 13: 3D component in Complex Applications [7]. The textile preform should be in most exact 4.1 Textile Preform accordance with the component geometry The following steps are necessary to make a desired. In particular, for the realization of textile preform with the component design free-form surfaces, it is necessary to cut the being very complex: fabric or multiaxial structures so that it may pattern design in accordance with be shaped later without irregular folds. After material behavior the patterns have been developed with cutting regard to functional requirements using a stacking three-dimensional model, surface generation prefabrication and placing of the z and the development of the two-dimensional reinforcement patterns are made feasible by an efficient assembly of the 3D preform software tool (Figure 14). Most of the components may be produced using various procedures. Material considerations, design and economic aspects should determine the procedure chosen.

4.2 Pattern Construction under Consideration of the Material Behavior

If curved element contours of lightweight textile structures are covered with an undefined shape of the reinforcing textile, the mechanical component properties may deteriorate. The patterns should be Figure 14: Conical shell – shearing of a developed directly on the object to apply the carbon fabric reinforcing structures to the desired 3D Article Designation: Scholarly Works 6 JTATM Volume 1, Issue 4, Summer 2001

Shearing in the pattern as well as material 5. CONCLUSIONS tension stresses and stretching may be analyzed to provide the designer with The working methods outlined in this information that enables one to produce research can assist designers with work and suitable patterns from the reinforcing textile also enable designers to deal with the material. implementation of designs in view of pattern construction, without limiting creativity. The material data obtained for the shearing, the material tension stress and also the 6. REFERENCES stretching behavior may be implemented in the simulation program by scanning the [1] Schenk, A.: Berechnung des measurement curves and subsequent scaling Faltenwurfs textiler Flächengebilde, or by loading a file in the ASCII format Dissertation TU Dresden, 1996. [11]. This investigation starts from an [2] Brummund, J.; Schenk, A.; Ulbricht, orthotropic structure for the majority of V.: Beitrag zur Modellierung des Fall- fabrics tested. When high modulus carbon verhaltens in der Textilindustrie, yarns are processed (E modulus > 650.00 2 Proceedings GAMM 1998, Bremen, N/mm ), a starting point is the knowledge Germany. that of potential deformation between the [3] Krzywinski, S.: Design und two-dimensional cutting and the multicurved Materialverhalten – Gestaltungseinheit component surface results from the shearing zur Schnittentwicklung, Mittex 4/1999, deformation. After the computation has been S.9-11. completed, the shearing in the shaped [4] Krzywinski, S.; Rödel, H.; Schenk, A.: patterns may be analyzed. A comparison Design und Materialverhalten – Gestal- with the critical shearing angle, which tungseinheit zur Schnittentwicklung indicates how far the share of threads can be DWI Reports 2000, S. 182-189. twisted or compressed without folds, helps [5] Krzywinski, S.: Design und Material- the designer to decide if the pattern is suited verhalten, Bekleidung und Wear for the component surface. (2000)3, S. 12-17. [6] Kirstein, T.; Krzywinski, S.; Rödel, H.: Another sample product is a spherical Pattern construction for close-fitting segment (Figure 15). One can see the garments made of knitted fabrics developed pattern and also get information Melliand English 3/1999, S. E 46 - E about its behaviors. For the flattening 48. process, a shear angle of approximately 40 [7] Krzywinski, S.; Herzberg, C.; Rödel, degree is necessary. H.: Computer-aided product development and the making-up of multilayer 3D-preforms for composites, AUTEX CONFERENCE, Technical Textiles, Juni 2001, Portugal. [8] Reference Manual DesignConcept3D, Volume II, Grand Rapids, 1996. [9] Reference Manual AUTOCAD 2000, San Rafael, CA [10] CATIA Dassault Systems, 2001, http://www.catia.com [11] ASCII, Joan G. Stark, 2001, http://www.ascii-art.com Figure 15: Spherical Segment

Article Designation: Scholarly Works 7 JTATM Volume 1, Issue 4, Summer 2001

Prof. Dr.-Ing. habil. H. Rödel, Technische Universität Dresden, Institut für Textil- und Bekleidungstechnik, D-01062 Dresden, Deutschland, Tel.: +351/4658 267, Fax: +351/4658 361, E-Mail: [email protected]

Dr.-Ing. S. Krzywinski, Technische Universität Dresden, Institut für Textil- und Bekleidungstechnik, D-01062 Dresden, Deutschland, Tel.: +351/4658 359, Fax: +351/4658 361, E-Mail: [email protected]

Dr.-Ing. A. Schenk, Technische Universität Dresden, Institut für Textil- und Bekleidungstechnik, D-01062 Dresden, Deutschland, Tel.: +351/4658 359, Fax: +351/4658 361, E-Mail: [email protected]

Article Designation: Scholarly Works 8 JTATM Volume 1, Issue 4, Summer 2001