Drape simulation

Since the mid-eighties, researchers have been developing alternative numerical techniques for simulating the draping process for fabrics and garments(Chen, Hu and Teng 2001; Chen and Govindaraj 1995; Stump and Fraser 1996; West, Pipes and Keefe 1990; Potluri, Sharma and Ramgulam 2001; Mccartney et al. 2000; Collier et al. 1991; Yu, Kang and Chung 2000; Pandurangan et al. 2008; Kenkare et al. 2008; Lo, Hu and Li 2002; Stylios, Wan and Powell 1995; Hu, Chen and Teng 2000; Fischer et al. 1999; Hwan Sul et al. 2006; Stylios and Wan 1999; Bendali, Koko and Quilliot 1999; Postle and Postle 1999; Stylios and Wan 1997; Gan, Ly and Steven 1995). Prediction and simulation of fabric and garment drape allowed drape researchers to know how fabric properties affected drape shape rather than comparing between drape coefficients of different fabrics. Different combinations of fabric mechanical properties were used as input data to obtain a drape model shape (Stylios and Wan 1997).

Ngoc and Anh used pictures captured from front, back and side views for skirts worn by a mannequin to obtain virtual simulation for them using 3D simulation software (V- Stitcher 4.3). They found similarity between actual and virtual skirts; however the first had bigger and deeper folds than the second (Ngoc and Anh 2008).

The importance of accurate fabric drape simulation (3D presentation),and methods and technologies used to accomplish this would be reflected in computer graphics (fabric representation) and the textile and apparel industries (Collier and Collier 1990).

In computer graphics, the generation of satisfactory simulated/virtual output could improve this industry and satisfy users, manufacturers and designers. Workers in the apparel industry (including: design, product development and manufacturing) would be able to simulate, quantify and compare the drape of apparel virtually, consequently producing improved products with high success rates; reduced quantities of incorrect prototype products and enhanced business processes.

In design and product optimisation and development areas, it is becoming more difficult to depend on specialists’ experience to evaluate and predict the drape behaviour of fabrics with the increasing number of new fibres, yarns and fabrics with different properties (Kenkare 2005). This makes predicting and modelling fabric appearance, including drape prediction, highly important for end product aesthetics and manufacturing. Virtual 3D modelling would be at the base of producing improved accuracy, efficient and quick clothing Computer Aided Design (CAD) systems as CAD software users always expect accurate and rapid fabric drape simulation (Chen, Hu and Teng 2001; Stylios, Wan and Powell 1995). CAD systems provide designers with virtual environments by which they can view their designed garment before making it which guides them to the appropriateness of a fabric and garment fit (Hardaker and Fozzard 1998).

Moreover, researchers proposed using dynamic fabric simulation as a way of coping with low sales of fabric products due to design and/or style faults. The designer could visualise his design using the proposed fabric which would give him a reliable 3D presentation before production which make designers abandon making prototypes. Development of products using conventional methods is time and resource consuming, however employing simulation methods for visualising developed garment saves time and cost (Kenkare 2005). It was supposed that this system could be used by designers and technologists to develop their new materials (fabrics) by the process of reverse engineering (Stylios and Wan 1999).

In communication within the textile and apparel industry, simulation of fabric and garment drape could allow different departments or organisations to

exchange and share viewing draped garment which would enhance apparel design, manufacture and management.

E-commerce is increasingly being used all over the world. However, the percentage of sold apparel online is very low compared to apparel is being sold with the conventional methods and other goods such as books are being sold online. Accurate product characterisation is one of the factors which causes this small portion of selling apparel online (Kenkare 2005). Therefore, improving virtual simulation of fabric drape could affect the global retailing systems and enhance competiveness in the textile and apparel market over the world (Stylios and Wan 1999).

From this review the importance of the input data to achieve the best visualisation of fabric drape is obvious. Therefore working on revealing the combination of fabric properties which would be used as input data for this simulation is essential.

4.12 Summary

Fibre and fabric physical properties affecting fabric drape have been investigated by different researchers. Fibre fineness was found to generally improve fabric drapeability(Werner and James 1952). Fibre cross sectional morphology and moment of inertia had an impact on fabric drapeability (Chu, Platt and Hamburger 1960) and increased space ratio increased fabric drapeability (Matsudaira, Tan and Kondo 1993). Yarn characteristics had also an effect on fabric drape behaviour (Backer 1948). Increased yarn diameter decreased drapeability (Chu, Platt and Hamburger 1960). However, yarn count in another study had a contradictory effect on different fabrics (between increasing and decreasing drapeability) (Matsudairaa, Yamazaki and Hayashi 2008). Yarn count and density had more impact on drape than fibre cross sectional shape (Matsudaira, Tan and Kondo 1993). Yarn interaction in terms of shear rigidity had more impact on drape than 𝐵𝑅(Jeong and Phillips 1998).

With regard to fabric construction, increased yarn floats increased drapeability (Chu, Platt and Hamburger 1960). However in another investigation Basket twill fabrics (with longer floats and fewer interlacings than broken twill) had lower drapeability than broken twill (Quirk, Martin and Jones 2009). Increased cover factor decreased drapeability (Chu, Platt and Hamburger 1960) and increase its instability (Jeong and Phillips 1998). Higher weave crimp and tightness was found to decrease fabric drape (Jeong and Phillips 1998). Skew weaves produced high drape coefficient (Frydrych, Dziworska and Cieslinska 2000). Fabrics with similar warp and weft twist (Z) directions had less drapeability than fabrics with different warp and weft twist directions (Z and S respectively) (Al-Gaadi, Göktepe and Halász 2011).

The relation between fabric drape and handle was found to be poor (Howorth and Oliver 1958) and strong (Elder et al. 1984; Kim and Slaten 1999).

Fabric anisotropy behaviour had an impact on its drapeability. In terms of the relation between 𝐵𝑅 of warp and weft directions, when the warp direction had higher 𝐵𝑅, drape profile was oriented vertically. If weft 𝐵𝑅 was higher, drape profile was oriented horizontally, however when they were similar the drape profile exhibited the lowest level of anisotropy (Sidabraitė and Masteikaitė 2003). As anisotropy degree increased, the difference between warp and weft 𝐵𝑅 generated clear stable and good node arrangement in the drape profile (Hu, Chung and Lo 1997).

Relationships between fabric drape and mechanical properties were investigated. It was found that the following properties correlated with drape: Bending properties (Shyr, Wang and Cheng 2007) including bending length (Chu, Platt and Hamburger 1960) , bending rigidity (Pierce method) (Collier 1991; Behera and Pattanayak 2008) bending modulus (Collier 1991) and bending hysteresis (pure bending tester) (Collier 1991),shear properties (Shyr, Wang and Cheng 2007) including shear rigidity (Cusick 1965) (Kawabata tensile and shear tester) (Collier 1991; Behera and Pattanayak 2008), shear hysteresis (Kawabata tensile and shear tester) (Collier 1991), residual bending curvature and residual of shear angle (Jeong and Phillips 1998), extensibility at 45°(Okur and Gihan 1993) and at low loads (Behera and Pattanayak 2008), formability (𝐵𝑅/ITM) (Frydrych, Dziworska and Cieslinska 2000), fabric liveliness (Brand 1964), friction properties including static friction coefficient (Kim and Slaten 1999), kinetic coefficient friction (Kim and Slaten 1999), surface friction (Tandon and Matsudaira 2010), roughness (Kim and Slaten 1999), tensile properties including tensile behaviour (Tandon and Matsudaira 2010), initial tensile modulus (Frydrych, Dziworska and Cieslinska 2000), tensile energy (analogous to initial modulus)(Behera and Pattanayak 2008).Compressional properties (Behera and Pattanayak 2008) including thickness had different relations with drape between inexistent (Collier 1991), existent effect (Tandon and Matsudaira 2010) and improving stability of drape profile (with increasing thickness) (Kim and Slaten 1999, Hu, Chung and Lo 1997(Hu, Chung and Lo 1997).

Fabric weight as well had different effects on drapeability between inexistent (Collier 1991), existent (Tandon and Matsudaira 2010), positive (Frydrych, Dziworska and Cieslinska 2000)(Kim and Slaten 1999) and negative relations (Uçar et al. 2004) effects.

With regard to fabric finishing treatment, chemical relaxation treatment increased fabric drapeability (Collier 1991). Weight reduction was found to increase drapeability (Matsudaira and Yang 2003a). Washer relaxation effect was stronger than the jet machine relaxation in decreasing the drape

coefficient(Matsudaira et al. 2003). Dyeing and raising processes did not affect fabric drapeability (Matsudaira et al. 2003). Using a softener in a washing process and wash ageing (20 th washing) improved drapeability (Agarwal, Koehl and Perwuelz 2011).

In test procedures, it was found that the lower the contact between the operator and the sample tested in the mounting procedure, the higher the reproducibility of drape test (Morooka and Niwa 1976). A small diameter supporting disc increased drapeability and reproducibility of drape values (Cusick 1962).

It was found that drape coefficient deceased with time (Cusick 1965) and reached a stable state at minute 7 (Jeong 1998).

Comparison between drape parameters measured using fabrics and garments confirmed that garment drape was not predicted precisely using the fabric drape parameters (Ng, Hui and Tam 2002). This is important as the author of this thesis agrees with this.

Drape coefficient increased with the number of layers and width in circular samples and with bonded circular edges in circular samples (Hu, Chung and Lo 1997). Factors which dominated the effect of interlinings on composite fabric shear stiffness were the interconnection density (stitching or fusing) and the shear rigidity ratio of interfacing to the shell fabric used (Collier, Paulins and Collier 1989).

The addition of seams increased fabric DC(Jevšnik and Žunič-Lojen 2007). Increased seam allowance reduced fabric drapeability and large nodes were generated along the seam (Hu, Chung and Lo 1997, Uçar et al. 2004). Radial Seam number increased fabric DC, this effect was more obvious with increased seam number (Uçar et al. 2004). Seaming swung the highest node to the seamed part, while seamed parts stabilised the nodes at it. The more seams added to a fabric, the more stable the drape profile and NN was. Number of seams showed great effect on the drape profile of heavyweight fabrics, but very little effect on lightweight fabrics (Hu and Chung 1998). The higher the localised fabric weight generated due to a pressing SA in one direction, the lower the drapeability of the fabric was (Chung, Hu and Lo 1997). If seamed fabric became triple layered, the addition of extra stitches or layers did not have a significant effect (Sharma

et al. 2005).

Fabric skew, asymmetrical body, tilted grain line and unbalanced seams could deform garment drape (Moore 1992).

In subjective assessment of fabric drape, evaluation would be carried out by viewing their photos or by draping them in front of assessors (Cusick 1965; 1962).

This review shows that extensive research has been carried out by many researchers over most of the twentieth century. Many findings are consistent with each other but some contradict or conflict with each other. There has not been a lot of research on nonwoven fabrics yet, this is probably because the interest in using nonwoven fabrics in fashion apparel has only been increasing over the last decade. Therefore this current research is aimed at this area. Also, there seems to have been an increasing opinion that the measurement of flat fabric parameters does not enable the accurate measurement of the many parameters which influence garment drape both subjectively and objectively.

Chapter 5