A Structured Methodology For

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A Structured Methodology for the Design and Development of Textile Structures in a Concurrent Engineering Framework a

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R. Rajamanickam , S. Park & Sundaresan Jayaraman

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School of Textile and Fiber Engineering, Georgia Institute of Technology , Atlanta, GA, US Published online: 30 Mar 2009.

To cite this article: R. Rajamanickam , S. Park & Sundaresan Jayaraman (1998) A Structured Methodology for the Design and Development of Textile Structures in a Concurrent Engineering Framework, Journal of The Textile Institute, 89:3, 44-62, DOI: 10.1080/00405009808658682 To link to this article: http://dx.doi.org/10.1080/00405009808658682

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A Structured Methodology for the Design and Development of Textile Structures in a Concurrent Engineering Framework R. Rajamanickam, S. Park, and Sundaresan Jayaraman' School of Textile and Fiber Engineering, Georgia Institute of Technology, Atlanta, GA, US Downloaded by [Hanyang University Seoul Campus] at 19:20 08 November 2013

Received as an invited paper

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,

. •

To whom correspondence must be addressed A structured methodology for the design and development of textile structure.s within a concurrent eugineering framework ha.s been proposed and developed. The framework has been validated using the design and development of a Sensate Liner for Combat Casualty Care (or Sensate Liner) as an example. Key requirements for tbe product are identified using a modified QFD-type (Quality Function Deployment) approacb and other tools used in concurrent engineering; and tbe design and development framework is ^tablisbed. This is followed by an in-deplh analysis of tbe various issues involved in tbe design of the Sensate Liner (fabric/garment structure, materials and fabrication technologies) to meet tbe desired performance criteria. Candidate solutions are proposed with appropriate justifications. Finally, the successful application of tbe structured metbodology in realizing tbe product is covered. 1. INTRODUCTION The engineering design of textile structures is a complex task. The task is made even more complex hecause of the significant interactions between the different design parameters that ultimately determine the properties of a textile structure. To illustrate this, consider Tahle I which depicts the interrelationships between major design parameters and functional characteristics of woven structures (Anon., 1987). The variables in the first column (fiher linear density, yam count, thread spacing, etc.) have a significant influence on the resulting functional properties of the fabric (tensile strength, air permeability, tlexural rigidity, etc.) shown in the other columns. Thus, if we try to increase the fabric tensile strength by increasing the thread density, it will make the fabric stiffer and reduce air-permeability. Therefore, engineering the desired end-use properties into textile structures requires many trade-offs and becomes more complicated if the design has to accommodate additional constraints imposed by fabrication technologies, marketing, and so on. Traditionally, the various operations in developing a fabric or garment, such as design, engineering, manufacturing, and marketing, have been carried out sequentially and as separate functions. This leads to conflicting goals for the various functions and the strategic intent of the enterprise is lost. To avoid this prohlem, more and more enterprises are resorting to cross-functional teams and techniques such as Quality Function Deployment (QFD). Design for Manufacturing (DFM), and Total Quality Management (TQM). As a result, the time from concept to market is typically reduced (Jayaraman, 1995, pp.239269). This technique of integrating all the steps in the product life-cycle - from design conceptualization to marketing - during the product design process is called concurrent engineering. '*'*

J Text. Inst., 1998. 89Part 3 © Textile In.Uitutt

A Methodology for the Design and Development of Textile Structures in an Engineering Framework Table I Engineering Design of Woven Structures (from Anon. (t987))

Increase Only

Tensile Streng*

Iniiial Modulus

Tearing Strenglh

Fibci Linear Deiurity (Cross-Sectional Area)

Yarn Linear Density

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Y»m Twist

Threads/inch

Inlcrlacmjis per Unit Area (Weave Patteni)

t R R

i

Bending Stiffiiess

t t t

t i t i i i

t t t

Ail Permeability

t i

Abrasion Resiiitsncc

t t

t

R

i i

t

t

Shear Resistance

Reiural EnUurancc

i t R t R t i t i

Thickresi

1 t r

t t

In this paper, a structured framework for designing textile structures using the concurrent engineering approach is presented using the design and development of a Sensate Liner for Cotnbat Casualty Care as the case study or real-world example. The paper is organized as follows: The relevant tools and techniques used in concurrent engineering are discussed in Section 2. In Section 3, the proposed design and development framework is discussed using the Sensate Liner as the example. The realization of the product design is discussed in Section 4. The overall conclusions from this research are presented in Section 5. 2. LITERATURE REVIEW 2.1 Overview In this section, the concept of Quality Futiction Deployment is discussed along with an overview of the Seven Management and Planning Tools that can be applied in the practice of concurrent engineering. 2.2 Quality Function Deployment 2.2.1 The Concept The concept of Quality Function Deployment (QFD) was introduced in Japan by Yoji Akao in 1966 (Akao et ai, 1983, pp.61-67). According to Akao (Akao, 1990), QFD 'is a method for developing a design aimed at satisfying the consumer and then translating the consumer's demand into design targets and major quality assurance points to be used throughout the production phase.... (QFD) is a way to assure design quality while the product is still in the design stage*. Akao points out that, when appropriately applied, QFD has demonstrated the reduction of development time by one-half to one-third. Sullivan (1986) says that 'The main objective of any manufacturing company is to bring out new products to market sooner than the competition with lower cost and improved quality. The mechanism to do this is called Quality Function Deployment.... (QFD) is an overall concept ihat provides a means of translating customer requirements into the appropriate technical requirements for each stage of product development and production (i.e. marketing strategies, planning, product design and engineering, prototype evaluation, production process development, production, sales).... In QFD. all operations are driven by the "voice of the customer"; QFD therefore represents a change from manufacturing-process quality J. Text. Inst.. 1998. 89 Part 3 © Textile Institute

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Rajamanickam, Park, and Jayaraman

control to product-development quality control'. SuHivan further notes that 'The QFD system has been used by Toyola since 1977, following four years of training and preparation. Results have been impressive.... Between January 1977 and April 1984. Toyota introduced four new van-type vehicles. Using 1977 as a base. Toyota reported a 20% reduction in start-up costs on the launch of the new van in October 1979; a 38% reduction in November 1982: and a cumulative 6!% reduction in April 1984. During this period, the product development cycle (time to market) was reduced by one-third with a corresponding Improvement in quality because of a reduction in the number of engineering changes'. Dean (1992) views QFD as a system etigineering process that transforms the desires of the customer/user into the language required by the design process. It also provides the glue necessary, at all project levels, to tie all components together and to manage them. It is an excellent method to ensure the customer obtains a high value from the product; actually the intended purpose of QFD. At its core, QFD is a structured process that uses a visual language and a set of interlinked engineering and management charts to transform customer requirements into design, production, and tiianufacturing process characteristics. The result is a systems engineering process which prioritizes and links the product development process to the design so that it assures product quality as defined by the customer. Additional power is derived when QFD is used within a concurrent engineering environment. 2.2.2 The House of Quality The full benefit of the QFD process comes from tailoring a sequence of matrices to guide product or service development decisions. When many people hear the term QFD, they think of the House of Quality. QFD is actually a process that uses many matrices, only one of which is the famed House of Quality. The House of Quality is the most commonly used matrix, and many teams do not go beyond it, tnissing a lot of additional benefits. Because the House of Quality is so commonly used in QFD. a brief description is in order. Fig. 1 illustrates the House of Quality (Guinta and Praizler, 1993).

Q uality Charactaistics J

Cud ana' Needs and Rdatiue Importance

\

Rdatimdhips ® a r m9 O Meitjm A Weak

o

Market Analyas and Product

m

Planning

A Pritritis Pa'ftrmance Mffiai'e^ andTar^t

Valus Fig. I 46

House of Quality

/ Text. Inst.. 1998. 89 Pan 3 © Textile Institute

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A Methodology for the Design and Development of Textile Structures in an Engineering Framework

The 'house' is divided into several "rooms', each completed in a logical sequence. The first section. Customer needs, is a structured list of what customers are looking for, typically obtained through qualitative market research such as interviews and focus groups. They are staled in the customers' words and language. Quaniitalive data fills out the second section known as Market Analysis and Product/ Service Planning. This data typically consists of the relative importance of the customer needs contained in the first section, customer satisfaction ratings of the company's current offerings and customer satisfaction ratings of the competition's offerings. Using this data, the QFD team sets goals for improving new products or services relative to the competition, and calculates the final priority of the customer needs that the team will use. Using the expertise of the cross-functional team, the Quality Characteristics of the planned product or service are listed in the third section. These characteristics are expressed in the company's terminology of products and services. (Quality Characteristics are also sometimes called the company's "Technical Response'.) The central room of the House of Quality contains the team's judgment of how strongly each Quality Characteristic (or Technical Response) contributes to meeting each customer need. The 'roof of the House of Quality is not always used, but can illuminate trade-offs that may exist among the Quality Characteristics. For example, apparel buyers may want both a "durable, soft fabric' and a garment that is 'easy to care for'. These wants tnay be reflected in quality characteristics of fabric areal density and fiber type. The roof is used to document these trade-offs, as well as other positive or negative interrelationships. Lastly, the teatn computes the rank ordering of the quality characteristics, using the relative priorities of the customer needs and the strength of the relationships from the central room of the House. The team also includes Performance Measures of how well the cotiipetition's product or service performs, which are used to set Target Values for implementing the quality characteristics. 2.3 The Seven New Management and Planning Tools 2.3.1 Overview According to MIzuno and Akao (1994), the seven new tools are the products of the Japanese Society for Quality Control Technique Development. After a worldwide search, in 1976 they proposed the following new tools useful for the practice of concurrent engineering: (i) (ii) (iii) (vi) (v) (vi) (vii)

Affinity diagram Interrelationship digraph Tree diagram Matrix diagram Prioritization matrices Process decision program chart Activity network diagram

' .

They were chosen to meet the following criteria: • • • • •

the ability the ability the ability the ability the ability

to complete tasks; to eliminate failure; to assist in the exchange of information; to disseminate information to concemed parties; and to use "unfiltered expression'. • .

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Rajamanickam, Park, and Jayaraman

The seven new tools constitute a rich visual language that allows the user to easily explore and decompose complexity which cannot be dealt with otherwise. The first step in using these tools is brainstorming - a process that promotes the free expression of ideas in a team setting without immediate comments, criticisms or analysis from fellow team members. The results of the brainstonning session are then structured using the Seven Management and Planning Tools to yield productive and pragmatic solutions that can be implemented to realize the overall goals of the design project. ,

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2.3.2 Affinity Diagram

. ,

-

The Affinity Diagram is a tool for organizing language data (Fig. 2). After ideas are brainstonned and written on cards, they are grouped together with similar ideas. A header card is created which captures the meaning of each group of ideas.

\

Fig. 2

Affinity diagram

•

,

* r •

, ,

2.3.3 tnterrelationship Digraph The interrelationship digraph shows the relationships between items by drawing an arrow from one idea that causes another idea, to an idea that is the result (Fig. 3). Sometimes the arrow is drawn from one action that occurs before another action. The items that have mostly arrows going in are long-range targets, and the items with most arrows going out are initial action items.

Fig. 3

Interrelationship digraph

2.3.4 Tree Diagram

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A Methodology for the Design and Development of Textile Structures in an Engineering Framework

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The tree diagram takes a purpose and logically breaks it into action items, When read from left to right (Fig. 4), it goes in a logical progression from general to specific. If it is read from left to right, it answers the question 'how is the process accomplished?'. If it is read from right to left, it answers the question 'why?'.

Fig. 4

Tree diagram

2.3.5 Matrix Diagram The matrix diagram shows the relationship between two or more sets of items. It can be very useful in facilitating an analysis of the relationship of each item in one set to all items in the other set. This often triggers some thinking that would not have happened if this organized approach were not used. It is also helpful to see pattems of relationships: which items don't relate to anything and which ones are critical. a

Fig. 5

b

c

d

Matrix diagram

2.3.6 Prioritization Matrix The prioritization matrix enables the selection of priority items by applying a set of criteria to each item. Sometimes the list of criteria is fairly simple; other times it is weighted with a great deal of precision.

Text. inst.. 1998, 89 Part 3 © Textite Institute

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Rajamanickam, Park, and Jayaraman

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a

Fig. 6

Prioritization matrix

b

c

d

'

- •

2.3.7 Process Decision Program Chart

,'

The process decision program chart (PDPC) is a tool for contingency planning. It begins by listing the steps in a particular activity. It then lists what could go wrong at each step and finally it lists the counter measures for things that can go wrong. Sometimes it is drawn in the flow chart format below. Other times it is shown as a numerical tree diagram.

X Fig. 7

Process decision program chart

2.3,8 Activity Network Diagram The activity network diagram is a simplified version of PERT (Program Evaluation and Review Technique). It is a method for mapping out the sequence in which activities will be undertaken. One of its benefits is that it indicates which tasks can be executed simultaneously. Another benefit is that it makes it clear what set of activities will take the longest and where time efficiencies can be achieved. Thus, these Seven Managetnent and Planning Tools taken together can be very effective in helping a textile enterprise design a successful product in a concurrent engineering environment. Jayaraman has discussed the importance of concurrent engineering for product development in the textile-apparel complex and identified the key informationrelated issues associated with the practice of concurrent engineering (Jayaraman 1993 pp.723-726).

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J. Text, Inst.. 1998. 89 Part 3 © Textile Institute

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A Methodology for the Design and Development ofTextile Struclurci in an Engineering Framework

fig. 8

Activity network diagram

3. METHODOLOGY FOR DESIGN AND DEVELOPMENT OF THE SENSATE LINER 3.1 Overview In this section, the methodology for the design and development of the sensate liner using some of the tools described in Section 2 is presented. 3.2 Broad Performance Requirements* The US Department of Navy put out a 'broad agency announcement' inviting white (concept) papers to create a system for the soldier that was capahle of alerting the medical triage unit (stationed near the battlefield) when a soldier was shot, along with some information on the soldier's condition characterizing the extent of injury. As such, this announcement was very broad in the definition of the requirements and specified the following two key broad objectives of the Sensate Liner: • •

Detect the penetration of a projectile (e.g. bullets and shrapnel); and Monitor the soldier's vital signs.

The vital signs would be transmitted to the triage unit by interfacing the Sensate Liner with a Personal Status Monitor developed by the US Defense Advanced Research Projects Agency (DARPA). 3.3 Design Conceptualization: Detailed Analysis of the Key Performance Requirements The goals of the research project undertaken at Georgia Tech and reported in this paper have been to conceptualize a system that would meet the two broad performance requirements, design the system applying the principles of concurrent engineering, produce the Sensate Liner, and demonstrate the realization of the pertbrmance requirements. The first step in the QFD process is to clearly identify the various characteristics required by the customer in the product being designed. Therefore, using the information obtained (Anon., ]996a,b) at pre-proposal briefings from the US Navy (the 'customer') on the two key performance requirements for the proposed Sensate Liner, an extensive analysis was carried out. A detailed and more specific set of performance requirements was defmed; the result is shown in Fig. 9. These are Functionality, Usability in Combat, Wearability,

' Georgia Institute of Technology subtnitted a white paper conceptualizing the system to meet these two broad performance requirements and outlined Ihe research methodology lo realize this concept (sysiem). The Navy invited Georgia Tech to submit a detailed proposal that was subsequently selected for funding to carry out this research. / Te.xt. lust.. 1998, 89 Pan 3 © Textile InsUtule

5|

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Rajamanickam, Park and Jayaraman

4>

OS

a. u

V

c

3 u

Fig. 9

52

Sen.sate Liner performance requirements 7. Text. Inst., 1998, 89 Part J © Textite Institute

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A Methodology for the Design and Development of Textile Structures in an Engineering Framework

Durability. Manufacturability, Maintainability, Connectability and Affordability. The next step was to examine these requirements in-depth and to identify the key factors associated with each of them. These are also shown in the figure. For example. Functionality implies that the Sensate Liner must be able to detect the penetration of a projectile and should also monitor hody vital signs - these are the two requirements identified in the broad agency announcement from the Navy. The factors deemed critical in battlefield conditions are shown under Usahilitv in Cotnbat in the figure. These include providing physiological thermal protection, providing resistance to petroleum products and EMI (electromagnetic interference), minimizing signature detectability (thermal, acoustic, radar, and visual), offering hazard protection while facilitating electrostatic charge decay and being flame- and directed-energy retardant. Likewise, as shown in the figure, Wearability implies that the Sensate Liner should be lightweight, breathable, comfortable (form-fitting), easy to wear and take-off, and provide easy access to wounds - critical requirements in combat conditions so that the soldier's performance is not hampered by the protective garment. Durability of the Sensate Liner is another important performance requirement; it should have a wear life of 120 combat days and should withstand repeated flexure and abrasion - both of which are characteristic of combat conditions. Manufacturability is another key requirement since the design (garment) should be eventually produced in large quantities over the size range for the soldiers; moreover, it should be compatible with standard issue clothing and equipment. Maintainability of the Sensate Liner is an important requirement for the hygiene of the soldiers in combat conditions; it should withstand/JeW laundering, should dry easily and be easily repairable (for minor damages). The developed Sensate Liner should be easily connectable to sensors and to the Personal Status Monitor (PSM) on the soldier. Finally, affordability of the proposed Sensate Liner is another major requirement so that the garment can be made widely available to all combat soldiers to ensure their security, and hence that of the nation. Thus, in the first step of the design conceptualization process, the broad performance requirements were translated into a larger set of clearly defined requirements along with the associated factors (Fig. 9). 3.4 Design and Development Framework Once the detailed performance requirements were defined, the need for an overall design and development framework became obvious. Since no comprehensive framework was found in the literature, one was developed. Fig. 10 shows the resulting overall Sensate Liner Design and Development Framework and it encapsulates the modified QFD-type methodology developed for achieving the project goals. As shown at the top of the figure, the first step has been to identify the key performance requirements for the Sensate Liner (details shown in Fig. 9). These Requirements are then tran.slated itito appropriate Properties of the Sensate Liner: sets of Sensing and Comfort properties. The Properties lead to the specific Design for the Sensate Liner: dual structure meeting the twin requirements of 'sensing' and "comfort'. These Properties in the Design are achieved through the appropriate choice of Materials & Fabrication Technologies by applying the corresponding Design Parameters as shown in the figure. These major facets in the proposed framework are linked together as shown by the arrows between the dotted boxes in Fig. 10. This overall comprehensive design and development framework is now analyzed in greater detail in the following sections.

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Rajamanickam, Park, and Jayaraman

Fig. 10

Sensate Liner design and development framework

J, Te.xt, hut,, I99H, R9 Part ,i S) TextiU' Institute

A Methodology for the Design and Development of Textite Structures in an Engineering Framework

3.5 Arriving at the Design 3.5. J Overview The next step in the design process has been to translate the performance requirements (in Fig. 9) into specific properties that must be engineered into the Sensate Liner, leading to its design. The results of this step are shown in tbe second dotted box in the framework in Fig. 10.

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3.5.2 Desired Set of Properties The desired properties have been divided into Sensing and Comfort characteristics. For example, the Sensing properties include electrical/optical conductivity, resistance to signal disturbances, minimum signal attenuation due to deformation during manufacturing and/ or use, good mechanical properties and low weight. The key Comfort properties include fabric hand (e.g. how soft the fabric/garment feels to touch), air permeability and moisture absorption lo ensure a breathable and comfortable garment, static dissipation, strelchability to ensure a form-fitting garment, etc. Bending rigidity, flexural endurance, weight, and tensile properties are the common set of properties that are derived from oiherperformance requirements in Fig. 9. Manufacturability and cost are the two underlying parameters of the proposed design. 3.5.3 Proposed Design and Structure Based on a critical analysis of the set.s of Sensing and Comfort properties required of the Sensate Liner, the next step has been to propose a design to achieve the desired properties in the most cost-effective manner while ensuring manufacturability, The Sensate Liner will be an integrated structure comprising the major components shown at the bottom of the second dotted box (Design) in the framework in Fig. 10:

•

•

•

•

Penetration Sensing Component (PSC): will pinpoint the location of projectile penetration and will be linked to the Personal Status Monitor (PSM) through the connectors at the hip level; Electrical Conducting Component (ECC): will monitor body vital signs including pulse rate, temperature and blood pressure through sensors on the body and will be linked to the PSM at the hip level; Comfort Component (CC}: will be in immediate contact with the soldier's skin and will provide the necessary comfort properties for the garment (similar to the regular issue undershirt); Form-fitting Component (FFC): will provide the necessary form-fit to the soldier; more importantly, it will keep the sensors in place on the soldier's body during combat conditions; and Static Dissipating Component (SDC): will quickly dissipate any built-up static charge during usage.

The integrated structure will be produced using appropriate fabrication technologies discussed in the following section.

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Rajamanickam. Park, and Jayaraman

3.6 Realizing the Design; Materials and Fabrication Technologies

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3.6.1 Overview As shown in the framework in Fig. 10. the next step is to identify the materials and fabrication technologies that can be utilized to achieve the proposed design of the Sensate Liner with the desired properties. The results of the steps are shown in the third dotted box in the figure. The design parameters associated with the materials and fahrication technologies (shown at the far end of the third dotted box) denote the correspond! ng variables that can be modified to achieve the desired properties and performance in the Sensate Liner. 3.6.2 Materials Evaluation and Selection 3.6.2.1 Merhod The Sensate Liner Performance Requirements and Properties in Figures 9 and 10 were used to develop the criteria for evaluating the materials for the various components of the Sensate Liner. Based on these criteria, several materials were evaluated for each Sensate Liner component using a weighted prioritization matrix approach. The resulting matrix was used to identify the candidate materials for various components of the Sensate Liner. The candidate choices and corresponding design parameters are shown in the third dotted box in Fig. 10. This structured approach to the evaluation of multiple alternatives during product design ensures that the right choice is made. 3.6.2.2 Materials for Penetration Sensitjg Component (PSC) Penetration alert can be achieved by the use of either an electrically conductive mesh or an optical fiber mesh. The response time of an electrical mesh has been shown to be too slow to 'catch a bullet' (Anon., \996b). Also, conductive fibers are susceptible to electromagnetic interference and have to be shielded to prevent shorting when wet. Optical fibers do not suffer from these limitations. Based on these relative merits, optical fibers have been chosen over conductive fibers for the PSC. For sensing the penetration of the projectile, the choice has been narrowed down to silica-based optical fibers and plastic optical fibers (Kitazawa et ai, 1991; Chai, 1990). The design evaluation matrix shown in Table 11 provides a comparative evaluation of the two candidate materials for the PSC. The evaiuation criteria in the first column have been derived from the performance requirements (Fig. 9) and properties of the PSC (Fig. 10). The relative weights of these evaluation criteria are listed in the second column in the table. The weight denotes the importance of the specific criterion towards the performance of the Sensate Liner. For example, optical conductivity has the greatest impact on the performance of the PSC (and hence the Sensate Liner), and is therefore assigned the highest weight (20%). This is followed by resistance to electromagnetic interference (15%), attenuation of signal (15%), and so on. For each evaiuation criterion, a score is assigned to the material based on its ability to meet that criterion (0-poor to 4-best). For example, the bending rigidity/flexural endurance of silica-based optical fiber is considerably poor when compared to that of plastic optical fiber. Therefore, the former is assigned 1 while the latter is assigned 3 in the table. Based on the individual weights and corresponding scores, a weighted score (Iweight,*score.) is computed for each material choice and is shown in the last line of the table. The higher the fmal weighted score, the greater the probability tbat the material will successfully meet all the evaluation criteria and hence the higher the chance of producing an effective Sensate Liner for combat conditions. Based on the prioritization matrix in Table II, plastic optical fiber has been chosen for the PSC in the Sensate Liner. 56

J. Text, rnst., 199S. S9 Purr 3 © Textile Insututf

A Methodology for ihe Design and Develupment of Textile Structures in an Engineering Framework Table II Design Evaluation Matrix, Penetration Sensing Component (PSC)

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Property (Evaluation Criterion) Optical conductivity Resistance to electromagnetic interference Attenuation of signal Bending rigidity/flexural endurance Manufacturability Elongation and creep recovery Weight Tensile strength and modulus Availability Cost Total and weighted score

Weight {%)

Silica Optical Fiber (Score)

Plastic Optical Fiber (Score)

20 15

4 4

4 4

15 IS

3 1

3

10 7.5 7.5 5 2.5 2.5

1 2 2 2 4

3 3

100

3

2

4 3 4 2

2.7

3.4

Score: scale of 0 (worst) to 4 (best).

3.6.2.3 Materials for Electrical Conducting Component (ECC) The ECC will monitor body vital signs, including pulse rate, temperature, and blood pressure, through sensors on the body and will be linked to the PSM at belt level. The two key candidate materials initially considered for the ECC are: (i) thin copper wire with a polyethylene sheath, and (ii) polyacetylene filament with a polyethylene sheath. The design evaluation matrix shown in Table III provides a comparative evaluation of these two candidate materials. The matrix was derived along the lines of Table II. Based on the relative merits of the fibers shown in the table, the metallic fiber, i.e. copper core with polyethylene sheath, was chosen for the ECC in the Sensate Liner. Table III Design Evaluation Matrix, Electrical Conducting Component (ECC) Property (Evaluation Criterion)

Electrical conductivity Stability (chemical, thermal, water) Resistance to electromagnetic interference Bending rigidity/flexural endurance Availability Elongation and creep recovery Weight Tensile strength and modulus Cost Total and weighted score

Weight (%)

Copper Core with Polyethylene Sheath (Score)

Polyacetylene Coated Fibers with Polyethylene Sheath (Score)

30 20 15

4 4 2

1 1 2

10

3

3

10 5

4

t

5 5

2 1 4

2.5

3

3 4 3 1

3.43

1.73

100

Score: scale of 0 (worst) to 4 (best).

3.6.2.4 Materials for Comfort Component (CC) The CC will be in immediate contact with the soldier's skin and will provide the necessary comfort properties for the garment; therefore, the choice of material becomes critical and the one chosen should provide at least the same level of comfort and fit as the undershirt currently issued to the soldiers. The design evaluation matrix for the set of fibers for the CC is shown in Table IV. The evaluation criteria have been derived from Figures 9 and 10. Since the Sensate Liner will J. Text. Inst., I99S. 89 Part 3 © Textile Institute

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Riijaniankkam. Park, and Jayaraman

be in contact with the body, the material chosen should provide a good fabric hand, air permeability, moisture absorption and stretchability to the Sensate Liner and therefore these parameters are weighted high in the table. Table IV Design Evaluation Matrix, Comfort Component (CC) Weight (%)

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Property (Evaliiaiion Criterion) Fabric hand Air permeability Moisture absorption Strelchability (elasticity/recovery) Bending rigidity Weight Tensile properties Manufaciurability Cost Total and weighted score

•

Cotton (Score)

Meraklon Microdenier Polypropylene Polyester Fibers (Score) (Score)

4

15 15 15

4 4

3 4 4

2'

3

3

2"

10 10 10 5 5

3

3 4

4

2 4

4

3 ^

4

4

3.5

3.6

100

Poly-cotton Blend (Score)

Gore-Tex Film Liner (Score)

3

2 3 4 4

3

15

3

"'

•

4

'

4

... f • ^'

1

4t 3. 4 2

2 4 3 3 2

3

3.1

3.1

4 4

Score: scale of 0 (worst) to 4 (best).

As shown in the table, the major fibers evaluated for use in the CC are cotton, Meraklon, microdenier polyester, polyester/cotton blend and Gore-Tex film liner. Cotton and Meraklon are the two top choices for the CC. Based on the relative merits of the fibers shown in the table. Meraklon has been chosen for the CC in the Sensate Liner. Additionally, since one of the issue items to soldiers is underwear made from polypropylene fibers, the choice of Meraklon is fiarther justified. 3.6.2.5 Materials for Form-Fitting Component (FFC) The FFC will provide the necessary form-fit to the soldier; more importantly, it will keep the sensors in place on the soldier's body during combat conditions. Therefore, the material chosen should have a high degree of stretch to provide the required form-fit and, at the same time, be compatible with the materials chosen for the other components of the Sensate Liner. Spandex fiber is a block polymer with urethane groups. Its elongation at break ranges from 500 to 600% and thus can provide the necessary form-fit to the Sensate Liner. Its elastic recovery is also extremely high (99% recovery from 2-5% stretch) and its strength is in the 0.6-0.9 grams/denicr range. It is resistant to chemicals, and withstands repeated machine washings and the action of perspiration. It is available in a range of linear densities and is widely used in swimsuits. Therefore, Spandex has been chosen for the FFC of the Sensate Liner. 3.6.2.6 Materials for Static Dissipating Component (SDC) The purpose of the SDC is to quickly dissipate any built-up static charge during the usage of the Sensate Liner. Under certain conditions, several thousand volts may be generated and this can damage the sensitive electronic components in the PSM Unit. Therefore, the material chosen must provide adequate Electrostatic Discharge (ESD) protection in the Sensate Liner. Nega-Stat, a bicomponent fiber produced by DuPont has a trilobal-shaped conductive core that is sheathed by either polyester or nylon. This unique trilobal conductive core neutralizes the surface charge on the base material by induction, and dissipates the charge by air ionization and conduction; it covers the charge dissipation range required of the Sensate Liner (Anon., 1996/>). The nonconductive polyester or nylon surface of Nega-Stat 58

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A Methodology for the Design and Development ofTextile Structures in an Engineering Framework

fiber controls the release of surface charges from the thread to provide effective static control of material in the grounded or ungrounded applications according to specific enduse requirements. The outer shell of polyester or nylon ensures effective wear-life performance with high wash and wear durability and protection against acid and radiation. Therefore, Nega-Stat has been chosen for the SDC in the Sensate Liner.

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3.6.3 Evaluation of Fabrication Technologies The key fabrication technologies evaluated for creating the integrated Sensate Liner comprising the various components are shown in the framework in Fig. 10, along with the corresponding design parameters. These include tubular weaving, in-lay knitting, fullfashioned knitting, and embroidery on two different substrates; a knitted fabric and a Gore-Tex film. Table V shows the design evaluation matrix for the candidate fabrication technologies. Table V Design Evaluation Matrix, Fabrication Techaologies Property Form fitting (elasticity/flexural endurance) Fabric hand Air permeability (brealhability) Durability Manufacturability Technology complexity Cost Total

Weight (%)

Tubular Weaving

in-lay Knitting

30

3

4

4

2

3

20 15

3 4

4 4

4

2 3

1 1

10 10

4 3 3 2

3 4

3 2 2 4

3 2 2 3

3 2 2 2

3.2

3.7

3.7

2.4

2.2

10 5 100

4 2

Full-fashioned Embroidery Embroidery Knitting on Knit on Gore-Tex

4

Score: scale of 0 (worst) to 4 (best),

Since form-fitting and fabric hand are the two principal performance requirements (Figures 9 and 10), they are weighted high when evaluating the technologies. Tubular Weaving and In-Lay knitting are the two top fabrication technologies for producing the Sensate Liner. Although Full-Fashioned Knitting (FFK) also ranks high, its technological complexity precludes its usage in the development phase of the Sensate Liner. Moreover, the design of the Sensate Liner is such that the technological complexity outweighs some of the advantages of FFK. Since the two fabrication technologies (Tubular Weaving and In-Lay knitting) are ranked high and have distinctive characteristics required, they have been selected for manufacturing the Sensate Liner. Thus, the proposed Design and Development Framework and the methodology have been very effective in translating the "customer's' broad requirements into a product design and into engineering design parameters that can be varied (based on underlying fundamental principles) to ultimately arrive at the right materials, the right structure, and the right fabrication technology to create the Sensate Liner with the optimal performance. 4. DESIGN REALIZATION: PRODUCTION OF WOVEN SENSATE LINER 4.1 The Sensate Liner The specific baseline design for the Sensate Liner has been developed based on the results from the extensive analysis presented in Section 3, covering performance requirements, the overall components, and the choice of materials and fabrication technologies. As the

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next logical step in applying the methodology and realizing the product design, weaving was chosen to produce the Sensate Liner. Fig. 11 shows the photograph of the woven Sensate Liner that was manufactured utilizing the baseline design. It consists of a single-piece garment similar to a regular T-shirt. The initial prototype is of medium-size to fit a 38-40" chest. It is made from the materials selected in Section 3.6.2. The plastic optical fiber (POF) is spirally integrated into the structure during the fabric production process, without any discontinuities at the armhole or the seams, using a novel modification in the weaving process. With this innovative design, there is no need for the 'cut and sew' operations required to produce a garment from a two-dimensional fabric. .>-^ . , ,

Fig. 11

PhotographoftheSensateUner(wovenWearableMotherboard)

4.2 Use and Operation of the Sensate Liner

^.

4,2,1 Uses of the Sensate Liner , . ' ! . . . The Sensate Liner can be used in two distinct modes: (i) in combat or field operations, and (ii) in monitoring. In the battlefield or combat casualty care mode, the Sensate Liner can detect the penetration of the projectile (e.g. bullet or shrapnel) while simultaneously monitoring the vital signs such as heart rate, blood pressure, and temperature. Thus, in this mode, the Sensate Liner will be used by soldiers, police, and other law enforcement personnel. 60

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A Methodology for the Design and Development of Textile Structures in an Engineering Framework

In the monitoring mode, the Sensate Liner will not include the penetration detection component and it will he used to monitor the vital signs of individuals very effectively and in a less cumbersome manner than is possible today. Thus, in this mode, the Sensate Liner will he used mainly by space explorers, medical patients, and athletes (Giri, 1998, p.65). It could also he used to monitor the conditions of pets under acute care. 4.2.2 Operation of the Sensate Liner: Penetration Alert

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(i)

Precisely timed pulses from the first transceiver at belt level are sent to the second transceiver near the shoulder through the POF integrated into the Sensate Liner. (ii) If there is no rupture of the POF, the signal pulses are received hy the second transceiver and an "acknowledgment' is sent to the PSM Unit indicating that there is no penetration, (iii) If the optical fibers are ruptured at any point due to penetration by a projectile, the signal pulses bounce back to the first transceiver from the point of impact, i.e. the rupture point. The time elapsed between the transmission and acknowledgment of the signal pulse indicates the length over which the signal has traveled until it reached the rupture point, thus identifying the exact point of penetration. (iv) The PSM unit transmits a penetration alert via the transmitter mounted in the backpack to the field command unit specifying the location of the penetration. The two transceivers are then switched-off to conserve power. 4.2.3 Operation of the Sensate Liner: Vital Signs Monitoring (i)

The signals from the sensors are sent to the PSM Unit through the Electrical Conducting Component (ECC) of the Sensate Liner, (ii) If the signals from the sensors are within the normal range and if the PSM Unit has not received a penetration alert, the vital sign readings are recorded by the PSM unit for later processing, (iii) However, if the readings deviate from the normal, or if the PSM unit has received a penetration alert, the vital sign readings are transmitted to the field control unit using the transmitter mounted in the soldier's backpack. Thus, the design and development framework developed as part of this research has been the key to the realization of the research goals. 5. CONCLUSIONS A structured methodology for the design and development of textile structures has been developed and its usefulness has been clearly demonstrated through the design and development of a Sensate Liner'. This is a generic methodology for product design and development in a concurrent engineering environment. In this methodology, cu.stomer requirements are translated into appropriate properties that the textile structure must possess to fulfill the requirements. The Properties lead to the specific design for the textile structure. These Properties in the Design are achieved through the appropriate choice of Materials * During the latter stages of the research, the name 'Wearable Motherboard' was coined to better describe and encapsulate the overall concept and realization of the Sensate Liner. Just as chips and other devices can be plugged into a computer motherboard, sensors and other informaiion processing devices can be plugged into the Sensate Liners produced during the course of the research. Therefore, the name "Wearable Motherboard" is apt for the nexible. wearable, and comfortable Sensate Liners, This name - Wearable Motherboard - represents a natural evolution of the earliernames Sensate Liner and Woven Motherboard. J. Text. Inst., / 998. S9 Part S © Textile Institute

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Rajamanickam, Park, and Jayaraman

& Fabrication Technologies by applying the corresponding design parameters. All the.se major facets in the proposed framework are linked together and help the product design team make the logical progression from general ideas to specific parameters and instantiations. This methodology has been validated by successfully designing and fabricating a Sensate Liner for the US Navy. The concurrent engineering approach led to a design being realized in the short time of 6 months, requiring very few design modifications during the production and testing phases. Thus, the textile/apparel industry can adopt tbis framework for product design in a concurrent engineering environment and become successful in the context of a dramatically decreasing 'concept-to-market' timeframe and the highly competitive global marketplace. ACKNOWLEDGEMENTS The authors would like to thank Dr E. Lind of the US Department of Navy, Mr D. O" Brien of the US Defense Logistics Agency, and Dr R. Satava of DARPA for identifying the need for a soldier protection system, and for providing the funds to carry out this research under Contract # N66001-96-C-8639. They also thank the Navy, DARPA. the US Defense Logistics Agency, and Georgia Tech Research Corporation for helping fund the research. REFERENCES Akao. Y.. Ono. S., Harada. A.. Tanaka. H., and Iwasawa, K., 1983. Quality Deployment Including Cost, Reliability, and Technology. Quality, 13. 3. Akao. Y. (ed.). 1990. Quality Function Deployment, Productivity Press, Cambridge, MA, US. Anon.. 1987. Mhimy inicvnmonaX,Albany tnt. Res. Newsletter, W\, 1. Anon,, 1996a. Proceedings of the DLA/ARPA/NRaD Sensate Liner Workshop, April 11, Columbia, Soulh Carolina, US. Anon.. 1996b. Proceedings of tbe Pre-Propo.'ial Sensate Liner Workshop. June 27, Phoenix. Arizona, US. Chai. Y., \990. Handbook of Fiber Optics ~ Theory and Applications, Academic Press Inc., New York, NY, US. Dean. E.B.. 1992. Quatiiy Function Deployment for Large Systems. Proceedings of the 1992 international Engineering Management Conference, 25-28 October. Eatontown, NJ, US. Giri,P., 1998. 'Smart Shirt'in'21 Breakthroughs thai Could Change your Life in the2]st Century".Z7F£.Special Issue on Medical Miracles for the Ne.xt Millennium, Fall 1998, New York, NY, US. Guinia. L.R., and Praizler, N.C.. 1993. The QFD Book, American Management Association, New York, NY, US. Jayaraman. S., 1993. On Concurrent Engineering in the Textile/Apparel Complex, Proceeding.^ of the 9th international Conference on Engineering Design, August 17-19, The Hague. The Netherlands. Jayaraman, S.. 1995. Computer-Aided Design and Manufacmring: A Textile-Apparel Perspective, la Advancements iirtd Applications of Mechaironics Design in Textile Engineering, (Acar, M., ed.), Kluwer Academic Publishers, The Netherlands. Kitazawa, M., KreidI, J.F.. and Steele, R.E. (eds.), 1991. Plastic Optical Fibers, SPIE Proceedings, SPIE international Society of Optical Engineering, September, Boston, MA, US. Mizuno. S.. and Akao, Y. (eds.). 1994. QFD: The Customer-driven Approach to Quality Planning and Dewlopment, Asian Productivity Organization, Tokyo, Japan, available from Quality Resources, One Water Strcec. White Plains. NY,US, U)60l. Sullivan, L.P, 1986. Quality Function Deployment. Quality Progress, June.

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