Archive for the ‘innovation’ Category

Walking Meditation for the 21st Century

December 13, 2016

The labyrinth often based on a spiral is known to be a design feature likely 4,000 years old. This art form can be found in many cultures around the world such as India, France, Egypt, Scandinavia, Crete, Samaria, America, the British Isles, and Italy, and in all cases, they were built to share a common celtic-spiraltheme of pilgrimage and spiritual reward. Most are created as a spiral path leading to a central point and then back out again. For instance one of the oldest depictions of a Celtic Spiral that could have served as inspiration is found in a passage tomb Near Kells  Meath, Ireland.  Here we can see a series of three spirals.

Says Avia Venefica, “This is where labyrinths are often confused with mazes. Big difference.  Mazes are designed to challenge intellect and strategic skills.  Whereas the labyrinth is an exercise in soul development.”

wakehurst-labyrinthThe spiral, unlike that pesky maze, can be found in nature in a shell, a pine cone or even in the rose blossom are reflected in a labyrinth as a curving line around a central point. This might mean movement, growth, change or providing a continuously shifting perspective that can be inspiring and sometimes life renewing. (1)  Its a nice idea that walking a labyrinth is a metaphor for life -the path shifts in unexpected ways, sometimes away from your goal, but ultimately leading you to the center. Says a Labyrinth Facilitator; Chris Beam, “it is a powerful meditation tool, helping to quiet the mind and allowing time of reflection.”

maze

In contrast, passing through a maze – one in which the path divides repeatedly and there is a risk of becoming disoriented and lost – is a much more individual and potentially threatening exercise. It symbolizes the way in which the mind can easily become confused and sidetracked. In the maze, unlike the labyrinth, we are faced by many choices with outcomes that are uncertain (2).

So what path are we on in today’s world?  I would like to think we are on a pre-planned “labyrinth” path where even though twisting and turning directions seem confusing, there is some set celtic-spiral-ix-by-larkin-jean-van-horndestination or ending point in store.  However, I think more often that life in the over informed, technology imbued, speed of light 21st century is more like the maze mentioned earlier – our path constantly challenges us to evaluate progress and decide to turn left or right, back up or move ahead.

Maybe the group DEVO had it right and our philosophy should be to just to “Shape it up, Get straight, Go forward, Move ahead, Try to detect it, It’s not too late to whip it, Whip it good.”

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(1) http://www.ancient-wisdom.com/labyrinths.htm

(2) http://www.wolindia.com/2011/12/symbols-mazes-and-labyrinths.html

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Mechanisms of Fabric Failure

December 5, 2016
img_2563

Photo Jonathan Long

Fabric fibers that wear out fast, make garments that fail faster.  Working within the Protective Products and Equipment (PPE) industry, we are inundated with data, test procedures (whether ISO or ASTM or AATCC), and if honest, scratch our heads to understand how data and test procedures can be used to predict future performance. To add complexity, in many cases the ISO and ATSM test methods do not directly correlate because the test apparatus are different.

 

We all know humans are good at measuring things and textile engineers are no exception and excel in this area! If we can develop a scientific test to measure how one type of fiber or fabric performs to another; we are happy. For instance, we are pretty good at measuring several independent elements of textile performance one being fiber tensile strength. We then can compare the results from one fiber to another and claim victorious insight. However in looking at staple fibers which are blended for better performance

nylon-staple-fiber

Photo Jonathan Long

like those found in military uniforms, there are a couple of things that impact strength. Once we compound fibers with other natural or synthetic fibers during the spinning process strength changes. One fiber’s performance shouldn’t be the final determination of how that yarn will perform or how that fabric once woven will perform. However, tensile strength is important (photo NYLON Fiber)

 

To measure tensile strength, common test methods used in the Technical Military Fabrics worlds you find are ASTM D5034-09(2013) Standard Test Method for Breaking Strength and Elongation of Textile Fabrics (Grab) or Test Method D3822 Standard Test Method for Tensile Properties of Single Textile Fibers. While these tests are great for comparing fibers and fabrics I am not sure they really tell the whole performance story. We rely on tests to predict which fabric will perform better in a military environment where fabric failure from rips and tears in high abrasion areas such as the knees, elbows, and seat are common. Tensile strength alone may not answer that question but is the most common place to start.

fiber-micronWhat we do know about tensile strength (or think w do) is that its related to “abrasion resistance” (stated as the number of cycles on a machine, using a technique to produce abrasion) and “durability” (here defined as the ability to withstand deterioration or wearing out a garment fabric in use which includes the effects of abrasion) (1). Higher tensile strength is often thought to indicate better abrasion and durability performance.

In addition to tensile strength we want to measure abrasion and there are three dominant tests.

  1. Martindale Abrasion (ASTM D4966) This test method covers the determination of the martindale-testing-credit-association-contract-textilesabrasion resistance of textile fabrics abraded against crossbred, worsted wool fabric. Fabric samples to be mounted flat and rubbed in an enlarging elliptical T shape using a piece of worsted wool cloth as the abrading material. The end is reached when two yarn breaks occur or when there is an appreciable change in shade or appearance.
  2. Tabor Abrasion (ASTM D4060) This test method covers the determination of the abrasion resistance of organic coatings to abrasion produced by the Tabor Abrader on coatings applied to a plane, rigid surface, such as a metal panel.
  3. Wyzenbeek (ASTM D4157) This test method covers the determination of the abrasion wyzenbeek-test-machine-credit-association-contract-textilesresistance of woven textile fabrics using oscillatory cylinder tester. The Wyzenbeek testing process requires samples of the test fabric to be pulled taut in a frame and held stationary. Individual test specimens cut from the warp and weft directions are then rubbed back and forth using an ACT approved #10 cotton duck fabric as the abradant. The end is reached when two yarn breaks occur or when appreciable wear is reached.

Note to product developers and evaluation teams – both test methods are limited to measuring flat abrasion resistance of a textile. Soldiers are fully three dimensional so these tests don’t consider edge abrasion or other types of surface wear that may occur in soldier uniform applications.

Fibers have different tensile strength but they also have different elongation characteristics. When considering fiber properties, fiber tenacity should not be viewed in isolation. Fiber elongation is at least as important –  why?  If a fiber cant stretch and recover somewhat, that fiber will break sooner than one that has elongation. Elongation is specified as a percentage of the starting length. The elastic elongation is important since textile products without elasticity would hardly be useable. They must be able to deform and return to shape (2).

fiber-elongation

Photo INTECH

My thoughts about selecting the optimal fabrics and fiber for military technical fabrics are that we should focus more on the mechanisms of failure. How does a fabric fail? I think we can rightly see that a fiber’s tensile strength is critical but so is a fabrics resistance to abrasion – maybe these two measurements can tell us which fabrics are likely to be the most “durable.”

How does failure actually happen? Its related to how a yarn and fabric’s structure is

fibre-rupture-abdullah-et-al-2006

Photo Abdullah 2006

modified in use. Lets face it – a fabric that is never used will last a long, long time so its something in use that wears a fabric out. In terms of wear mechanism in textiles, abrasion first modifies the fabric surface and then affects the internal structure of the fabric, damaging it (Manich et.al, 2001; Kaloğlu et al., 2003). Good abrasion resistance depends more on a high energy of rupture than on high tenacity at break. Abrasion is not influenced so much by the energy absorbed in the first deforming process (total energy of rupture), as by the activity absorbed during repeated deformation. This activity is manifested in the “elastic energy” or the “recoverable portion” of the total energy. Thus, to prevent abrasion damage, the material must be capable of absorbing energy and releasing that energy upon the removal of load (3).

The mechanical properties and dimensions of the fibers are important for abrasion. Fiber type, fiber fineness and fiber length are the main parameters that affect abrasion. Fibers with high elongation, elastic recovery and work of rupture have a good ability to withstand repeated distortion; so a good degree of abrasion resistance is achieved. Nylon is generally considered to have the best abrasion resistance, followed by polyester, polypropylene (Hu, 2008) (4).

cotton-polymer-yarn-detail-v2

Photo Jonathan Long

 

Something to think about is what is the optimal mix between fiber tensile strength and elongation and understanding how that mix performs during abrasion testing. If we find that higher tensile strength and greater elongation results in a more abrasion resistant fabric then we can add another test method to our toolbox to provide insight in failure prediction.  Fabrics with lower yarn tensile strength and lower fiber elongation should result in poorer abrasion testing and in turn wear out faster in wear and use. Lets test it and see!   (Photo natural cotton, key nylon intermediates, hexamethylene diamine (HMD) and adipic acid, Nylon Cotton Yarn and fabric)

 

(1) http://cdn.intechopen.com/pdfs/31704/ Abdullah et al., 006 Analysis_of_abrasion_characteristics_in_textiles.pdf

(2) http://www.definetextile.com/2013/04/fiber-elongation.html

(3) Analysis of Abrasion Characteristics in Textiles by Nilgün Özdil, Gonca Özçelik Kayseri2 and Gamze Süpüren Mengüç; Ege University, Textile Engineering Department, Izmir, Turkey

(4) Analysis of Abrasion Characteristics in Textiles by Nilgün Özdil, Gonca Özçelik Kayseri2 and Gamze Süpüren Mengüç; Ege University, Textile Engineering Department, Izmir, Turkey

Pounds to Grams – not always straight forward in textiles

October 26, 2016

conversion-3Converting weight from one country’s system to another, especially for those of us with military experience in Europe jumps right to converting miles to kilometers where we know its about 1 mile to 1.6 KM – or next converting the price of fuel between gallons and liters? However, when we start talking about weight and working between the United States supply chain (with a few exceptions where companies continue to quote prices in meters and not yards!) we have to convert fabric weight from ounces per square yard to ounces per square meter (lets not get into denier and dtex!).

So why is this important? In the world of military personal protection, there are numerous measurable factors that when combines add up to some notion of comfort and performance.  MOLLEComfort translates into mission performance and staying focuses. At the crux of the issue is human performance and this really means managing the human core physiology. The amount of weight a soldier carriers is a key component to how well the conversion-2core performs and for how long. Weight can also impact how durable a textile material remains although the textile composition may be more important. How a fabric is constructed will also impact how well that material holds up. construction also impacts how air permeates through the fabric which enables the process of moisture evaporation and cooling of the core. Again, a more air permeable fabric may have tradeoffs with a less permeable fabric – but we stray.  We are talking about weight.

In many areas of human endeavor achieving the same or better performance with lessconversion-1 weight is usually a good thing and so it is with combat uniforms (to a point). So we need to know how to communicate current weight as accepted by US Military Specifications into a scale that international militaries can understand and use – enter grams per square meter.

The formula is pretty strain forward – one ounce is equal to one sixteenth of a pound or 16 drams or 28.349 grams.  WAIT – don’t use that formula! While a great formula for cooking recipes and drug measurements, it wont work for textiles because we have to consider the meter and yard lengths. Bates Jungle Boot

The answer is 1 gram = 0.03527 ounces. The textile geniuses assume we are converting between ounce-force/square yard and gram-force/square meter.   The derived unit for pressure is the pascal.  1 pascal is equal to 3.00750253989 ounces per (square yard), or 101.971621298 grams per (square meter).   The super smart people at http://www.ginifab.com/feeds/ozyd2_gm2/ helped me out with an example.

Question : If a fabric is 5.5oz/sq yard, how much is the weight in grams/sq meter ?
Answer : 5.5 oz/sqyd x 33.906 = 186.483 gm/sqm   conversion-4

And the mystery of converting ounces per square yard to grams per square meter is solved!