Fabric structure

A fabric structure is a structure made of fabric, with or without a structural frame. The technology provides end users a variety of aesthetic free-form building designs. Custom-made structures are engineered and fabricated to meet worldwide structural, flame retardant, weather-resistant, and natural force requirements.
Fabric structures are considered a sub-category of tensile structure.
A fabric structure's material selection, design, engineering, fabrication, and installation are integral components to ensuring a sound structure.
Fabric structure basics.
Membrane materials.
Most fabric structures are composed of actual fabric rather than meshes or films. Typically, the fabric is coated and laminated with synthetic materials for increased strength, durability, and environmental resistance. Among the most widely used materials are polyesters laminated or coated with polyvinyl chloride (PVC), and woven fiberglass coated with polytetrafluoroethylene (PTFE).
Cotton canvas.
The traditional fabric for fabric structures is light cotton twill, light canvas, or heavy proofed canvas.
Polyesters.
Strength, durability, cost, and stretch make polyester material the most widely used in fabric structures. Polyesters that are laminated or coated with PVC films are usually the least expensive option for longer-term fabrications.
Laminates generally consist of vinyl films over woven or knitted polyester meshes (called scrims or substrates), while vinyl-coated polyesters usually have a high-count, high-tensile base fabric coated with a bondable substance that provides extra strength. Precontraint fabric is made by placing the polyester fabric under tension both before and during the coating process. This results in a weave that has increased dimensional stability.
Vinyl-laminated polyesters.
A laminated fabric usually is composed of a reinforcing polyester scrim pressed between two layers of unsupported PVC film. For most fabric structure uses, however, it refers to two or more layers of fabric or film joined by heat, pressure, and an adhesive to form a single ply.
With an open-weave or mesh polyester scrim, the exterior vinyl films bond to themselves through the openings in the fabric. Heavier fabric scrims, however, are too tightly woven to allow the same bonding. In this case, an adhesive is used to bond the exterior films to the base fabric.
A good chemical bond is critical to both prevention of delamination and development of seam strengths. The seam is created when vinyl-coated fabrics are welded together. The adhesive enables the seam to meet shear forces and load requirements for a structure at all temperatures. The adhesive prevents wicking of moisture into the scrim’s fibers, which also prevents fungal growth or freezing that could affect the exterior coating's adhesion to the scrim. Adhesives are water-based to comply with EPA regulations.
Open-weave scrims generally make the fabric more economical, although this can also depend on the number and type of features that you require in the vinyl. Almost any color, UV resistance vinyl coated polyester, and colorfastness may be incorporated into the vinyl. However, the more features added, the higher the cost of the fabric.
Vinyl-coated polyester.
Vinyl coated polyester is the most frequently used material for flexible fabric structures. It is made up of a polyester scrim, a bonding or adhesive agent, and exterior PVC coatings. The scrim supports the coating (which is initially applied in liquid form) and provides the tensile strength, elongation, tear strength, and dimensional stability of the resulting fabric. Vinyl-coated polyester is manufactured in large panels by heat-sealing an over-lap seam with either a radio-frequency welder or a hot-air sealer. A proper seam will be able to carry the load requirements for the structure. The seam area should be stronger than the original coated fabric when testing for tensile strength.
The base fabric's tensile strength is determined by the size (denier) and strength (tenacity) of the yarns and the number of yarns per linear inch or meter. The larger the yarn and the more yarns per inch, the greater the finished product's tensile strength.
The adhesive agent acts as a chemical bond between the polyester fibers and the exterior coating and also prevents wicking, or fibers absorbing water, which could result in freeze-thaw damage in the fabric.
The PVC coating liquid (vinyl Organisol or Plastisol) contains chemicals to achieve the desired properties of color, water and mildew resistance, and flame retardancy. Fabric can also be manufactured that contains high levels of light transmission or can be made completely opaque. After the coating has been applied to the scrim, the fabric is put through a heating chamber that dries the liquid coating. PVC coatings are available in a range of colors, although non-standard colors can be pricey. Colors may be subject to minimum order runs that allow the coating machine to clear out traces of any previous color.
Fiberglass.
Woven fiberglass coated with PTFE (Teflon or silicone) is also a widely used base material. Glass fibers are drawn into continuous filaments, which are then bundled into yarns. The yarns are woven to form a substrate. The fiberglass carries a high ultimate tensile strength, behaves elastically, and does not suffer from significant stress relaxation or creep. The PTFE coating is chemically inert, can withstand temperatures from 100 °F upwards to 450 °F+. It is also immune to radiation and can be cleaned with water. PTFE fiberglass is additionally Energy Star and Cool Roof Rating Council certified. During scientific tests of its solar properties, it was discovered that PTFE fiberglass membranes reflect as much as 73 percent of the sun’s energy while holding just seven percent on its exterior surface. Certain grades of PTFE fiberglass can absorb 14 percent of the sun’s energy while allowing 13 percent of natural daylight and seven percent of re-radiated energy (solar heat) to transmit through.
Because of its energy efficiency, high melting temperature and lack of creep, fiberglass-based fabrics have been the material of choice for stadium domes and other permanent structures, particularly in the United States. However, when properly constructed, polyester structures may be equally durable.
Olefin / polyolefin.
A number of polymers consisting mainly of polyethylene, polypropylene or combinations of the two are available for fabric structures.
PVDF woven.
PVDF woven fabric are available for fabric structures.
ePTFE woven.
ePTFE woven fabric are available for fabric structures..
Blackout fabric.
Blackout material, also known as blockout material, is an opaque fabric. Blackout fabric consists of a laminate that sandwiches an opaque layer between two white exterior layers. Heating and lighting of a structure may be controlled because the fabric does not allow light to permeate the top or walls. The opaque quality also prevents stains, dirt, repairs, or slightly mismatched panels on the structure's exterior from being noticed from the inside.
Topcoatings.
Most fabrics used for fabric structures have some form of topcoating applied to the exterior or coating to make cleaning easier. Topcoating provides a hard surface on the outside of the material, forming a barrier that aids in preventing dirt from sticking to the material, while allowing the fabric to be cleaned with water. As the material ages, the topcoating will eventually erode, exposing the fabric to dirt and making it more difficult to clean. The thicker the topcoating, the longer it will last. However, coatings that are too thick will embrittle and crack when folded.
There are several commonly used topcoatings:
Fabric properties.
When discussing fabric properties for use on a structure, there are several terms that are commonly used:
Structural properties.
When deciding on a fabric it is imperative to keep certain fabric properties in mind. These include stress versus strain (unit load versus unit elongation), expected service life, the mechanisms of joining the material together (welding, gluing, etc.), and the fabric’s behavior in or around fire.
Stress versus strain data should be obtained in both uniaxial and biaxial forms. This information characterizes the fabric in terms of stiffness, elasticity, and plasticity. This is essential information when determining the material's response under load in a load-carrying application. Shear strength, shear strain, and Poisson's ratios, though difficult to obtain, are fundamental when analyzing a fabric as a structural material.
Cost savings of fabric structures.
There can be multiple advantages to fabric structures over traditional buildings in certain scenarios. In some cases, no lighting is required as the fabric used is generally translucent, which makes it an energy efficient solution. Mobility: You can move them, either on wheels or relocate them completely. Savings: They cost about half of what a traditional structure costs.
Fabric properties: When discussing fabric properties for use on a structure, there are several terms that are commonly used:
Tensile strength is a basic indicator of relative strength. It is fundamental for architectural fabrics that function primarily in tension.
Tear Strength is important in that if a fabric ruptures in place, it generally will do so by tearing. This can occur when a local stress concentration or local damage results in the failure of one yarn, which thereby increases the stress on remaining yarns.
Adhesion strength is a measure of the strength of the bond between the base material and coating or film laminate that protects it. It is useful for evaluating the strength of welded joints for connecting strips of fabric into fabricated assembly.
Flame retardancy does not have the same meaning as flameproofing. Fabric that contains a flame-retardant coating can withstand even a very hot point source. However, it can still burn if a large ignition source is present.
Of course, other properties must be factored in when determining a material's suitability for a structure. To fully understand a fabric's value and usefulness, consider the following:
Gallery.
Fabric roof in Tulsa, Oklahoma: