Expert: Carolyn Primus - 4/21/2004

Question
Dear Sir,

Could you tell me which firms currently offer shape memory polymers?

What are possible substitute products for these polymers in the future?

Yours faithfuuy,

Corinne

Answer
Its not always a Sir that answers your questions.....

Try this company.

Elastic Memory Composite (EMC) Material

Composite Technology Development, Inc. has developed Elastic Memory Composite (EMC) materials, based on thermoset shape memory polymers developed by CTD, which enables the practical use of the shape memory properties in fiber-reinforced composites and other specialty materials. The applications for these revolutionary new materials are broad ranging, including mission-enabling components for spacecraft, performance enhancing and cost saving industrial and medical applications, deployable equipment for emergency and disaster relief, and improvements in the performance of sports equipment.

What Are Elastic Memory Composite (EMC) Materials?

EMC materials are similar to traditional fiber-reinforced composites except for the use of an elastic memory thermoset resin-matrix, developed by CTD. The elastic memory matrix is a fully cured polymer, which can be combined with a wide variety of fiber and particulate reinforcements and fillers. The unique properties of the matrix enable EMC materials to achieve high packaging strains without damage. Strains are induced by elevating the temperature of the EMC material and then applying a mechanical force. The shape memory characteristics enable the high packaging strains to be “frozen” into the EMC by cooling. Deployment (i.e., shape recovery) is effected by elevating the temperature. The temperature at which these operations occur is adjustable.
At lower temperatures, the performance of EMC materials follows classical composite laminate theory. At higher temperatures, EMCs exhibit dramatically reduced stiffnesses due to significant matrix softening of the resin. Adequately addressing the mechanics of the “soft-resin” will enable the EMC materials to provide repeatable stowage and deployment performance without damage and or performance changes. Products fabricated from these materials can be deformed and reformed repeatedly. Products utilizing EMC materials can be fabricated with conventional composite fabrication processes and tooling.

EMC Materials:

*   Can be formulated with low cost components
*   Use standard existing polymer and composite manufacturing processes
*   Regain original shape with applied heat, no other external force is required
*   Possess widely adjustable deformation and reformation temperatures are
*   Are suitable for repeated deformation and reformation cycles
*   Reform accurately to original shape
*   Maintain high strain capability when heated
*   Enable large volume reduction for packing
*   Issues such as shelf life, chemical reaction, toxicity, explosion hazard, or environmental impact are not of concern


What is an Elastic Memory Polymer?

Polymers have a characteristic temperature, called the glass transition temperature (Tg), at which the polymer softens. CTD's elastic memory polymer becomes both soft and highly ductile above this transition temperature. Below this temperature the polymer is hard and rigid, or glassy. Above TG the elastic memory polymer can be highly deformed and stretched into a different shape, such as folded into a compact shape. When held in this shape and cooled, it retains the new shape indefinitely. When reheated above TG, the material reforms to its original shape without external force, and regains its original properties once cooled. Thus an EMC tubular structure could be heated, collapsed and stowed, and then later reformed simply by heating.

EMC materials can revolutionize:

*   Industrial Products
*   Construction Materials
*   Toys and Sporting Goods
*   Medical Equipment and Devices
*   Automobiles and Transportation Components
*   Packaging
*   Aerospace and Space Deployable Structures
*   Military Components and Structures


EMC Materials are Ideal for Deployable Structures

EMC materials are ideally suited for deployable components and structures because they possess high strain-to-failure ratios, high specific modulus, and low density. By contrast, most traditional materials used for deployable structures have only two of these three attributes.

Initial Uses of EMC may be for Space Applications
Initial EMC development efforts have targeted space applications. Tremendous support for the development of CTD's EMC materials has been received from NASA, the Air Force, BMDO and other Government agencies, and the aerospace industry. EMC materials have the potential to enable a new generation of space deployable components and structures, which would eliminate nearly all the limitations and shortfalls of current spacecraft deployable technologies.

The first flight-qualified EMC components are likely to be improved versions of current state-of-the-art space deployable structures, such as carpenter tape hinges, STEMs, and/or coilable longeron booms. EMC has the potential to dramatically improve the capabilities of these systems, while providing a low-risk path for introduction and flight validation. It is also anticipated that the unique performance capabilities of EMC materials will stimulate the development of entirely new and more efficient deployable structure designs.

Composite Technology Development, Inc. is dedicated to readying EMC technology, while working collaboratively with industry partners to conceive and develop the next generation of space deployable structures. To date, EMC materials have been fabricated into a variety of components for deployable structures, including laminated plates and shells, open-grid lattices, pultruded rods, and hinges. Each component presents a unique set of requirements for both packaging performance and deployed structural performance.

Carpenter Tape Hinge:
The so-called “carpenter tape” hinge is one of the simplest and oldest types of deployable spacecraft components. The biggest drawbacks to traditional steel carpenter tape hinges are size limitations and shock loads during deployment. In an effort to overcome these drawbacks, prototype EMC carpenter tape hinges have been tested.

Prototype EMC carpenter tape hinge:
The prototype EMC hinge elements weighed about 2 grams and were able to repeatedly deploy a 60-gram mass against gravity. Because of the viscoelastic behavior of EMC resins, EMC components deploy gradually upon application of heat. In the case of the EMC carpenter tape hinge, this effect leads to a gentle, shockless deployment at a rate that is controllable by adjusting the heater power.

Reel-Stored Extendible Boom:
The Storable Tubular Extendible Member (STEM) is one of the oldest and most successful deployable boom designs in the history of space flight. Current Stems use either beryllium copper or stainless steel construction. Due to the high density and high stored strain energy of these metals, current Stems are limited in size. EMC should enable scale up to larger diameters and/or thicknesses. Analysis also indicates a significant mass reduction, improved specific stiffness, and reduced stored strain energy. (This picture shows up as a black box on my computer.)

Design of EMC STEM

Coilable Longeron Deployable Boom:
Coilable longeron booms, as shown in the figure, are very successful space deployable structures. The longerons are the primary structural member of the boom, and determine most its post-deployment stiffness and strength. The longerons are also the most highly strained component in the launch package. For packaging, the longerons are bent into a helix with a diameter equal to the diameter of the deployed boom. Deployment force is primarily provided by the strain energy stored in the longerons. Current longerons are made of unidirectional S-glass/epoxy due to the high strength and strain capability of this material. However, the use of S-glass/epoxy limits the diameter of current coilable booms to roughly 16” due to safety concerns related to the high stored strain energy.



To overcome this scaling limitation, EMC longerons have been evaluated. Prototype EMC longerons exhibited highly predictable and repeatable structural response and packaging performance. In addition, analysis has indicated the potential for significant reduction in system mass and stored strain energy.

Please contact CTD for more information regarding Elastic Memory Composites.


   
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
       
 
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