The field of this application generally relates to composite materials, methods for forming them, and their uses.
Conventional structural composites, such as rebar-reinforced concrete, laminated wood, and carbon fiber-reinforced composites, have static physical and mechanical properties (e.g., shape, strength, conformability, etc.). Such structures cannot be easily altered and, if damaged, are difficult to repair. Thus, it is sometimes advantageous to form a composite material that is configurable to fit customized needs.
Composite materials that are configurable, their preparation, and their uses are described.
Disclosed subject matter includes, in one aspect, a composite article, which includes a plurality of sheets positioned to interleave and partially overlap with each other and held together by interactions between the plurality of sheets and a compressive force across the plurality of sheets, wherein each of the plurality of sheets is infused with a plastic (e.g., an elastomer) and forms at least one smooth surface, wherein each of the plurality of sheets is in close contact with adjacent ones of the plurality of sheets, wherein an overlapping area of the plurality of sheets provides resistance to a shear force applied to the composite article.
In some embodiments, the plurality of sheets include fabric sheets.
In some embodiments, the plurality of sheets include at least one of carbon fabric sheets, metallic meshes, or papers.
In some embodiments, the elastomer contains polydimethylsiloxane (PDMS).
In some embodiments, the composite article also includes a deformable container enclosing the plurality of sheet, wherein the compressive force is generated by a pressure difference between the outside and inside of the deformable container.
In some embodiments, the deformable container is air tight.
In some embodiments, the compressive force is approximately 1 bar.
In some embodiments, the compressive force is generated by an electric field.
In some embodiments, the compressive force is generated by a magnetic field.
In some embodiments, the composite article also includes at least one end region coupled to an external coupling.
In some embodiments, the resistance to the shear force increases when the number of the plurality of sheets increases.
In some embodiments, the resistance to the shear force increases when the overlapping area increases.
In some embodiments, the at least one smooth surface has an average roughness Ra of about 200 nm.
Disclosed subject matter includes, in another aspect, a method of preparing a composite article, which includes providing a plurality of sheets, infusing each of the plurality of sheets with a plastic (e.g., an elastomer) to form at least one smooth surface, interleaving and partially overlapping the plurality of sheets with each other, and applying a compressive force across the plurality of sheets, wherein each of the plurality of sheets is in close contact with adjacent ones of the plurality of sheets and wherein an overlapping area of the plurality of sheets provides resistance to a shear force applied to the composite article.
In some embodiments, the method also includes providing a substrate with a second smooth surface, applying the elastomer on the second smooth surface of the substrate, placing each of the plurality of sheets onto the second smooth surface of the substrate, pressing the each of the plurality of sheets against the substrate to infuse the elastomer into the each of the plurality of sheets, curing the elastomer infused in the each of the plurality of sheets, and removing the each of the plurality of sheets from the substrate, wherein the at least one smooth surface is formed on the each of the plurality of the sheet.
In some embodiments, the plurality of sheets include fabric sheets.
In some embodiments, the plurality of sheets include at least one of carbon fabric sheets, metallic meshes, or papers.
In some embodiments, the elastomer contains polydimethylsiloxane (PDMS).
In some embodiments, the method also includes placing the plurality of sheets inside a deformable container, and lowering air pressure inside the deformable container, wherein the compressive force is generated by a pressure difference between the outside and inside of the deformable container.
In some embodiments, the compressive force is approximately 1 bar. The compressive force can be less than 1 bar and greater than 0 bar. In some examples, the compressive force is in the range of 640 mbar to about 1 bar.
In some embodiments, the compressive force is generated by an electric field.
In some embodiments, the compressive force is generated by a magnetic field.
In some embodiments, the method also includes increasing the number of the plurality of sheets to increase the resistance to the shear force.
In some embodiments, the method also includes increasing the overlapping area to increase the resistance to the shear force.
In some embodiments, the at least one smooth surface has an average roughness Ra of about 200 nm.
Disclosed subject matter includes, in yet another aspect, a composite article, which includes a first plurality of tiles at a first layer, and a second plurality of tiles at a second layer, positioned over the first layer, wherein each of the first and second plurality of tiles is infused with an elastomer and forms at least one smooth surface, wherein each of the second plurality of tiles at the second layer partially overlaps with and bridges at least two of the first plurality of tiles at the first layer, wherein the first and second plurality of tiles are held together by interactions among the first and second plurality of tiles and a compressive force across the first and second plurality of tiles and remain immobile to each other, wherein an overlapping area of the first and second plurality of tiles provides resistance to a shear force applied to the composite article.
In some embodiments, the first and second plurality of tiles become mobile to each other when the compressive force is relieved.
In some embodiments, the first and second plurality of tiles include fabric-based tiles.
Disclosed subject matter includes, in yet another aspect, a method of preparing a configurable composite article, which includes preparing a first plurality of tiles at a first layer, overlaying a second plurality of tiles at a second layer on top of the first layer, wherein each of the second plurality of tiles partially overlaps with and bridges at least two of the first plurality of tiles, applying a compressive force across the first and second pluralities of tiles so that the first and second pluralities of tiles are in close contact and immobile to each other, fitting the first and second pluralities of tiles to a profile of an object, relieving the compressive force so that the first and second pluralities of tiles become mobile to each other, rearranging the first and second pluralities of tiles to conform with the profile of the object, and applying a second compressive force across the first and second pluralities of tiles so that the first and second pluralities of fabric tiles are again in close contact and immobile to each other.
In some embodiments, the first and second plurality of tiles include fabric-based tiles.
The following figures are provided for the purpose of illustration only and are not intended to be limiting.
The patent and scientific literature referred to herein establishes knowledge that is available to those of skill in the art. The issued U.S. patents, allowed applications, published foreign applications, and references, that are cited herein are hereby incorporated by reference to the same extent as if each was specifically and individually indicated to be incorporated by reference.
For convenience, certain terms employed in the specification, examples and claims are collected here. Unless defined otherwise, all technical and scientific terms used in this disclosure have the same meanings as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The initial definition provided for a group or term provided in this disclosure applies to that group or term throughout the present disclosure individually or as part of another group, unless otherwise indicated.
Composites that can be reconfigured into a load-bearing structure, on command, can enable the fast construction of temporary structures. The composites themselves can be transported as flat sheets; materials with a flat geometry can be easier and less expensive to transport than a pre-assembled structure since the composites can be stacked. Structures formed with these configurable composites can be customized for the circumstance.
In some embodiments, configurable composite articles, which are made of interleaved sheets and compressed together (e.g., using vacuum-jam, electric field, magnetic field, etc.), can hold large loads, can be fashioned into various shapes, and can be changed with varying internal pressures. If a load-bearing system were to break, the composite can be re-assembled and re-constructed by interleaving and vacuum-sealing in a fast and convenient manner. In some embodiments, load-bearing prostheses made of configurable composites can shape-shift into a load-bearing structure and do not need to be replaced periodically as patients age.
In one aspect of the disclosed subject matter, the physical and mechanical properties of the configurable composite articles can be configured to fit various needs. In one example, the number of interleaved sheets, the overlapping area of the interleaved sheets, the compressive force across the interleaved sheets, and/or the composition of the interleaved sheets can be adjusted to configure the configurable composite articles. In another example, properties of the individual sheets can also be altered to adjust the physical and mechanical properties (e.g., conductivity, optical transparency, chemical resistance, etc.) of the configurable composite article.
Each of the plurality of sheets 110 can be infused with a material 120 to form a smooth surface 130 on the sheet 110. The material 120 can be in many forms, such as gels, thermoplastics, rigid plastics, and clays, etc. In some embodiments, the material 120 can be an elastomer 120. Examples of the elastomer include polydimethylsiloxane (PDMS) and urethane rubbers (e.g., ReoFlex), etc. In some embodiments, the sheets 110 can have a network-like quality that can be slightly porous. This can help the material 120 such as an elastomer to infuse the fabric sheet 110 more easily. The elasticity of the material 120 along with the extensibility of the fabrics can allow the composite article 100 to stretch. In addition, the elastomer 120 infused in the sheets 110 can help provide mechanical flexibility to the composite article 100.
The plurality of sheets 110 can interleave with each other. In some embodiments, the plurality of sheets do not completely overlap with each other. For example, sheets 110-1, 110-2, 110-3, 110-4, and 110-5 only partially overlap with each other and form an overlap area 140. A non-overlapping portion 150 of the sheets can be connected to an external coupling (e.g., a clamp). In some embodiments, a force can be exerted across the plurality of sheets to compress the plurality of sheets against each other. The smooth surfaces 130 can help ensure the sheets are in close contact with each other.
Close contact between elastomer-infused sheets can increase the effective contact surface area and thus increase the shear resistance of the configurable composites. More points of contacts can increase interactions between two adjacent sheets. Interactions can include covalent or non-covalent interactions. For example, urethanes that are partially cured can form covalent bonds between neighboring sheets over time. Examples of the non-covalent interactions include van der Waals forces, pi-pi stacking, hydrogen-bonding, charge-transfer, and electrostatics, etc. The elastomers can also be selected to have adhesive attraction to one another, to thereby increase the inherent shear resistance between adjacent layers. These inter-sheets interactions can provide resistance (e.g., friction) to sliding (e.g., shear force).
As discussed earlier, infusing sheets 110 with a material such as an elastomer 120 can help improve the smoothness of the surfaces 130, which increases surface contact area. Table 1 lists the average roughness Ra and its standard deviation for some exemplary surfaces.
As illustrated in Table 1, carbon fabric can have an average roughness in the order of 20 μm. When infused with an elastomer (e.g., PDMS), the average roughness can be reduced to the order of 200 nm. The elastomer on the surface, when compressed, can deform and increase the amount of contact area as well. Therefore, the elastomer-infused surface can have large surface contact at least due to its smooth surfaces and deformability.
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As discussed above, adjacent ones of the plurality of sheets 110 only partially overlap so that there are non-overlapping region 150 at one or two ends of the configurable composite article. An external load can be coupled onto the end regions 150 to apply tensile force along the longitude direction of the plurality of sheets 110. In some embodiments, without pulling both ends of each sheet 110 at the same time, the shear force resistance (e.g., against sliding) between two adjacent sheets (in addition to the tensile strength of each individual sheet itself) can provide the tensile strength of the configurable composite article 100.
Still referring to
In some embodiments, the compressive force across the sheets of the configurable composite 100 can be generated by other mechanisms. In one embodiment, the compressive force can be generated using an electric field. For example, two separated plates can be oppositely charged (like a capacitor); the resulting Maxwell stress can exert compressive force upon the sheets. In another embodiments, each sheet is individually charged. Adjacent sheets can be charged oppositely, thus creating an ‘interleaved’ capacitor. In another embodiment, the compressive force can be generated using a magnetic field. For example, neighboring sheets can be magnetically polarized in the same direction; the magnetic interactions between the two neighboring sheets can exert compressive force upon the sheets. In yet another embodiment, the compressive force can be generated using a magnetic field. For example, strong magnets on the two opposite sides of a composite article can exert compressive force upon the sheets. In yet another embodiment, mechanical constraints, such as clamps, rubber bands, or plates screwed together, can be used to physically compress the sheets. In yet another embodiment, a pneumatic bladder can be wrapped around the sheets and inflated to compress the sheets.
In another aspect of the disclosed subject matter, the shape of a configurable composite article can be adjusted to fit customized needs by altering the layouts of the individual interleaving sheets.
The configurable composite article 800 can be placed inside a deformable container (not shown in
Those skilled in the art would readily appreciate that all parameters and configurations described herein are meant to be exemplary and that actual parameters and configurations will depend upon the specific application for which the systems and methods of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that the invention may be practiced otherwise than as specifically described. The present invention is directed to each individual feature, system, or method described herein. In addition, any combination of two or more such features, systems or methods, if such features, systems or methods are not mutually inconsistent, is included within the scope of the present invention.
This application claims the benefit of the earlier filing date of U.S. Patent Application No. 61/886,210, filed on Oct. 3, 2013, the contents of which are incorporated by reference herein in its entirety.
This invention was made with support from the United States government under Grant No. W911NF-09-1-0746 awarded by the US Army. The United States government has certain rights to this invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/058739 | 10/2/2014 | WO | 00 |
Number | Date | Country | |
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61886210 | Oct 2013 | US |