DE2716325A1 - METHOD FOR MANUFACTURING COMPOSITE STRUCTURES - Google Patents

Description

PFENNING MAAS SEILER MEINIG LEMKE SPOTT

PATENT LAWYERS L 1 A O 3 2 5

BERLIN · MUNICH · AUGSBURG

Patent attorneys ■ Kurfurstendamm 170 ■ D 1000 Berlin 15 Your message from
Your letter of Our sign
Our reference 7th J Pfenning, DIpI -Ing Berlin
Dr. I Maas, Dipl Chem Munich
H Seiler. Dipl-Ing - Berlin
K H Mine. Dipl -Phys - Berlin
J M Lemke, Dipl -Ing. - Augsburg
Dr. G. Spott, Dipl.-Chem. - Munich ME / SUN / ST I BERLIN OFFICE:
I Kurfürstendamm 170
I D 1000 Berlin 15 675 635 Phone:
030-8812008 / 8812009 Telegram address:
Cable defense patent Berlin
Date Your mark
Your reference April 1977

WILLIAM W. MILBURN, Jr. 945 9th Street, Boulder, Colorado 80302, V. St. A.

Process for the manufacture of composite structures

The present invention relates generally to a method of making from a pneumatic air mold, a damping and insulating material of low density and strength, and a load-bearing layer composed of a cementitious material structure, and it relates in particular on a method for the economical production of structures, in which the insulating material on a inflated airform is sprayed and the air pressure is maintained within the airform for the purpose of wearing another layer of load-bearing fabric.

Despite its attractive simplicity, its use has grown of pneumatic air molds for shaping sprayed, diohthous load-bearing materials, such as cement-containing materials,

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proved difficult. Such dense fabrics tend to distort the air and make it vibrate. Especially when spraying onto the inner surface of the air form the substances are moved as a result.

The benefits of using a pneumatically inflatable airform as the base structure for one from a sprayed on structure made of polymeric foam, however, are recognized and disclosed in U.S. Patent 3,277,219 dated October 4, Was disclosed in 1966 by the applicant Lloyd S. Turner.

Heretofore, a two-step process has been used to make a polymeric mold for a more durable fabric such as concrete used. First, a pneumatic air mold is inflated. Then on the inner surface of the inflated Air form a light material, e.g. a plastic foam, sprayed on to form a self-supporting polymer foam form that gives additional layers of e.g. concrete an independent initial support. The pneumatic air form is inflated by an air compressor that runs until completion of foam spraying is kept in operation. So far it has been assumed that the polymer foam is a self-supporting layer of sufficient thickness and strength forms to itself and later applied layers load-bearing material, such as sprayed concrete, without the help of the original positive air pressure with this previous method, the compressor is no longer required. After the self-supporting foam layer has hardened it forms a convenient, relatively inexpensive form for the concrete layer. The reinforced concrete layer gives strength and durability to the structure, and it it is not necessary to remove the foam layer after the concrete layer has hardened, as the latter is used to isolate the Structure contributes.

The Turner process has proven to be advantageous for the structures mentioned. With large structures

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a self-supporting foam layer as an initial support for the layer of cementitious or the like Substance uneconomical. In order to achieve self-supporting of the foam layer, it must be uneconomically thick. That Turner's method offers beneficial for smaller structures Layer thickness ratios, i.e. 76 - 127 mm foam layer thickness is sufficient for a self-supporting form for the concrete layer. However, when creating larger structures must, the necessary foam layer thickness reaches an order of magnitude that is not necessary for insulation and therefore is uneconomical. The manufacture of large structures using a self-supporting foam layer was therefore so far not economical. It could also use the Turner method only for relatively expensive foamed polymers with sufficient strength to form a self-supporting shape be used. Cheaper, non-polymeric insulation materials do not have sufficient strength to be "self-supporting" as defined by Turner.

The object of the invention is therefore to create an improved process for the production of layers composed of layers Structures.

Another task is to create a method for Manufacture of a structure with optimal insulating properties together with optimal strength properties of a load-bearing Fabric.

Another object is to provide a method of making a structure from insulating material, e.g. foamed polymers, and of load-bearing material, such as cementitious material, in a preferred embodiment the insulating material protects the load-bearing material from temperature changes protects as a result of weather conditions and other causes.

Another object of the invention is to provide one

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new and improved method for rapidly fabricating a composite structure in an enclosed environment.

In order to achieve these objects, a method is provided according to the invention proposed for making a composite structure in which an air mold is inflated, a layer of insulating The substance is sprayed onto the air mold and the sprayed-on insulating substance is allowed to cure, this process characterized in that the structure consisting of air form and insulating material is also maintained by maintaining it an overpressure of air within the structure during application a hardenable, load-bearing material supported on the structure formed from air form and insulating material air pressure is maintained within the composite structure until the structural fabric cures is and supports the structure.

A description of some preferred embodiments follows of the invention with reference to the accompanying Pig. 1-9 * where:

Pig. 1 is a simplified section through a means of the invention Process made structure;

Pig. 2-6 sections through further exemplary embodiments of structures produced by means of the method according to the invention;

Pig. 7 is a simplified section to show a preferred one Method for applying insulating material;

Pig. θ a section similar to Pig. 7 to illustrate a preferred Method of applying load-bearing fabric; and

Pig. 9 a plot of the necessary thickness of polymeric material for a self-supporting foam layer at various Spans of a dome structure. - 5 -

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* - ⁹ " $ 271632

In Pig. 1, the reference numeral 10 indicates a device according to the invention composite structure. The structure 10 consists of an air mold 12 which integrates with the structure as shown may be, or optionally removable from the structure 10, an insulating layer H and a load-bearing layer 16 can be.

If the air mold 12 is removable, it is preferably made of polyethylene laminate. In general, it is polyethylene laminate waxed enough to allow the air form 12 to be removed from the structure 10. If, however If other materials are used, it may be desirable to apply a release agent to the sprayed areas to prevent the To facilitate removal of the air mold 12.

In the preferred embodiment of the invention, however, the air form 12 is intentionally provided with the insulating layer H glues together and forms an integral part of the structure 10. In such a case, a textile fabric made of polyethylene terephthalate, what is available under the trade name Dacron is a preferred material. Nylon is less preferred because it stretches more easily when exposed to radiation, especially ultraviolet radiation, is less resistant and, since it is hygroscopic when wet its Dimensions changes. In any event, it is desirable to have durable air-form fabrics with urethane compounds be coated to make them impermeable to water and air.

It is preferred that the air shape 12, and accordingly ultimately the structure 10, be round for several reasons Have shape. Such shapes have a high strength-to-material ratio, a low external surface area to volume ratio for the purpose of energy saving and are easy to manufacture. Although the one shown Embodiment the air form 12 has a round shape, it can have a variety of shapes including

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those with straight delimiting surfaces aiii show. vertical Walls and flat or sloping roofs can be provided according to the invention. Since the invention allows, however, in a simple Wise, aesthetically attractive and spatially strengthening To produce curved surfaces, such constructions are preferred according to the invention.

Layer H consists of a sprayable material of low strength, preferably made of a polymeric material with a multiplicity of gas-filled cavities. However, others are similar sprayable materials can also be used. In addition to having an insulating function, layer H must, the follows in its shape the structure 10, also perform other tasks.

The insulating layer H consists of spray-on substances, which have relatively low strength, low density and low thermal conductivity. Such substances show generally a two-phase structure in which a solid material has a plurality of gas-filled cavities, preferably closed cavities. Since the insulating material has a low density, it can be used Spray directly onto the taut form of air 12 without causing it to vibrate, causing the fabric would be shaken by the air form 12. For example, if a heavier load-bearing material such as liquid concrete were to be placed on the Luftform 12 are sprayed, it would deform considerably when it hit the concrete and vibrate, whereby the concrete would be shaken off the air form 12.

In addition to the preferred expanded polymer material, such as, for example, polyurethane foams or urea-formaldehyde foams, other materials can also be used. For example, thermoplastic materials in the form of particles or pellets, which preferably have gas-filled cavities - as unmelted particles with sticky surfaces - as a result of Er- '- 7H

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heating or applying an adhesive to the particles are sprayed. Expanded polystyrene particles are typical of such fabrics. When the particles hit the air form, the sticky surface adheres to the air form and to the other particles being sprayed on. In addition to the voids, which are preferably present in the particles per se , additional voids are formed between the particles because the particles adhere to one another in relatively small areas. Simple adhesives of animal origin or similar adhesives can be used.

Another useful insulating material consists of expanded cellulose or finely divided paper, which substances with a The adhesive is mixed and sprayed onto the air mold 12 serving as a support surface. The resulting sprayed on After the adhesive has set, the layer resembles paper mache and has low strength but excellent insulation properties. Such a paper-based insulating material is economical and readily available.

The insulating properties of various substances depend on the particular composition, application method, degree of expansion, etc., but a typical polymer foam with a layer thickness of 152 mm has an insulation value of R42, with a layer thickness of 76 mm an insulation value of R21. The paper-based and thermoplastic-based fabrics exhibit approximately the same insulation values. From this it is seen; borrowed that a foam layer with a thickness of more than 76 to 102 mm does not provide any economically significant additional insulation for most applications. In particular in the case of the paper-based fabric, a very thick layer would be needed to make a self-supporting insulating To create structure, i.e. a structure that can support its own weight and the weight of a later applied Layer could support. Although the foamed or expanded polymeric materials compared to the insulating materials on the basis of paper have an increased strength,

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These fabrics are also comparatively expensive when used as a load-bearing fabric for making a self-supporting Form can be used. When used in optimal quantities, foamed or polymeric materials are very effective and economical as insulating materials.

In summary, it can be stated that the inventive insulating layer 14 acts as a damping layer on the air form 12 and a later application of heavier, load-bearing materials are permitted. The insulating layer 14, however, is not primarily intended for the load-bearing capacity of the structure contribute and should not wear layers applied later. After the load-bearing layer 16 has been applied and is cured, the insulating layer 14 is used to isolate the structure 10 with respect to its interior and to protect the inner load-bearing layer 16 from thermal shock, as explained below.

In general, the insulating materials can be sprayed on and then form a cured layer with a density of preferably less than 1200 kp / m, desirably less than 160 kp / m, most preferably less than 80 kp / m, a thermal conductivity of preferably less than 1.24 (cal / St cm cm ⁰ C), desirably below 0.62, preferably below 0.31, and a compressive breaking strength of usually below 14 kp / cm, mostly below 3.5 kp / cm. Of course, the strength of the insulation should be as high as possible, but sprayable high strength insulation is not readily available.

Finally, the load-bearing layer 16 is preferably made of a cementitious material, such as a hydraulic one Cement such as Portland cement, Grips cement, plaster of paris, stucco, etc. preferably in a sprayable form. Also the fabrics "Gunite" and "Shotcrete" manufactured according to protected processes can be used here. The cementitious substances can be used reinforced or without reinforcement. In the case of reinforced fabrics, the reinforcing material is

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-Jf- 271632b

preferably provided adjacent to the insulating layer 14, after which the zenient-containing substance on and around the reinforcing material is sprayed. Steel fibers are particularly suitable because they are sprayed on together with the cementitious substance can be.

In Pig. 1, a special interaction is achieved in that the insulating layer 14 is provided further outward relative to the cement-containing load-bearing layer 16. Zementhaitiger fabric is excellent as a supporting component of a structure, but suffer crazing and quality losses, when subjected to temperature cycles below ⁰ C, especially in the case of relatively thin layers. On the other hand, if the insulating layer 14 consists of the above-mentioned substances, it tends to melt and decompose when exposed to elevated temperatures. In the embodiment shown in Fig. 1, the development of a fire within the structure 10 would not affect the insulating layer 14 for a considerable period of time if the load-bearing layer 16 consists of a cement-containing material, since this is quite inert and resistant to the effects of heat. There must be a longer fire time before the cement-containing substance fails or allows enough heat to reach the insulating layer to destroy it. On the other hand, the insulating layer 14 protects the cementitious layer 16 against temperature cycles caused by the weather. Since the inside of the structure 10 has a constant temperature and since the cement-containing substance of the load-bearing layer 16 represents a considerable heat accumulator on the inner wall of the structure 10, the cement-containing substance forming the load-bearing layer 16 is effectively protected from harmful temperature cycles.

In addition to the reinforced and non-reinforced, preferably cement-based materials for the load-bearing layer 16, other known substances with a high level of pest

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keits: weight or strength: volume ratio used will. For example, glass fiber reinforced polymers or unreinforced polymers such as epoxies, polyesters and vinyl compounds are suitable, albeit the cost and effectiveness such load-bearing materials are generally less than the preferred cementitious materials. Although it is possible is to reinforce the insulating layer 14, the use of reinforcing materials is preferred, whether in Form of microparticles or macroparticles, to limit the supporting layer 16. Reinforcement is not only more effective, if it is applied to the fabrics forming the supporting layer 16, but reinforcing elements in the insulating Layer H can become thermal conduction paths. the Reinforcing substances can in any case be used in a known manner. In the case of polymer fabrics can be chopped Glass fibers are sprayed on.

The materials suitable for forming the supporting layer 16 are generally dense, strong, especially with regard to Compressive stresses, however, usually have a fairly high level of heat permeability. Cementitious substances, in particular Hydraulic types of cement such as Portland cement, plaster of paris, cement mortar, etc. are typical for such substances. A sprayable one Fabric is preferred, but different methods of application such as plastering can be used.

Such load-bearing materials should have a compressive strength of at least 35.2 kgf / cm, desirably at least 105 »5

ρ p

kp / cm, most preferably at least 352 kp / cm. In order to achieve such Pestigkeitswerte, fabrics bearing having a thermal conductivity (cal / St cm cm ⁰ C) of usually more than 1.86, but most of more than 6.2. Of course, such materials are also very dense, ie over 1600 kp / m. In this way, insulating materials and load-bearing materials are clearly different from each other.

Pig. 3 to 6 show further embodiments of the invention

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application, i.e. structure 10. Fig. 2 shows an enlarged Section of Fig. 1, wherein the air mold 12 forms the outer surface, followed by an intermediate insulating Layer 14 and an inner load-bearing layer 16. The embodiment according to FIG. 3 is the reverse of Fig. 2, however, has the disadvantage that the supporting layer 16 is exposed to temperature fluctuations. With some However, this embodiment may be desirable in certain applications be to make the outer surface of the structure 10 weather and abrasion resistant.

In FIGS. 4 and 5, structures 10 are shown in which the insulating layer 14 is provided outside and the supporting layer 16 is provided inside the air mold 12, or the insulating layer is provided inside and the supporting layer outside the air mold. The embodiments according to FIGS. 4 and 5 lead to more difficult construction conditions, while they offer hardly any functional advantages. These embodiments are only intended to demonstrate the versatility of the present invention.

In Fig. 6 a particularly complicated structure is shown both on the inner surface and on the outer surface insulating layers 14 are sprayed onto the air mold 12. Then it is applied to both the internal and the the outer insulating layer 14 has a load-bearing layer 16 applied to it. This structure is more difficult to manufacture, and two insulating layers H offer hardly any advantages over a layer with the summed layer thickness. However, for some applications it may be desirable, both on the inside and on the outside of the Structure 10 to have a supporting layer 16 each.

Depending on the environmental requirements for the structure 10, the air form 12, insulating layer (s) 14 and load-bearing layer (s) 16 can be provided in many combinations.

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The method for manufacturing the structure 10 is from FIG. 7 and 8 can be seen. As shown in Fig. 7, the air form 12 is inflated by means of a compressor 18, e.g. is by means of a hose 20 with a partially limited by the air form 12 cavity in connection. The air form 12 is inflated in this way, and it thus assumes a first stable shape. Although the level of internal pressure of the air shape 12 is determined by various circumstances

can be, an overpressure of 1.0 kp / m is generally sufficient in order to ensure the air mold 12 a stable, tensioned shape. The preferred one formed from a skin Airform 12, of course, has a force equal to the projected area of the airform 12 times the internal overpressure that occurs Kraft strives to solve the air mold 12 from the floor or a corresponding surface. But there are several possibilities to securely attach the air mold 12 to its base. Such possibilities are partly described in the USA patent 3,277,219 to Turner. This problem is avoided with a differently designed air shape 12.

After the air form 12 has been inflated, means are provided to keep a person in close proximity to the air form 12 preferred embodiment near the inside of the Air form 12-to let go. In the execution shown sbeispiel serves this purpose a lifting platform 24, which is operated by the Person can be controlled. Of course, a scaffold or similar device could also be used. The components of the insulating material are made in a known manner produced or mixed at a source 26, then pumped through a line 27 and sprayed onto the air form 12 through nozzle 30, to form the insulating layer 14. After the insulating layer 14 has been completely created, is the supporting layer 16, preferably - as shown in FIG. 8 - applied by spraying onto the insulating layer. The insulating layer 14, although not self-supporting, is used for spraying or some other type of application the supporting layer for stabilization and damping

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of the air form 12. As in the present invention, in contrast to known methods, the insulating layer 14 is not self-supporting enough to be used as a self-supporting form for the To serve the supporting layer 16, the compressor 18 must continue to operate even after the application of the insulating layer 14 will. At the beginning of the spraying of the load-bearing layer 16, it may be desirable to keep the air pressure within

of the structure 10 to an overpressure of approx. 75 kp / m, in order to thereby create the non-load-bearing insulating layer 14 to give an increased rigidity. Although in some embodiments an increased air pressure results in increased stress on the hold-down devices of the air mold 12 can lead, the weight of the insulating layer 14 and the load-bearing layer 16 are opposing forces to the releasing force at this connection level. Therefore: the more material in the form of insulating layer 14 or supporting layer 16 on the Structure 10 is sprayed on, the further the pressure within the structure 10 can be increased.

Although, as in Pig. 7 and 8, the insulating layer 14 is preferably sprayed onto the inside of the air form ^ like the load-bearing layer 16, it is easily possible to use the insulating layer 14 and / or spray the load-bearing layer 16 onto the outside of the air mold 12. Here, however, the spraying must be done Person with expensive means to be carried over the air form 12, and the value of the air form 12 as weatherproof Sheath for the insulating layer 14 is lost. On the other hand, when people are inside the closed air form 12 apply polymeric material, they must be equipped with breathing apparatus to protect against the vapors generated be.

In Pig. 9 is across the span of the structural dome in feet (= »0.305 m) the critical structure thickness in inches (= 2.54 cm) applied. The two straight lines apply to foamed insulation materials with densities of 0.032 and 0.064 kp / dm, respectively. The presented

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The conditions set are typical for a 50-Dome under the

It should be noted that the foamed material has to carry 53 »7 kgf / m of foam, load-bearing material, etc. Under these typical conditions, a given span in the area to the right of the corresponding straight line in the diagram is to be regarded as "non-load-bearing ^11. Large spans are therefore either non-load-bearing or require uneconomical thicknesses of insulating material in order for the foam itself and for a typical second load-bearing layer to ensure adequate support.

In summary, it can be said that the present invention results in a composite structure in which the special structural properties of the substances used, such as low density and low strength of the insulating fabric and high density and high strength of the load-bearing Substance that can be better utilized in the composite structure. So the insulating layer will not how this was previously the case, used as a supporting form for subsequent layers, but as a lighter, highly insulating form Substance that is only available in one for optimalization with these properties sufficient thickness is applied. Instead of focusing on the load-bearing capacity of the insulating layer can rely on the non-load-bearing insulating layer Layer-bearing materials are applied by maintaining or even increasing the air pressure within the air form will. As a result, dome-shaped buildings of large spans with optimal thicknesses of the insulating and load-bearing Layers can be produced in a simple, economical way.

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Claims (5)

Claims 1.) Method of making a composite structure by inflating an air mold, a layer of insulating The substance is sprayed onto the air mold and the sprayed-on insulating substance is allowed to harden, thereby characterized in that the structure consisting of air form (12) and insulating material also by maintaining a Excess air pressure within the structure during the application of a hardenable, load-bearing substance to the air mold (12) and insulating material formed structure is supported, with the excess air pressure within the composite Structure is maintained until the load-bearing fabric has cured and supports the structure. 2. A method for producing composite structures according to claim 1, characterized in that the load-bearing Substance is a hydraulic, cementitious substance. 3. A method for producing composite structures according to claim 1, characterized in that the load-bearing Fabric a polymeric fabric reinforced with glass fibers. 4. A method for the production of zueammenetzen structures according to claim 1, 2 and 3, characterized in that the cured load-bearing layer (16) has a compressive strength of has at least 35 kp / cm and a specific weight of more than 1600 kp / m. 5. A method for the production of zueammenetzen structures according to claim 1, 2, 3 and 4, characterized in that the Air pressure within the air mold (12) during the application of the insulating layer (14) and the supporting layer (16) on the air form (12) is increased. 709843/0911