RU2479432C1 - Method of making bicurved laminar composite shell - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to ship building etc, particularly, to production of bicurved shells from laminar composites including layers from high-elasticity polymers. Said shell has outer layers of elastomer and interlayers of composite alternating with elastomer layers. Proposed method comprises forming elastomer and composite layers in turn and cutting produced stack. Note here that, first, flat plate from undercured elastomer is cut into strips. Note also that said strips are laid line-on-line in paired layers into tooling. In one layer, strips are arranged parallel with one line of primary curvature extending nearby shell surface centre while, in another layer, strips are located parallel with second line of primary curvature unless preset thickness of elastomer is reached. Then, polymer composite layer is formed, and so on unless preset shell thickness with alternating layers is ensured. Now, produced sandwich is cured.

EFFECT: higher homogeneity and strength, simplified procedure.

6 cl, 3 ex

Description

FIELD OF TECHNOLOGY

The invention relates to shipbuilding and other engineering industries, where products are used in the form of double-curvature shells of reinforced polymer matrix composites with coatings or intermediate layers of elastomers.

BACKGROUND

The traditional method of coating an elastomer with a small coating thickness is spraying. Thick-walled coatings are applied by gluing cured coating elements in the form of flat squares or rectangles. To hold the coating elements on the surface of shells of double curvature until the adhesive layer hardens, special devices are used, and the cavities formed between the glued elements require filling with the same material as the elastomer used to make the coating, or with special sealant.

The disadvantages of this method of coating are: high complexity associated with the installation and dismantling of devices that hold the coating elements in a curved state corresponding to the surface of the product, until the adhesive has cured; small sizes and, therefore, a large number of elements; the need for additional operations to fill the voids.

Another disadvantage of this method of coating is the occurrence of residual stresses in the adhesive joint. In addition, the material for filling the voids usually has properties that differ from the properties of the coating, which creates a heterogeneity of the latter.

Closest to the proposed is the method of forming a coating (shell), disclosed in EP 2014452 A1, which consists in the fact that according to this method, the coating (shell) is made up of a large number of tapes of a predetermined length and width. Tapes are applied in turn, one after another, at a slight angle to each other. The disadvantage of this method is that during application, voids may occur between the coating elements.

DESCRIPTION OF THE INVENTION

The objective of the invention is to provide a coating method that minimizes residual stresses, eliminates voids between the coating elements and reduces the complexity of installation.

This problem is solved using the proposed method for manufacturing a multilayer composite shell of double curvature.

The technical result of the invention lies in the fact that no empty voids form between the strips, the coating does not require processing of the surface on which it is applied, and the use of adhesives and sealants is not required.

According to one embodiment of the invention, a method for manufacturing a multilayer composite shell of double curvature with outer layers of a highly elastic polymeric material - an elastomer and intermediate layers of a polymer matrix composite material, which alternate with layers of an elastomer, including the steps of alternately molding in the technological equipment of the layers of the elastomer and layers of the composite material and curing of the collected package, and

first, a flat plate of the uncured elastomer is cut into strips, stacked end-to-end in pairs in layers, in one of which the strips are parallel to one line of the main curvature that runs near the center of the shell surface, and in the other, parallel to the second line of the main curvature until the specified elastomer layer thickness and then form a layer of polymer composite material, and so on until the full thickness of the shell with a given alternation of layers is obtained, after which the specified material is cured with after-cure elastomeric layers.

According to one embodiment of the invention, the snap is placed so that the normal to the surface near its center is close to the vertical.

According to another embodiment of the invention, the formation of an elastomer layer begins with a strip located near the center of the surface of the shell, having the following stripes on different sides of the first strip.

According to a further embodiment of the invention, the elastomer strip is made having a thickness that is a multiple of half the thickness of its layer in the shell, and cut into strips with a width of 1/10 to 1/20 of the smallest radius of curvature of the shell.

According to another embodiment of the invention, the first strip in each pair layer is laid in sections with maximum curvature.

According to one preferred embodiment of the invention, the elastomer is a foamed paraoxybenzoic acid oligoester or polyurethane. Other suitable foamed polymers may be selected by one of ordinary skill in the art from known polymeric materials suitable for the purposes of the present invention.

When applying a coating or an intermediate layer of a multilayer shell made of composite material in the form of strips of an uncured material, the occurrence of residual stresses in the compounds that relax during the post-curing process is excluded.

Stacked layers take the form of the surface of the matrix or the previous layer due to the highly elastic deformation (fluidity) of the uncured material. For the same reason, voids do not occur between adjacent layers. The location of the strips in the directions of the main curvature of the shell prevents or reduces their curvature in the plane of the strip during laying and curing and sliding along the surface of the shell. For the same purpose, the formation of the shell begins with a strip passing through the center of the surface of the shell. Located on both sides of the central strip are pressed against it by gravity.

The location of the strips in two mutually perpendicular directions eliminates the coincidence on a significant length of the boundaries between the strips.

The width of the strip is selected from the conditions of convenience of its laying and the possibility of deformation along the surface of the shell without expansion. The advantage of foamed polyurethane and paraoxybenzoic acid oligoesters is their high sound absorption capacity and the possibility of curing simultaneously with the curing of the composite.

EXAMPLES

The above description can be better understood with the help of the following examples, intended to illustrate and not limit the scope of the invention.

Example 1

Obtaining a multilayer composite shell by forming a coating 16 mm thick from a foamed paraoxybenzoic acid oligoester with a hardener on a fiberglass shell having a hemisphere shape of 22 mm thick.

The radius of curvature of the shell was 1.5 m, size 3 × 3 m. The matrix for the manufacture of the shell was set so that in its center the normal to the tangent plane is vertical.

The oligomer-hardener mixture was applied onto a 2 × 2 m flat glass or metal plate previously treated with a release agent. The layer of the mixture in the foamed state should be 4 ± 0.5 mm. Then the mixture was kept at a temperature of + 60 ° C for 2 hours. Next, the resulting semi-cured plate was cut into strips 100 mm wide, which were laid on the matrix in parallel, starting from the center line. Then the process was repeated 3 more times, and in the 2nd and 4th case (2nd and 4th repeat), the bands were laid in the direction perpendicular to the first, and in the 3rd case - parallel to the first.

The formed product was cured according to the regime necessary for curing fiberglass: holding at a temperature of 80 ° C for 8 hours and at a temperature of 140 ° C for 2 hours to obtain the finished product.

Example 2

The coating was formed on the fiberglass shell similarly to Example 1, and then additionally applied the inner coating layer according to the method described in Example 1.

Example 3

The coating was formed on a fiberglass shell similarly to Example 1 with the difference that foamed polyurethane was used as the coating material.

For the obtained multilayer composite shells, defects in the form of voids on the line of the joints of the strips, between the coating layers and between the coating and the shell were not detected during ultrasonic inspection. Residual stresses by notching the coating were not identified.

The complexity of obtaining coatings compared with gluing elements of size 500 × 500 mm and a thickness of 16 mm is reduced by 40-50%.

The above results show that the multilayer composite shell obtained by the method according to the present invention is characterized by the absence of detectable residual stresses and the absence of voids between the coating elements, while the labor required to install the shell elements is almost halved.

Preferred embodiments of the proposed method are described below in the dependent claims.

Claims (6)

1. A method of manufacturing a multilayer composite shell of double curvature with the outer layers of a highly elastic polymer material - elastomer and intermediate layers of a polymer matrix composite material, which alternate with layers of elastomer, which includes alternating operations in technological equipment of the layers of elastomer and layers of the composite material and curing the collected package wherein, first, a flat plate of an uncured elastomer is cut into strips, characterized in that
the strips are laid end-to-end in rigging in pairs of layers, in one of which the strips are parallel to one line of the main curvature, passing near the center of the shell surface, in the other, parallel to the second line of the main curvature until a specified thickness of the elastomer layer is set, and then a layer of polymer composite material is formed, and so until the full thickness of the shell is obtained with a predetermined alternation of layers, after which the specified material is cured with additional curing of the elastomeric layers. 2. A method of manufacturing a multilayer composite shell of double curvature according to claim 1, characterized in that the snap is placed so that the normal to the surface near its center is close to the vertical. 3. A method of manufacturing a multilayer composite shell of double curvature according to claim 1, characterized in that the formation of an elastomer layer begins with a strip located near the center of the surface of the shell, placing the following stripes on different sides from the first strip. 4. A method of manufacturing a multilayer composite shell of double curvature according to claim 1, characterized in that the elastomer strips are made having a thickness that is a multiple of half the thickness of its layer in the shell, and cut into strips with a width of 1/10 to 1/20 of the smallest radius of curvature of the shell. 5. A method of manufacturing a multilayer composite shell of double curvature according to claim 1, characterized in that the first strip in each pair of layers is laid in sections with maximum curvature. 6. A method of manufacturing a multilayer composite shell of double curvature according to claim 1, characterized in that the elastomer is a foamed paraoxybenzoic acid oligoester or polyurethane.