RU2416844C1 - Method of making dielectric cowling - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: layers of Optex glass fabric saturated with binder based on polysaturated resin are successively worn on a special form and fibre glass filament is wound on top of each packet consisting of two layers of glass fabric except the last. Winding is done from top to bottom while increasing the winding spacing from 5 to 16 mm, and final moulding is carried out in a drying cabinet at temperature not higher than 50°C.

EFFECT: method increases strength, wear resistance, reduces polythickness of the walls of the cowling, increases resistance to breakdown due to biocorrosion.

Description

The invention relates to the manufacture of fiberglass fairings for fuselage antennas designed to protect printed circuit boards of antennas from aerodynamic, mechanical impact, as well as from moisture and solar radiation on electrical circuits of emitting and receiving antennas.

A known method of manufacturing fairings made of fiberglass [B.A. Prigoda, B.C. Kapunko. Aircraft fairings. M .: Engineering, 1970], consisting of the preparation of fiberglass and binder. To do this, first remove the sizing from the fiberglass, then it is cut for subsequent gluing on a special form that repeats the shape of the product. Then the fiberglass cutting is applied to the mold and impregnated with a binder. A set of fiberglass fabric by this method allows further formation of the product without high pressure. In addition, this method facilitates the laying of fiberglass on the mold. However, it also has significant drawbacks: the duration of the molding process, difficult working conditions for staff, a significant variation in the physical and mechanical properties of the finished product, even when using fiberglass and a single batch of binder.

Closest to the proposed invention is a method consisting in the fact that the fiberglass is impregnated, dried, cut and then laid on the form [B.A. Prigoda, B.C. Kapunko. Aircraft fairings. M.: Mechanical Engineering, 1970]. The final molding occurs by pressing the laid layers of fiberglass impregnated with a binder, by applying pressure to the surface of the formed product. This is achieved, for example, by heating in a vacuum bag.

However, it was experimentally established that molding in a vacuum bag does not provide uniform distribution of the binder over the surface of the product, resulting in a displacement of the layers relative to each other and the formation of folds, especially in places of bending. It was found that if the fabric is dense, for example, type T-10-80 (GOST 19170-2001), the binder is extruded into the lower part of the molded product. If the fabric is less dense, the binder is squeezed out through the gaps between the threads of the fabric to the surface, while there is a decrease in the content of the latter between the layers and the delamination of the layers of fiberglass in the finished product.

It was also found that molding (pasting) of a dielectric fairing, for example, with a wall thickness of 4 mm, lasts 14 days, and fiberglass itself based on phenol-formaldehyde or epoxy, for example vinyl-fiber (VFT polyvinyl formaldehyde resin - TU 2257-047-05015227-2003) and fiberglass T-10-80 is not mushroom resistant, therefore, during operation, especially in a humid environment, it will be destroyed.

The objective of the invention is to reduce the complexity, manufacturing time of the dielectric fairing, increase the mechanical and operational characteristics, giving it mushroom resistance.

The specified technical result is achieved by the fact that in the method of manufacturing a dielectric fairing, including the sequential application of fiberglass to a special form, impregnation with a binder and molding, an adhesive composition based on a polyunsaturated resin is used as a binder, and Optex fiberglass is used as a forming fiberglass, the adhesive composition put on top of each layer of fiberglass, and on top of each bag, consisting of two layers of impregnated fiberglass, wrap glass, while winding carried out from top to bottom with an increase in the gap between the turns from bag to bag from 5 to 16 mm, the final molding is carried out in an oven at a temperature not exceeding 50 ° C, and the glass fiber is not wound onto the last bag of fiberglass.

The method is as follows. A release coating and a fiberglass bag, for example, Ortex, are successively applied to the surface of the conical shape, each layer of which is impregnated externally with a polyunsaturated resin adhesive, for example PN-1 (GOST 27952-88), and then glasswound with a coil spacing of 5 mm is wound. Withstand in air for 30 minutes, after which the process of laying, impregnation and winding is repeated to a predetermined thickness. The last (outer) two layers of fiberglass are laid without winding. The final molding of the product is carried out in an oven at a temperature not exceeding 50 ° C for two hours. The time of complete molding of the product (fairing) with a wall thickness of 4 mm is 3 days.

It was experimentally established that the tensile strength of the walls of a fairing with a thickness of 4 mm is 30% more than that of a prototype of a similar thickness. The unevenness of the walls in thickness is not more than 4-5%, fiberglass delamination and the formation of wrinkles in the molded product, unlike the prototype, are absent. It was also established that fiberglass made from polyunsaturated resin and Ortex fiberglass is not biocorrosed, has mushroom resistance [GOST 9.049-91 “Polymer materials and their components”, method 1]. It has been established that if the temperature in the drying cabinet is higher than 50 ° C, the polymerization reaction of the adhesive composition occurs with very strong self-heating and the formation of air bubbles in the molded product.

Reducing the distance between the turns of glass fiber less than 5 mm does not increase the tensile strength of fiberglass, while increasing the consumption of glass fiber.

An increase in the distance between the turns of more than 16 mm leads to a decrease in the tensile strength of fiberglass.

It was experimentally established that in the manufacture of a dielectric fairing with a wall thickness of 4 mm according to the above method, but using a adhesive composition based on phenol-formaldehyde or epoxy resin lasting 20 days, folds form on the walls, air bubbles are present in the hardened adhesive composition, it has fiberglass stratification place.

Claims (1)

A method of manufacturing a dielectric fairing, comprising sequentially applying fiberglass to a special form, impregnating with a binder and molding, characterized in that the adhesive composition based on the polyunsaturated resin is used as the binder, and Optex fiberglass is used as the forming fiberglass, the adhesive composition being applied on top of each layer fiberglass, and on top of each bag, consisting of two layers of impregnated fiberglass, wrap glass fiber, while winding is carried out from top to bottom with an increase the gap between the turns from packet to packet 5 to 16 mm, the final molding is carried out in an oven at a temperature of not higher than 50 ° C, and the last packet is not wound fiberglass and fiberglass.