Composite material with local hybrid reinforcement

Abstract

This utility model relates to design and technological solutions for increasing the local strength of composite materials in the area of ​​a hole. The technical result sought by the claimed utility model is to increase the local crushing strength of composite structures in the area of ​​fastener holes. This is achieved by forming a localized reinforcement zone in the area of ​​the hole between regular woven layers in the composite part using Tailored Fiber Placement (TFP) technology. The zone is divided into eight sectors in the form of triangular spirals, the apices of which point toward the center of the hole.Reinforcement is provided by a hybrid metal-composite material, comprising carbon fiber and metal wire, which exhibits high crushing strength and a greater deformation capacity than the fibers of the woven preform. This increases the composite material's ability to deform without failure in the hole area. The additional reinforcement zone also creates a region with an increased filling factor of the reinforcing material, further enhancing the material's crush resistance.

Description

[0001] This utility model relates to design and engineering solutions for increasing the localized strength of a composite material in the area of ​​a hole. This design and engineering solution, based on localized reinforcement with a hybrid metal-composite material comprising carbon fiber and thin metal wire, offers superior crush resistance and will improve the load-bearing capacity of the hole by increasing the crushing strength of the surrounding composite material under concentrated loads transmitted by fasteners.

[0002] A design and technological solution is known for increasing the strength of fastener holes in composite parts during their joining (Pedro J. Herrera-Franco, Gary L. Cloud 1992. Strain-Relief Inserts for Composite Fasteners - An Experimental Study, Journal of Composite Materials Volume 26, Issue 5 Pages: 751-768). This solution consists of a metal sleeve secured inside the composite body's hole using an adhesive bond. The metal sleeve increases the useful area of ​​the hole in the composite part, thereby allowing for uniform distribution of the load from the fastener.

[0003] The disadvantages of this design and technological solution are the possibility of destruction of the adhesive bond between the sleeve and the composite, after which the sleeve ceases to distribute the load evenly, an increase in the weight of the finished product if there are a large number of fastening points, as well as the complexity of manufacturing due to the addition of an additional gluing operation.

[0004] A design and technological solution is known for reinforcing holes for mechanical fasteners in products made of composite materials (Nasonov F.A., Morozov B.B., Bukharov S.V., Zinin A.V. 2018, Design and technical solution for reinforcing holes for mechanical fasteners in structural carbon fiber reinforced plastics using fiberglass bushings. Polymer composite materials and new generation production technologies. - Pp. 245-255.) This solution is a ready-made integrated composite bushing made of fiberglass with lower rigidity compared to the product material. The composite fiberglass bushing is installed using the thermocompression method and undergoes a mechanical processing operation as part of the finished product.

[0005] The disadvantage of this design and technological solution is the complex process of integrating the bushing into the mounting hole, as well as the relatively low strength of the fiberglass bushing itself.

[0006] A design and technological solution is known that makes it possible to strengthen holes in fiber-reinforced composite products (Patent Number: US4545837A USA Classifications B32B5 / 26, B29C70 / 545, B29C70 / 347, B32B5 / 28, Molded-in composite bushings : No. 499,699 May 31, 1983, Filed: Jan. 18, 1985). This solution is a composite bushing formed by tightly twisting impregnated fibers to form a plug in which the fibers are oriented around its axis. The formed plug is placed into a prepared hole in the impregnated composite preform and cured. After this, a hole is made in the molded blank.

[0007] The disadvantage of this design and technological solution is the lack of connection between the sleeve and the reinforcing frame of the composite part, which reduces its strength potential.

[0008] A design and technological solution is known that relates to methods for reducing stress concentration in structures made of fiber composites in the areas of fastening holes (Polilov A.N. 2014. Mechanisms for reducing stress concentration in fiber composites / / Applied mechanics and technical physics. Vol. 55. - No. 1. - Pp. 187-197.) This solution is a method for reducing stress concentration around the hole by using a curvilinear envelope of the laying of reinforcing fibers of the preform around it, thereby ensuring a rational distribution of stresses around the hole.

[0009] The disadvantage of this method is the risk of formation of zones with increased resin content and voids after molding, which significantly reduces the strength of the material.

[0010] This design and technological solution is closest to the declared utility model and is accepted as a prototype.

[0011] The problem is the low local crushing strength of composite structures in the area of ​​holes for fasteners.

[0012] The technical result that the claimed utility model is aimed at achieving is to increase the local crushing strength of structures made of composite materials in the area of ​​holes for fasteners.

[0013] The technical result is achieved by forming a localized reinforcement zone in the hole area between regular woven layers in the composite part using Tailored Fiber Placement (TFP) technology. This zone is divided into eight sectors in the form of triangular spirals, the main lines of which are directed toward the center of the hole. The reinforcement is a hybrid metal-composite material consisting of carbon fiber and metal wire, which has high crushing strength and a greater deformation capacity than the fibers of the woven preform, increasing the composite material's ability to deform without fracture in the hole area. The additional reinforcement zone also creates an area with an increased filling factor of the reinforcing material, further enhancing the material's ability to resist crushing.

[0014] The essence of the utility model is shown in Fig. 1-4, where:

[0015] Fig. 1 – example of a laying pattern of layers of a composite blank with local reinforcement with hybrid roving on each layer: n – layer number, 1 – hybrid roving laid in a triangular spiral pattern over 8 sectors of a circle, 2 – layers of woven fibrous material; Fig. 2 – molded composite blank with local reinforcement: 3 – consolidated plate with local reinforcement around the hole, 4 – fastener; Fig. 3 – connection of a composite, locally reinforced with hybrid roving, with a metal plate using a fastener: 5 – composite product, 6 – zone of reinforcement with hybrid roving, 7 – bolt, 8 – nut, 9 – metal plate (theoretical part that must be connected to the composite product), Fig. 4 – microstructure of hybrid roving of one of the sectors: 10 – carbon fibers, 11 – metal wire.

[0016] Using Tailored Fiber Placement (TFP) technology, a pattern of densely packed triangular spirals, arranged in eight sectors of a circle, is formed from hybrid roving between layers of the dry preform (2) of the future composite product in the area where the hole will be made. The main lines of these spirals are directed toward the center of the future hole. The hybrid roving, in turn, consists of metal wire (11) and carbon fibers (10). The number of preform layers (n), the density of the triangular spiral sectors (1), and the diameter of the reinforcement zone (6) are selected taking into account the product configuration, thickness, and the loads the structure will withstand. After the final appearance of the preform is formed, the dry preform is impregnated with polymer resin and cured.The process of joining a composite product having local reinforcement with a hybrid metal-composite material to another part, for example a metal plate, will be as follows: the composite product (5) is drilled through in the center of the reinforcement zone with hybrid roving (6), a fastening element, for example a bolt (7), is installed in the formed hole, then a metal plate (9) is attached and a nut (8) is tightened.

Claims

1. A composite material with local hybrid reinforcement consisting of woven layers including a local reinforced area around an opening located in the woven layers, characterized in that the local reinforcement is a hybrid roving made in the form of a pattern of triangular spirals laid out in 8 sectors of a circle, the vertices of which are directed towards the center of the circle.

2. The material according to paragraph 1, characterized in that the hybrid roving is a hybrid metal-composite material.

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