Manufacturing process for waste fiber-reinforced multifunctional sandwich composites

Abstract

The present invention relates to a manufacturing process for waste fiber-reinforced multifunctional sandwich composites, developed as a solution to the problems encountered in prior art applications involving the use of waste material, the joining of the structure with out-of-plane seams, the toughness and energy absorption obtained by the high-performance p-aramid fibers for the structure, and the thermal / acoustic insulation properties provided by PU (polyurethane) foam and waste fiber filling, characterized in that it comprises the process steps of transferring p-aramid into a cut form, mixing polyol and cut p-aramid fibers in predetermined ratios using a mechanical mixer and / or ultrasonic mixer, adding isocyanate to the mixture in predetermined ratios, and coating the molds with non-stick Teflon as a result of introducing the mixture into the molds.The process includes shaping the mixture at predetermined temperature, time, and pressure, and manufacturing the core structure of the sandwich composite; aligning the edge fringes for the bottom surface of the sandwich composite; placing the manufactured core structure on the aligned edge fringes; aligning the edge fringes for the surface of the sandwich composite; fixing the structure with aligned edge fringes on the bottom surface; placing the core structure in the middle layer and aligned edge fringes on the surface on the frame; infusing the matrix material into the fixed frame; curing the matrix material and removing the structure from the mold; drilling holes in the sandwich composite; inserting the perforated sandwich composite into the robotic sewing frame and performing the sewing process; and coating and curing the sewing threads with a polymer matrix during or after sewing.

Description

Technical field:

[0001] The present invention relates to a manufacturing process for waste fiber reinforced multifunctional sandwich composites, which was developed as a solution to the problems that arise in prior art applications involving the use of waste material, the joining of the structure with out-of-plane seams, the toughness and energy absorption obtained by the high-performance P-aramid fibers for the structure, and the thermal / acoustic insulation properties provided by PU (polyurethane) foam and waste fiber filling. State of the art:

[0002] Sandwich composite materials consist of a thin, stiff and robust outer surface and a thick, low-density core material between these outer surfaces.

[0003] Sandwich composite materials present problems such as high cost, loss of structural integrity due to delamination, especially under impact loading, low damage tolerance, and the need for additional materials for sound and heat insulation. Due to the high cost of sandwich composite components, the cost of the final product is also high, limiting its widespread use.

[0004] In sandwich composites, there are no bonding elements between the outer surface and the core structure other than polymeric adhesives. Weak structural components and honeycomb-like materials, which can be made from raw materials such as foam, aluminum, Nomex, and polypropylene (PP) as core material, or corrugated structures or unreinforced foam fillers, reduce damage tolerance in sandwich composites. Furthermore, the absence of an out-of-plane component joining the sandwich structure and / or the absence of fiber reinforcements in the core structure reduces damage tolerance, with an increasing effect on delamination.

[0005] Sandwich composites generally transfer the insulating properties of the core structure to the final product, making the insulating properties of the core material crucial. It is known that honeycomb core structures or various polymeric foams without fibrous additives do not provide sufficient insulation. This leads to the problem that the finished sandwich composite does not offer the desired insulating properties when additional material is required, resulting in a functionally inadequate product that incurs further costs and increases factors such as thickness / volume in the application area.

[0006] Sandwich composites, manufactured by companies using state-of-the-art technology, are materials with low mechanical strength and impact resistance, primarily used for insulation purposes in the construction sector. These materials typically incorporate foams such as various PUs and XPS in the core, while lightweight metals like aluminum are used on the outer surface. The concept of sandwich composites is evolving due to the need for multifunctional and high-performance materials, particularly in the defense industry. Although a small number of companies worldwide are attempting to develop specific products tailored to the properties required by their application, this is insufficient, and the desired performance cannot always be achieved.Because high-performance sandwich composites are inherently expensive due to the specialized nature of their components for the performance expected in their application, their widespread use in other sectors is limited. The sandwich composites used in this context are manufactured using honeycomb core structures or forms filled with various foams and fiber-reinforced polymer composites on the outer surface. They are produced by a limited number of manufacturers worldwide, and it is not entirely clear whether production adheres to the stated definition.

[0007] Patent application number TR199900507 describes "polyurethane composite sandwich terrace roof panels with a single-sided membrane". The sandwich roof panel with membrane is manufactured by spraying polyurethane between formed aluminum or galvanized sheet metal and a waterproof, flexible PVC film (membrane) reinforced with polyester fabric.

[0008] The patent application described above mentions a sandwich-style patio roof panel made of polyurethane composite material with a membrane on one side. The sandwich roof panel, produced by adding polyurethane foam to a plastic-based surface reinforced with aluminum or galvanized sheet metal and polyester, is a structural invention. The product is intended to make the 1.8 mm thick waterproof soft roofing lighter and easier to install. However, the galvanized sheet metal used in this application oxidizes its protective layer over time, corroding to white or gray, moldy residues, which is detrimental to the application.

[0009] “Impact response of sandwich composites with p-aramid (Kevlar ®The invention of the "waste fibre reinforcement" was presented by the inventor at AUTEX 2022 - 21st WORLD TEXTILE CONFERENCE. This paper presents a limited selection of the impact strength properties of the seamless forms of the sandwich composite materials according to the invention.

[0010] Similar topics were addressed by the inventor in Development of Multifunctional Sandwich Composites with Para-Aramid (Kevlar) ® ) Fibre Wastes, ISADET 2022 - International Symposium on Advanced Engineering Technologies. This paper presents a limited content (mechanical and insulating properties) of the seamless forms of the sandwich composite materials according to the invention.

[0011] Therefore, there is a need for a new manufacturing process for sandwich composites that can overcome the aforementioned disadvantages, in which the core structure is developed, the insulation is reinforced, and it is lightweight, durable, and cost-effective. Definition of the invention:

[0012] The present invention is a manufacturing process for waste fiber reinforced multifunctional sandwich composites, characterized in that it is a new manufacturing process for sandwich composites in which the core structure is improved, the insulation is enhanced, and the material is lightweight, durable and cost-effective.

[0013] To achieve the aforementioned objectives and the following detailed description, the invention relates to the production of sandwich composite materials by filling honeycomb-shaped cardboard core structures made of 100% recycled paper with polyurethane (PU) foam reinforced with p-aramid waste fibers in different ratios, and also to joining polymeric composite surface materials reinforced with p-aramid fibers (edge ​​fringes from textile waste) using out-of-plane sewing methods.

[0014] The invention relates to the production of a new sandwich composite material for use in various industrial sectors such as defense, automotive, energy, marine, construction, and aerospace, in order to improve insulation, increase strength, and solve problems that the current state of the art cannot solve.

[0015] The sandwich composites that are the subject of this invention exhibit high performance thanks to their independent approach to waste recovery, low cost, and engineered design. The sandwich composite comprises the consolidation of weaving process waste in the form of edge fraying on the outer surfaces, as well as the entire sandwich composite, with polymer matrix materials. Preferably, thermosetting epoxy, polyester, vinyl ester, etc. polymer matrix materials can be used.

[0016] This invention addresses a deficiency in the area of ​​waste recovery by producing a sandwich composite material from waste generated during the weaving of high-performance p-aramid fibers, which must be disposed of without being used for any purpose. Furthermore, by ensuring that the cardboard core structure obtained from recycled paper is not used in a value-adding sector, a deficiency in this sense is also eliminated.

[0017] The invention enables an improvement in the damage tolerance of sandwich composites by joining the core and outer surfaces through out-of-plane stitching. Compared to seamless sandwich composites, these stitched composites exhibit higher impact strength and retain their structural integrity. The stitching increases the flexural and compressive strength of the sandwich composites. Fiber reinforcement in the core structure enhances the structure's damage tolerance in impact compressive strength tests, improves impact energy absorption, ductility, and sound and thermal insulation.

[0018] The structural and characteristic features and all the advantages of the product according to the invention are better understood thanks to the drawings below and the detailed description which was prepared with reference to these drawings, so that the evaluation should be carried out taking these drawings and the detailed description into account. Description of the invention:

[0019] The invention comprises the process steps of transferring p-aramid into a cut form, mixing polyol and cut p-aramid fibers in predetermined ratios using a mechanical mixer and / or ultrasonic mixer, adding isocyanate to the mixture in predetermined ratios, coating the molds with non-stick Teflon after the mixture is introduced into the molds, forming the mixture at predetermined temperature, time, and pressure, and producing the core structure of the sandwich composite, aligning the edge fringes for the bottom surface of the sandwich composite, placing the produced core structure on the aligned edge fringes, aligning the edge fringes for the surface of the sandwich composite, fixing the structure with aligned edge fringes on the bottom surface, core structure in the middle layer and aligned edge fringes on the surface on the frame, and infusing the matrix material into the fixed frame.Curing of the matrix material and removal of the structure from the mold, drilling of holes in the sandwich composite, insertion of the perforated sandwich composite into the robot sewing frame and execution of the sewing process, coating and curing of sewing threads with polymer matrix during or after sewing.

[0020] The predetermined ratios in the invention are as follows: polyol / isocyanate in a ratio of 1 / 1.20 wt., p-aramid in the range of 0.1-50 wt.%, p-aramid in the size range of 1-20 mm, the mixture of polyol, isocyanate and p-aramid is kept at a temperature in the range of 20-25°C, the mixture of polyol, isocyanate and p-aramid is kept in the range of 30-90 minutes and under a pressure in the range of 4-6 bar.

[0021] According to the invention, the edge fringes are aligned on the top and bottom surfaces of the sandwich composite material. The core structure in the middle layer of the sandwich composite material has a honeycomb size in the range of 12-20 mm. The core structure in the middle layer of the sandwich composite material has a honeycomb height in the range of 10-20 mm. The core structure in the middle layer of the sandwich composite material has a fiber content of 2-10 wt.%.

[0022] The number of layers on the outer surface of the sandwich composite material is 1-10. The outer surface of the sandwich composite material has an orientation of 0 / 90°. The seam of the sandwich composite material has a seam spacing of 12-20 mm. The seam of the sandwich composite material has a hole diameter of 4 mm. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Impact response of sandwich composites with p-aramid (Kevlar ® ) waste fibre reinforcement” was presented by the inventor in this area at AUTEX 2022 - 21st WORLD TEXTILE CONFERENCE

[0009]

Claims

[1] Manufacturing process for waste fiber reinforced multifunctional sandwich composites, characterized by that it includes the following process steps - Converting p-aramid into trimmed form, - Mixing polyol and cut p-aramid fibers in predetermined ratios using a mechanical mixer and / or ultrasonic mixer, - Addition of isocyanate to the mixture in predetermined proportions, - Coating of the molds with non-stick Teflon as a result of the mixture being placed in the molds, - Shaping the mixture at predetermined temperature, time and pressure and producing the core structure of the sandwich composite material, - Alignment of the edge fringes for the underside of the sandwich composite material, - Placement of the manufactured core structure on the aligned edge fringe, - Alignment of the edge fringes for the surface of the sandwich composite material, - Attachment of the structure with aligned edge fringes on the underside, core structure in the middle layer and aligned edge fringes on the surface of the frame, - Infusion of the matrix material into the fixed frame, - Curing of the matrix material and removal of the structure from the mold, - Drilling holes in sandwich composite material, - Inserting the perforated sandwich composite material into the robot sewing frame and carrying out the sewing process, - Coating and curing of sewing threads with a polymer matrix during or after sewing. [2] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by , that predetermined ratios of polyol / isocyanate are added in a ratio of 1 / 1.20 wt. [3] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by, that predetermined ratios of p-aramid in the range of 0.1-50 wt.% are used. [4] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by , that p-aramid is added in predetermined ratios in a size range of 1-20 mm. [5] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by that the mixture of polyol, isocyanate and p-aramid is kept in predetermined ratios at a temperature in the range of 20-25°C. [6] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by that the mixture of polyol, isocyanate and p-aramid is held in predetermined ratios for 30-90 minutes. [7] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized bythat it is kept under pressure in the range of 4-6 bar in predetermined conditions. [8] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by that the edge fringes are aligned on the top and bottom surfaces of the sandwich composite material. [9] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by , that the core structure in the middle layer of the sandwich composite material has a honeycomb size in the range of 12-20 mm. [10] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by , that the core structure in the middle layer of the sandwich composite has a honeycomb height in the range of 10-20 mm. [11] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by, that the core structure in the middle layer of the sandwich composite material has a fiber content in the range of 2-10 wt. [12] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by , that the number of layers of the outer surface of the sandwich composite material is 1-10. [13] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by that the outer surface of the sandwich composite material has an orientation of 0 / 90°. [14] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized by that the seam of the sandwich composite material has a seam spacing of 12-20 mm. [15] Manufacturing process for waste fiber reinforced multifunctional sandwich composites according to claim 1, characterized bythat the seam of the sandwich composite material has a hole diameter of 4 mm.