Honeycomb composite panel

Abstract

The invention relates to a honeycomb composite panel cured with biobased furan resin.

Description

[0001] DESCRIPTION

[0002] HONEYCOMB COMPOSITE PANEL

[0003] Technical Field

[0004] The invention relates to a honeycomb composite panel cured with biobased furan resin.

[0005] State of the Art

[0006] For years, the concept of light weight has been a key element in promoting the use of polymer composites in the transport sector. Composites are complex materials because reinforcement, resin and additives can be combined in numerous ways to provide the optimum combination of properties required for a particular application. Many different machining methods are also available for turning materials into parts. This means that in order to develop composites, it is necessary to approach their development from different perspectives, considering the initial raw materials, the transformation process, and the possibilities of recycling at the end of their life cycle. Today, various factors such as increasing environmental awareness, legal pressures, depletion of fossil fuels and price increases lead to the search for new sustainable composites for the development of conventionally made products. The overall benefits of these sustainable composites can be listed as the use of naturally sourced and renewable materials with the traditional advantages associated with composites, as well as lightness, flexibility in part design and reduction in production costs. One of the biggest current limitations of composites is the applications that make it necessary to investigate flame retardant strategies that enable their use in different applications and sectors.

[0007] Honeycomb composite panels in the state of the art are obtained by dipping and curing kraft papers into phenolic resins. Phenol is a petroleum derivative and therefore its price depends on petroleum. Also, phenolic resins are not sustainable. Carbon emission is very high during its production and causes toxic formaldehyde release when used as a resin.

[0008] Furan resins are thermosetting resin systems obtained from the acid hydrolysis of natural resources such as agricultural by-products (pulp, oatmeal, corncob, cotton seed, sugarcane). These resins are the product of acid-catalyzed linear condensation of furfuryl alcohol (FA) or other condensates containing furan rings, and their polymerization is supported by heat. Furan resins exhibit high thermal stability and chemical resistance compared to other thermosetting resins. Other advantages of furan resins include the absence of organic solvents, good storage stability, and eco-sustainability as they are obtained from biomass. In addition, the fire behavior of furan resins is noteworthy, as they have little tendency to emit fumes due to their dense charring. When furan matrix composites are exposed to fire due to their high aromatic content, 40% of the resin surface turns into a carbonaceous barrier that acts as a thermal barrier, unlike polyester resins with 5-10% conversion in the carbonaceous layer. In addition, furan resins can be converted by microwave radiation, as they have OH groups in their chemical structure. This fact constitutes a significant advance in composite processing technologies as it will reduce cycle times and control resin hardening.

[0009] Detailed Description of the Invention

[0010] The invention relates to a honeycomb composite panel developed using furan resin obtained from sugar cane wastes. The main object of this development is to eliminate the disadvantages of phenolic resins and the negative consequences they cause.

[0011] Restrictions on the use of phenolic resin are imposed by the US Environmental Protection Agency (EP A) and San Diego Air Pollution Control Area (APCD) legislation and these restrictions are expected to increase in the future. Therefore, the invention was developed by using furan resin, which is a greener and sustainable material, in the honeycomb composite panel, which is widely used in the industry.

[0012] Since furan resins do not release formaldehyde and organic solvent to nature, such as phenolic resins, they are advantageous for both the environment and the health of the producer.

[0013] Formulation

[0014] The content of the furan resin used in the production of the honeycomb composite panel of the invention is given below in preferred weight ratios.

[0015] Poly (furfuryl alcohol): 40-90%

[0016] Solvent: 5-10%

[0017] Ethoxylated polydimethylsiloxane : 1-10%

[0018] Curing Agent: 1-5%

[0019] It is necessary to dilute the resin viscosity to make the honeycomb production suitable for the immersion method. Preferably, water was used as the solvent for this purpose. Ethoxylated polydimethylsiloxane (CAS: 67674-67-3) was used as a wetting agent.

[0020] Method The poly (furfuryl alcohol) resin, whose viscosity is specifically optimized for honeycomb production, is mixed in the above-mentioned ratios until the water is homogeneous with Ethoxylated polydimethylsiloxane and the curing agent used as a cross linker, respectively.

[0021] After the formulation is completed, additions are made to the immersion tanks. The honeycomb is immersed in the resin of the invention. The honeycomb, which is left to dry after the immersion process, is cured in high temperature ovens. The honeycombs, which are cut in the desired sizes after curing, are made ready for use after quality control.

[0022] Characterization

[0023] Furan-based resins exhibit much better Fire, Smoke, Toxicity (FST) performance than their phenolic counterparts.

[0024] Table 1 shows the Fire, Smoke, Toxicity (FST) results of biocomposite plates which consist of furan resin as a matrix according to FAR 25.853 standard. The test standards, limit criteria, and test results required to pass the test are given in Table 1 below. These are the test results of 1 layer, 2 layer, and 8-layer prepreg samples obtained with the resin subject to the invention. Table 2 shows the results of the oven-cured plates.

[0025] The explanations of the parameters given in the tables are as follows.

[0026] Burn length: The bum length is the length of the damage caused by the flame touching the sample.

[0027] HRR: The rate of heat release after the start of the fire (kW / m2). The (average) maximum heat dissipation rate (HRR) during the five-minute test must not exceed 65 kW / m2.

[0028] THR2minutes: The total amount of heat released 2 minutes after the start of the fire.

[0029] Dm (Ds): Smoke Density

[0030] AITM 3-0005 (issue 2): Determination of certain gas components in the smoke released during the combustion of aircraft interior materials.

[0031] Table 1: Results of composite plates

[0032] Table 2: Results of oven cured composite plates

[0033] As can be seen in Tables 1 and 2, the results far below the required values of the criteria were obtained with the resin subject to the invention.

[0034] In Table 3, the biobased furan resin results of the invention are compared with the phenolic resins included in the known state of the art. As can be seen from these results, the biobased furan resin subject to the invention reveals unexpected results compared to epoxy and phenolic resins.

[0035] Table 3: Comparative test results of Phenolic and Furan resins The mechanical test results obtained from the honeycomb produced using the biobased furan resin subject to the invention are given below.

[0036] NODE BOND TESTS (ASTM C363): This test is a tensile load test that causes the honeycomb to deteriorate by breaking the bond between the nodes.

[0037] COMPRESSION TEST (ASTM C365): Flat compressive strength and modulus are the basic mechanical properties of honeycomb cores used in the design of sandwich panels. With a simple assembly compression test, the strength and modulus that cause the deformation of the honeycomb are measured. SHEAR TEST (ASTM C273): This test method provides information on the force-deflection behavior of sandwich structures or cores when loaded at a shear force parallel to the plane of the coatings.

[0038] The results of the tests for the samples (Al, A2, A3 Bl, B2, B3) taken from the similarly produced plates (A, B) are given below.

[0039] NODE BOND TESTS (ASTM C363)

[0040] COMPRESSION TEST (ASTM C365)

[0041] ELONGATION TEST (ASTM C273)

Claims

CLAIMS1. A honeycomb panel, characterized in that it is cured with a biobased furan resin comprising 40-90% by weight of poly (furfuryl alcohol), 5-10% solvent, 1-10% ethoxylated polydimethylsiloxane and 1-5% curing agent.

2. The honeycomb panel according to Claim 1, characterized in that the solvent is water.

3. The composite plate, characterized in that it comprises at least 1 layer honeycomb panel according to Claim 1.

4. The composite plate according to Claim 3, characterized in that it comprises 8-layer panels according to Claim 1.

5. The composite plate according to Claim 4, characterized in that the combustion length is 16 mm.

6. The composite plate according to Claim 4, characterized in that the heat release rate (HRR) after the start of the fire is 17.9 kW / m27. The composite plate according to Claim 4, characterized in that the total amount of heat (THR2minutes) released 2 minutes after the start of the fire is 11.3 kW.min / m28. The composite plate according to Claim 4, characterized in that the smoke density (Dm (Ds)) is 5.

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