Adhesive curing sample preparation method suitable for aerospace evaluation

Abstract

The invention discloses an adhesive curing sample preparation method suitable for aerospace evaluation, which comprises the following steps: preheating a mold, and smearing a release agent in the mold; a groove matched with a to-be-prepared standard sample piece in shape is formed in the mold; carrying out vacuum centrifugal defoaming on the adhesive; the mold is fully paved with the defoamed adhesive through flowing of the defoamed adhesive; after the mold is fully paved with the adhesive, pressing a flat plate of which the surface is coated with a release agent above the mold; and curing the adhesive carrying the mold and the flat plate to obtain an adhesive cured sample. By means of the method, preparation of customized standard test samples can be achieved, meanwhile, high-quality formed samples with low porosity and high density are achieved, and improvement of evaluation quality and efficiency is remarkably promoted.

Description

Technical Field

[0001] This invention relates to a method for curing and preparing adhesive samples suitable for aerospace evaluation, which can achieve curing and preparing bulk adhesive samples with low porosity and high density, and belongs to the field of adhesive testing and analysis. Background Technology

[0002] Adhesives have wide applications in aerospace, including in the production of components, cables, and chips. Assessing the aerospace suitability of adhesives is a crucial step in ensuring their operational reliability. To evaluate the aerospace reliability of adhesives, a comprehensive assessment of multiple aspects, including physicochemical properties, mechanical properties, thermophysical properties, and electrical properties, is typically required. Each performance test, based on standard specifications, necessitates block samples of corresponding dimensions, placing significant demands on adhesive curing sample preparation. Due to the properties of adhesives—whether single-component or two-component mixtures, differences in flowability, and curing temperature requirements—current sample preparation often suffers from high air bubble content, uneven mixing, and uniform sample size. This results in low density and poor quality of the molded samples, making them unsuitable for the standard test requirements of different types of projects. This significantly interferes with the accuracy and validity of test results, thereby reducing the efficiency and accuracy of aerospace quality assurance for adhesives. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned shortcomings and provide an adhesive curing sample preparation method suitable for aerospace evaluation. This method solves the technical problems of existing samples having low density, poor quality, and difficulty in adapting to the testing standards required for different types of projects. This invention enables the preparation of customized standard test samples, while simultaneously achieving high-quality molded samples with low porosity and high density, significantly improving evaluation quality and efficiency.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] A method for preparing adhesive curing samples suitable for aerospace evaluation includes:

[0006] Preheat the mold and apply a release agent inside the mold; the mold has grooves that match the shape of the standard sample to be prepared.

[0007] Vacuum centrifugation is performed to degas the adhesive;

[0008] The degassed adhesive flows and fills the mold by its own movement;

[0009] After the adhesive is applied to the mold, a flat plate with a release agent applied to its surface is pressed onto the top of the mold.

[0010] The adhesive, which carries a mold and a plate, is cured to obtain a cured adhesive sample.

[0011] Furthermore, the preheating temperature of the substrate should not exceed the curing temperature of the adhesive.

[0012] Furthermore, the substrate preheating temperature is half of the curing temperature.

[0013] Furthermore, for room temperature curing adhesives, the substrate preheating temperature is 40–50°C.

[0014] Furthermore, during vacuum centrifugation for degassing, the centrifugation speed is 400–600 rpm, and the degassing time is 5–15 min.

[0015] Furthermore, to allow the degassed adhesive to flow and cover the mold, a gradient temperature heating method is applied to both the mold and the adhesive to promote adhesive flow. The gradient temperature heating method can be set to two or three steps.

[0016] Furthermore, when the degassed adhesive fills the mold by its own flow, the degassed adhesive is slowly poured into the mold groove from one side, allowing it to flow naturally to the other side and fill the entire mold groove.

[0017] Furthermore, the mold and the plate are made of polytetrafluoroethylene.

[0018] Furthermore, for water absorption and density tests, the standard sample is a block sample of 30mm×10mm×5mm;

[0019] For the linear expansion coefficient test, the standard sample is a block sample of 25mm×5mm×5mm;

[0020] For bending strength testing, the standard sample is a block sample of 30mm×5mm×3mm;

[0021] For tensile property testing, the standard specimen is a type 2 dumbbell-shaped specimen;

[0022] For the resistivity / breakdown voltage test, the standard sample is a 50mm×50mm×1mm block sample.

[0023] Compared with the prior art, the present invention has at least one of the following advantages:

[0024] (1) This invention creatively proposes an adhesive curing sample preparation method suitable for aerospace evaluation. Through substrate preheating, vacuum centrifugation degassing, self-leveling and flat plate pressing processes, the density, flatness and uniformity of the cured sample can be significantly improved, while having greater versatility and adjustability.

[0025] (2) The present invention designs a customized mold to specifically match the requirements of aerospace evaluation and testing projects. It designs a universal mold tooling for different projects, which improves the sample preparation efficiency. The prepared sample can be used in multiple testing projects. At the same time, the present invention designs a smaller sample size to avoid the phenomenon of air bubbles during casting due to excessively large grooves. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the custom mold for the linear expansion coefficient test sample (25mm×5mm×5mm) of this invention.

[0027] Figure 2 A schematic diagram of the custom mold for the volume resistivity test sample (50mm×50mm×1mm) of this invention. Detailed Implementation

[0028] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0029] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0030] To obtain high-density cured adhesive samples suitable for evaluating various aerospace projects, this invention proposes an adhesive curing and sample preparation technology applicable to aerospace evaluation. This technology mainly combines customized mold design with a high-density casting and curing process. It enables the preparation of customized standard test samples while simultaneously achieving high-quality molded samples with low porosity and high density, significantly improving evaluation quality and efficiency. Figure 1 and Figure 2 The customized mold design of this invention is specifically matched to the requirements of aerospace evaluation and testing projects. For example, basic physical and chemical properties such as water absorption rate and density testing require block samples similar to (30±10mm)*(10±5mm)*(10±5mm); thermophysical properties such as linear expansion coefficient testing require block standard samples similar to (25±5mm)×(5±2mm)×(5±2mm); mechanical properties such as bending strength require block standard samples similar to (35±5mm)×(5±2mm)×(3±1mm), and tensile properties require type 2 dumbbell-shaped tensile standard samples; electrical properties such as volume resistivity / breakdown voltage testing require block standard samples similar to (50±3mm)×(50±3mm)×(1.0±0.5mm). This invention provides customized design and preparation of corresponding mold sets for the above-mentioned testing projects.

[0031] The material required for customized molds is high-temperature resistant polytetrafluoroethylene, which has good machinability and high-temperature resistance. It is not prone to deformation after high-temperature curing and does not react with adhesives, making it easy to mold and sample.

[0032] Customized molds offer adjustable parameters such as mold shape, size, groove depth, arrangement, and quantity, allowing for adaptive adjustments based on the testing requirements, thus possessing universality and versatility. A single mold can contain a collection of multiple shaped grooves, with each shape constituting a test specimen.

[0033] The high-density casting and curing process mainly consists of four steps: substrate preheating, vacuum centrifugal degassing, self-leveling, and flat plate pressing. This process combination can significantly improve the density, flatness, and uniformity of cured samples. Furthermore, this process combination allows for adjustments to the specific operating procedures to suit different adhesive properties, such as preheating temperature, centrifugal speed and time for degassing, and the method and direction of self-leveling, demonstrating significant versatility and adjustability.

[0034] In the high-density casting and curing process, the preheating temperature of the substrate should not exceed the curing temperature, preferably half of the curing temperature. For adhesives that cure at room temperature, the preferred preheating temperature is 40-50°C, which can be adjusted according to the properties of the adhesive itself.

[0035] In the high-density casting and curing process, the vacuum centrifugal degassing process should select appropriate centrifugation speed and time according to the adhesive's fluidity and workability. For conventional adhesive materials, the preferred centrifugation speed is 400-600 rpm and the degassing time is 5-15 min. Improper parameter selection may lead to incomplete degassing or premature curing due to self-rotation and heating.

[0036] In the high-density casting and curing process, self-leveling aims to fill the mold by the flow of the adhesive itself, avoiding the formation of air holes during casting. For adhesives with poor flowability, appropriate heating can be used to promote flow.

[0037] In the high-density casting and curing process, flat plate lamination aims to obtain a cast block with flat upper and lower end faces. At the same time, a release agent is applied to the lamination surface to prevent the adhesive from sticking to the substrate and to promote smooth demolding. During lamination, it is necessary to press slowly from one end to the other to avoid the formation of air bubbles at the lamination interface.

[0038] By combining the above-mentioned customized mold design with high-density casting and curing process, dense and non-porous cured samples can be obtained, which can be directly used for testing without further processing, thereby improving sample quality and increasing testing efficiency.

[0039] This invention discloses a method for curing and preparing adhesive samples suitable for aerospace evaluation, enabling the curing and preparation of low-porosity, high-density bulk adhesive samples. The method mainly comprises two aspects: customized mold design and a high-density casting and curing process. The customized mold design is specifically tailored to the requirements of aerospace evaluation testing projects, such as water absorption, density, coefficient of linear expansion, and volume resistivity test samples. Universal mold tooling can be customized for different projects. The high-density casting and curing process mainly consists of four steps: substrate preheating + vacuum centrifugal degassing + self-leveling + flat plate pressing. This process combination significantly improves the density, flatness, and uniformity of the cured sample. Furthermore, this process combination can be adjusted to suit the specific properties of different adhesives, exhibiting significant versatility and adjustability. Through this curing and sample preparation technology, dense, non-porous cured adhesive samples can be obtained, requiring no further processing and directly used for testing, thus improving sample quality and increasing testing efficiency.

[0040] Example:

[0041] Example 1

[0042] The linear expansion test specimen of XY362 potting compound was prepared using the present invention for the linear expansion coefficient test. The specific steps are as follows:

[0043] (1) A polytetrafluoroethylene mold for a custom linear expansion test specimen, with an overall size of 30mm×8mm×10mm, and three rectangular grooves with a size of 25mm×5mm×5mm are machined inside. This size is the standard part size. This test requires three parallel specimens.

[0044] (2) The curing temperature of this adhesive is 24 hours at room temperature. Therefore, the mold is placed on a 40°C heating table for 10 minutes to preheat, and the mold release agent is applied inside the mold.

[0045] (3) Mix 40ml of XY362 potting compound A and B, place it in a homogenizer and centrifuge to remove bubbles. The vacuum degree is -100KPa, the rotation speed is 500rpm, and the degassing time is 10min to make the glue solution uniformly mixed and remove internal bubbles at the same time.

[0046] (4) Slowly pour the degassed mixed adhesive into the mold groove, pouring it from one side and letting it flow naturally to the other side and fill the entire mold groove. Fill the three grooves in sequence. The entire pouring process is carried out on a 40℃ heating table.

[0047] (5) Slowly press a flat polytetrafluoroethylene plate onto the upper part of the groove to cover the groove, and use dovetail clips to fix it to the mold. This ensures that the end face of the sample is flat. Place the whole sample at room temperature for 24 hours. After the time is up, take it out to obtain 3 dense and non-porous linear expansion cured samples.

[0048] (6) The density of the prepared sample was measured and reached 99.9%. The internal metallographic structure was observed and no defects such as pores were found.

[0049] Comparative Example 1

[0050] Linear expansion test specimens of the same XY362 potting compound were prepared using a conventional curing process, as follows:

[0051] (1) Use ordinary block molds with mold groove dimensions of 50mm×50mm×2mm, without preheating;

[0052] (2) Mix 40ml of XY362 potting compound A and B and stir manually for 10 minutes. Visually observe that the mixture is uniform, but small air bubbles still exist and cannot be eliminated.

[0053] (3) Pour the mixed adhesive directly into the mold groove. Because the groove is too large, it cannot be filled naturally from one side. Multiple locations need to be poured in this way. Air bubbles are likely to appear at the junction. After filling the 50mm×50mm×2mm groove, let it stand at room temperature for 24 hours. After the time is up, take it out of the mold.

[0054] (4) Three 25mm×5mm×3mm samples were cut from the 50mm×50mm×2mm large sample for linear expansion test. The sample thickness could not reach the standard sample requirement of 5mm, and the machining was time-consuming.

[0055] (5) The density of the prepared sample was measured to be 90%. The internal metallographic structure was observed and a number of small pores were found.

[0056] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0057] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing adhesive samples for aerospace evaluation, characterized in that, include: Preheat the mold and apply a release agent inside the mold; the mold has grooves that match the shape of the standard sample to be prepared. Vacuum centrifugation is used to degas the adhesive; The degassed adhesive flows and fills the mold by its own movement; After the adhesive is applied to the mold, a flat plate with a release agent applied to its surface is pressed onto the top of the mold. The adhesive, which carries a mold and a plate, is cured to obtain a cured adhesive sample.

2. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, The preheating temperature of the substrate should not exceed the curing temperature of the adhesive.

3. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 2, characterized in that, The substrate preheating temperature is half of the curing temperature.

4. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 2, characterized in that, For adhesives that cure at room temperature, the substrate preheating temperature is 40–50°C.

5. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, When degassing under vacuum, the centrifugation speed is 400-600 rpm and the degassing time is 5-15 min.

6. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, When the degassed adhesive flows and fills the mold, a gradient temperature heating method is set for the mold and the adhesive to promote the flow of the adhesive.

7. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, When the degassed adhesive fills the mold by its own flow, slowly pour the degassed adhesive into the mold groove from one side, allowing it to flow naturally to the other side and fill the entire mold groove.

8. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, The mold and plate are made of polytetrafluoroethylene.

9. The method for preparing adhesive curing samples suitable for aerospace evaluation according to claim 1, characterized in that, For water absorption and density tests, the standard sample is a block sample with dimensions of (30±10mm)*(10±5mm)*(10±5mm). For the linear expansion coefficient test, the standard sample is a block sample with dimensions of (25±5mm)×(5±2mm)×(5±2mm); For bending strength testing, the standard sample is a block sample with dimensions of (35±5mm)×(5±2mm)×(3±1mm); For tensile property testing, the standard specimen is a type 2 dumbbell-shaped specimen; For the resistivity / breakdown voltage test, the standard sample is a block sample of (50±3mm)×(50±3mm)×(1.0±0.5mm).

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