A laminated through-stitched fiber reinforced silica aerogel composite material and a preparation method thereof

Abstract

The application discloses a laminated through-stitching fiber-reinforced silica aerogel composite material and a preparation method thereof, and belongs to the technical field of aerogel heat-insulating composite materials. The material comprises a fiber bearing framework, through-stitching yarn and a silica aerogel matrix. The fiber bearing framework comprises a plurality of laminated fiber layer materials. The through-stitching yarn is through-stitched along the thickness direction of the fiber bearing framework, and locks the plurality of fiber layer materials to form a fiber preform whole body with a cross-layer load transmission channel. The silica aerogel matrix is formed by silica sol being impregnated into the inter-fiber pores and the inter-layer pores of the fiber preform whole body, and being subjected to in-situ gelation treatment and drying in the pores. The silica aerogel matrix forms a silica nano-attached layer on the fiber surface of the fiber layer material, and forms a bridging structure between adjacent fibers. The material has low thermal conductivity and high bearing capacity, and has good performance retention under high-temperature cyclic conditions, and is suitable for industrial high-temperature equipment and aerospace thermal protection fields.

Description

Technical Field

[0001] This invention belongs to the technical field of aerogel thermal insulation composite materials, specifically relating to a layered through-stitched fiber-reinforced silica aerogel composite material and its preparation method. Background Technology

[0002] The fields of industrial high-temperature equipment and aerospace thermal protection place high demands on the high-temperature resistance, thermal insulation performance, structural stability, and engineering applicability of thermal insulation materials. Especially in scenarios requiring long-term service or repeated use, materials must not only possess low thermal conductivity but also maintain good shape stability and mechanical integrity under high-temperature conditions and multiple thermal cycles. Existing thermal insulation materials often focus on a single performance characteristic, making it difficult to simultaneously meet the requirements of thermal insulation, load-bearing capacity, and service stability.

[0003] Silica aerogel is a typical SiO2-based porous nanomaterial with characteristics such as low density, high specific surface area, and low thermal conductivity. It can also be fabricated into large sizes or complex shapes, thus showing promising application prospects in the field of thermal insulation. Currently, silica aerogel has been applied in some thermal protection and high-temperature insulation scenarios.

[0004] However, conventional silica aerogels still have certain shortcomings under high-temperature conditions. On the one hand, they are prone to dehydroxylation condensation and sintering densification during heating, leading to changes in pore structure and coarsening of the skeleton, thus affecting the high-temperature stability of the material. On the other hand, due to their loose skeleton structure and weak interfacial bonding, the material is usually brittle and has limited load-bearing capacity. Under high-temperature, cyclic thermal effects, or repeated service conditions, these problems may further cause structural damage and performance degradation, making it difficult to meet the application requirements of simultaneously demanding thermal insulation performance, structural stability, and a certain load-bearing capacity.

[0005] To improve the brittleness of silica aerogel and meet the requirements of aerospace and other fields for thick, high-load-bearing components, existing technologies typically use fiber materials (such as fiberglass mat) to composite with aerogel, and increase the thickness through multi-layer stacking. To prevent interlayer slippage and delamination of the stacked structure under stress or high temperature, some existing technologies (such as patent application CN121340714A) use stitching yarn to stitch the dried and formed multi-layer aerogel mat through and through.

[0006] However, existing laminated aerogel composite materials still face the following insurmountable technical bottlenecks under extreme service conditions: the mechanical stitching process in the later stages damages the microstructure network, easily introducing a "thermal bridge effect." Due to the extreme brittleness of the aerogel matrix itself, when using the existing process of "preparing the aerogel mat first and then mechanically stitching," the suture needle severely compresses and destroys the nanoporous network around the stitching path during the piercing of the aerogel mat. This not only leads to severe localized powder shedding and structural collapse, but the physical gap left between the suture and the aerogel also forms a direct heat channel running through the thickness direction (i.e., a thermal bridge effect), resulting in a significant decrease in the overall thermal insulation performance of the material.

[0007] Therefore, there is an urgent need in this field for a novel aerogel composite material structure and its preparation method, in order to fundamentally solve the problems of weak interlayer connection, poor interface bonding and high-temperature thermal stress mismatch in multilayer aerogel composite materials without destroying the micro-insulating network of aerogel and eliminating suture pore defects, so as to truly meet the integrated requirements of thermal insulation and load-bearing in extreme high-temperature repeated service environments. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a laminated through-stitched fiber-reinforced silica aerogel composite material and its preparation method, thereby solving the problems in the prior art.

[0009] The objective of this invention can be achieved through the following technical solutions: A laminated, through-stitched, fiber-reinforced silica aerogel composite material, comprising: Fiber-supported skeleton, comprising multiple layers of fiber material; Through-thread stitching is used to stitch multiple layers of fiber material together along the thickness direction of the fiber load-bearing skeleton to form a fiber preform with a cross-layer load transfer channel. The silica aerogel matrix is ​​formed by infiltrating silica sol into the inter-fiber pores and interlayer pores of the fiber preform, and then undergoing in-situ gelation and drying within the pores. The silica aerogel matrix forms a silica nano-adhesion layer on the fiber surface of the fiber layer and forms a bridging structure between adjacent fibers.

[0010] Furthermore, the fiber layer material is high-silica glass fiber paper, wherein the mass fraction of SiO2 in the high-silica glass fiber paper is ≥95%, the single-layer thickness is 0.1~0.5mm, and the basis weight is 0.02~0.05g / cm³. 2 The fiber layer material has 5 to 100 layers.

[0011] Furthermore, the through-stitch yarn is a high-silica glass fiber yarn, wherein the mass fraction of SiO2 in the high-silica glass fiber yarn is ≥95%, and the linear density is 100~400Tex.

[0012] Furthermore, the needle density of the threaded stitch is 1 to 10 stitches / cm. 2 The suture path is one or more of the following: straight suture, zigzag suture, or staggered scattered suture.

[0013] Furthermore, the average particle size of the aerogel particles inside the silica aerogel matrix is ​​5~50nm; the average pore size inside the silica aerogel matrix is ​​5~50nm.

[0014] The preparation method of the above-mentioned laminated through-stitch fiber-reinforced silica aerogel composite material includes the following steps: After cutting the fiber layer material, multiple layers are stacked to obtain the fiber load-bearing skeleton; The fiber-supporting skeleton is stitched through the thickness direction using through-sewing yarn to obtain the whole fiber preform; The fiber preform is impregnated with silica sol to allow the silica sol to enter the pores of the fiber preform. Then, in-situ gelation and aging treatment are performed in the pores to obtain a silica wet gel composite. The silica wet gel composite was subjected to solvent displacement treatment followed by drying to obtain the composite material.

[0015] Furthermore, the preparation process of the silica sol is as follows: the silicon source precursor undergoes a hydrolysis-condensation reaction under the action of an alkaline catalyst; then it is concentrated to obtain a silica sol with a solid content of 10wt% to 30wt%.

[0016] Furthermore, the silicon source precursor is tetraethyl orthosilicate or tetramethyl orthosilicate.

[0017] Furthermore, the alkaline catalyst is ammonia.

[0018] Furthermore, the solvent replacement process sequentially includes an alcohol solvent replacement step and a non-polar solvent replacement step.

[0019] The beneficial effects of this invention are: 1. This invention breaks through the conventional process of "preparing aerogel felt first, then mechanically stitching," innovatively employing a process path of impregnating silica sol into a pre-stitched high-silica glass fiber substrate and performing in-situ gelation within the pores. This "stitching first, then in-situ gelation" method fundamentally avoids the compression and damage to the fragile aerogel nanonetwork caused by subsequent mechanical puncture, completely eliminating "powder shedding" and structural collapse defects around the stitched pores. Simultaneously, the in-situ generated silica aerogel matrix not only fills the pores between fibers but also encapsulates the threaded stitching, forming a continuous bridging structure and nano-attachment layer between adjacent fibers and yarns. This self-healing and bridging effect of the micro-interface fills the original physical gaps, successfully blocking the "thermal bridge channels" in the thickness direction, enabling the material to maintain excellent thermal insulation performance while possessing extremely high structural strength.

[0020] 2. This invention abandons traditional organic adhesives or simple physical stacking, constructing a load-bearing skeleton composed of multiple layers of high-silica glass fiber, and using high-silica glass fiber yarns for through-stitching along the thickness direction. This method strongly locks the discrete fiber layers into a unified whole, establishing an extremely stable cross-layer load transfer channel within the material. Under compression or shear forces in the thickness direction, the stitched-locked structure effectively suppresses interlayer slippage and delamination. The dual synergy of the macroscopic skeleton and the microscopic aerogel bridging network greatly enhances the overall stiffness and compressive strength of the composite material.

[0021] 3. This invention constructs a "high-silica homogeneous composite system", in which the supporting skeleton (high-silica glass fiber paper / felt), the stitching structure (high-silica glass fiber yarn), and the in-situ filling matrix (silica aerogel) are all dominated by silica (e.g., the mass fraction of fiber silica is ≥95%). This solves the problem of thermal expansion coefficient mismatch that easily occurs in heterogeneous material composites under extreme thermal shock. Combined with three-dimensional stitching and locking, the material of this invention does not experience thermal stress-induced delamination and degradation at the internal interface when facing harsh high-temperature repeated service conditions.

[0022] 4. The preparation process of this invention introduces a multi-level gradient displacement strategy using alcohol solvents and non-polar solvents (n-hexane) as media before drying the wet gel composite, followed by programmed slow atmospheric pressure drying. The low surface tension of the non-polar solvent is specifically utilized to weaken the capillary tensile stress during the atmospheric pressure liquid-gas phase transition, thus preventing shrinkage and cracking of the aerogel skeleton. This method not only eliminates the reliance on expensive and high-risk supercritical drying equipment but also endows the composite material with stable molding capabilities, enabling crack-free scale-up preparation of large-size, well-defined blocks. This provides a practical solution for large-scale engineering applications in industrial high-temperature equipment and aerospace fields. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the composite material preparation method of the present invention; Figure 2 This is a diagram illustrating the integral block of the aerogel composite material prepared in Example 1 and its scalable fabrication capability. Figure 3 X-ray CT slice image of the aerogel composite material prepared in Example 1; Figure 4 SEM image of the aerogel composite material prepared in Example 1; Figure 5 The figure shows the load-bearing capacity and high-temperature resistance of the aerogel composite material prepared in Example 1. Figure 6 This is a statistical graph showing the thermal conductivity of the aerogel composite material prepared in Example 2 at different temperatures; Figure 7 The compressive stress-strain curve along the thickness direction of the aerogel composite material prepared in Example 2; Figure 8 The graph shows the thermal conductivity of the aerogel composite material prepared in Example 2 after 100 cycles at 1000°C at different temperatures. Figure 9 The compressive stress-strain curve along the thickness direction of the aerogel composite material prepared in Example 2 after 100 cycles at 1000℃. Figure 10 The nitrogen adsorption-desorption isotherm of the aerogel composite material prepared in Example 3; Figure 11 The pore size distribution diagram is shown for the aerogel composite material prepared in Example 3. Figure 12 The compressive stress-strain curve of the aerogel composite material prepared in Example 3 along the in-plane direction of the material; Figure 13 The nitrogen adsorption-desorption isotherm of the aerogel composite material prepared in Example 4; Figure 14 The pore size distribution diagram is shown for the aerogel composite material prepared in Example 4. Figure 15 The compressive stress-strain curve along the thickness direction of the aerogel composite material prepared in Example 4; Figure 16The compressive stress-strain curve of the aerogel composite material prepared in Example 4 along the in-plane direction of the material. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] A laminated, through-stitched, fiber-reinforced silica aerogel composite material, comprising: Fiber-supported skeleton: formed by multiple layers of fiber material, wherein the fiber material is fiber paper and / or fiber felt made of high-silica glass fiber with silica as the main component; Through-seam yarn: High-silica glass fiber yarn with silica as the main component is used to perform through-seam stitching along the thickness direction of the fiber load-bearing skeleton, so that multiple fiber layers are locked together to form a fiber preform with cross-layer load transfer channels. Silica aerogel matrix: It fills the inter-fiber pores and interlayer pores of the sewn fiber preform, and is formed by in-situ gelation and drying of silica sol in the pores; the aerogel matrix is ​​impregnated and bonded to the fibers, forming a nano-adhesion layer on the fiber surface and forming a bridging structure between adjacent fibers.

[0027] like Figure 1 As shown, the preparation method of the laminated through-stitch fiber-reinforced silica aerogel composite material includes the following steps: (1) Mix deionized water and ethanol to form a reaction medium, add ammonia and stir; then add silicon source precursor to carry out hydrolysis and polycondensation reaction; adjust the solid content of sol by vacuum distillation, rotary evaporation or other concentration methods; the pH, temperature and reaction time of sol can be adjusted according to process requirements to control the gelation rate and avoid local excessively fast gelation inside the preform to obtain silica sol.

[0028] (2) High-silica glass fiber paper or fiber mat is used as fiber layer material. After being cut to the target size, it is stacked to form a multi-layer fiber preform (stacked preform). During the stacking process, molds or jigs are used for positioning and limiting, and slight pre-pressure or frame constraint can be applied to the preform to improve dimensional consistency.

[0029] (3) Using high-silica glass fiber yarn as the sewing yarn, the laminated preform is sewn through the thickness so that each layer forms an integral whole and establishes a cross-layer load transfer channel; during sewing, the interlayer constraint and overall stiffness can be controlled by controlling the stitch distance, sewing tension and misalignment distribution; and the sewn fiber preform is obtained as a whole.

[0030] (4) Introduce the silica sol obtained in step (1) into the sewn fiber preform and impregnate it to allow the sol to fully enter the pores between fibers and between layers. Then, complete in-situ gelation inside the preform and perform aging treatment; aging can be carried out at room temperature or under moderate heating conditions, and the time can be adjusted according to the gel system; a wet gel composite is obtained.

[0031] (5) The obtained wet gel composite is solvent replaced to reduce the drying capillary stress and crack risk; first, ethanol is used to replace the residual water and by-products in the pores, and then hexane is used for further replacement to reduce surface tension and prevent structural cracking.

[0032] (6) The wet gel composite that has been replaced is slowly dried under normal pressure. The sample is placed in a semi-closed container with limited volatilization conditions. The evaporation rate of the non-polar solvent is controlled by setting micropores. The drying is completed by staged heating and segmented heat preservation to reduce capillary stress and inhibit structural cracking.

[0033] The fiber layer material is preferably high-silica glass fiber paper, wherein the mass fraction of SiO2 in the high-silica glass fiber paper is ≥95%, preferably ≥98%, the single-layer thickness is 0.1~0.5mm, and the basis weight is 0.02~0.05g / cm³. 2 And the number of floors is 5 to 100.

[0034] The through-stitching yarn is preferably a high-silica glass fiber yarn, wherein the mass fraction of SiO2 in the high-silica glass fiber yarn is ≥95%, preferably ≥98%, and the linear density is 100~400Tex.

[0035] The density of the penetrating suture needles is 1~10 needles / cm. 2 2~6 needles / cm is preferred 2 The suture path can be one or more of the following: straight, zigzag, or staggered.

[0036] The silicon source precursor is TEOS or TMOS; the sol can be concentrated to a solid content of 10~30wt%.

[0037] The solvent replacement includes alcohol solvent replacement and non-polar solvent replacement, with 3 to 10 replacements, preferably no less than 5, and can be done in steps.

[0038] The average particle size of the aerogel particles inside the silica aerogel matrix is ​​5~50nm, preferably 10~30nm; the average pore size inside the silica aerogel matrix is ​​5~50nm, preferably 5~20nm.

[0039] The following examples are used to illustrate the feasibility and effects of the present invention and do not constitute a limitation on the scope of protection of the present invention. The sources of the relevant raw materials are as follows: High-silica glass fiber paper: Mainly composed of silicon dioxide, with a SiO2 mass fraction of 97%, a single-layer thickness of 0.2 mm, and a basis weight of 0.03 g / cm³. 2 .

[0040] High-silicon glass fiber yarn: with silicon dioxide as the main component, SiO2 mass fraction ≥95%, preferably ≥98%, and linear density of 100~400Tex.

[0041] Example 1 In this embodiment, a silica precursor system was prepared according to a volume ratio of tetraethyl orthosilicate (TEOS): anhydrous ethanol (EtOH): deionized water (H2O): ammonia (25% by mass) of approximately 1:5:5:0.07. Specifically, 500 mL of deionized water and 500 mL of anhydrous ethanol were mixed as the reaction medium, and 7 mL of ammonia was added under stirring at 30°C and 600 rpm to control the pH of the system at approximately 9.0. Subsequently, under the same temperature and stirring conditions, 100 mL of tetraethyl orthosilicate was slowly added dropwise over 2 hours. After the addition was completed, the reaction continued for 0.5 hours to obtain the initial silica sol. The sol was then transferred to a rotary evaporator and replaced with anhydrous ethanol at 50°C for 2 hours to reduce the water content. The sol was then concentrated by vacuum distillation at 40°C and 0.10 MPa until the solid content was approximately 20.0 wt%.

[0042] High-silica glass fiber paper is cut into specific shapes, and 12 sheets of fiber paper are stacked and fixed in a custom mold, with the stacking direction set perpendicular to the heat flow direction. High-silica glass fiber yarn is used to sew the layers together to obtain a fiber preform. The sewing method is straight stitching, and the stitch density is approximately 4 stitches / cm. 2 .

[0043] The regulated silica sol was impregnated into the sewn fiber preform, allowing the sol to fully penetrate the inter-fiber and interlayer pores. In this embodiment, impregnation was performed under normal pressure. After impregnation, the sample was placed in a sealed environment to allow the sol to gel in situ within the pores, and then aged at 40°C for 24 h to form a continuous Si-O-Si network and strengthen the fiber-matrix interface. Subsequently, the resulting wet gel composite was first replaced three times with anhydrous ethanol, and then four times with n-hexane, with each replacement lasting 6 h.

[0044] After hexane replacement, the free solvent on the sample surface was slightly drained, and the sample was placed in a covered polypropylene drying box, maintaining a gap between the sample and the box walls and bottom. Four micropores with a diameter of 0.8 mm were opened on the drying box lid to control the hexane evaporation rate in a confined manner, thereby reducing capillary stress concentration caused by rapid retreat of the liquid-gas interface. Subsequently, a programmed slow atmospheric pressure drying process was performed: first, static drying at 25℃ for 12 hours; then, the temperature was increased to 40℃ at a rate of 0.5℃ / min and held for 12 hours; next, the temperature was increased to 50℃ at a rate of 0.5℃ / min and held for 12 hours; finally, the temperature was increased to 60℃ at a rate of 0.5℃ / min and held for 12 hours. After drying, the sample was naturally cooled to room temperature to obtain a complete, block-like, multi-layered, through-stitched fiber-reinforced silica aerogel composite material.

[0045] Figure 2 The diagram shows the composite material monolith prepared in Example 1 and its scalable fabrication capability. It visually demonstrates that the method of this invention can achieve scaled-up molding from small-sized samples to large-sized blocks while maintaining the overall integrity of the material, with a density of approximately 0.34 g / cm³. 3 The porosity is 78%. In addition, the large-sized blocks have a regular appearance and clear boundaries, indicating that the process of the present invention has good molding stability and applicability to scale-up preparation, thus providing support for its scalable preparation and application in engineering scenarios such as heat insulation load-bearing components of reusable thermal protection systems.

[0046] Figure 3 The image shows an X-ray CT slice of the composite material prepared in Example 1, illustrating the layered structure of the material and its through-thickness stitching characteristics. The distribution of interlayer interfaces in the multilayer fiber material is identifiable in the image, and the continuous through-stitching morphology in the thickness direction is also observable. This indicates that the through-stitching effectively connects the various laminated units into a whole and forms a cross-layer load transfer channel, thereby providing support for the structural stability and anti-delamination ability of the material.

[0047] Figure 4 The SEM image of the composite material prepared in Example 1 visually demonstrates the aerogel bridging structure formed at the fiber micro-interface of the material of the present invention. The image shows that silica aerogel continuously adheres to the fiber surface and forms bridging connections between adjacent fibers, thereby transforming the discrete contact between fibers into a continuous interfacial connection and support structure. This bridging morphology indicates that the in-situ gelation of sol within the pores in this invention can enhance the fiber-matrix wetting bond and interfacial synergy, providing support for the structural integrity and stability of the composite material under thermal insulation load conditions.

[0048] Figure 5The diagram illustrates the load-bearing capacity and high-temperature resistance of the composite material prepared in Example 1. The prepared material can withstand a static load of approximately 70 kg while maintaining the integrity of its macroscopic structure. Furthermore, under short-term direct exposure to a flame at approximately 1300 °C, the material can still maintain the integrity of its macroscopic structure and retain its thermal insulation effect, indicating that the material of the present invention is suitable for high-temperature service scenarios such as thermal insulation load-bearing components of reusable thermal protection systems.

[0049] Example 2 Compared to Example 1, Example 2 uses the same high-silica glass fiber paper, high-silica glass fiber yarn, and silica aerogel composite material preparation steps as Example 1, with the only difference being the fiber preform molding stage. Specifically, in order to improve the thermal cycling structural stability and load-bearing capacity of the aerogel composite material, the number of fiber paper layers was increased from 12 to 16, while the other processes were exactly the same as in Example 1; its structural features remain the same: layered high-silica glass fiber paper serves as a load-bearing frame, with through-thickness stitching to form interlayer locking and load channels, and silica aerogel phase gelling in situ within the pores to form a uniform filling and bridging network.

[0050] Figure 6 The thermal conductivity of the composite material prepared in Example 2 along its thickness direction (perpendicular to the laminate plane) under different temperature conditions is shown in the test results. The thermal conductivity was measured using a Swedish Hot Disk TPS 3500 thermal constant analyzer based on the transient plane heat source method. Figure 6 As shown, the thermal conductivity of the material is approximately 0.060 W / mK at room temperature, and approximately 0.090 W / mK and 0.130 W / mK at 400℃ and 800℃, respectively. This indicates that the material of the present invention has good high-temperature thermal insulation applicability and can meet the high-temperature thermal insulation performance requirements of the thermal insulation load-bearing components of reusable thermal protection systems.

[0051] Figure 7 The image shows the compressive stress-strain curve along the thickness direction of the composite material prepared in Example 2. The compressive performance test was conducted according to GB / T 8813-2020 standard using a China Sansi UTM4103 universal testing machine at a loading rate of 1 mm / min. Figure 7 As shown, the stress increases continuously with increasing strain, reaching as high as 27.06 MPa under approximately 60% compressive strain conditions. This indicates that the present invention significantly improves the compressive load-bearing capacity of aerogel materials in the thickness direction by forming a cross-layer locking and load transfer channel through the layered fiber load-bearing skeleton and through-thickness stitching. This can meet the structural strength and stability requirements of the thermal insulation load-bearing components of reusable thermal protection systems.

[0052] Figure 8The thermal conductivity test results of the composite material prepared in Example 2 after 100 cycles of thermal cycling at 1000℃ are shown. The thermal cycling conditions are as follows: the sample is placed in a muffle furnace at 1000℃ and held for 10 minutes, then removed and allowed to cool naturally to room temperature, which is recorded as one thermal cycle. The above process is repeated for a total of 100 cycles. The method for measuring the thermal conductivity is the same as... Figure 6 Same. For example... Figure 8 As shown, the thermal conductivity of the material after thermal cycling is approximately 0.070, 0.109, and 0.144 W / mK at 30℃, 400℃, and 800℃, respectively. Compared with before thermal cycling, the increase in thermal conductivity is relatively small, indicating that the material of the present invention has good thermal insulation performance retention under high temperature cycling conditions and can meet the requirements of long-term service stability of thermal insulation load-bearing components of reusable thermal protection systems.

[0053] Figure 9 The compressive stress-strain curve along the thickness direction of the composite material prepared in Example 2 after 100 cycles at 1000°C demonstrates the load-bearing capacity retention of the composite material after high-temperature cyclic service. The compressive performance test conditions are the same as those in Example 2. Figure 7 The same. As shown in the figure, the material still exhibits a continuous load-bearing response during compression. Under approximately 60% compressive strain, the compressive stress can reach approximately 18.19 MPa. This indicates that the present invention, through the layered fiber load-bearing skeleton and the through-thickness stitched locking structure, can maintain the cross-layer load transfer channel and structural integrity under thermal cycling conditions. Thus, the material still has the mechanical support capacity to meet the thermal insulation load-bearing scenario after experiencing high-temperature cycling, and is suitable for the long-term service requirements of thermal insulation load-bearing components of reusable thermal protection systems.

[0054] Example 3 Compared to Example 1, Example 3 uses the same high-silica glass fiber paper, high-silica glass fiber yarn, and silica sol preparation route as Example 1. The difference lies in the fiber preform molding parameters and the sol solid content. Specifically, in Example 3, 16 sheets of high-silica glass fiber paper are stacked, with the stacking direction still set perpendicular to the heat flow direction; high-silica glass fiber yarn is used for interlayer through-thickness stitching, with a straight stitching method and a stitch density of 2 stitches / cm. 2 .

[0055] After concentration, the silica sol was adjusted to a solid content of 18 wt%. Then, the sol was introduced into the stitched fiber preform using a vacuum impregnation method, allowing it to penetrate the inter-fiber and interlayer pores and complete in-situ gelation within the pores. After gelation, it was aged at 40°C for 24 hours. Subsequently, the wet gel composite was replaced three times with ethanol, followed by three times with n-hexane, each replacement lasting 6 hours. Finally, the sample was placed in a semi-closed container with micropores and dried according to the same programmed slow atmospheric pressure drying procedure as in Example 1, yielding a laminated, through-stitched fiber-reinforced silica aerogel composite material.

[0056] Figure 10 The nitrogen adsorption-desorption isotherm diagram of the composite material prepared in Example 3 illustrates the porous structure characteristics inside the material of the present invention. Figure 10 As shown, its adsorption-desorption isotherm exhibits a type IV pattern with a significant hysteresis loop, indicating that a nanoporous network structure dominated by mesopores has formed inside the silica aerogel matrix. Simultaneously, the adsorption amount increases significantly in the high relative pressure region, indicating the existence of a well-developed pore structure within the material, with a specific surface area as high as 179.54 m². 2 / g provides a structural basis for the lightweight thermal insulation performance of composite materials.

[0057] Figure 11 The image shows the pore size distribution of the composite material prepared in Example 3, further revealing the material's predominantly mesoporous pore structure. Figure 11 As shown, the pore size of the composite material is mainly concentrated in the nanoscale range, with an average pore size of 8.39 nm, indicating that a relatively well-developed nanoporous network structure has been formed inside the material. This pore structure characteristic helps to suppress gas-phase heat conduction, thereby reducing the thermal conductivity of the material. Compared with Example 1, Example 3 uses a lower stitching density, resulting in a corresponding reduction in the solid heat transfer pathways in the thickness direction, thus further reducing its thermal conductivity to approximately 0.056 W / mK at room temperature.

[0058] Figure 12 The compressive stress-strain curves along the in-plane direction of the composite material prepared in Example 3 reveal the mechanical response characteristics of the composite material under in-plane compression. The compressive performance test was conducted according to GB / T 8813-2020 standard using a China Sansi UTM4103 universal testing machine at a loading rate of 1 mm / min, with the test direction being the in-plane direction of the material. Figure 12As shown, the composite material experiences a rapid increase in stress during the initial compression phase, exhibiting a local peak, followed by a fluctuating load-bearing stage. This indicates that the internal layered fiber skeleton, aerogel matrix, and through-stitch structure undergo synergistic deformation and gradual load redistribution during loading. With further strain increase, the stress continues to rise, reaching 4.16 MPa at approximately 50% compressive strain, demonstrating that the composite material still possesses good in-plane load-bearing capacity. These results indicate that through-thickness stitching structures can effectively bind multiple fiber layers together, suppressing interlaminar slip and promoting load transfer, thereby improving the structural stability of the composite material. It is worth noting that despite using a lower stitch density in Example 3, the prepared composite material still maintained high in-plane compressive performance.

[0059] Example 4 Compared to Example 1, Example 4 uses the same high-silica glass fiber paper, high-silica glass fiber yarn, and silica sol preparation route as Example 1. The difference lies in the fiber preform molding parameters and the sol solid content. Specifically, in Example 4, 30 sheets of high-silica glass fiber paper are stacked, with the stacking direction still perpendicular to the heat flow direction; high-silica glass fiber yarn is used for interlayer through-thickness stitching, with a straight stitching method and a stitch density of 6 stitches / cm. 2 .

[0060] After concentration, the silica sol was adjusted to a solid content of 28 wt%. Then, it was introduced into the stitched fiber preform using an atmospheric pressure impregnation method, allowing it to penetrate the inter-fiber and interlayer pores and complete in-situ gelation within the pores. After gelation, it was aged at 50°C for 24 hours. Subsequently, the wet gel composite was replaced four times with ethanol, followed by four times with n-hexane, each replacement lasting 6 hours. Finally, the sample was placed in a microporous semi-closed container and dried according to the same programmed slow atmospheric pressure drying procedure as in Example 1, yielding a laminated, through-stitched fiber-reinforced silica aerogel composite material.

[0061] Figure 13 The nitrogen adsorption-desorption isotherm diagram for the composite material prepared in Example 4 illustrates the pore structure characteristics of the composite material under conditions of high layer number and high stitch density. Figure 13 As shown, the composite material still exhibits a type IV adsorption-desorption isotherm with a certain hysteresis loop, indicating that it retains a predominantly mesoporous nanoporous structure. However, compared to Example 3, its overall adsorption capacity is significantly reduced, indicating that the effective pore volume inside the material has decreased, and the specific surface area has also decreased to 53.76 m². 2 / g indicates that as the number of high-silica glass fiber paper layers and the density of through stitches increase, the internal structure of the composite material tends to become more compact, and some pore structures of the silica aerogel matrix are compacted or constrained.

[0062] Figure 14 The image shows the pore size distribution of the composite material prepared in Example 4, further revealing the pore structure characteristics of the composite material under conditions of high layer count and high stitch density. Figure 14 As shown, the pore size of the composite material is still mainly distributed in the nanoscale range, with an average pore size of approximately 9.26 nm, indicating that its internal structure still maintains a porous network structure dominated by mesopores. Compared with Example 3, the pore size distribution range of Example 4 is wider, and a certain distribution appears in the larger mesopore region, indicating that as the number of high-silica glass fiber paper layers and the density of through-stitching increase, the internal structure of the composite material tends to be more compact, but the silica aerogel matrix still retains a relatively continuous mesoporous network. At the same time, due to the increase in the number of layers and stitching density, the solid heat transfer pathways in the thickness direction of the material are increased, so its room temperature thermal conductivity is higher than that of Example 3, approximately 0.071 W / mK.

[0063] Figure 15 The compressive stress-strain curve along the thickness direction of the composite material prepared in Example 4. The compressive performance test conditions are the same as those in Example 4. Figure 7 Same. For example... Figure 15 As shown, the composite material exhibits a continuously increasing load-bearing response trend during compression, with a similar variation pattern to Example 2. However, it demonstrates higher load-bearing capacity under the same compressive strain conditions; specifically, the compressive stress reaches 33.28 MPa at 60% compressive strain. This result indicates that with the increase in the number of high-silica glass fiber paper layers and the density of through-stitching, the interlayer interlocking effect and cross-layer load transfer capacity within the composite material are further enhanced, thereby giving the material stronger compressive load-bearing capacity and structural stability in the thickness direction.

[0064] Figure 16 The compressive stress-strain curves along the in-plane direction of the composite material prepared in Example 4 are shown. The compressive performance test conditions are the same as those in Example 4. Figure 12 Same. For example... Figure 16As shown, the composite material exhibits a relatively stable load-bearing response during in-plane compression. A local peak occurs in the initial stage of compression, followed by a fluctuating load-bearing phase, and then a stress increase trend under larger strain conditions; the compressive stress reaches 5.71 MPa under 50% compressive strain. This result indicates that the composite material of Example 4 also possesses good mechanical support capacity in the in-plane direction. Compared to Example 3, the in-plane compressive performance is improved due to the further increase in the number of high-silica glass fiber paper layers and the density of through-stitching, which enhances interlayer bonding and load transfer.

[0065] The above embodiments demonstrate that the present invention has the following beneficial effects: 1) This invention utilizes an integrated construction method involving layered fibers, through-stitching, and in-situ gelation to achieve high load-bearing capacity in the thickness direction while maintaining low thermal conductivity. The thermal conductivity at room temperature is approximately 0.060 W / mK, and it remains low even at high temperatures, demonstrating excellent suitability for high-temperature insulation. The compressive stress at 60% strain reaches approximately 27.06 MPa, indicating that the material of this invention possesses both thermal insulation performance and load-bearing capacity.

[0066] 2) After 100 thermal cycles at 1000℃, the material retains good thermal insulation and load-bearing properties. The thermal conductivity is approximately 0.070, 0.109, and 0.144 W / mK at 30℃, 400℃, and 800℃, respectively. The compressive stress when compressed to approximately 60% of the strain in the thickness direction can still reach approximately 18.19 MPa, indicating that it is suitable for the cyclic service requirements of integrated thermal insulation and load-bearing components in reusable thermal protection systems.

[0067] 3) The material can be molded into a whole block and prepared on a scaled-up scale, and maintains the integrity of the macroscopic structure under static load and direct flame burning conditions, which further demonstrates its engineering application potential in the heat insulation load-bearing components of reusable thermal protection systems.

[0068] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A layered, through-stitched, fiber-reinforced silica aerogel composite material, characterized in that, include: Fiber-supported skeleton, comprising multiple layers of fiber material; Through-thread stitching is used to stitch multiple layers of fiber material together along the thickness direction of the fiber load-bearing skeleton to form a fiber preform with a cross-layer load transfer channel. The silica aerogel matrix is ​​formed by infiltrating silica sol into the inter-fiber pores and interlayer pores of the fiber preform, and then undergoing in-situ gelation and drying within the pores. The silica aerogel matrix forms a silica nano-adhesion layer on the fiber surface of the fiber layer and forms a bridging structure between adjacent fibers.

2. The laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 1, characterized in that, The fiber layer material is high-silica glass fiber paper, wherein the SiO2 mass fraction of the high-silica glass fiber paper is ≥95%, the single-layer thickness is 0.1~0.5mm, and the basis weight is 0.02~0.05g / cm³. 2 The fiber layer material has 5 to 100 layers.

3. The laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 1, characterized in that, The through-stitching yarn is a high-silica glass fiber yarn, wherein the mass fraction of SiO2 in the high-silica glass fiber yarn is ≥95% and the linear density is 100~400Tex.

4. The laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 1, characterized in that, The needle density of the threaded stitch is 1-10 stitches / cm. 2 The suture path is one or more of the following: straight suture, zigzag suture, or staggered scattered suture.

5. The laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 1, characterized in that, The average particle size of the aerogel particles inside the silica aerogel matrix is ​​5~50nm; the average pore size inside the silica aerogel matrix is ​​5~50nm.

6. A method for preparing a laminated, through-stitched, fiber-reinforced silica aerogel composite material according to any one of claims 1-5, characterized in that, Includes the following steps: After cutting the fiber layer material, multiple layers are stacked to obtain the fiber load-bearing skeleton; The fiber-supporting skeleton is stitched through the thickness direction using through-sewing yarn to obtain the whole fiber preform; The fiber preform is impregnated with silica sol to allow the silica sol to enter the pores of the fiber preform. Then, in-situ gelation and aging treatment are performed in the pores to obtain a silica wet gel composite. The silica wet gel composite was subjected to solvent displacement treatment followed by drying to obtain the composite material.

7. The method for preparing a laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 6, characterized in that, The preparation process of the silica sol is as follows: the silicon source precursor undergoes a hydrolysis-condensation reaction under the action of an alkaline catalyst; then it is concentrated to obtain a silica sol with a solid content of 10wt% to 30wt%.

8. The method for preparing a laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 6, characterized in that, The silicon source precursor is tetraethyl orthosilicate or tetramethyl orthosilicate.

9. The method for preparing a laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 6, characterized in that, The alkaline catalyst is ammonia.

10. The method for preparing a laminated through-stitched fiber-reinforced silica aerogel composite material according to claim 6, characterized in that, The solvent replacement process includes, in sequence, an alcohol solvent replacement step and a non-polar solvent replacement step.

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