Multi-scale simulation method for improving mechanical and heat transfer properties of fiber reinforced resin composites

Abstract

The present application relates to the technical field of fiber reinforced composites, in particular to a multiscale simulation method for improving the mechanical properties and heat transfer performance of fiber reinforced resin composites, and application and fiber reinforced resin composites thereof. The method comprises the following steps: designing the interface structure of silane coupling agent, carbon nanotube and graphene, fiber and resin by using molecular dynamics simulation technology, and evaluating the functionalization, lapping degree, interface mechanics and heat transfer performance of raw materials; based on the molecular dynamics simulation results, using the representative volume element method and finite element analysis, simulating the heat transfer performance of the composite material, the fiber-resin interface stress transfer and the stress distribution of the composite material. The method can design the multifunctional interface of the fiber reinforced composite material, realize the application of multiscale simulation to the interface structure design of the fiber reinforced composite material, not only improve the mechanical properties and thermal conductivity of the composite material, but also provide theoretical guidance and experimental basis for the development of a new generation of high-performance multifunctional composite materials.

Description

Technical Field

[0001] This invention relates to the field of fiber-reinforced composite materials technology, and more specifically, to a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composite materials, its application, and fiber-reinforced resin composite materials. Background Technology

[0002] Fiber-reinforced thermoplastic resin composites exhibit unique competitive advantages in high-temperature heat transfer applications due to their excellent heat resistance, chemical stability, and significant cost-effectiveness. However, common interfacial problems in fiber-reinforced composites, such as insufficient fiber-matrix interfacial bonding strength and excessively high interfacial thermal resistance, limit their full performance. Novel nanomaterials such as carbon nanotubes (CNTs) and graphene (GR), with their superior structural characteristics and excellent physicochemical properties, are widely used to improve the interfacial strength, mechanical properties, and thermal conductivity of composite materials.

[0003] In practical applications, a key performance trade-off is encountered: while functionalizing CNTs or GR can effectively improve the interfacial bonding strength between fibers and resins, it also disrupts the intrinsic structure of these nanomaterials, leading to a significant reduction in the overall thermal conductivity of the composite material. This trade-off between interfacial strength and thermal conductivity not only reflects the complex challenges faced by nanotechnology in improving the overall performance of composite materials, but also highlights the importance of balancing different performance indicators in the design of multifunctional composite materials.

[0004] Current experimental methods for investigating the effects of nanoparticles on the properties of fiber-reinforced composites have many limitations, such as low efficiency, inability to reveal details at the molecular scale, and numerous influencing factors. Furthermore, they cannot be applied to the design or preparation of fiber-reinforced composites.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites, its application, and fiber-reinforced resin composites. The multi-scale simulation method provided in this invention can efficiently pre-design and optimize material structure and properties, reduce experimental costs and time, improve interfacial properties, shorten the time for designing or preparing fiber-reinforced composites, save production costs, and the fiber-reinforced composites designed or prepared according to this method can balance interfacial strength and thermal conductivity.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites, comprising:

[0009] Molecular scale: Using molecular dynamics simulations, we designed synergistic interfacial structures of silane coupling agents, carbon nanotubes and graphene, and fibers and resins, and evaluated the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interfacial mechanics between carbon nanotubes, graphene and resin; the interfacial mechanics between fibers and resin; and the heat transfer properties between carbon nanotubes, graphene and resin.

[0010] Macroscale: Based on molecular dynamics simulation results at the molecular scale, the representative volume element method and finite element analysis are used to simulate the heat transfer performance of composite materials, stress transfer at the fiber-resin interface, and stress distribution of composite materials.

[0011] In an optional implementation, the molecular-scale operation includes: constructing a molecular-scale interface model;

[0012] Preferably, the molecular-scale interface model includes: interface models of carbon nanotubes before and after modification with silane coupling agent and graphene before and after modification with silane coupling agent, interface models of carbon nanotubes modified with silane coupling agent, graphene modified with silane coupling agent and resin, and interface models of fibers and resin before and after modification with silane coupling agent.

[0013] Preferably, the method includes: performing heat transfer performance analysis and interfacial mechanical analysis on the molecular-scale interface model, respectively.

[0014] In an optional implementation, the molecular-scale simulation method includes at least one of the following features:

[0015] (1): The molecular model was constructed using Materials Studio software; the heat transfer performance and interfacial mechanics of the molecular-scale interface model were analyzed using LAMMPS software, and the PCFF force field was used in the molecular-scale interface model.

[0016] (2): The interface models of carbon nanotubes and graphene before and after modification with silane coupling agent, as well as the interface models of carbon nanotubes modified with silane coupling agent, graphene modified with silane coupling agent and resin, were first used for geometric optimization and kinetic equilibrium, and then the heat transfer performance was analyzed by non-equilibrium molecular dynamics.

[0017] (3): Interfacial mechanical analysis of the interface model of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin includes simulation of silane coupling agent modified carbon nanotubes being pulled out of resin and tensile simulation of the interface model of silane coupling agent modified carbon nanotubes, graphene and resin.

[0018] (4): The interface model of fiber and resin is to combine fiber and resin, wherein the fiber is grafted with silane coupling agent.

[0019] The simulation of interface mechanics includes three modes of traction separation.

[0020] In an optional implementation, the non-equilibrium molecular dynamics heat transfer performance analysis includes: calculating the thermal conductivity according to Fourier's law, whereby the thermal conductivity k is calculated using the following formula:

[0021] , where J is the heat flux density and dT / dx is the temperature gradient;

[0022] And / or, perform heat transfer simulations on the interface models of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin, and analyze the vibrational dynamic density of the materials in the models.

[0023] And / or, the cumulative correlation factor used to assess the degree of overlap in the phonon spectral density of states is calculated according to the following formula:

[0024] In this context, the subscripts "A" and "B" represent the two material components that form the interface. Given the cutoff frequency;

[0025] Preferably, the three traction separation modes of the interface mode include Mode I, Mode II, and a hybrid mode.

[0026] In an optional implementation, the macro-scale operation includes: performing micromechanical analysis on unidirectional representative volumetric units of the fiber, resin, and fiber-resin interface before and after silane coupling agent modification.

[0027] The heat transfer performance and stress distribution of the composite material were analyzed by finite element method for the fiber-embedded resin model before and after silane coupling agent modification and the composite model of the composite material.

[0028] In an optional implementation, the macroscopic-scale simulation method includes at least one of the following features:

[0029] (1): The finite element heat transfer model used in the finite element analysis is to embed the fiber braid before and after silane coupling agent modification into the resin to represent the segment of fiber-reinforced composite material. The transient finite element method is used, and a Gaussian heat source with maximum intensity is applied at the center of the model.

[0030] (2): The representative volume element is composed of fibers embedded in the resin, and the interface between the fiber and the resin before and after the modification of the silane coupling agent is a very thin interface. Stress is applied to the model, and the stress distribution in the fiber, resin and resin-fiber interface before and after the modification of the silane coupling agent is analyzed.

[0031] (3) Finite element mechanical simulation of composite materials: Apply load to the composite material model and analyze the stress distribution of the composite material.

[0032] In an optional embodiment, the resin includes thermosetting resins and thermoplastic resins;

[0033] Preferably, the resin includes epoxy resin and nylon 66 resin;

[0034] The fibers include basalt fibers.

[0035] In a second aspect, the present invention provides a fiber-reinforced resin composite material, the raw materials of which include carbon nanotubes, graphene, resin, fibers and silane coupling agents.

[0036] The carbon nanotubes, graphene, resin, fiber, and silane coupling agent were determined using the multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites described in the foregoing embodiments.

[0037] In an optional embodiment, the mass ratio of the carbon nanotubes, the graphene, the resin, the fiber, and the silane coupling agent is 1.0:1.0:(40-45):(50-57):1.0.

[0038] In an optional embodiment, the silane coupling agent comprises 3-ureapropyltrimethoxysilane;

[0039] Preferably, the fiber comprises basalt fiber;

[0040] Preferably, the resin includes thermosetting resin and thermoplastic resin;

[0041] Preferably, the resin includes epoxy resin and nylon 66 resin.

[0042] Thirdly, the present invention provides an application of a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites as described in any of the foregoing embodiments in the design or preparation of fiber-reinforced composites.

[0043] The present invention has the following beneficial effects: The multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites provided in the embodiments of the present invention can design multifunctional interfaces of fiber-reinforced composites, realize the application of multi-scale simulation technology in the interface structure design of fiber-reinforced composites, not only improve the mechanical properties and thermal conductivity of composites, but also provide theoretical guidance and experimental basis for the development of a new generation of high-performance multifunctional composites. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a molecular dynamics model diagram of silane coupling agent modified carbon nanotubes and graphene composite nylon 66 that form a bridging structure, provided in Example 1 of the present invention.

[0046] Figure 2 This is a thermal conductivity diagram in the z and y directions of the carbon nanotube and graphene composite nylon 66 composite models with different degrees of overlap constructed in Example 1 of the present invention.

[0047] Figure 3 This is a diagram of the interface model of the basalt fiber and nylon 66 composite constructed in Embodiment 1 of the present invention;

[0048] Figure 4 This is a diagram showing the maximum separation stress of the three basalt fiber and nylon 66 composite interface models in Example 1 of this invention during traction separation in Mode I. Among them, BF / PA66 is the basalt fiber and nylon 66 composite interface model, BF-gSCA / PA66 is the fiber-nylon 66 composite interface model with a small amount of 3-ureapropyltrimethoxysilane grafted on the surface, and BF-SCA / PA66 is the interface model with a silane coupling agent layer on the surface of the basalt fiber.

[0049] Figure 5 This is a thermal conductivity diagram of the basalt fiber reinforced nylon 66 composite material prepared in Example 1 of the present invention. Among them, BF / PA66 is a composite material without modification materials, BF-SCA / PA66 is a basalt fiber reinforced nylon 66 composite material modified by 3-ureapropyltrimethoxysilane, BF / CNT-GR / PA66 is a basalt fiber reinforced nylon 66 composite material modified by carbon nanotubes and graphene, and BF-SCA / CNT-GR / PA66 is a basalt fiber reinforced nylon 66 composite material modified by 3-ureapropyltrimethoxysilane, carbon nanotubes and graphene.

[0050] Figure 6 This is a tensile strength diagram of the basalt fiber reinforced nylon 66 composite material prepared in Example 1 of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0052] A multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites includes the following steps:

[0053] S1, Molecular-scale simulation;

[0054] This process mainly utilizes molecular dynamics simulation technology to design synergistic interfacial structures of silane coupling agents, carbon nanotubes and graphene, and fibers and resins. It evaluates the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interfacial mechanics between carbon nanotubes, graphene and resin; the interfacial mechanics between fibers and resin; and the heat transfer performance between carbon nanotubes, graphene and resin. The process elucidates the mechanism of interfacial performance enhancement at the molecular level.

[0055] For reference, molecular-scale interface models were constructed, including interface models of carbon nanotubes and graphene before and after silane coupling agent modification, interface models of carbon nanotubes modified with silane coupling agent, interface models of graphene modified with silane coupling agent and resin, and interface models of fibers and resin before and after silane coupling agent modification; and thermal transfer performance analysis and interfacial mechanical analysis were performed on the molecular-scale interface models respectively.

[0056] The above process uses Materials Studio software to construct molecular models. LAMMPS software is then used to analyze the heat transfer performance and interfacial mechanics of the molecular-scale interface model, employing a PCFF force field within the model.

[0057] The interface models of carbon nanotubes and graphene before and after silane coupling agent modification, as well as the interface models of silane-coupled carbon nanotubes, silane-coupled graphene, and resin, were first geometrically optimized and kineticly balanced, followed by heat transfer performance analysis using non-equilibrium molecular dynamics. The interfacial mechanical analysis of the interface models of silane-coupled carbon nanotubes, silane-coupled graphene, and resin included simulations of silane-coupled carbon nanotubes being pulled out of the resin and tensile simulations of the interface models of silane-coupled carbon nanotubes, silane-coupled graphene, and resin. The interface models of fibers and resin before and after silane coupling agent modification involved composites of fibers and resin, with the fibers grafted using a silane coupling agent. The interfacial mechanical simulations included three modes of traction separation: Mode I, Mode II, and a hybrid mode.

[0058] Non-equilibrium molecular dynamics heat transfer simulation includes: calculating thermal conductivity according to Fourier's law. The formula for calculating thermal conductivity k is as follows:

[0059] , where J is the heat flux density and dT / dx is the temperature gradient. Heat transfer simulations were performed on interface models of silane-coupled carbon nanotubes, silane-coupled graphene, and resin, and the vibrational density of the materials in the models was analyzed. The cumulative correlation factor used to evaluate the overlap of phonon spectral density of states was calculated using the following formula:

[0060] In this context, the subscripts "A" and "B" represent the two material components that form the interface. The given cutoff frequency.

[0061] In some implementations, step S1 may be performed as follows:

[0062] S1.1: An interface model of the silane coupling agent 3-ureapropyltrimethoxysilane, carbon nanotubes, and graphene was constructed using Materials Studio software. Resin molecules were added to the interface model bridging carbon nanotubes and graphene to construct an interface model of carbon nanotubes, graphene, and resin. The interface model was then geometrically optimized and its dynamics optimized.

[0063] S1.2: Non-equilibrium molecular dynamics analysis was performed using LAMMPS software to analyze the heat transfer performance of the interface models of silane coupling agent-modified nanotubes, silane coupling agent-modified graphene, and resin. A temperature gradient was established in the system, and after the system reached steady state, the temperature gradient and heat flux were calculated. Then, the thermal conductivity was calculated using Fourier's law. The formula for calculating thermal conductivity k is as follows:

[0064] , where J is the heat flux density and dT / dx is the temperature gradient. Heat transfer simulations were performed on interface models of silane-coupled carbon nanotubes, silane-coupled graphene, and resin, and the vibrational density of the materials in the models was analyzed. The cumulative correlation factor used to evaluate the overlap of phonon spectral density of states was calculated using the following formula:

[0065] In this context, the subscripts "A" and "B" represent the two material components that form the interface. The given cutoff frequency.

[0066] S1.3: Interfacial mechanical analysis of the interface models of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene, and resin includes simulations of silane coupling agent-modified carbon nanotubes being pulled out of resin and tensile simulations of the interface models of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene, and resin. The simulation of silane coupling agent-modified carbon nanotubes being pulled out of resin uses a fixed z-axis at both ends of the composite model, with the silane coupling agent-modified carbon nanotubes being pulled out of the interface model of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene, and resin at a constant speed. The overall mechanical properties of the interface models of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene, and resin are obtained through tensile simulation of the model. Statistical analysis is performed on the stress-displacement curves, resin orientation parameters, and entanglement parameters during the tensile process.

[0067] S1.4: Interface simulation of fibers and resins before and after silane coupling agent modification was performed using Materials Studio software to construct fiber and resin models separately, which were then combined to form an interface model. The interface models of fibers and resins modified with silane coupling agents included two types: one where a small amount of 3-ureapropyltrimethoxysilane was grafted onto the fiber surface, and another where a layer of 3-ureapropyltrimethoxysilane coupling agent was placed between basalt fibers and nylon 66 resin. The silane coupling agent was present both chemically grafted onto the fiber surface and through physical mixing and chemical self-crosslinking. The composite model was equilibrated through multiple kinetic processes, and the equilibrated model was then used for interface mechanical simulation in LAMMPA software. In the traction separation simulation, the top portion of the resin was fixed, and the fiber was moved at a constant speed along different directions (Mode I, Mode II, and a mixed mode). During the traction separation process, the stress changes, energy changes, and motion behavior of atoms in the interface model were statistically analyzed.

[0068] For example, the resins mentioned above include thermosetting epoxy resin and thermoplastic nylon 66 resin.

[0069] The preset fiber is basalt fiber. In other embodiments, the fiber can be adjusted to other types of fiber as needed.

[0070] S2, on a macro scale;

[0071] Based on the results of major molecular simulations, this process uses the representative volume element method and finite element analysis to simulate the heat transfer properties of composite materials, stress transfer at the fiber-resin interface, and stress distribution of composite materials.

[0072] For reference, based on the representative volume element method and finite element analysis, the simulation of the heat transfer performance, fiber-resin interface stress transfer, and stress distribution of the composite material includes: performing micromechanical analysis on the unidirectional representative volume elements (RVE) of the fiber, resin, and fiber-resin interface before and after silane coupling agent modification; performing finite element analysis on the heat transfer performance of the fiber-embedded resin model before and after silane coupling agent modification and the composite model of the composite material, as well as the stress distribution of the composite material.

[0073] The finite element heat transfer model used in the finite element analysis represents a segment of fiber-reinforced composite material by embedding the fiber weave before and after silane coupling agent modification into the resin. The transient finite element method is used, and a Gaussian heat source with maximum intensity is applied at the center of the model.

[0074] The representative volume element is composed of fibers embedded in resin, and the interface between the fiber and the resin is a very thin interface. Stress is applied to the model to analyze the stress distribution in the fiber, resin, and resin-fiber interface before and after silane coupling agent modification.

[0075] Finite element mechanical simulation of composite materials involves applying loads to the composite material model and analyzing the stress distribution of the composite material.

[0076] In some implementations, step S2 may be performed as follows:

[0077] S2.1: A segment of the fiber-reinforced composite material is represented by embedding the fibers, both before and after silane coupling agent modification, into the resin. A transient finite element method is used, with a Gaussian heat source applied at the center of the model. The same loading procedure is applied to both basalt fiber and resin composite models with and without silane coupling agent modification, and the temperature distribution within the composite model is observed.

[0078] S22: The representative volumetric element model consists of fibers embedded in resin, and a very thin interface is constructed between the fibers and resin before and after silane coupling agent modification. Stresses in different directions are applied to the model, and the stress distribution in the fibers, resin, and fiber-resin interface before and after silane coupling agent modification is observed.

[0079] S23: Construct a finite element simulation model of the composite material, apply a line load to the model, and analyze the stress distribution of the composite material.

[0080] The composite material model described in the embodiments of the present invention refers to a composite material model formed by carbon nanotubes, graphene, fibers, resin and silane coupling agent.

[0081] Furthermore, the multi-scale simulation method provided by the present invention may also include:

[0082] S3, Composite material performance testing.

[0083] The process mainly involves preparing fiber-reinforced resin composites synergistically modified with silane coupling agents, carbon nanotubes, and graphene, and testing the enhancing effect of silane coupling agents and nanoparticles on the mechanical and heat transfer properties of the fiber-reinforced composites to verify the simulation results.

[0084] In some implementations, step S3 may be performed as follows:

[0085] S3.1: Cut commercial basalt fiber fabric into uniform sizes, immerse in ethanol, replacing the ethanol periodically to clean the chemical reagents from the fiber surface, and then dry the fabric. Add 3-ureapropyltrimethoxysilane to a mixed solution of ethanol and water, stir for 1-2 hours to prepare a 5%-8% silane coupling agent solution. Add carbon nanotubes and graphene to the silane coupling agent solution, stir for 3-5 hours to disperse evenly. Immerse the fabric in the silane coupling agent solution, then in the mixed solution of carbon nanotubes and graphene. Place the modified BF fabric in a forced-air drying oven and cure at 80-110℃ for 1-2 hours. Clean the fabric to remove loosely bonded silane coupling agent, carbon nanotubes, and graphene from the surface, and dry the cleaned fabric at 80-90℃ for 2-4 hours. Six to ten pieces of fiber fabric and resin are stacked alternately and placed in a flat vulcanizing machine (the temperature of the flat plate is 180 to 200°C) for hot pressing to prepare fiber-reinforced composite materials.

[0086] S3.2: The surface chemical structure of the fibers before and after modification was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS); the morphology of the fiber surface was characterized by scanning electron microscopy (SEM); the tensile strength, flexural strength, interlaminar shear strength and compressive strength of the composite material were tested by a universal tensile testing machine; and the thermal conductivity of the composite material was tested by the transient planar heat source method.

[0087] As can be seen, in a second aspect, the present invention provides a fiber-reinforced resin composite material, the raw materials of which include carbon nanotubes, graphene, resin, fiber and silane coupling agent, wherein the carbon nanotubes, graphene, resin, fiber and silane coupling agent are determined by the multi-scale simulation method for improving the mechanical properties and thermal transfer properties of the fiber-reinforced resin composite material as described in the foregoing embodiments.

[0088] The fiber-reinforced resin composite material was prepared according to the above method. At the same time, the performance of the fiber-reinforced resin composite material was tested, which further proved that the multi-scale simulation method provided in this embodiment of the invention can accurately simulate the fiber-reinforced resin composite material while taking into account both interfacial strength and thermal conductivity.

[0089] Meanwhile, in the multi-scale simulation method of this invention, carbon nanotubes, graphene, resin, fiber and silane coupling agent are first determined, and then the simulation results are determined. Based on the results, the original carbon nanotubes, graphene, resin, fiber and silane coupling agent are used to prepare fiber-reinforced resin composite material to verify the simulation results, and a new fiber-reinforced resin composite material is obtained.

[0090] The mass ratio of carbon nanotubes, graphene, resin, fiber and silane coupling agent is 1.0:1.0:(40-45):(50-57):1.0.

[0091] In an optional embodiment, the silane coupling agent includes 3-ureapropyltrimethoxysilane; the fiber includes, but is not limited to, basalt fiber; the resin includes thermosetting resins and thermoplastic resins; for example, including but not limited to epoxy resins and nylon 66 resin.

[0092] Building upon the above, the multi-scale simulation method proposed in this invention combines computational simulations at multiple scales with experimental structures. This enables the exploration of interfacial structure properties at the molecular level and the explanation of the mechanisms underlying the enhanced mechanical and thermal transfer at the molecular level. It also reveals the mechanical and thermal properties of composite materials at a macroscopic scale.

[0093] Accordingly, the interface structure designed by the multi-scale simulation method provided by this invention can be used to improve the interfacial mechanical properties, mechanical properties, and heat transfer properties of fiber-reinforced composite materials. In other words, this invention provides an application of the multi-scale simulation method for improving the mechanical and heat transfer properties of fiber-reinforced resin composite materials as described in any of the foregoing embodiments in the design or preparation of fiber-reinforced composite materials.

[0094] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0095] Example 1

[0096] This embodiment provides a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites, including the following steps:

[0097] S1: Using molecular dynamics simulation techniques, we will design interfacial structures for synergistic interaction between silane coupling agents, carbon nanotubes and graphene, and fibers and resins, evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interfacial mechanics between carbon nanotubes, graphene and resin; the interfacial mechanics between fibers and resin; and the heat transfer performance between carbon nanotubes, graphene and resin, elucidating the mechanism of interfacial performance enhancement at the molecular level.

[0098] S1.1: Molecular models of carbon nanotubes and graphene modified with the silane coupling agent 3-ureapropyltrimethoxysilane were constructed using Materials Studio software. Nylon 66 resin molecules were added to the molecular model bridging 3-ureapropyltrimethoxysilane-modified carbon nanotubes and 3-ureapropyltrimethoxysilane-modified graphene to construct interface models of the 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin. Geometric optimization and kinetics were performed on the interface models of the 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin. The equilibrium molecular models are shown below. Figure 1 As shown.

[0099] S1.2: Non-equilibrium molecular dynamics analysis of the interfacial model of carbon nanotubes, graphene, and resin was performed using LAMMPS software. A temperature gradient was established in the system, and after the system reached steady state, the temperature gradient and heat flux were calculated. Then, the thermal conductivity was calculated using Fourier's law. The formula for calculating thermal conductivity k is as follows:

[0100] Where J is the heat flux density and dT / dx is the temperature gradient. The thermal conductivity in the z and y directions of the constructed carbon nanotube and graphene composite nylon 66 (PA66) models with different degrees of overlap is shown in the following figures. Figure 2 As shown, heat transfer simulations were performed on the interface models of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin, and the vibrational density of the materials in the models was analyzed. The cumulative correlation factor used to evaluate the overlap of phonon spectral density of states was calculated according to the following formula:

[0101] In this context, the subscripts "A" and "B" represent the two material components that form the interface. The given cutoff frequency.

[0102] S1.3: Interfacial mechanical analysis of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin includes simulations of the pull-out of 3-ureapropyltrimethoxysilane-modified carbon nanotubes from nylon 66 resin and tensile simulations of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin. The pull-out simulation of 3-ureapropyltrimethoxysilane-modified carbon nanotubes from resin uses a fixed z-axis, with the 3-ureapropyltrimethoxysilane-modified carbon nanotubes being pulled out of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin at a constant speed. The overall mechanical properties of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin were simulated by tensile testing. Statistical analysis was performed on the stress-displacement curves, nylon 66 orientation parameters, and entanglement parameters during the tensile process.

[0103] S1.4: Interface simulation of 3-ureapropyltrimethoxysilane-modified fiber and resin: Models of 3-ureapropyltrimethoxysilane-modified basalt fiber and nylon 66 resin were constructed separately using Materials Studio software. Then, the two were combined to form an interface model. The interface model of basalt fiber combined with nylon 66 is shown below. Figure 3 As shown. Interface models for silane coupling agent-modified fibers and resins include two types: one where only a small amount of 3-ureapropyltrimethoxysilane is grafted onto the fiber surface, and the other where a layer of 3-ureapropyltrimethoxysilane coupling agent is placed between basalt fibers and nylon 66 resin. The silane coupling agent can be chemically grafted onto the fiber surface or physically mixed and chemically self-crosslinked. The composite model was equilibrated through multiple kinetic processes, and then the equilibrated model was used for interface mechanical simulation in LAMMPA software. In the traction separation simulation, the top portion of the nylon 66 resin was used to move the basalt fiber at a constant speed along different directions (Mode I, Mode II, and a mixed mode). During the traction separation process, the stress changes, energy changes, and motion behavior of atoms in the interface model were statistically analyzed. The maximum separation stress in Mode I traction separation for the three basalt fiber and nylon 66 composite interface models was as follows: Figure 4 As shown.

[0104] S2: Based on the main molecular simulation results, the representative volume element method and finite element analysis are used to simulate the heat transfer performance of the composite material, the stress transfer at the basalt fiber-nylon 66 resin interface, and the stress distribution of the composite material.

[0105] S2.1: A segment representing a basalt fiber-reinforced nylon 66 fiber-reinforced composite material is shown, in which basalt fibers are woven and embedded into a nylon 66 resin matrix. A transient finite element method is used, with a Gaussian heat source applied at the center of the model. The same loading procedure is applied to both basalt fiber and nylon 66 resin composite models with and without silane coupling agent modification, and the temperature distribution within the composite models is observed.

[0106] S2.2: The representative volumetric element model consists of fibers embedded in resin, with a very thin interface constructed at the fiber-resin interface. Stresses in different directions are applied to the model, and the stress distribution in the fibers, resin, and fiber-resin interface is observed.

[0107] S2.3: Construct a finite element simulation model of the composite material, apply a line load to the composite model of fiber and resin, and analyze the stress distribution of the composite material.

[0108] In a second aspect, the present invention provides a fiber-reinforced resin composite material, comprising:

[0109] Commercial basalt fiber fabric was cut into uniform sizes and immersed in ethanol. The ethanol was replaced periodically to clean the chemical reagents from the fiber surface. The fabric was then dried. A 5% (w / w) silane coupling agent solution was prepared by adding 3-ureapropyltrimethoxysilane to a mixture of ethanol and water and stirring for 1-2 hours. 2 mg of carbon nanotubes and 2 mg of graphene were added to 296 ml of the silane coupling agent solution and stirred for 3 hours to ensure uniform dispersion. The fabric was then immersed in the silane coupling agent solution for 60 minutes, followed by immersion in the mixed solution of carbon nanotubes and graphene for 60 minutes. The modified BF fabric was placed in a forced-air drying oven and cured at 110°C for 1 hour. The fabric was then cleaned to remove loosely bonded silane coupling agent, carbon nanotubes, and graphene from the surface. The cleaned fabric was then dried at 80°C for 2 hours. Six pieces of fiber fabric and nylon 66 resin film were alternately stacked and placed in a flat vulcanizing machine (the plate temperature was 180°C) for hot pressing to prepare fiber-reinforced composite materials.

[0110] The surface chemical structure of basalt fibers before and after modification was analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The morphology of the fiber surface was characterized using scanning electron microscopy (SEM). The thermal conductivity of the composite material was tested using the transient planar heat source method. The thermal conductivity of the prepared basalt fiber reinforced nylon 66 composite material is as follows: Figure 5 As shown. The tensile strength, flexural strength, interlaminar shear strength, and compressive strength of the composite material were tested using a universal tensile testing machine. The tensile strength of the prepared basalt fiber reinforced nylon 66 composite material is shown in the figure. Figure 6 As shown.

[0111] The test results above verify the simulation results.

[0112] Example 2

[0113] This embodiment provides a multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites, including the following steps:

[0114] S1: Using molecular dynamics simulation techniques, we will design interfacial structures for synergistic interaction between silane coupling agents, carbon nanotubes and graphene, and fibers and resins, evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interfacial mechanics between carbon nanotubes, graphene and resin; the interfacial mechanics between fibers and resin; and the heat transfer performance between carbon nanotubes, graphene and resin, elucidating the mechanism of interfacial performance enhancement at the molecular level.

[0115] S1.1: Molecular models of carbon nanotubes and graphene modified with the silane coupling agent 3-ureapropyltrimethoxysilane were constructed using Materials Studio software. Epoxy resin molecules were added to the molecular model bridging the 3-ureapropyltrimethoxysilane-modified carbon nanotubes and graphene to construct interface models for the carbon nanotubes, graphene, and resin. Geometric optimization and kinetics were performed on the interface models of the 3-ureapropyltrimethoxysilane-modified carbon nanotubes, graphene, and resin. A crosslinking script was used to perform a crosslinking reaction on the epoxy resin model.

[0116] S1.2: Non-equilibrium molecular dynamics analysis was performed using LAMMPS software to investigate the heat transfer properties of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin. A temperature gradient was established in the system, and after the system reached steady state, the temperature gradient and heat flux were calculated. Then, the thermal conductivity was calculated using Fourier's law. The formula for calculating thermal conductivity k is as follows:

[0117] , where J is the heat flux density and dT / dx is the temperature gradient. Heat transfer simulations were performed on the interface models of carbon nanotubes, graphene, and resin, and the vibrational density of the materials in the models was analyzed. The cumulative correlation factor used to assess the overlap of phonon spectral density of states was calculated using the following formula:

[0118] In this context, the subscripts "A" and "B" represent the two material components that form the interface. The given cutoff frequency.

[0119] S1.3: Interfacial mechanical analysis of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin includes simulations of the pull-out of 3-ureapropyltrimethoxysilane-modified carbon nanotubes from epoxy resin and tensile simulations of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin. The pull-out simulation of 3-ureapropyltrimethoxysilane-modified carbon nanotubes from resin uses a fixed z-axis, with the carbon nanotubes pulled out of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin at a constant speed. The overall mechanical properties of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene, and resin are determined through tensile simulation of the model. Statistical analysis was performed on the stress-displacement curves, epoxy resin orientation parameters, and entanglement parameters during the tensile process.

[0120] S1.4: Interface simulation of 3-ureapropyltrimethoxysilane-modified fiber and resin: MaterialsStudio software was used to construct separate models of 3-ureapropyltrimethoxysilane-modified basalt fiber and epoxy resin, which were then combined to form an interface model. The interface models of the silane coupling agent-modified fiber and resin included two types: one where a small amount of 3-ureapropyltrimethoxysilane was grafted onto the fiber surface, and another where a 3-ureapropyltrimethoxysilane layer was placed between the basalt fiber and nylon 66 resin. The silane coupling agent was applied both chemically to the fiber surface and through physical mixing and chemical self-crosslinking. The composite model was equilibrated through multiple kinetic processes, and the equilibrated model was then used for interface mechanical simulation in LAMMPA software. In the traction separation simulation, the basalt fiber was moved at a constant speed along different directions (Mode I, Mode II, and a mixed mode) at the top of the epoxy resin. During the traction separation process, the stress changes, energy changes, and motion behavior of atoms in the interface model were statistically analyzed.

[0121] S2: Based on the main molecular simulation results, the representative volume element method and finite element analysis are used to simulate the heat transfer performance of composite materials, stress transmission at the basalt fiber-epoxy resin interface, and stress distribution of composite materials.

[0122] S2.1: A segment representing a basalt fiber-reinforced epoxy fiber-reinforced composite material is represented by basalt fiber braiding embedded in an epoxy resin matrix. A transient finite element method is used, with a Gaussian heat source applied at the center of the model. The same loading procedure is applied to both basalt fiber and epoxy resin composite models with and without silane coupling agent modification, and the temperature distribution within the composite model is observed.

[0123] S2.2: The representative volumetric element model consists of fibers embedded in resin, with a very thin interface constructed at the fiber-resin interface. Stresses in different directions are applied to the model, and the stress distribution in the fibers, resin, and fiber-resin interface is observed.

[0124] S2.3: Construct a finite element simulation model of the composite material, apply a line load to the composite model of fiber and resin, and analyze the stress distribution of the composite material.

[0125] In a second aspect, the present invention provides a fiber-reinforced resin composite material, comprising:

[0126] Commercial basalt fiber fabric was cut into uniform sizes and immersed in ethanol. The ethanol was replaced periodically to clean the chemical reagents from the fiber surface, followed by drying. 3-Ureapropyltrimethoxysilane was added to a mixture of ethanol and water and stirred for 1 hour to prepare a 5% (w / w) silane coupling agent solution. 2 mg of carbon nanotubes and 2 mg of graphene were added to 296 ml of the silane coupling agent solution and stirred for 3 hours to ensure uniform dispersion. The fiber fabric was immersed in the silane coupling agent solution for 60 minutes, then immersed in a mixture of carbon nanotubes and graphene for 60 minutes. The modified BF fabric was placed in a forced-air drying oven and cured at 80°C for 1 hour. The fabric was then cleaned to remove loosely bonded silane coupling agent, carbon nanotubes, and graphene from the surface. The cleaned fiber fabric was dried at 80°C for 2 hours. Six pieces of fiber fabric were coated with a mixture of epoxy resin monomer and curing agent, placed in a flat vulcanizing machine (flat plate temperature 200°C), and hot-pressed to prepare fiber-reinforced composite materials.

[0127] The surface chemical structure of basalt fibers before and after modification was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS); the morphology of the fiber surface was characterized by scanning electron microscopy (SEM); the tensile strength, flexural strength, interlaminar shear strength and compressive strength of the composite material were tested by a universal tensile testing machine; and the thermal conductivity of the composite material was tested by the transient planar heat source method.

[0128] The test results above verify the simulation results.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-scale simulation method for improving the mechanical and thermal properties of fiber-reinforced resin composites, characterized in that, include: S1.1: An interface model of silane coupling agent 3-ureapropyltrimethoxysilane, carbon nanotubes and graphene was constructed using Materials Studio software; resin molecules were added to the interface model bridging carbon nanotubes and graphene to construct an interface model of carbon nanotubes, graphene and resin, and the interface model was geometrically optimized. S1.2: The heat transfer performance of the interface models of silane coupling agent modified nanotubes, silane coupling agent modified graphene and resin was analyzed using non-equilibrium molecular dynamics with LAMMPS software. Heat transfer simulations were performed on the interface models of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene, and resin, and the vibrational dynamic density of the materials in the models was analyzed. The cumulative correlation factor used to evaluate the overlap of phonon spectral density of states was calculated according to the following formula: In this context, the subscripts "A" and "B" represent the two material components that form the interface. Given the cutoff frequency; S1.3: Interfacial mechanical analysis of the interface models of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin, including simulation of silane coupling agent modified carbon nanotubes being pulled out of resin and tensile simulation of the interface models of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin. S1.4: Interface simulation of fiber and resin before and after silane coupling agent modification: Fiber and resin models were constructed separately using Materials Studio software, and then the two were combined to form an interface model. The equilibrium of the composite model is achieved through multiple dynamic processes, and then the equilibrium model is simulated in the LAMMPA software for interface mechanics. S2.1: Embed the fiber weave before and after silane coupling agent modification into the resin to represent a segment of the fiber-reinforced composite material; use the transient finite element method and apply a Gaussian heat source at the center of the model; use the same loading steps for the basalt fiber and resin composite models without silane coupling agent modification and with silane coupling agent modification, and observe the temperature distribution in the composite model; S2.2: The representative volumetric unit model is composed of fibers embedded in resin, and a very thin interface is constructed at the fiber and resin interface before and after silane coupling agent modification; stresses in different directions are applied to the model to observe the stress distribution in the fiber, resin and fiber-resin interface before and after silane coupling agent modification. S2.3: Construct a finite element simulation model of the composite material, apply a line load to the composite material model, and analyze the stress distribution of the composite material.

2. The multi-scale simulation method according to claim 1, characterized in that, Non-equilibrium molecular dynamics heat transfer performance analysis includes: calculating thermal conductivity according to Fourier's law. The formula for calculating thermal conductivity k is as follows: , where J is the heat flux density and dT / dx is the temperature gradient.

3. The multi-scale simulation method according to claim 1, characterized in that, The resins include epoxy resin and nylon 66 resin.

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