Multi-scale simulation method for improving mechanical property and heat transfer property of fiber reinforced resin composite material, application of multi-scale simulation method and fiber reinforced resin composite material

Abstract

The invention relates to the technical field of fiber reinforced composite materials, in particular to a multi-scale simulation method for improving the mechanical property and the heat transfer property of a fiber reinforced resin composite material, application of the multi-scale simulation method and the fiber reinforced resin composite material. Comprising the steps that a molecular dynamics simulation technology is used for designing an interface structure where a silane coupling agent, a carbon nano tube, graphene, fiber and resin cooperate, and the functionalization, the lap joint degree, the interface mechanics and the heat transfer performance of raw materials are evaluated; based on a molecular dynamics simulation result, a representative volume element method and finite element analysis are adopted, and the heat transfer performance of the composite material, fiber-resin interface stress transfer and stress distribution of the composite material are simulated. According to the method, the multifunctional interface of the fiber reinforced composite material can be designed, the application of multi-scale simulation on the interface structure design of the fiber reinforced composite material is realized, the mechanical property and the heat conductivity of the composite material are improved, and theoretical guidance and experimental basis are provided for developing a new generation of high-performance multifunctional composite materials.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber reinforced composite materials, and in particular to a multi-scale simulation method for improving the mechanical properties and heat transfer properties of a fiber reinforced resin composite material, and its application and a fiber reinforced resin composite material. Background Art

[0002] Rock fiber reinforced thermoplastic resin composites have shown unique competitive advantages in high temperature environment heat transfer applications due to their excellent heat resistance, chemical stability and significant cost-effectiveness. However, the common interface problems of fiber reinforced composites, such as insufficient fiber-matrix interface bonding strength and excessively high interface thermal resistance, restrict their full performance. New nanomaterials such as carbon nanotubes (CNT) and graphene (GR) are widely used to improve the interface strength, mechanical properties and thermal conductivity of composite materials due to their excellent structural characteristics and excellent physical and chemical properties.

[0003] In practical applications, there is a key performance trade-off problem: although functionalization of CNT or GR can effectively improve the interfacial bonding strength between the fiber and the resin, it will also destroy the intrinsic structure of these nanomaterials, resulting in a significant decrease in the overall thermal conductivity of the composite material. This trade-off between "interface strength and thermal conductivity" not only reflects the complex challenges faced by nano-modification technology in improving the comprehensive performance of composite materials, but also highlights the importance of weighing different performance indicators in the design of multifunctional composite materials.

[0004] Current experimental methods for studying the effects of nanoparticles on the performance of fiber-reinforced composites have many limitations, such as low efficiency, inability to reveal details at the molecular scale, and a large number of influencing factors, and 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 the present invention is to provide a multi-scale simulation method for improving the mechanical properties and heat transfer properties of fiber-reinforced resin composite materials, and its application and fiber-reinforced resin composite materials. The multi-scale simulation method provided by the embodiment of the present invention can efficiently pre-design and optimize material structure and performance, reduce experimental costs and cycles, improve interface performance, shorten the time for designing or preparing fiber-reinforced composite materials, save production costs, and the fiber-reinforced composite materials designed or prepared according to the method can take into account both interface strength and thermal conductivity.

[0007] The present invention is achieved in that:

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

[0009] Molecular scale: Molecular dynamics simulation technology is used to design the interface structure of silane coupling agent, carbon nanotubes and graphene, fiber and resin, and evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interface mechanics between carbon nanotubes, graphene and resin; the interface mechanics between fiber and resin; and the heat transfer performance between carbon nanotubes, graphene and resin;

[0010] Macroscale: Based on the 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 the composite material, the fiber-resin interface stress transfer, and the stress distribution of the composite material.

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

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

[0013] Preferably, it includes: performing heat transfer performance analysis and interface mechanics analysis on the molecular scale interface model respectively.

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

[0015] (1): Materials Studio software was used to construct the molecular model; LAMMPS software was used to analyze the heat transfer performance and interface mechanics of the molecular scale interface model, and the PCFF force field was used in the molecular scale interface model;

[0016] (2): Using the interface models of carbon nanotubes before and after silane coupling agent modification and graphene before and after silane coupling agent modification, as well as the interface models of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin, geometric optimization and dynamic equilibrium are first performed, and then heat transfer performance analysis is performed in non-equilibrium molecular dynamics;

[0017] (3): Interface mechanics analysis of the interface model of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin, including the simulation of pulling out the carbon nanotubes modified by silane coupling agent from the resin and the tensile simulation of the interface model of carbon nanotubes modified by silane coupling agent, graphene and resin;

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

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

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

[0021] Where J is the heat flux, dT / dx is the temperature gradient;

[0022] and / or, performing heat transfer simulation on an interface model of carbon nanotubes modified by a silane coupling agent, graphene modified by a silane coupling agent, and a resin, and analyzing the vibrational density of the material in the model;

[0023] And / or, the cumulative correlation factor used to evaluate the degree of overlap of the phonon spectral state density is calculated as follows:

[0024] The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency;

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

[0026] In an optional embodiment, the macro-scale operation includes: performing a mesomechanical analysis on a unidirectional representative volume unit of the fiber, the resin, and the fiber-resin interface before and after modification with the silane coupling agent;

[0027] The finite element method was used to analyze 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.

[0028] In an optional embodiment, the macro-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 weaving and embedding into the resin to represent the fiber reinforced composite material fragment before and after the modification of the silane coupling agent. The transient finite element method is used, and the Gaussian heat source with the maximum intensity is applied at the center of the model;

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

[0031] (3) Finite element mechanical simulation of composite materials: Loads are applied to the composite material model to analyze the stress distribution of the composite material.

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

[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, fiber and silane coupling agent;

[0036] The carbon nanotubes, the graphene, the resin, the fibers and the 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 described in the aforementioned embodiment.

[0037] In an optional embodiment, the mass ratio of the carbon nanotube, 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 includes 3-ureapropyltrimethoxysilane;

[0039] Preferably, the fibers include basalt fibers;

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

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

[0042] In a third aspect, the present invention provides an application of a multi-scale simulation method for improving the mechanical properties and thermal transfer properties of fiber-reinforced resin composite materials as described in any of the aforementioned embodiments in the design or preparation of fiber-reinforced composite materials.

[0043] The present invention has the following beneficial effects: the multi-scale simulation method for improving the mechanical properties and thermal transfer properties of fiber-reinforced resin composites provided by the embodiment of the present invention can design the multifunctional interface of fiber-reinforced composites, and realize the application of multi-scale simulation technology in the interface structure design of fiber-reinforced composites, which not only improves the mechanical properties and thermal conductivity of the composites, but also provides theoretical guidance and experimental basis for the development of a new generation of high-performance multifunctional composites. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

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

[0046] Figure 2 : is a graph of thermal conductivity in the z direction and the y direction of the composite model of carbon nanotubes and graphene composite nylon 66 with different overlapping degrees 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 Example 1 of the present invention;

[0048] Figure 4 It is the maximum separation stress diagram of the three composite interface models of basalt fiber and nylon 66 in Example 1 of the present invention during traction separation in mode I, wherein BF / PA66 is a composite interface model of basalt fiber and nylon 66, BF-gSCA / PA66 is a fiber composite nylon 66 interface model with a small amount of 3-ureapropyltrimethoxysilane grafted on the surface, and BF-SCA / PA66 is an interface model of a silane coupling agent layer on the surface of the basalt fiber;

[0049] Figure 5 : is a thermal conductivity diagram of the basalt fiber reinforced nylon 66 composite material prepared in Example 1 of the present invention, wherein BF / PA66 is a composite material without modified 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 graph of the tensile strength of the basalt fiber reinforced nylon 66 composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0052] A multi-scale simulation method for improving the mechanical properties and thermal transfer performance of fiber reinforced resin composite materials comprises the following steps:

[0053] S1, molecular scale simulation;

[0054] This process mainly uses molecular dynamics simulation technology to design the synergistic interface structure of silane coupling agents, carbon nanotubes and graphene, fibers and resins, evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interface mechanics between carbon nanotubes, graphene and resins; the interface mechanics between fibers and resins; and the heat transfer performance between carbon nanotubes, graphene and resins, and clarify the mechanism of interface performance improvement from a molecular level.

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

[0056] The above process uses Materials Studio software to build a molecular model. LAMMPS software is used to analyze the heat transfer performance and interface mechanics of the molecular scale interface model, and the PCFF force field is used in the molecular scale interface model.

[0057] The interface models of carbon nanotubes before and after silane coupling agent modification and graphene before and after silane coupling agent modification, as well as the interface models of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin are first subjected to geometric optimization and dynamic equilibrium, and then the heat transfer performance is analyzed in non-equilibrium molecular dynamics. The interface mechanics analysis of the interface models of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin includes the simulation of pulling out carbon nanotubes modified by silane coupling agent from resin and the tensile simulation of the interface models of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin. The interface model of fiber and resin before and after silane coupling agent modification is to composite fiber and resin, wherein the fiber is grafted with silane coupling agent. The simulation of interface mechanics includes three modes of traction separation. The three traction separation modes of the interface mode include mode I, mode II and mixed mode.

[0058] The non-equilibrium molecular dynamics heat transfer simulation includes: calculating the thermal conductivity according to Fourier's law. The calculation formula of thermal conductivity k is calculated according to the following formula:

[0059] Where J is the heat flux and dT / dx is the temperature gradient. Heat transfer simulation is performed on the interface model of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene and resin, and the vibrational state density of the materials in the model is analyzed. The cumulative correlation factor used to evaluate the overlap degree of the phonon spectral state density is calculated according to the following formula:

[0060] The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency.

[0061] In some embodiments, step S1 can be performed as follows:

[0062] S1.1: Materials Studio software was used to construct the interface model of silane coupling agent 3-ureapropyltrimethoxysilane, carbon nanotubes and graphene. Resin molecules were added to the interface model of carbon nanotubes and graphene bridges to construct the interface model of carbon nanotubes, graphene and resin, and the interface model was geometrically optimized and dynamic.

[0063] S1.2: LAMMPS software is used to perform non-equilibrium molecular dynamics to analyze the heat transfer performance of the interface model of silane coupling agent-modified nanotubes, silane coupling agent-modified graphene and resin. A temperature gradient is established in the system, and when the system reaches a steady state, the temperature gradient and heat flow of the system are calculated, and then the thermal conductivity is calculated according to Fourier's law. The calculation formula of thermal conductivity k is calculated according to the following formula:

[0064] Where J is the heat flux and dT / dx is the temperature gradient. Heat transfer simulation is performed on the interface model of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene and resin, and the vibrational state density of the materials in the model is analyzed. The cumulative correlation factor used to evaluate the overlap degree of the phonon spectral state density is calculated according to the following formula:

[0065] The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency.

[0066] S1.3: The interfacial mechanical analysis of the interface model of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin includes the simulation of pulling out the silane coupling agent modified carbon nanotubes from the resin and the tensile simulation of the interface model of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin. The simulation of pulling out the silane coupling agent modified carbon nanotubes from the resin adopts the upper and lower ends of the z-axis of the fixed composite model, and the silane coupling agent modified carbon nanotubes are pulled out from 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 model of silane coupling agent modified carbon nanotubes, silane coupling agent modified graphene and resin are simulated by stretching the model. The stress displacement curve, resin orientation parameters and entanglement parameters during the stretching process are statistically analyzed.

[0067] S1.4: Interface simulation of fiber and resin before and after silane coupling agent modification. The fiber and resin models are constructed separately using Materials Studio software, and then the two are composited to form an interface model. The interface model of fiber and resin modified by silane coupling agent includes two types: only a small amount of 3-ureapropyltrimethoxysilane is grafted on the fiber surface, and a silane coupling agent 3-ureapropyltrimethoxysilane layer is placed between basalt fiber and nylon 66 resin, in which the silane coupling agent includes both chemical grafting on the fiber surface and physical mixing and chemical self-crosslinking. The equilibrium of the composite model adopts multiple dynamic processes, and then the equilibrium model is used for interface mechanics simulation in LAMMPA software. In the traction separation simulation, the top part of the resin is fixed, and the fiber is moved at a constant speed in different directions (mode I, mode II and mixed mode). During the traction separation process, the stress changes, energy changes and movement behaviors of atoms in the interface model are statistically analyzed.

[0068] By way of example, the above-mentioned resin includes epoxy resin which is a thermosetting resin and nylon 66 resin which is a thermoplastic resin.

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

[0070] S2, on a macroscopic scale;

[0071] The process is based on the main molecular simulation results, using representative volume element method and finite element analysis to simulate the heat transfer performance of the composite material, fiber-resin interface stress transfer and stress distribution of the composite material.

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

[0073] The finite element heat transfer model used in the finite element analysis is to embed the fibers before and after modification with silane coupling agent into the resin to represent the fragments of the fiber reinforced composite material. The transient finite element method is used to apply the maximum intensity Gaussian heat source at the center of the model.

[0074] The representative volume unit 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 modification with silane coupling agent.

[0075] Finite element mechanics simulation of composite materials applies loads to the composite model and analyzes the stress distribution of the composite material.

[0076] In some embodiments, step S2 can be performed as follows:

[0077] S2.1: The fiber before and after silane coupling agent modification is woven and embedded into the resin to represent the fragment of the fiber reinforced composite material. Using the transient finite element method, a Gaussian heat source is applied at the center of the model. The same loading steps are used for the basalt fiber and resin composite model without silane coupling agent modification and with silane coupling agent modification to observe the temperature distribution in the composite model.

[0078] S22: The representative volume unit model is composed of fibers embedded in resin, and a very thin interface is constructed between the fiber and resin before and after silane coupling agent modification. Stress in different directions is applied to the model to observe the distribution of stress in the fiber, resin, and fiber-resin interface before and after silane coupling agent modification.

[0079] S23: 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.

[0080] The model of the composite material described in the embodiment of the present invention refers to a model of the composite material 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 prepares fiber-reinforced resin composites modified synergistically by silane coupling agents, carbon nanotubes and graphene, and tests the enhancement effect of the synergistic modification of silane coupling agents and nanoparticles on the mechanical properties and thermal transfer properties of fiber-reinforced composites to verify the simulation results.

[0084] In some embodiments, step S3 can be performed as follows:

[0085] S3.1: Cut the commercial basalt fiber fabric into the same size, immerse it in ethanol, replace the ethanol at regular intervals, clean the chemical reagents on the fiber surface, and then dry the fiber fabric. Add 3-ureapropyltrimethoxysilane to the mixed solution of ethanol and water, stir for 1 to 2 hours, and prepare a silane coupling agent solution with a mass concentration of 5% to 8%. Add carbon nanotubes and graphene to the silane coupling agent solution, stir for 3 to 5 hours, and disperse evenly. Immerse the fiber fabric in the silane coupling agent solution and then in the mixed solution of carbon nanotubes and graphene. Put the modified BF fabric in a blast drying oven and cure it at 80 to 110°C for 1 to 2 hours. Wash the fabric to remove the silane coupling agent, carbon nanotubes and graphene that are not firmly bonded on the surface, and dry the washed fiber fabric at 80 to 90°C for 2 to 4 hours. 6 to 10 sheets of fiber fabrics and resin are alternately stacked, placed in a flat plate vulcanizer (the plate temperature is 180 to 200° C.), and subjected to hot pressing to prepare a fiber-reinforced composite material.

[0086] S3.2: The surface chemical structure of the fiber before and after modification was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The surface morphology of the fiber 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. The thermal conductivity of the composite material was tested by the transient plane heat source method.

[0087] It can be seen that, in the second aspect, the present invention provides a fiber-reinforced resin composite material, whose raw materials include carbon nanotubes, graphene, resin, fibers and silane coupling agents, and the carbon nanotubes, the graphene, the resin, the fibers and the 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 aforementioned embodiment.

[0088] The fiber-reinforced resin composite material was prepared according to the above method, and the performance of the fiber-reinforced resin composite material was tested, which further proved that the multi-scale simulation method provided by the embodiment of the present invention can simulate and determine the fiber-reinforced resin composite material that takes into account both interface strength and thermal conductivity.

[0089] At the same time, when performing a multi-scale simulation method, the embodiment of the present invention will first determine the carbon nanotubes, graphene, resin, fiber and silane coupling agent, and then perform a simulation to determine the result. According to the result, the initial carbon nanotubes, graphene, resin, fiber and silane coupling agent are used to prepare a fiber-reinforced resin composite material to verify the simulation result, and a new fiber-reinforced resin composite material is obtained.

[0090] The mass ratio of the carbon nanotube, the graphene, the resin, the fiber and the 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 resin and thermoplastic resin; for example, including but not limited to epoxy resin and nylon 66 resin.

[0092] In the above, the multi-scale simulation method proposed in the embodiment of the present invention combines computational simulation with experimental structure at multiple scales, can explore the performance of the interface structure at the molecular level and explain the mechanism of mechanical and heat transfer enhancement at the interface molecular level, and show the mechanical and heat transfer performance of the composite material at the macroscopic scale.

[0093] Accordingly, the interface structure designed by the multi-scale simulation method provided by the present invention can be used to improve the interface mechanical properties of fiber-reinforced composite materials, the mechanical properties of composite materials, and the thermal transfer properties of composite materials. That is, the present invention provides an application of a multi-scale simulation method for improving the mechanical properties and thermal transfer properties of a fiber-reinforced resin composite material as described in any of the aforementioned embodiments in the design or preparation of a fiber-reinforced composite material.

[0094] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0095] Example 1

[0096] This embodiment provides a multi-scale simulation method for improving the mechanical properties and heat transfer properties of a fiber-reinforced resin composite material, comprising the following steps:

[0097] S1: Molecular dynamics simulation technology is used to design the synergistic interface structure of silane coupling agent, carbon nanotubes and graphene, fiber and resin, evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interface mechanics between carbon nanotubes, graphene and resin; the interface mechanics between fiber and resin; and the heat transfer performance between carbon nanotubes, graphene and resin, and explain the mechanism of interface performance improvement from the molecular level.

[0098] S1.1: Materials Studio software was used to construct molecular models of carbon nanotubes and graphene modified with silane coupling agent 3-ureapropyltrimethoxysilane. Nylon 66 resin molecules were added to the molecular models of carbon nanotubes modified with 3-ureapropyltrimethoxysilane and graphene bridged with 3-ureapropyltrimethoxysilane to construct the interface models of carbon nanotubes modified with 3-ureapropyltrimethoxysilane, graphene modified with 3-ureapropyltrimethoxysilane and resin. The interface models of carbon nanotubes modified with 3-ureapropyltrimethoxysilane, graphene modified with 3-ureapropyltrimethoxysilane and resin were geometrically optimized and dynamically optimized. The molecular models after equilibrium are shown in Figure 1. Figure 1 shown.

[0099] S1.2: LAMMPS software is used to perform non-equilibrium molecular dynamics analysis of the heat transfer performance of the interface model of carbon nanotubes, graphene and resin. A temperature gradient is established in the system, and when the system reaches a steady state, the temperature gradient and heat flow of the system are calculated, and then the thermal conductivity is calculated according to Fourier's law. The calculation formula of thermal conductivity k is calculated according to the following formula:

[0100] Where J is the heat flux density and dT / dx is the temperature gradient. The thermal conductivity of the composite model of carbon nanotubes and graphene composite nylon 66 (PA66) with different overlap degrees in the z direction and y direction is as follows: Figure 2 As shown. Heat transfer simulation was performed on the interface model of 3-ureidopropyltrimethoxysilane-modified carbon nanotubes, 3-ureidopropyltrimethoxysilane-modified graphene and resin, and the vibrational state density of the materials in the model was analyzed. The cumulative correlation factor used to evaluate the overlap degree of the phonon spectral state density was calculated according to the following formula:

[0101] The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency.

[0102] S1.3: The interface mechanical analysis of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene and resin includes the simulation of pulling out the 3-ureapropyltrimethoxysilane-modified carbon nanotubes from nylon 66 resin and the tensile simulation of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene and resin. The simulation of pulling out the 3-ureapropyltrimethoxysilane-modified carbon nanotubes from the resin adopts the upper and lower ends of the z-axis of the fixed composite model, and the 3-ureapropyltrimethoxysilane-modified carbon nanotubes are pulled out from 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 stretching the model. The stress-displacement curve, nylon 66 orientation parameters and entanglement parameters during the stretching process were statistically analyzed.

[0103] S1.4: Interface simulation of fiber and resin modified with 3-ureapropyltrimethoxysilane MaterialsStudio software was used to construct basalt fiber and nylon 66 resin models, respectively, and then the two were composited to form an interface model. The interface model of basalt fiber composite nylon 66 is shown in Figure 3 As shown. The interface model of the fiber and resin modified by silane coupling agent includes two categories: only a small amount of 3-ureapropyltrimethoxysilane is grafted on the fiber surface, and a silane coupling agent 3-ureapropyltrimethoxysilane layer is placed between the basalt fiber and the nylon 66 resin, wherein the silane coupling agent includes both chemical grafting on the fiber surface and physical mixing and chemical self-crosslinking. The equilibrium of the composite model adopts multiple dynamic processes, and then the equilibrium model is subjected to interface mechanics simulation in the LAMMPA software. In the traction separation simulation, the basalt fiber is moved at a constant speed in different directions (mode I, mode II and mixed mode) at the top of the nylon 66 resin. During the traction separation process, the stress changes, energy changes and movement behaviors of the atoms in the interface model are statistically analyzed. The maximum separation stress of the three basalt fiber and nylon 66 composite interface models during mode I traction separation is shown as follows Figure 4 shown.

[0104] S2: Based on the main molecular simulation results, the representative volume element method and finite element analysis were 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: Basalt fiber braided and embedded in nylon 66 resin matrix represents a fragment of basalt fiber reinforced nylon 66 fiber reinforced composite material. Using transient finite element method, a Gaussian heat source is applied at the center of the model. The same loading steps are used for the composite model of basalt fiber and nylon 66 resin without silane coupling agent modification and with silane coupling agent modification to observe the temperature distribution in the composite model.

[0106] S2.2: The representative volume unit model is composed of fibers embedded in resin, and a very thin interface is constructed at the fiber-resin interface. Stress is applied to the model in different directions to observe the distribution of stress in the fiber, resin, and fiber-resin interface.

[0107] S2.3: Construct a finite element simulation model of the composite material, apply a line load in 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 fabrics were cut into the same size and immersed in ethanol. The ethanol was replaced at regular intervals. After cleaning the chemical reagents on the fiber surface, the fiber fabrics were dried. 3-Ureapropyltrimethoxysilane was added to a mixed solution of ethanol and water, stirred for 1 to 2 hours, and a 5% silane coupling agent solution was prepared. 2 mg of carbon nanotubes and 2 mg of graphene were added to 296 ml of silane coupling agent solution, stirred for 3 hours, and dispersed evenly. The fiber fabric was immersed in the silane coupling agent solution for 60 minutes and then immersed in the mixed solution of carbon nanotubes and graphene for 60 minutes. The modified BF fabric was placed in a blast drying oven and cured at 110°C for 1 hour. The fabric was washed to remove the silane coupling agent, carbon nanotubes and graphene that were not firmly bonded on the surface, and the washed fiber fabric was dried at 80°C for 2 hours. Six pieces of fiber fabrics and nylon 66 resin films were alternately stacked, placed in a flat-plate vulcanizer (plate temperature was 180°C), and subjected to hot pressing to prepare a fiber-reinforced composite material.

[0110] The surface chemical structure of the basalt fiber 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 thermal conductivity of the composite material was tested by transient plane heat source method. The thermal conductivity of the prepared basalt fiber reinforced nylon 66 composite material is shown in Figure 5 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 Figure 6 shown.

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

[0112] Example 2

[0113] This embodiment provides a multi-scale simulation method for improving the mechanical properties and heat transfer properties of a fiber-reinforced resin composite material, comprising the following steps:

[0114] S1: Molecular dynamics simulation technology is used to design the synergistic interface structure of silane coupling agent, carbon nanotubes and graphene, fiber and resin, evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interface mechanics between carbon nanotubes, graphene and resin; the interface mechanics between fiber and resin; and the heat transfer performance between carbon nanotubes, graphene and resin, and explain the mechanism of interface performance improvement from the molecular level.

[0115] S1.1: Materials Studio software was used to construct the molecular models of carbon nanotubes and graphene modified by silane coupling agent 3-ureapropyltrimethoxysilane. Epoxy resin molecules were added to the molecular models of carbon nanotubes and graphene bridged by 3-ureapropyltrimethoxysilane to construct the interface models of carbon nanotubes modified by 3-ureapropyltrimethoxysilane, graphene modified by 3-ureapropyltrimethoxysilane and resin, and the interface models of carbon nanotubes modified by 3-ureapropyltrimethoxysilane, graphene modified by 3-ureapropyltrimethoxysilane and resin were geometrically optimized and dynamic, and the epoxy resin model was cross-linked using a cross-linking script.

[0116] S1.2: LAMMPS software was used to perform non-equilibrium molecular dynamics analysis of the heat transfer performance of the interface model of 3-ureidopropyltrimethoxysilane-modified carbon nanotubes, 3-ureidopropyltrimethoxysilane-modified graphene and resin. A temperature gradient was established in the system, and the temperature gradient and heat flow of the system were calculated after the system reached a steady state. Then, the thermal conductivity was calculated according to Fourier's law. The calculation formula of thermal conductivity k is calculated according to the following formula:

[0117] Where J is the heat flux and dT / dx is the temperature gradient. Heat transfer simulation is performed on the interface model of carbon nanotubes, graphene and resin, and the vibrational state density of the materials in the model is analyzed. The cumulative correlation factor used to evaluate the overlap degree of the phonon spectral state density is calculated according to the following formula: The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency.

[0118] S1.3: The interfacial mechanical analysis of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene and resin includes the simulation of pulling out the 3-ureapropyltrimethoxysilane-modified carbon nanotubes from epoxy resin and the tensile simulation of the interface model of 3-ureapropyltrimethoxysilane-modified carbon nanotubes, 3-ureapropyltrimethoxysilane-modified graphene and resin. The simulation of pulling out the 3-ureapropyltrimethoxysilane-modified carbon nanotubes from the resin adopts the upper and lower ends of the z-axis of the fixed composite model, and the carbon nanotubes are pulled out from 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 simulated by tensile simulation of the model. The stress-displacement curves, epoxy resin orientation parameters and entanglement parameters during the stretching process were statistically analyzed.

[0119] S1.4: Interface simulation of fiber and resin modified by 3-ureapropyltrimethoxysilane The basalt fiber and epoxy resin models modified by 3-ureapropyltrimethoxysilane were constructed by MaterialsStudio software, and then the two were composited to form an interface model. The interface model of fiber and resin modified by silane coupling agent includes two types: only a small amount of 3-ureapropyltrimethoxysilane is grafted on the fiber surface, and a silane coupling agent 3-ureapropyltrimethoxysilane layer is placed between the basalt fiber and nylon 66 resin, in which the silane coupling agent includes both chemical grafting on the fiber surface and physical mixing and chemical self-crosslinking. The equilibrium of the composite model adopts multiple dynamic processes, and then the equilibrium model is used for interface mechanics simulation in LAMMPA software. In the top part of the epoxy resin in the traction separation simulation, the basalt fiber is moved at a constant speed along different directions (mode I, mode II and mixed mode). During the traction separation process, the stress changes, energy changes and movement behaviors of atoms in the interface model are statistically analyzed.

[0120] S2: Based on the main molecular simulation results, Cheng used the representative volume element method and finite element analysis to simulate the heat transfer performance of the composite material, the basalt fiber-epoxy resin interface stress transfer, and the stress distribution of the composite material.

[0121] S2.1: Basalt fiber braid embedded in epoxy matrix represents a fragment of basalt fiber reinforced epoxy fiber reinforced composite. Using transient finite element method, a Gaussian heat source is applied at the center of the model. The same loading steps are used for the basalt fiber and epoxy resin composite models without silane coupling agent modification and with silane coupling agent modification to observe the temperature distribution in the composite model.

[0122] S2.2: The representative volume unit model is composed of fibers embedded in resin, and a very thin interface is constructed at the fiber-resin interface. Stress is applied to the model in different directions to observe the distribution of stress in the fiber, resin, and fiber-resin interface.

[0123] S2.3: Construct a finite element simulation model of the composite material, apply a line load in the composite model of fiber and resin, and analyze the stress distribution of the composite material.

[0124] In a second aspect, the present invention provides a fiber-reinforced resin composite material, comprising:

[0125] Commercial basalt fiber fabrics were cut into the same size and immersed in ethanol. The ethanol was replaced at regular intervals. After cleaning the chemical reagents on the fiber surface, the fiber fabrics were dried. 3-Ureapropyltrimethoxysilane was added to a mixed solution of ethanol and water, stirred for 1 hour, and a 5% silane coupling agent solution was prepared. 2 mg of carbon nanotubes and 2 mg of graphene were added to 296 ml of silane coupling agent solution, stirred for 3 hours, and dispersed evenly. The fiber fabric was immersed in the silane coupling agent solution for 60 minutes and then immersed in the mixed solution of carbon nanotubes and graphene for 60 minutes. The modified BF fabric was placed in a blast drying oven and cured at 80°C for 1 hour. The fabric was washed to remove the silane coupling agent, carbon nanotubes and graphene that were not firmly bonded on the surface, and the washed fiber fabric was dried at 80°C for 2 hours. Six pieces of fiber fabrics were coated with a mixture of epoxy resin monomer and curing agent, placed in a flat plate vulcanizer (plate temperature was 200°C), and hot pressed to prepare fiber-reinforced composite materials.

[0126] Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface chemical structure of basalt fibers before and after modification. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the fibers. Universal tensile testing machine was used to test the tensile strength, flexural strength, interlaminar shear strength and compressive strength of the composites. The transient plane heat source method was used to test the thermal conductivity of the composites.

[0127] The above test results verify the simulation results.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-scale simulation method for improving the mechanical properties and thermal transfer properties of fiber-reinforced resin composite materials, characterized in that: include: Molecular scale simulation: Molecular dynamics simulation technology is used to design the interface structure of silane coupling agent, carbon nanotubes and graphene, fiber and resin, and evaluate the functionalization of carbon nanotubes and graphene; the degree of overlap between carbon nanotubes and graphene; the interface mechanics between carbon nanotubes, graphene and resin; the interface mechanics between fiber and resin; and the heat transfer performance between carbon nanotubes, graphene and resin; Macro-scale simulation: Based on the 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 the composite material, the fiber-resin interface stress transfer, and the stress distribution of the composite material.

2. The multi-scale simulation method according to claim 1, characterized in that: Molecular-scale operations include: constructing molecular-scale interface models; Preferably, the molecular scale interface model includes: an interface model of carbon nanotubes before and after modification with a silane coupling agent and graphene before and after modification with a silane coupling agent, an interface model of carbon nanotubes modified with a silane coupling agent, graphene modified with a silane coupling agent and resin, and an interface model of fibers and resin before and after modification with a silane coupling agent; Preferably, it includes: performing heat transfer performance analysis and interface mechanics analysis on the molecular scale interface model respectively.

3. The multi-scale simulation method according to claim 1 or 2, characterized in that: Molecular-scale simulation methods include at least one of the following features: (1): Materials Studio software was used to construct the molecular model; LAMMPS software was used to analyze the heat transfer performance and interface mechanics of the molecular scale interface model, and the PCFF force field was used in the molecular scale interface model; (2): Using the interface models of carbon nanotubes before and after silane coupling agent modification and graphene before and after silane coupling agent modification, as well as the interface models of carbon nanotubes modified by silane coupling agent, graphene modified by silane coupling agent and resin, geometric optimization and dynamic equilibrium are first performed, and then heat transfer performance analysis is performed in non-equilibrium molecular dynamics; (3): Interface mechanics analysis of the interface model of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene and resin, including the simulation of pulling out the silane coupling agent-modified carbon nanotubes from the resin and the tensile simulation of the interface model of silane coupling agent-modified carbon nanotubes, silane coupling agent-modified graphene and resin; (4): The interface model of fiber and resin is to composite the fiber and resin, wherein the fiber is grafted with a silane coupling agent; The simulation of interface mechanics includes three modes of traction separation.

4. The multi-scale simulation method according to claim 3, characterized in that: The heat transfer performance analysis by non-equilibrium molecular dynamics includes: calculating the thermal conductivity according to Fourier's law. The calculation formula of thermal conductivity k is calculated according to the following formula: Where J is the heat flux, dT / dx is the temperature gradient; and / or, performing heat transfer simulation on an interface model of carbon nanotubes modified by a silane coupling agent, graphene modified by a silane coupling agent, and a resin, and analyzing the vibrational density of the material in the model; And / or, the cumulative correlation factor used to evaluate the degree of overlap of the phonon spectral state density is calculated as follows: The subscripts "A" and "B" represent the two material components that form the interface. is a given cutoff frequency; Preferably, the three traction separation modes of the interface mode include mode I, mode II and mixed mode.

5. The multi-scale simulation method according to claim 1, characterized in that: Macro-scale operations include: mesomechanical analysis of unidirectional representative volume elements of the fiber, resin, and fiber-resin interface before and after modification with silane coupling agents; The finite element method was used to analyze 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.

6. The multi-scale simulation method according to claim 1 or 5, characterized in that: Macroscale simulation methods include at least one of the following features: (1): The finite element heat transfer model used in the finite element analysis is to embed the fiber weaving and embedding into the resin to represent the fiber reinforced composite material fragment before and after the modification of the silane coupling agent. The transient finite element method is used, and the Gaussian heat source with the maximum intensity is applied at the center of the model; (2): The representative volume unit is composed of fibers embedded in resin, and the interface between the fiber and the resin before and after silane coupling agent modification is a very thin interface. Stress is applied to the model to analyze the distribution of stress in the fiber, resin, and resin-fiber interface before and after silane coupling agent modification; (3) Finite element mechanical simulation of composite materials: Loads are applied to the composite material model to analyze the stress distribution of the composite material.

7. The multi-scale simulation method according to claim 1, characterized in that: The resin includes thermosetting resin and thermoplastic resin; Preferably, the resin includes epoxy resin and nylon 66 resin; The fibers include basalt fibers.

8. A fiber-reinforced resin composite material, characterized in that: Its raw materials include carbon nanotubes, graphene, resin, fiber and silane coupling agent. The carbon nanotubes, the graphene, the resin, the fibers and the silane coupling agent are determined by the multi-scale simulation method for improving the mechanical properties and thermal transfer properties of fiber-reinforced resin composite materials according to claim 1.

9. The fiber-reinforced resin composite material according to claim 8, characterized in that: The mass ratio of the carbon nanotube, the graphene, the resin, the fiber and the silane coupling agent is 1.0:1.0:(40-45):(50-57):1.0; Preferably, the silane coupling agent includes 3-ureapropyltrimethoxysilane; Preferably, the fibers include basalt fibers; Preferably, the resin includes a thermosetting resin and a thermoplastic resin; Preferably, the resin includes epoxy resin and nylon 66 resin.

10. Use of the multi-scale simulation method for improving the mechanical properties and thermal transfer properties of fiber-reinforced resin composite materials as claimed in any one of claims 1 to 6 in the design or preparation of fiber-reinforced composite materials.

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