Test method for micro-mechanical behavior of TATB / fluoroelastomer interface

Abstract

The application discloses a TATB / fluorine rubber interface micromechanics behavior test method. By performing interface mechanics behavior research on PBXs with different structural adhesive components, the relative change of the interface stress of the PBXs can be obtained. The method has high precision, can simultaneously obtain stress-strain change analysis, and can realize measurement of the force (displacement) load of the sample and collection of Raman spectrum while a small tensile force is applied to the PBX sample. The method is a new test method for evaluating the micro morphology and interface mechanics of energetic materials.

Description

Technical Field

[0001] This invention relates to the field of stress measurement technology, and in particular to a method for testing the micromechanical behavior of the TATB / fluororubber interface. Background Technology

[0002] Polymer-bonded explosives (PBX) are essentially highly packed polymer-based composite materials containing explosive particles. Their mechanical properties primarily depend on the internal binder and the interfacial characteristics between the explosive and the binder. The interfacial microstructure is a two-dimensional region where abrupt changes in the physical and chemical properties of the mixed explosive occur; it is the origin region leading to debonding and cracking. However, the complexity of the interfacial microstructure and the difficulty in identifying the components of the transition layer region result in a lack of effective characterization methods. Furthermore, PBX has unique components—the explosive crystals are highly packed and their modulus is much higher than that of the binder. The molding process of PBX is also complex—press-fit products require granulation and high-temperature, high-pressure pressing. This results in numerous interfaces within PBX, with an exceptionally complex structure, inevitably leading to jumps in thermophysical and mechanical properties at the interfaces. Therefore, studying the interfacial interaction between explosive crystals and the binder is crucial for evaluating and improving the mechanical, detonation, and safety performance of PBX explosives.

[0003] While the mechanical aspects can explain the interfacial debonding process of explosive crystals to some extent, the lack of reliable, intuitive analysis and quantitative characterization of the interfacial interaction between explosive crystals and binders makes it insufficiently clear and accurate in explaining crack formation and interfacial reinforcement modification in PBX explosive components. There is an urgent need to employ advanced analytical methods and characterization techniques to directly observe and quantitatively analyze the interfacial interaction between explosive crystals and binders in PBXs, in order to fully understand the interfacial bonding effect and debonding causes of explosive crystals.

[0004] Micro-Raman spectroscopy is a novel microscale experimental measurement technique developed in recent years. It measures the changes in the frequency shift positions of characteristic peaks in the Raman spectrum of a tested object before and after deformation, and utilizes the strain-frequency shift analytical relationship of the corresponding material to measure and characterize mechanical parameters such as strain and stress. It features non-destructive and non-contact operation, micrometer-level spatial resolution, and sensitivity to both intrinsic and extrinsic stresses. Applying it to the study of interfaces in energetic materials will provide a novel testing method for evaluating the microscopic interface mechanics of energetic materials. However, energetic materials are special hazardous materials with numerous interfaces and high brittleness. The direction and components of stress in composite materials are difficult to determine, and there is currently no testing method for measuring micro-stress at the interface of energetic material PBXs, posing many challenges to micro-Raman mechanical measurements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for testing the micromechanical behavior of the TATB / fluororubber interface in order to solve the above-mentioned problems. This invention provides a sample testing method and a stress analysis method, which belongs to the category of establishing new methods and applications for the study of the micromechanical behavior of energetic materials using micro Raman technology, and provides a new opportunity for studying the interfacial interaction between explosive crystals and binders and the mechanical enhancement of PBX.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A method for preparing a PBX micro-stress test specimen involves mixing TATB explosive particles and a binder at a mass ratio of 1:5-10, and then spin-coating the mixture into a film to form a double cantilever beam test specimen with a thickness not exceeding 1 cm and a width not exceeding 1 cm.

[0008] A further embodiment is that the TATB particles have a particle size of not less than 20 micrometers;

[0009] The binder is an ethyl acetate solution of F2314, F2313 or F2311, and the concentration of F2314, F2313 or F2311 in the binder is 8-10%;

[0010] The specimen is dumbbell-shaped and is laser-cut into small specimens with an aspect ratio of no more than 0.8:1 after spin coating.

[0011] In another aspect, the present invention provides a method for testing the micromechanical behavior of the TATB / fluororubber interface, comprising the following steps:

[0012] Step 1: Using a micro-mechanical loading stage, set the initial tensile deformation and deformation rate, apply tension to the specimen, and use a displacement sensor to read the specimen deformation.

[0013] Step 2: Place the micro-mechanical loading stage in the confocal Raman spectroscopy system and perform Raman testing on the loaded specimen using the confocal Raman spectroscopy system. The testing range should be no less than 50-3500 cm⁻¹. -1 The test microscopic area was the interface between the TATB crystal and the binder. The TATB Raman signal was collected to obtain the Raman spectral response signal at the interface between TATB and the binder, and the spectral shift difference under load was calculated.

[0014] Step 3: The TATB {002} crystal plane in the sample is measured first. The upper plane of the TATB single crystal particle is located using a confocal microscope. A sample coordinate system is established on the {002} crystal plane to be tested. Raman test is performed on the loaded specimen. The focusing is adjusted by the focusing lens and focused on the {002} crystal plane by the microscope. The scattered signal is controlled to be polarized light in the common optical path.

[0015] Step 4: Construct the relationship between the Raman spectral shift increment in the Raman spectral information and the stress on the TATB{002} crystal plane to be measured. The relationship between the stress components during the tensile process of the sample is as follows:

[0016]

[0017] in θ represents the angle between the polarization direction of the incident light and the polarization direction of the scattered light and the X-axis, respectively. This is a combination of polarization angles; The combination of polarization angles is represented as The frequency shift of the acquired Raman spectrum relative to its stress-free state is the increment; σ x σ is the normal stress component in the X-axis direction. y τ is the normal stress component in the Y-axis direction. xy This refers to the shear stress component; The combinations of polarization angles are respectively: σ x σ y and τ xy A constant factor relating the linear relationship with the Raman frequency shift increment;

[0018] Step 5: Calibrate the micro-mechanical loading stage with a lightweight spring to obtain the loading coefficient of the mechanical loading stage, and use it as the quasi-load to determine the initial deformation; solve the equations from Step 4 to obtain the Raman frequency shift increment expression equations for the stress components of the {110} crystal plane under three different polarization angle combinations at the measuring points; substitute the Raman frequency shift increments measured under the three different polarization angle combinations at the measuring points into the stress component expression equations to obtain the stress components, and combine them with a displacement sensor to obtain its apparent stress-strain curve.

[0019] A further approach is to set the initial tensile deformation and deformation rate in step 1, and to apply an additional load and deform at a constant rate.

[0020] A further embodiment is that, in step 3, the sample coordinate system is a spatial rectangular coordinate system, the X-axis and Y-axis of the sample coordinate system are orthogonal directions within the {002} crystal plane to be measured, and the Z-axis is the outward normal; during measurement, an angular polarized Raman optical path is used, the incident laser is 532nm, and the incident light is in the opposite direction to the Z-axis; the controller is a polarizer; and the numerical aperture of the microscope is 0.45.

[0021] A further embodiment is that, in step 4, the specimen is dumbbell-shaped, and the stress components of the specimen can be simplified as follows:

[0022] The normal stress component in the Y-axis direction is equal to the normal stress component in the X-axis direction, so it is written as twice the normal stress in the X-axis direction. The normal stress in the Z-axis direction is affected by polarization deviation and is considered as a canceled term.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention discloses a method for testing the micromechanical behavior of TATB / fluororubber interfaces. By studying the interfacial mechanical behavior of PBX with different binder components, the relative changes in interfacial stress can be obtained. This method is highly accurate and can simultaneously obtain stress-strain variation analysis. While applying a small tensile force to the PBX sample, it can measure the force (displacement) load of the sample and collect Raman spectra. It is a novel testing method for evaluating the microstructure and interfacial mechanics of energetic materials. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The image shows the {002} crystal plane of the TATB-based PBX material to be tested in this invention.

[0027] Figure 2 Raman images of PBX materials of TATB composited with different binders (F2314, F2313, F2311) of the present invention under micro-stress loading.

[0028] Figure 3 The stretching process of the TATB / F2314 composite of the present invention; Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] Example 1:

[0031] TATB explosive particles with a diameter of 20 micrometers and a binder were mixed uniformly at a mass ratio of 1:10 and spin-coated to form a dumbbell-shaped double cantilever beam test specimen with a thickness of 0.5 mm and a width of 0.6 mm. The binder was pre-dissolved in ethyl acetate at a dilution ratio of 8%. Using a micro-mechanical loading stage, the initial tensile deformation and deformation rate of the equipment were monitored, and the deformation was read using a displacement sensor. The micro-mechanical loading stage required mechanical calibration before use. The elasticity of the lightweight spring was zeroed before testing. The applied load and deformation were applied at a uniform rate. The micro-mechanical loading stage was placed in a confocal Raman spectroscopy system. Figure 1 As shown, the {002} crystal plane of TATB is located and measured using a confocal microscope. The upper plane of the TATB crystal grain is located using a confocal microscope, and a sample coordinate system is established on the {002} crystal plane to be measured. The sample coordinate system is a spatial rectangular coordinate system. The X-axis and Y-axis of the sample coordinate system are orthogonal directions within the {002} crystal plane to be measured, and the Z-axis is the outward normal.

[0032] Raman spectroscopy was used to perform Raman tests on loaded specimens, with a testing range of 50-3500 cm⁻¹. -1 The test microscopic area was at the interface between the TATB crystal and the binder, and the main focus was on collecting TATB Raman signals.

[0033] Example 2:

[0034] According to Example 1, composite materials of TATB with F2311, F2314, and F2313 were prepared respectively, and Raman spectroscopy was performed on them. Figure 2 As shown, the bonding abilities of F2311, F2314, and F2313 with TATB before mechanical loading exhibit certain differences. Compared with the TATB powder sample, the TATB / F2314 composite shows a more significant blue shift, indicating that the introduction of F2314 weakens the hydrogen bonding interaction between the amino group and C-NO2 in the TATB molecule. There may be intermolecular hydrogen bonding between the amino group of TATB and the CF group of F2314, but this interaction is weak and shows no obvious characteristic changes in F2314. The F2311 / TATB composite exhibits excellent elasticity; debonding begins at 100% deformation, but fracture does not occur at 166% deformation. The F2313 / TATB phenomenon is similar to that of F2311 / TATB.

[0035] F2314 / TATB has high strength. When stretched to 45% deformation, obvious debonding is visible, and it breaks at 58.71% deformation.

[0036] Example 3:

[0037] As described in Examples 1 and 2, a full-process tensile test was conducted on the TATB / F2314 system, which exhibits good strength properties. Figure 3 As shown, during the loading and stretching process, the nitro peak of TATB in the TATB / F2314 composite shifts to lower wavenumbers, with a maximum shift of approximately 3.6 cm⁻¹. -1 The stress-strain curve of the composite material under tension was obtained. In the initial stage of tensile deformation, the strain of the composite material increases linearly, then the increase slows down until significant debonding occurs at the interface, at which point the stress begins to decrease. The entire tensile process can be roughly divided into three stages: elasticity, strengthening, and fracture. Based on the stress-strain curve and a stress decoupling model established for this system based on the {002} crystal plane to be measured, its effective tensile strength is determined to be 2.36 GPa.

[0038] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed in the present invention.

Claims

1. A method for testing the interfacial micromechanical behavior of TATB / vinyl fluoride rubber, characterized by, Includes the following steps: Step 1: Using a micro-mechanical loading stage, set the initial tensile deformation and deformation rate, apply tension to the specimen, and use a displacement sensor to read the specimen deformation. Step 2, place the micro-mechanical loading station in the confocal Raman spectroscopy system, and use the confocal Raman spectroscopy system to perform Raman testing on the test piece under load, the testing range is not less than 50-3500cm -1 , the test micro area is at the interface between the TATB crystal and the binder, and the TATB Raman signal is collected to obtain the Raman spectroscopy response signal at the interface between the TATB and the binder, and the frequency spectrum displacement difference under load is calculated; Step 3: The TATB {002} crystal plane in the sample is measured first. The upper plane of the TATB single crystal particle is located using a confocal microscope. A sample coordinate system is established on the {002} crystal plane to be tested. Raman test is performed on the loaded specimen. The focusing is adjusted by the focusing lens and focused on the {002} crystal plane by the microscope. The scattered signal is controlled to be polarized light in the common optical path. Step 4: Construct the relationship between the Raman spectral shift increment and the stress on the TATB{002} crystal plane in the Raman spectral information. The relationship between the stress components during the tensile process of this sample is as follows: ； wherein are the angles between the polarization direction of the incident light and the polarization direction of the scattered light, respectively, and the X-axis direction, taken is the polarization angle combination; represents the frequency shift of the Raman spectrum acquired when the polarization angle combination is ; is the X-axis direction normal stress component, is the Y-axis direction normal stress component, is the shear stress component; , , represent the constant factors of the linear relationship between the Raman frequency shift increment and , , and when the polarization angle combination is Step 5: Calibrate the micro-mechanical loading stage with a lightweight spring to obtain the loading coefficient of the mechanical loading stage, and use it as the quasi-load to determine the initial deformation; solve the equations from Step 4 to obtain the Raman frequency shift increment expression equations for the stress components of the {110} crystal plane under three different polarization angle combinations at the measuring points; substitute the Raman frequency shift increments measured under the three different polarization angle combinations at the measuring points into the stress component expression equations to obtain the stress components, and combine them with a displacement sensor to obtain its apparent stress-strain curve.

2. The method of testing the interfacial micromechanical behavior of TATB / fluoroelastomer of claim 1, wherein, In step 1, the initial tensile deformation and deformation rate are set, and the applied load and deformation are uniform.

3. The method of testing the interfacial micromechanical behavior of TATB / fluoroelastomer of claim 1, wherein, In step 3, the sample coordinate system is a spatial rectangular coordinate system, and the X-axis and Y-axis of the sample coordinate system are orthogonal directions within the {002} crystal plane to be measured, and the Z-axis is the outward normal direction; an angular polarized Raman optical path is used for measurement, the incident laser is 532nm, and the incident light is in the opposite direction to the Z-axis; the controller is a polarizer; and the numerical aperture of the microscope is 0.

45.

4. The method for testing the micromechanical behavior of the TATB / fluororubber interface as described in claim 1, characterized in that, In step 4, the specimen shape is dumbbell, and the stress component of the specimen can be simplified as: ; The normal stress component in the Y-axis direction is equal to the normal stress component in the X-axis direction, so it is written as twice the normal stress in the X-axis direction. The normal stress in the Z-axis direction is affected by polarization deviation and is considered as a canceled term.

5. A method for testing the micromechanical behavior of a TATB / fluororubber interface as described in any one of claims 1 to 4, characterized in that: The specimen was prepared by the following method: TATB explosive particles and binder were mixed evenly at a mass ratio of 1:5-10 and spin-coated into a film to form a double cantilever beam test specimen with a thickness not exceeding 1 cm and a width not exceeding 1 cm. The particle size of the TATB explosive is not less than 20 micrometers; The binder is an ethyl acetate solution of F2314, F2313, or F2311, and the concentration of F2314, F2313, or F2311 in the binder is 8-10%. The specimen is dumbbell-shaped and is laser-cut into small specimens with an aspect ratio of no more than 0.8:1 after spin coating.

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