Method for measuring deformation of fiber composite material under impact of projectile body

Abstract

The invention belongs to the field of terminal ballistic tests, and relates to a method for measuring deformation of a fiber composite material under impact of a projectile body, which comprises the following steps of: arranging a sensor assembly on the fiber composite material, and connecting the sensor assembly with a sensor driver, a data converter and a signal processor; establishing a three-dimensional coordinate system by taking the impact point as an origin of coordinates and in the ballistic line direction and the radial direction and the latitudinal direction of the bullet-facing surface fiber layer; the sensor assembly measures to obtain the deformation of the fiber composite material, and the signal processor calculates to obtain a curve of a strain value epsilon of an impact point changing along with time t; measuring the deformation response condition of the fiber composite material under the conditions that the positions DN of the fiber cloth layers are the same and are different from the ballistic line distance DR, and the positions DN of the fiber cloth layers are different and are the same as the ballistic line distance DR; and the signal processor calculates the strain value of the fiber composite material at the impact point. According to the invention, the overall, continuous and accurate measurement of the internal deformation of the fiber composite material under the projectile body impact transient condition can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of terminal ballistic test and relates to a method for measuring deformation of a fiber composite material under the impact of a projectile. Background Art

[0002] In the field of terminal ballistics, when the projectile penetrates the fiber composite target plate at ultra-high speed, the target plate material within a certain range around the impact point deforms and absorbs energy through different methods such as stretching, compression and shearing. The deformation of the target plate varies with the distance between the material and the impact point and the ballistic line. The dynamic measurement of the deformation of the material in different areas of the target plate is of great significance to the design of fiber composite armor.

[0003] At present, the measurement of the deformation of fiber composite target plates under projectile impact mainly focuses on the measurement of the deformation of the back surface of the sample. The measurement methods include digital image correlation (DIC), all-fiber laser displacement interferometry (DISAR), high-speed photography and flash X-ray methods. There are few studies on the measurement of the internal deformation of the target plate and its three-dimensional reconstruction.

[0004] The digital image correlation method obtains the deformation information of the target plate surface area by calculating and comparing two digital images before and after the target plate is deformed. The all-fiber laser displacement interferometry uses the principle of laser displacement interferometry to measure the target plate surface deformation. The high-speed photography method obtains the object motion image and estimates the deformation speed through continuous shooting. The measurement position of the above measurement methods is limited to the back surface of the target plate. The flash X-ray method can observe the overall deformation of the target plate, but the number of recorded photos is limited and it is impossible to effectively track and observe a certain position.

[0005] Fiber optic sensors can sense changes in light flux when target plate samples are deformed, and are used to measure the internal deformation of samples. However, the response time of fiber optic sensor detection equipment (such as high dynamic Bragg grating demodulators, etc.) is in the millisecond level, which cannot meet the needs of microsecond-level measurement of transient impact of target plates. At the same time, the strength and modulus of fiber optic sensors are much lower than those of fiber composite materials. When large deformation is measured, the target plate samples are easily broken and damaged, which cannot meet the needs of the measurement range. Strain gauges have the advantages of small size, fast response speed, large range and high accuracy. They can be pasted on the surface of an object to measure deformation, or pre-placed inside an object to measure residual strain of composite material curing, deformation of concrete structure, etc. There is no corresponding measurement method for the measurement and reconstruction of transient impact deformation inside the target plate sample.

[0006] The patent "Method for assessing damage caused by projectile penetration of target" (CN113237910A) conducts test and analysis of typical microscopic evolution characteristics of material failure and assessment of damage caused by projectile penetration of target based on the analysis of the macroscopic failure and destruction mode of the target after the impact of the target plate. It cannot measure the damage and deformation of the target plate under the transient conditions of target plate impact. The patent "Method for testing the deformation strain rate of the back side of the target plate under ballistic impact conditions" (CN112710249A) can only measure the deformation of the back side of the target plate during the transient process of target plate impact, but cannot measure the deformation of the material inside the target plate.

[0007] Therefore, the existing measurement methods cannot meet the needs of measuring the overall deformation of fiber composite target plates under projectile impact. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method for measuring the deformation of fiber composite materials under projectile impact. The method is implemented by effectively dividing the spatial area and pre-setting sensors before preparing the target plate sample, which can provide effective data support for the analysis of the target plate deformation energy absorption mechanism and the design of composite armor.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A method for measuring deformation of a fiber composite material under impact of a projectile, wherein the fiber composite material is composed of a plurality of layers of single-layer fiber cloths stacked and pressed, and the plane of the single-layer fiber cloth is perpendicular to the direction of the ballistic line, comprising the following steps:

[0011] A set of sensor components is arranged on the fiber composite material, the number of sensors in the sensor component is at least five, the sensors are arranged between adjacent single-layer fiber cloths with the impact point as the center, the direction of the sensor's sensitive deformation is consistent with the stretching direction of the single-layer fiber cloth, and the position coordinates of the sensors are recorded;

[0012] The sensor assembly is electrically connected to the sensor driver, the data converter and the signal processor in sequence through a signal line passing through the fiber composite material;

[0013] A three-dimensional coordinate system is established with the impact point as the origin of coordinates and the direction of the trajectory and the radial and latitudinal directions of the fiber layer on the bullet-facing surface of the fiber composite material.

[0014] A projectile is launched at the fiber composite material by using a launching device. After the projectile penetrates the fiber composite material, the sensor component measures the deformation of the fiber composite material, and the signal processor calculates a curve of the strain value ε at the impact point versus time t; a ballistic test is carried out to measure the deformation response of the fiber composite material under two conditions: the fiber cloth layer position DN where the sensor is located is the same and the distance DR from the ballistic line is different; and the fiber cloth layer position DN is different and the distance DR from the ballistic line is the same;

[0015] The signal processor calculates the strain value of the fiber composite material at the impact point.

[0016] Preferably, when measuring the deformation response of the fiber composite material where the fiber cloth layer position DN where the sensor is located is the same and the distance DR from the ballistic line is different, a curve of the strain value ε of each measuring point changing with time t is measured, and the number of sensors required for the measurement is at least three. The strain value of each measuring point caused by the propagation of the stress wave is taken to establish a curve of the change of the in-plane strain value with the distance DR from the ballistic line, and the curve equation is fitted as shown in formula (1):

[0017] ε DR =ε DR (DR) (1).

[0018] Preferably, when measuring the deformation response of the fiber composite material where the fiber cloth layer position DN is different and the distance DR from the ballistic line is the same, the curve of the strain value ε of each measuring point changing with time t is measured, and the number of sensors required for the measurement is at least three. The strain value of each measuring point caused by the propagation of the stress wave is taken to establish the curve of the change of the in-plane strain value with the fiber cloth layer position DN, and the curve equation is fitted as shown in formula (2):

[0019] ε DN =ε DN (DN) (2).

[0020] Preferably, based on the known sensor pasting position R(DN R ,DR R ) and its strain measurement value ε R-max , calculate the measured position M(DN) of the fiber composite material impact point M ,DR M ) strain value ε M-max The calculation equation is shown in formula (3):

[0021]

[0022] R corresponds to the position where the sensor is bonded, and M corresponds to the position where the sensor is not bonded and the deformation value is calculated based on the fitting curve obtained by measurement.

[0023] Preferably, the sensor driver uses an ultra-dynamic strain gauge, the data converter uses a high-speed data acquisition card, the signal processor uses a computer, and the sensor uses a thin film strain gauge. Multiple sensor drivers and data converters can be used to meet the needs of multi-channel sensor data acquisition.

[0024] The beneficial effects of the present invention are:

[0025] The present invention can realize the overall, continuous and accurate measurement of the internal deformation of fiber composite materials under the transient working condition of ultra-high-speed projectile impact, and provide effective data for the design of fiber composite armor and the analysis of protective performance; according to the deformation measurement results, it is determined how many layers of single-layer fiber cloth are needed to design armor under different protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the layout of a fiber composite material deformation measuring device according to the first embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of sensor arrangement of the 200th single-layer fiber cloth according to the first embodiment of the present invention;

[0028] Figure 3 is a curve showing the change of the strain value ε of the measuring point with time t under the conditions of the same DN and different DR in the first embodiment of the present invention;

[0029] Figure 4 is a curve showing the change of the strain value ε of the measuring point with time t under the conditions of different DN and the same DR in the first embodiment of the present invention;

[0030] Among them, 1 is a launching device, 2 is a projectile, 3 is a speed measuring device, 4 is a test target board, 5 is a sensor assembly, 6 is a sensor driver, 7 is a data converter, 8 is a signal processor, 9 is a sensor one, 10 is a sensor two, and 11 is a sensor three. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1

[0033] A method for measuring deformation of a fiber composite material target under projectile impact comprises the following steps:

[0034] 1. Assemble the fiber composite material deformation measurement device.

[0035] A schematic diagram of a fiber composite material deformation measurement device under projectile impact provided by the first embodiment of the present invention is shown in FIG. Figure 1As shown, it includes a launching device 1, a projectile 2, a speed measuring device 3, a test target plate 4, a sensor assembly 5, a sensor driver 6, a data converter 7 and a signal processor 8. The launching device 1, the speed measuring device 3 and the test target plate 4 are sequentially placed at a certain distance, the launching device 1 is used to launch the projectile 2, and the speed measuring device 3 measures the speed of the projectile 2 when the projectile 2 passes through the speed measuring device 3, the sensor assembly 5 is attached to the test target plate 4, and is adhesively sandwiched between adjacent single-layer fiber cloths, and the sensor assembly 5 is electrically connected to the sensor driver 6, the data converter 7 and the signal processor 8 in sequence.

[0036] The launching device 1 is a ballistic gun.

[0037] Projectile 2 is a 1.1g cylindrical wedge-shaped fragmentation simulation projectile.

[0038] The speed measuring device 3 is a light curtain target speed measuring device.

[0039] The test target plate 4 is an ultra-high molecular weight polyethylene laminate, which is composed of 200 layers of single-layer fiber cloth.

[0040] The sensor driver 6 is an ultra-dynamic strain gauge.

[0041] The data converter 7 is a high-speed data acquisition card.

[0042] The signal processor 8 is a computer.

[0043] The sensor array 5 includes sensor 1 9, sensor 2 10, sensor 3 11, sensor 4, sensor 5 and sensor 6. Sensor 1 9, sensor 2 10, sensor 3 11, sensor 4, sensor 5 and sensor 6 use thin film strain gauges.

[0044] When selecting the sensor and its signal line, it is required that the measurement range of the sensor can meet the measurement requirements of the maximum deformation of the fiber composite material; the sensor response speed can meet the impact deformation measurement requirements of the ultra-high-speed test target plate 4; the sensor can be firmly attached to the measured position and has no position change relative to the test target plate 4 when the test target plate 4 is deformed by bullet impact; the use conditions of the sensor and its signal line meet the temperature and pressure parameter requirements related to the fiber composite material laminate manufacturing process; the size of the sensor and its signal line does not affect the structure and protective performance of the fiber composite material laminate.

[0045] When arranging the sensor assembly 5, it is required that the direction of the sensor's sensitive deformation is consistent with the tensile direction of the fiber composite material. The sensor is firmly attached to the position to be tested and the position coordinates of the sensor are recorded. A signal line is reserved to connect to the outside of the test target plate 4. A high-speed data acquisition system is used to collect and record the deformation signal of the test target plate 4 output by the sensor.

[0046] For the test target plate 4 obtained by lamination, the sensors are arranged according to the fiber cloth layer position DN in the thickness direction and the distance DR from the ballistic line as position constraints. The number of sensors is related to the curve fitting method and fitting accuracy. The number of sensors under each constraint condition is generally not less than three. If three sensors are arranged under each constraint condition and one of the sensors is shared, the number of sensors in the sensor assembly 5 is five.

[0047] 2. Use the fiber composite material deformation measuring device to measure the deformation of the fiber composite material under the impact of the projectile.

[0048] A three-dimensional coordinate system is established with the impact point as the coordinate origin and the direction of the trajectory line and the radial and latitudinal directions of the fiber layer of the projectile-facing surface of the test target plate 4;

[0049] According to the setting conditions of the fiber cloth layer position DN in the thickness direction and the distance DR from the trajectory line, the sensor arrangement methods include the following two:

[0050] a) The sensor is located at the same fiber cloth layer position DN and different distances from the trajectory line DR. The sensor is arranged at different positions of a single layer of fiber cloth with the impact point as the center. At this time, it is used to measure the deformation of the single layer of fiber cloth in the plane direction. Under this condition, the curve of the strain value ε of each measuring point changing with time t can be measured. The curve diagram is shown in the figure Figure 3 As shown. Take the maximum strain value of each measuring point caused by stress wave propagation to establish the maximum value of in-plane strain ε DR-max As the distance DR from the trajectory changes, the curve equation is fitted as shown in formula (4):

[0051] ε DR-max =ε DR-max (DR) (4)

[0052] b) The sensor is located in different fiber cloth layers with the same distance DR from the ballistic line. The sensor is arranged on different layers of single-layer fiber cloth with the impact point as the center. At this time, it is used to measure the deformation of the fiber composite material in the direction of the ballistic line. Under this condition, the curve of the strain value ε of each measuring point changing with time t can be measured. The curve diagram is shown in the figure below. Figure 4 As shown. Take the maximum strain value of each measuring point caused by stress wave propagation to establish the maximum value of in-plane strain ε DN-max The curve of the change of the fiber layer position DN is fitted and established as shown in formula (5):

[0053] ε DN-max =ε DN-max (DN) (5)

[0054] The formula in the first embodiment uses the maximum value of the strain value, and the maximum value of the strain value may not be used during calculation during the measurement process.

[0055] Based on the known sensor pasting position R(DN R ,DR R ) and its maximum strain measurement value ε R-max , calculate the measured position M(DN) of the impact point of the test target plate 4 M ,DR M ) of the maximum strain value ε M-max The calculation equation of is shown in formula (6). R corresponds to the position where the sensor is actually bonded; M corresponds to the position where the sensor is not bonded and the deformation value is calculated based on the fitting curve obtained by measurement.

[0056]

[0057] The deformation response of the test target plate 4 is measured in two cases: the fiber cloth layer position DN where the sensor is located is the same and the distance DR from the ballistic line is different, and the fiber cloth layer position DN is different and the distance DR from the ballistic line is the same. The preparation temperature of the test target plate 4 is 127°C and the preparation pressure is 15MPa.

[0058] It is known from experience that when the single-bundle fiber strength of the ultra-high molecular weight polyethylene fiber cloth laminate is 3 GPa, the minimum thickness of the test target plate 4 that can effectively protect against 1.1g FSP 2000m / s penetration is about 220 layers through the deformation measurement of the fiber composite material under projectile impact.

[0059] The sensor uses a thin film strain gauge, which is uniaxial, with a base material of polyimide amide, a sensitive grid material of Cu-Ni, a thickness of 0.1 mm, a strain limit of 3%, a temperature range of -30°C to 150°C, a resistance of 120Ω, and a sensor signal line diameter of 0.1 mm. Before preparing the test target plate 4 by a high temperature pressurization process, the sensor is pre-fixed on the surface of a single-layer fiber cloth at different positions inside the test target plate 4 by gluing, and the sensors are arranged in an array, as shown in Table 1.

[0060] Table 1 Strain gauge array arrangement

[0061] Strain gauge number Layer Distance from the center of the test target plate (mm) 200-50 200 50 200-80 200 80 200-120 200 120 10-50 10 50 80-50 80 50 140-50 140 50

[0062] The sensor arrangement on the inner surface of the 200th single-layer fiber cloth is as follows: Figure 2 As shown, Figure 2 The X-axis and Y-axis in the figure represent the radial direction and the weft direction of the fiber of the single-layer fiber cloth, respectively. The sensor 2 10 is numbered 200-50, and the distance from the center of the test target plate 4 is 50 mm; the sensor 1 9 is numbered 200-80, and the distance from the center of the test target plate 4 is 80 mm; the sensor 3 11 is numbered 200-120, and the distance from the center of the test target plate 4 is 120 mm.

[0063] The sensors on the inner surface of the 10th, 80th and 140th layers of single-layer fiber cloth are respectively: numbered 10-50, located on the 10th layer, with a distance of 50 mm from the center of the test target plate 4; numbered 80-50, located on the 80th layer, with a distance of 50 mm from the center of the test target plate 4; numbered 140-50, located on the 140th layer, with a distance of 50 mm from the center of the test target plate 4.

[0064] The strain measurement results in the two cases are as follows: Figure 3 , Figure 4 As shown, the triggering time of the test data converter 7 for the two cases is different. The measurement curves of each sensor and the maximum strain measurement results caused by the stress wave are shown in Table 2.

[0065] Table 2 Maximum strain measurement results

[0066] Strain gauge number The corresponding measurement curve Maximum strain measurement value (με) 200-50 Figure 3 Middle curve 12 5567.72 200-80 Figure 3 Middle curve 13 4616.52 200-120 Figure 3 Middle curve 14 3485.56 10-50 Figure 4 Middle curve 15 2335.40 80-50 Figure 4 Middle curve 16 1585.20 140-50 Figure 4 Middle curve 17 3053.23

[0067] According to the test results, ε DR-max The expression is: DR-max =0.049DR 2 -38.082DR+7349.2, the reliability determination coefficient of the fitting curve is R 2 =1.

[0068] According to the test results, ε DN-max The expression is: DN-max =0.2137DN 2 -27.369DN+2547, the reliability determination coefficient of the fitting curve is R 2 =0.9948.

[0069] The sensor "200-50" is used as the reference point R, and the maximum strain measurement values ​​of other sensors are used as the measured position M to verify formula (3). The results are shown in Table 3. The calculation of the relative deviation δ is shown in formula (4):

[0070] δ=(ε M-max-cal -ε R-max-mea ) / ε R-max-mea (4)

[0071] In the formula, ε M-max-cal is the maximum strain value of the measuring point calculated according to formula (3), ε R-max-mea is the maximum strain value of the measuring point obtained by measurement.

[0072] Table 3 Verification results of strain gauge calculation formula at measured point

[0073]

[0074] It can be seen from Table 3 that the relative deviation δ between the calculated value obtained based on the calculation formula of the maximum strain value at the measured position of the test target plate 4 and the actual measured value is ≤7.79%, indicating that the deformation value at any position of the test target plate 4 calculated based on this measurement method has high reliability.

[0075] Embodiment 2

[0076] The difference from the first embodiment is that:

[0077] Conduct ε DN-max During the calculation, there are four layers of single-layer fiber cloth where the sensor component 5 is installed, namely the 20th, 60th, 120th and 190th layers of single-layer fiber cloth, which are respectively located in the three intervals of 0-20%, 20%-60%, and 60%-100% in the thickness direction, and two sensors are installed in the three intervals of 60%-100%.

[0078] The second embodiment illustrates that when the sensor assembly 5 is arranged, the number of sensors does not need to be the same as that in the first embodiment when the fiber cloth layer position DN is different and the distance DR from the ballistic line is the same. DN-max During calculation, it is only necessary to arrange a number of sensors dispersedly along the thickness direction of the test target plate 4 .

[0079] Embodiment 3

[0080] The difference from the first embodiment is that:

[0081] The projectile 2 used in the test of Example 3 is a spherical fragmentation simulation projectile with a diameter of 6.35 mm, a weight of 1.03 g, and a projectile speed of 1800 m / s. The test target plate 4 used in the test is a 200-layer thick aramid woven cloth laminate.

[0082] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for measuring deformation of a fiber composite material under impact of a projectile, wherein the fiber composite material is composed of several layers of single-layer fiber cloth laminated and pressed, and the plane of the single-layer fiber cloth is perpendicular to the direction of the ballistic line, characterized in that: The following steps are involved: A set of sensor components is arranged on the fiber composite material, the number of sensors in the sensor component is at least five, the sensors are arranged between adjacent single-layer fiber cloths with the impact point as the center, the direction of the sensor's sensitive deformation is consistent with the stretching direction of the single-layer fiber cloth, and the position coordinates of the sensors are recorded; The sensor assembly is electrically connected to the sensor driver, the data converter and the signal processor in sequence through a signal line passing through the fiber composite material; A three-dimensional coordinate system is established with the impact point as the origin of coordinates and the direction of the trajectory and the radial and latitudinal directions of the fiber layer on the bullet-facing surface of the fiber composite material. A projectile is launched at the fiber composite material by using a launching device. After the projectile penetrates the fiber composite material, the sensor component measures the deformation of the fiber composite material, and the signal processor calculates a curve of the strain value ε at the impact point versus time t; a ballistic test is carried out to measure the deformation response of the fiber composite material under two conditions: the fiber cloth layer position DN where the sensor is located is the same and the distance DR from the ballistic line is different; and the fiber cloth layer position DN is different and the distance DR from the ballistic line is the same; The signal processor calculates the strain value of the fiber composite material at the impact point.

2. The method for measuring deformation of a fiber composite material under projectile impact according to claim 1, characterized in that: When measuring the deformation response of fiber composite materials with the same fiber cloth layer position DN and different distances DR from the ballistic line, the curve of the strain value ε of each measuring point changing with time t is measured. The number of sensors required for the measurement is at least three. The strain value of each measuring point caused by stress wave propagation is taken to establish the curve of the in-plane strain value changing with the distance DR from the ballistic line. The curve equation is fitted as shown in formula (1): e DR =e DR (DR) (1).

3. The method for measuring deformation of a fiber composite material under projectile impact according to claim 1, characterized in that: When measuring the deformation response of fiber composite materials with different fiber cloth layer positions DN and the same distance DR from the ballistic line, the curve of the strain value ε of each measuring point changing with time t is measured. The number of sensors required for the measurement is at least three. The strain value of each measuring point caused by stress wave propagation is taken to establish the curve of the in-plane strain value changing with the fiber cloth layer position DN. The curve equation is fitted as shown in formula (2): e DN =e DN (DN) (2).

4. The method for measuring deformation of a fiber composite material under projectile impact according to claim 1, characterized in that: Based on the known sensor pasting position R(DN R ,DR R ) and its strain measurement value ε R , calculate the measured position M(DN) of the fiber composite material impact point M ,DR M ) strain value ε M The calculation equation is shown in formula (3): R corresponds to the position where the sensor is bonded, and M corresponds to the position where the sensor is not bonded and the deformation value is calculated based on the fitting curve obtained by measurement.

5. A method for measuring deformation of a fiber composite material under projectile impact according to any one of claims 1 to 4, characterized in that: The sensor driver adopts an ultra-dynamic strain gauge, the data converter adopts a high-speed data acquisition card, the signal processor adopts a computer, and the sensor adopts a thin film strain gauge.

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