CN113627012A - Method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratch - Google Patents

Method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratch Download PDF

Info

Publication number
CN113627012A
CN113627012A CN202110904176.XA CN202110904176A CN113627012A CN 113627012 A CN113627012 A CN 113627012A CN 202110904176 A CN202110904176 A CN 202110904176A CN 113627012 A CN113627012 A CN 113627012A
Authority
CN
China
Prior art keywords
carbon fiber
test piece
composite structure
metal
structure test
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110904176.XA
Other languages
Chinese (zh)
Other versions
CN113627012B (en
Inventor
王斌华
康思思
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Changan University
Original Assignee
Changan University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Changan University filed Critical Changan University
Priority to CN202110904176.XA priority Critical patent/CN113627012B/en
Publication of CN113627012A publication Critical patent/CN113627012A/en
Application granted granted Critical
Publication of CN113627012B publication Critical patent/CN113627012B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/18—Complex mathematical operations for evaluating statistical data, e.g. average values, frequency distributions, probability functions, regression analysis
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/26—Composites
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention discloses a method for predicting the fracture strength of a carbon fiber/metal laminated structure after surface scratching, which comprises the steps of selecting a carbon fiber plate with the size consistent with that of a carbon fiber layer in a carbon fiber/metal laminated composite structure test piece to be predicted; carrying out a direct tensile test on the carbon fiber plate, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of the carbon fiber plate; thereby obtaining the direct tensile strength f of the carbon fiber platet‑T(ii) a Direct tensile strength f by carbon fiber platet‑TReplacing the tensile strength of the carbon fiber/metal laminated composite structure test piece in the fracture strength analysis modelTensile strength ftAnd (3) the breaking strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxThe problems of complex steps, large test error and size effect existing in the prior art can be effectively solved by calculating.

Description

Method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratch
Technical Field
The invention belongs to the field of mechanical properties of engineering structures, and relates to a method for predicting the fracture strength of a carbon fiber/metal laminated structure after surface scratches.
Background
Carbon Fiber (CFRP) is large in brittleness and poor in impact resistance, and the CFRP formed by gluing contains about 30% of brittle resin matrix, so that the mechanical property of the CFRP is obviously influenced by micro defects on the surface or inside of the matrix, the mechanical property size effect is obvious, when the CFRP plate is used for adhering and reinforcing mechanical equipment or a metal structure, micro damage defects such as shallow scratches are easy to occur on the surface of the brittle CFRP plate in the operation stage of the whole structure, and at the moment, whether the mechanical property of a carbon fiber/steel laminar composite structure test piece containing surface damage can continuously meet the use requirements or not is judged.
At present, most of methods for predicting breaking strength are single materials, carbon fibers are brittle materials, a damaged area can appear on a carbon fiber/metal laminated composite structure after scratches and damages are generated on the surface of the carbon fibers, damage modes are complex and various, so that more consideration factors are caused, a large number of parameters are needed, the process of the prediction method is complex, the accuracy is not high, and no good prediction method is provided for the breaking strength of the carbon fiber/metal laminated composite structure.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for predicting the fracture strength of a carbon fiber/metal laminated structure after surface scratches, which can effectively solve the problems of complex steps, large test error and size effect existing at present.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a method for predicting the breaking strength of a carbon fiber/metal laminated structure after surface scratches comprises the following steps:
s1, selecting a carbon fiber plate consistent with a carbon fiber layer in a carbon fiber/metal layered composite structure test piece to be predicted;
s2, performing a direct tensile test on the carbon fiber plate, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of the carbon fiber plate;
s3, analyzing and calculating the load/displacement curve to obtain the direct tensile strength f of the carbon fiber platet-T；
S5, predicting the breaking strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxAnd (3) calculating:
Figure BDA0003200901040000021
wherein, B is the width of the carbon fiber/metal layered composite structure test piece; x is the distance from the internal bending moment M of the cross-middle section of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer and the metal layer; n is the ratio of the elastic modulus of the metal layer to the carbon fiber layer; h is1Is the thickness h of the metal layer in the carbon fiber/metal layered composite structure test piece2The thickness of a carbon fiber layer in a carbon fiber/metal layered composite structure test piece is shown; s is a fulcrum span for carrying out three-point bending loading on the carbon fiber/metal layered composite structure test piece; a is0The initial crack length of the surface of the carbon fiber layer of the carbon fiber/metal layered composite structure test piece is obtained; Δ aficThe crack propagation length of the carbon fiber/metal laminated composite structure test piece, CchThe structural characteristic parameters of the carbon fiber/metal layered composite structure test piece are shown; a iseThe equivalent crack length of the carbon fiber/metal layered composite structure test piece is obtained;
Figure BDA0003200901040000022
the characteristic crack length of the carbon fiber/metal layered composite structure test piece is obtained; sigmanIs a virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within a range; f. oftIs the tensile strength of the carbon fiber layer in the carbon fiber/metal layered composite structure, wherein ftBy using ft-TInstead.
Preferably, the structural characteristic parameter CchThe calculation process of (2) is as follows:
Δafic＝β·G＝1.5Cch
wherein beta is a discrete coefficient, assuming normal distribution, the mean value of beta is 1.5, and G is a second structural characteristic parameter.
Preferably, the equivalent crack length a of the carbon fiber/metal laminated composite structure test pieceeThe calculation process of (2) is as follows:
Figure BDA0003200901040000031
wherein α is a0And the total thickness h of the carbon fiber/metal laminated composite structure test piece1+h2Y (α) is a geometric factor, α is less than 1, and Y (α) is 1.12.
Preferably, the characteristic crack length of the carbon fiber/metal laminated composite structure test piece
Figure BDA0003200901040000032
The calculation process of (2) is as follows:
Figure BDA0003200901040000033
wherein KICThe fracture toughness of the carbon fiber/metal layered composite structure test piece is shown.
Preferably, the virtual crack delta a of the carbon fiber/metal laminated composite structure test pieceficNominal stress within the range σnThe calculation process of (2) is as follows:
Figure BDA0003200901040000034
preferably, the balance relation between the cross-section internal bending moment M of the carbon fiber/metal laminated composite structure test piece and the stress and strain on the section is as follows:
Figure BDA0003200901040000035
wherein the stress at the upper surface of the metal layer is σs(ii) a The stress at the interface of the metal layer and the carbon fiber layer is sigma'sIs strained to ε's(ii) a The strain of the carbon fiber layer in the crack tip damage area is epsilonnThe equivalent elastic modulus of the carbon fiber layer is En。
Preferably, the cross-middle section internal bending moment M of the carbon fiber/metal laminated composite structure and the peak load P of the carbon fiber/metal laminated composite structure test piecemax-iThe relation of (A) is as follows:
Figure BDA0003200901040000041
a system for predicting the breaking strength of a carbon fiber/metal laminated structure after surface scratching comprises;
the carbon fiber plate selection module is used for selecting a carbon fiber plate consistent with a carbon fiber layer in a carbon fiber/metal layered composite structure test piece to be predicted;
the load/displacement curve acquisition module is used for carrying out a direct tensile test on the carbon fiber plate, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of the carbon fiber plate;
the direct tensile strength calculation module is used for analyzing and calculating the load/displacement curve to obtain the direct tensile strength f of the carbon fiber platet-T；
The fracture strength calculation module is used for calculating the fracture strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxAnd (3) calculating:
Figure BDA0003200901040000042
wherein, B is the width of the carbon fiber/metal layered composite structure test piece; x is the distance from the internal bending moment M of the cross-middle section of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer and the metal layer; n is the ratio of the elastic modulus of the metal layer to the carbon fiber layer; h is1Is the thickness h of the metal layer in the carbon fiber/metal layered composite structure test piece2The thickness of a carbon fiber layer in a carbon fiber/metal layered composite structure test piece is shown; s is a fulcrum span for carrying out three-point bending loading on the carbon fiber/metal layered composite structure test piece; a is0The initial crack length of the surface of the carbon fiber layer of the carbon fiber/metal layered composite structure test piece is obtained; Δ aficThe crack propagation length of the carbon fiber/metal laminated composite structure test piece, CchThe structural characteristic parameters of the carbon fiber/metal layered composite structure test piece are shown; a iseEquivalent crack length of carbon fiber/metal laminated composite structure test piece；
Figure BDA0003200901040000043
The characteristic crack length of the carbon fiber/metal layered composite structure test piece is obtained; sigmanIs a virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within a range; f. oftIs the tensile strength of the carbon fiber layer in the carbon fiber/metal layered composite structure, wherein ftBy using ft-TInstead.
A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method for predicting the fracture strength of a carbon fiber/metal layered structure after surface scratches as described in any one of the above when executing the computer program.
A computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the method for predicting the fracture strength of a carbon fiber/metal layered structure after surface scratches as described in any one of the above.
Compared with the prior art, the invention has the following beneficial effects:
the invention is based on the boundary effect theory, considers the complex damage area on the surface of the carbon fiber, the processing and manufacturing process and the like, establishes the fracture strength analytical model of the carbon fiber/metal laminated composite structure test piece, has simple established analytical model, carrying out three-point bending test on the carbon fiber/metal laminated composite structure, substituting the geometric parameters into an analytic model to obtain the tensile strength of the carbon fiber in the composite structure, by replacing the tensile strength of a carbon fiber/metal layered composite structure test piece in a fracture strength analysis model with the direct tensile strength of a carbon fiber plate, therefore, the breaking strength of the carbon fiber/metal laminated composite structure test piece with the damaged surface can be predicted through the direct tensile strength of the carbon fiber plate, the needed parameters are few, the breaking strength prediction of the laminated composite structure is realized, the damage tolerance design is realized, and the tensile strength f of the carbon fiber/metal laminated composite structure test piece is realized.tDirect tensile strength f with carbon fiber sheett-TAnd comparing, wherein the deviation between the two is less than 10%, which proves that the error of the method is smaller.
Drawings
FIG. 1 is a schematic structural diagram of a carbon fiber/metal layered composite structure test piece according to the present invention;
FIG. 2 is a stress-strain diagram of a cross-section at a crack in a carbon fiber layer according to the present invention;
FIG. 3 is a schematic polished cross-section of a carbon fiber layer of the present invention;
FIG. 4 is a metallographic microscopic crack propagation length plot taken at A-A of a first sample of the present invention;
FIG. 5 is a metallographic microscopic crack propagation length plot at B-B for a first sample of the invention;
FIG. 6 is a metallographic microscopic crack propagation length plot taken at A-A of a second sample in accordance with the invention;
FIG. 7 is a metallographic microscopic crack propagation length plot at B-B for a second sample of the invention;
FIG. 8 is P of a carbon fiber/steel composite structure of the present inventionmax-AeA graph;
FIG. 9 is a sigma of a carbon fiber/steel composite structure of the present inventionn-aeA graph;
FIG. 10 is P of a carbon fiber/steel composite structure of the present inventionmax-AeA curve prediction graph;
FIG. 11 is a sigma of a carbon fiber/steel composite structure of the present inventionn-aeAnd (4) curve prediction.
Wherein: 1-a metal layer; 2-carbon fiber layer.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, it is a carbon fiber/metal layered composite structure test piece according to the present invention.
The size of the carbon fiber/metal layered composite structure test piece is (h)1+h2) xBxL, wherein W is the height of the test piece; b is the width of the test piece; l is the length of the specimen, h1Is the thickness of the metal layer 1 in the composite structure test piece, h2Thickness of carbon fiber layer 2 in test piece of composite structureAnd (4) degree.
As shown in FIG. 2, the initial crack length of the carbon fiber surface of the carbon fiber/metal layered composite structure test piece is a0The method comprises the steps of adopting a three-point bending loading mode, enabling the fulcrum span to be S, carrying out static test on a carbon fiber/metal laminated composite structure test piece on an electronic universal testing machine, stopping loading when the load of the testing machine is set to be reduced by about 10%, recording the peak load of each test piece in each group in the testing process, and recording the peak load as Pmax-i。
Taking off the carbon fiber layer 2 of the carbon fiber/metal layered composite structure test piece to be bonded with the flat steel sheet again, then carrying out sample inlaying and side polishing treatment, and calculating the crack propagation length delta a by observing and measuring the crack depth difference between two adjacent fracture surfacesficAnd further determining a structural characteristic parameter Cch(ii) a Calculating the equivalent crack length a of the carbon fiber/metal laminated composite structure test piecee。
Calculating the characteristic crack length of the carbon fiber/metal laminated composite structure test piece
Figure BDA0003200901040000071
Calculating the virtual crack delta a of the test piece with the carbon fiber/metal laminated composite structureficNominal stress within the range σn(ii) a Calculating a balance relation between the cross-section internal bending moment M of the carbon fiber/metal laminated composite structure test piece and the stress and strain on the cross section; calculating the cross-section internal bending moment M and the peak load P of the carbon fiber/metal laminated composite structure test piecemax-iThe relational expression of (1); obtaining the tensile strength f of the carbon fiber layer 2 in the carbon fiber/metal layered composite structure test piecet。
The fracture strength analytical model is as follows:
Figure BDA0003200901040000072
order to
Figure BDA0003200901040000073
Figure BDA0003200901040000074
Wherein x is the distance from the cross-middle section internal bending moment M of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer 2 and the metal layer 1; n is the ratio of the elastic modulus of the metal layer 1 to the carbon fiber layer 2; h is1Is the thickness h of the metal layer 1 in the carbon fiber/metal laminated composite structure test piece2The thickness of the carbon fiber layer 2 in the carbon fiber/metal layered composite structure test piece.
And manufacturing a group of carbon fiber plate test pieces with the size of W multiplied by B multiplied by L, wherein W is the height of the test piece, and the number of the carbon fiber layers 2 of the tensile carbon fiber plate test piece and the carbon fiber/metal laminated composite structure test piece is kept consistent. Carrying out direct tensile test on the carbon fiber plate test piece on an electronic universal testing machine, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of each test piece; analyzing and calculating the load/displacement curve to obtain the elastic modulus E of the carbon fiber platenAnd direct tensile strength ft-T。
The tensile strength f of a carbon fiber/metal laminated composite structure test piecetDirect tensile strength f with carbon fiber sheett-TBy contrast, the deviation between the two is less than 10%, the direct tensile strength f through the carbon fiber sheett-TReplacing the tensile strength f of the carbon fiber/metal layered composite structure test piece in the fracture strength analysis modelt. Namely, the breaking strength of the carbon fiber/metal laminated composite structure test piece after surface damage can be predicted through the direct tensile strength of the carbon fiber plate.
Structural feature parameter CchThe calculation formula is as follows:
Δafic＝β·G＝1.5Cch
beta is a discrete coefficient, assuming normal distribution obeys, and the mean value of beta is 1.5;
equivalent crack length aeThe calculation formula is as follows:
Figure BDA0003200901040000081
alpha is a0And the total thickness h of the carbon fiber/steel laminated composite structure test piece1+h2Y (α) is a geometric factor, and since this patent predicts the surface microcrack fracture strength of the laminated sheet, α is much less than 1, Y (α) is taken to be approximately 1.12.
Characteristic crack length
Figure BDA0003200901040000082
The calculation formula is as follows:
Figure BDA0003200901040000083
KICthe fracture toughness of the carbon fiber/metal laminated composite structure.
Virtual crack delta a based on boundary effect theoryficNominal stress within the range σnThe calculation formula of (2) is as follows:
Figure BDA0003200901040000084
as shown in fig. 2, the equation for the equilibrium relationship between the internal bending moment M across the middle section and the stress and strain on the section is:
Figure BDA0003200901040000091
as shown in fig. 2, the internal bending moment M across the mid-section and the peak load P obtained in step (5)max-iThe formula for calculating the relation is:
Figure BDA0003200901040000092
as shown in fig. 2, the formula for x is:
Figure BDA0003200901040000093
n is the ratio of the modulus of elasticity of the metal to the carbon fiber, and x is the distance between the mid-span section M and the carbon fiber-metal interface.
For the test results of group d (d ═ 1,2,3 … …), the test yielded group d Pmax-iThus d groups f can be obtained by testingt-iRandom property similar to β, assuming Pmax-iObey a normal distribution, so ft-i～N(μ，σ2)；
Figure BDA0003200901040000094
Example 1: the selected metal material is a steel plate with the model number of Q235, the carbon fiber cloth is 2D plain woven, the model number of A-38/3K, the length L of the carbon fiber plate subjected to direct tensile test is 150mm, and the width B of the carbon fiber plate subjected to direct tensile test is 25 mm. The length L of the carbon fiber/steel laminar composite structure test piece is 150mm, the width B is 25mm, and the h of the steel plate1The thickness of the test piece is 3mm, 8 layers are selected for the number of carbon fiber layers in the direct tensile test and the number of carbon fiber layers 2 of the carbon fiber/steel layered composite structure test piece, and the number of effective test pieces of the carbon fiber plate in the direct tensile test is 6.
And (3) manufacturing initial crack depths of 0.2mm and 0.4mm on the surface of the carbon fiber/steel laminar composite structure test piece by using a nicking tool, wherein each group of test pieces is 8.
A direct tensile test is carried out on the CFRP plate by using a 100kN electronic universal testing machine in a displacement control mode of 1mm/min, an extensometer YYU-25/50 is arranged to test the elastic modulus of the CFRP plate in the tensile load direction, after the test piece is broken, the elastic modulus and the breaking load result are shown in table 1, and the average value of the obtained direct tensile strength of the CFRP plate is ft-TWhen the average value of the elastic modulus is 41GPa at 424.31MPa, the test result is En＝41GPa。
TABLE 1CFRP Panel direct tensile test results
Figure BDA0003200901040000101
A three-point bending loading mode is adopted, the pivot span S is 96mm, a static test is carried out on the carbon fiber/steel layered composite structure test piece on an electronic universal testing machine, the loading is stopped when the load of the testing machine is set to be reduced by about 10%, and the three-point bending test data of the carbon fiber/steel layered composite structure test piece is shown in table 2.
TABLE 2 three-point bending test data of test piece with carbon fiber/steel layered composite structure
Figure BDA0003200901040000102
Taking off the carbon fiber plate of the carbon fiber/steel laminar composite structure test piece to bond with the flat steel sheet again, then carrying out sample inlaying and side polishing treatment, and calculating the crack propagation length delta a by observing and measuring the crack depth difference between two adjacent fracture surfacesficAnd further determining a structural characteristic parameter Cch(ii) a The specific observation method is as follows: (1) taking down the carbon fiber plate of the tested carbon fiber/steel laminated composite structure test piece to be bonded with the flat steel sheet again, then carrying out sample inlaying and side polishing treatment, and carrying out observation and measurement under a metallographic microscope; (2) the polishing observation schematic diagram is shown in fig. 3, fig. 4-7 are respectively adjacent carbon fiber bundle sections of two different samples, as can be seen from fig. 4 and 6, cracks of a carbon fiber plate expand into a transverse carbon fiber bundle region, the transverse carbon fiber bundle region is closed after re-flattening and bonding treatment, while cracks of fig. 5 and 7 expand into a longitudinal carbon fiber region, and the cracks cannot be closed due to contraction after the carbon fiber bundles break, so that the crack expansion length, namely the virtual crack expansion length delta a in a boundary effect theoretical model can be determined by observing and measuring the crack depth difference between two adjacent fracture surfacesfic. Therefore, if the crack lengths in fig. 4 and 6 are 103.4 μm and 92.52 μm, and the crack lengths in fig. 5 and 7 are 196.91 μm and 142.66 μm, the crack propagation lengths of the two samples are 196.91-103.4-93.51 μm and 142.66-92.52-50.14 μm, respectively, and both values are taken to obtain an average crack propagation length of 72 μm, and the structural characteristic parameter C can be obtained from formula (II)chIs 48 μm.
Obtaining test piece with carbon fiber/steel laminated composite structure
Figure BDA0003200901040000111
Curve sum σn-aeCurves, as shown in fig. 8 and 9. As the carbon fibers are made of the anisotropic material, random factors such as size deviation, defect difference and the like exist among samples, so that the data of the samples with the same initial crack depth have certain dispersibility, and the data of the samples are still within a 95% confidence interval range through reliability evaluation, so that the analytic model can describe the fracture behavior of the 2D-carbon fiber/steel laminar composite structure test piece with the crack damage on the surface of the carbon fiber layer. In FIG. 8, least squares fitting is performed on test data of two carbon fiber/steel layered composite structure test pieces with different initial crack lengths, the slope of the fitting curve is 427.88MPa, and f can be obtained by analyzing model sample estimationt430.20MPa, and the relative error of the two is 0.54 percent, which shows that the consistency of the analytical model analysis result and the fitting result of the linear least square method is good. As can be seen from Table 4, the tensile strength f is determined in comparison with the direct tensile testt-TWhen the average tensile strength of the carbon fiber plate is 424.31MPa, the average tensile strength of the carbon fiber plate is 430.20MPa, the relative error of the average tensile strength and the carbon fiber plate is 1.39%, and the deviation is small, so that the effectiveness of the analytic model is indicated.
Limit bearing capacity P of carbon fiber/steel laminated composite structure test piece with initial crack length of 0.001mm, 0.01mm and 0.1mmmaxMaking a prediction, as shown in FIG. 10; sigman-aeThe prediction graph is shown in fig. 11, and the upper limit and the lower limit of the ultimate bearing capacity of 95% reliability are obtained, as shown in table 3.
TABLE 3 carbon fiber/Steel laminar composite structural test piece ultimate bearing capacity P of different surface crack lengthsmaxPrediction value
Initial notch depth/mm Upper limit/N of ultimate bearing capacity Ultimate bearing capacity lower limit/N Ultimate bearing capacity mean/N Mean decrease amount
0 3274.20 2711.28 2992.74 /
0.001 3262.51 2701.60 2982.06 0.36％
0.01 3163.28 2619.43 2891.36 3.39％
0.1 2532.87 2097.41 2315.14 22.64％
0.2 2084.79 1809.17 1996.98 33.27％
0.4 1859.02 1539.40 1699.21 43.22％
The implementation also discloses a system for predicting the breaking strength of the carbon fiber/metal laminated structure after surface scratches, which comprises the following steps of;
and the carbon fiber plate selecting module is used for selecting the carbon fiber plate with the size consistent with that of the carbon fiber layer 2 in the carbon fiber/metal layered composite structure test piece to be predicted.
And the load/displacement curve acquisition module is used for performing direct tensile test on the carbon fiber plate, loading the test piece to complete fracture and damage, and recording the load/displacement curve of the carbon fiber plate.
The direct tensile strength calculation module is used for analyzing and calculating the load/displacement curve to obtain the direct tensile strength f of the carbon fiber platet-T。
The fracture strength calculation module is used for calculating the fracture strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxAnd (3) calculating:
Figure BDA0003200901040000121
wherein, B is the width of the carbon fiber/metal layered composite structure test piece; x is the distance from the mid-span section internal bending moment M of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer 2 and the metal layer 1; n is the ratio of the elastic modulus of the metal layer 1 to the carbon fiber layer 2; h is1Is the thickness h of the metal layer 1 in the carbon fiber/metal laminated composite structure test piece2The thickness of the carbon fiber layer 2 in the carbon fiber/metal layered composite structure test piece is shown; s is to test the carbon fiber/metal laminated composite structureCarrying out fulcrum span of three-point bending loading; a is0The initial crack length of the surface of the carbon fiber layer 2 of the carbon fiber/metal layered composite structure test piece is obtained; Δ aficThe crack propagation length of the carbon fiber/metal laminated composite structure test piece, CchThe structural characteristic parameters of the carbon fiber/metal layered composite structure test piece are shown; a iseThe equivalent crack length of the carbon fiber/metal layered composite structure test piece is obtained;
Figure BDA0003200901040000131
the characteristic crack length of the carbon fiber/metal layered composite structure test piece is obtained;xnis a virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within a range; f. oftIs the tensile strength of the carbon fiber layer 2 in the carbon fiber/metal layered composite structure, wherein ftBy using ft-TInstead.
The implementation also discloses a computer device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the computer program to realize the steps of the method for predicting the fracture strength of the carbon fiber/metal laminated structure after surface scratch.
The implementation also discloses a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the steps of the method for predicting the fracture strength of the carbon fiber/metal laminated structure after surface scratches.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (10)

1. A method for predicting the fracture strength of a carbon fiber/metal laminated structure after surface scratches is characterized by comprising the following steps:
s1, selecting a carbon fiber plate consistent with the carbon fiber layer (2) in the carbon fiber/metal layered composite structure test piece to be predicted;
s2, performing a direct tensile test on the carbon fiber plate, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of the carbon fiber plate;
s3, analyzing and calculating the load/displacement curve to obtain the direct tensile strength f of the carbon fiber platet-T；
S5, predicting the breaking strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxAnd (3) calculating:
Figure FDA0003200901030000011
wherein, B is the width of the carbon fiber/metal layered composite structure test piece; x is the distance from the mid-span section internal bending moment M of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer (2) and the metal layer (1); n is the ratio of the elastic modulus of the metal layer (1) to the elastic modulus of the carbon fiber layer (2); h is1The thickness h of the metal layer (1) in the carbon fiber/metal layered composite structure test piece2The thickness of a carbon fiber layer (2) in a carbon fiber/metal layered composite structure test piece is shown; s is a fulcrum span for carrying out three-point bending loading on the carbon fiber/metal layered composite structure test piece; a is0The initial crack length of the surface of the carbon fiber layer (2) of the carbon fiber/metal layered composite structure test piece is obtained; Δ aficThe crack propagation length of the carbon fiber/metal laminated composite structure test piece, CchThe structural characteristic parameters of the carbon fiber/metal layered composite structure test piece are shown; a iseThe equivalent crack length of the carbon fiber/metal layered composite structure test piece is obtained;
Figure FDA0003200901030000012
the characteristic crack length of the carbon fiber/metal layered composite structure test piece is obtained; sigmanIs a virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within a range; f. oftIs the tensile strength of the carbon fiber layer (2) in the carbon fiber/metal layered composite structure, wherein ftBy using ft-TInstead.
2. The method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratching according to claim 1, wherein the structural characteristic parameter CchThe calculation process of (2) is as follows:
Δafic＝β·G＝1.5Cch
wherein beta is a discrete coefficient, assuming normal distribution, the mean value of beta is 1.5, and G is a second structural characteristic parameter.
3. The method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratching according to claim 1, wherein the equivalent crack length a of the carbon fiber/metal laminated composite structure test pieceeThe calculation process of (2) is as follows:
Figure FDA0003200901030000021
wherein α is a0And the total thickness h of the carbon fiber/metal laminated composite structure test piece1+h2Y (α) is a geometric factor, α is less than 1, and Y (α) is 1.12.
4. The method for predicting breaking strength of carbon fiber/metal laminated structure after surface scratching according to claim 1, wherein the characteristic crack length of the carbon fiber/metal laminated composite structure test piece
Figure FDA0003200901030000022
The calculation process of (2) is as follows:
Figure FDA0003200901030000023
wherein KICThe fracture toughness of the carbon fiber/metal layered composite structure test piece is shown.
5. Post surface scratch carbon fiber ∑ according to claim 1The method for predicting the fracture strength of the metal laminated structure is characterized in that the virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within the range σnThe calculation process of (2) is as follows:
Figure FDA0003200901030000024
6. the method for predicting the fracture strength of the carbon fiber/metal laminated structure after surface scratches as recited in claim 1, wherein the balance relation between the bending moment M in the cross-section and the stress and strain on the cross-section of the carbon fiber/metal laminated composite structure test piece is as follows:
Figure FDA0003200901030000031
wherein the stress at the upper surface of the metal layer (1) is sigmas(ii) a The stress at the interface of the metal layer (1) and the carbon fiber layer (2) is sigma'sIs strained to ε's(ii) a The strain of the carbon fiber layer (2) in the crack tip damage area is epsilonnThe carbon fiber layer (2) has an equivalent elastic modulus of En。
7. The method for predicting the fracture strength of the carbon fiber/metal laminated structure after surface scratches as claimed in claim 1, wherein the cross-section internal bending moment M of the carbon fiber/metal laminated composite structure and the peak load P of the carbon fiber/metal laminated composite structure test piecemax-iThe relation of (A) is as follows:
Figure FDA0003200901030000032
8. a system for predicting the fracture strength of a carbon fiber/metal laminated structure after surface scratching is characterized by comprising;
the carbon fiber plate selecting module is used for selecting a carbon fiber plate consistent with the carbon fiber layer (2) in the carbon fiber/metal layered composite structure test piece to be predicted;
the load/displacement curve acquisition module is used for carrying out a direct tensile test on the carbon fiber plate, loading the test piece to be completely broken and damaged, and recording a load/displacement curve of the carbon fiber plate;
the direct tensile strength calculation module is used for analyzing and calculating the load/displacement curve to obtain the direct tensile strength f of the carbon fiber platet-T；
The fracture strength calculation module is used for calculating the fracture strength P of the carbon fiber/metal laminated composite structure test piece to be predictedmaxAnd (3) calculating:
Figure FDA0003200901030000041
wherein, B is the width of the carbon fiber/metal layered composite structure test piece; x is the distance from the mid-span section internal bending moment M of the carbon fiber/metal laminated composite structure test piece to the interface of the carbon fiber layer (2) and the metal layer (1); n is the ratio of the elastic modulus of the metal layer (1) to the elastic modulus of the carbon fiber layer (2); h is1The thickness h of the metal layer (1) in the carbon fiber/metal layered composite structure test piece2The thickness of a carbon fiber layer (2) in a carbon fiber/metal layered composite structure test piece is shown; s is a fulcrum span for carrying out three-point bending loading on the carbon fiber/metal layered composite structure test piece; a is0The initial crack length of the surface of the carbon fiber layer (2) of the carbon fiber/metal layered composite structure test piece is obtained; Δ aficThe crack propagation length of the carbon fiber/metal laminated composite structure test piece, CchThe structural characteristic parameters of the carbon fiber/metal layered composite structure test piece are shown; a iseThe equivalent crack length of the carbon fiber/metal layered composite structure test piece is obtained;
Figure FDA0003200901030000042
the characteristic crack length of the carbon fiber/metal layered composite structure test piece is obtained; sigmanIs a virtual crack delta a of a carbon fiber/metal laminated composite structure test pieceficNominal stress within a range; f. oftIs the tensile strength of the carbon fiber layer (2) in the carbon fiber/metal layered composite structure, wherein ftBy using ft-TInstead.
9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor when executing the computer program implements the steps of the method for predicting the fracture strength of a carbon fiber/metal layered structure after surface scratching according to any one of claims 1 to 7.
10. A computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, carries out the steps of the method for predicting the fracture strength of a carbon fiber/metal layered structure after surface scratching according to any one of claims 1 to 7.
CN202110904176.XA 2021-08-06 2021-08-06 Method for predicting fracture strength of carbon fiber/metal layered structure after surface scratch Active CN113627012B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110904176.XA CN113627012B (en) 2021-08-06 2021-08-06 Method for predicting fracture strength of carbon fiber/metal layered structure after surface scratch

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110904176.XA CN113627012B (en) 2021-08-06 2021-08-06 Method for predicting fracture strength of carbon fiber/metal layered structure after surface scratch

Publications (2)

Publication Number Publication Date
CN113627012A true CN113627012A (en) 2021-11-09
CN113627012B CN113627012B (en) 2023-06-20

Family

ID=78383484

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110904176.XA Active CN113627012B (en) 2021-08-06 2021-08-06 Method for predicting fracture strength of carbon fiber/metal layered structure after surface scratch

Country Status (1)

Country Link
CN (1) CN113627012B (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08101105A (en) * 1994-09-30 1996-04-16 Hideki Sekine Method and device for measuring fracture toughness of fiber-reinforced composite material
US5602329A (en) * 1995-08-09 1997-02-11 Massachusetts Institute Of Technology Method and apparatus for measuring fracture toughness of a material
JP2010175479A (en) * 2009-01-30 2010-08-12 Ihi Corp Method for evaluating life of minute notched material
CN105928784A (en) * 2016-04-14 2016-09-07 华北水利水电大学 Method for measuring rupture toughness of hot-rolled carbon steel under plane stress
US20160299046A1 (en) * 2014-09-25 2016-10-13 East China University Of Science And Technology A method of measurement and determination on fracture toughness of structural materials at high temperature
CN109991077A (en) * 2019-03-18 2019-07-09 重庆大学 A kind of prediction technique of composite material Mixed-Mode Delamination resistance curve
CN110907269A (en) * 2019-12-09 2020-03-24 大连理工大学 Titanium alloy fatigue life prediction method based on micro scratches

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08101105A (en) * 1994-09-30 1996-04-16 Hideki Sekine Method and device for measuring fracture toughness of fiber-reinforced composite material
US5602329A (en) * 1995-08-09 1997-02-11 Massachusetts Institute Of Technology Method and apparatus for measuring fracture toughness of a material
JP2010175479A (en) * 2009-01-30 2010-08-12 Ihi Corp Method for evaluating life of minute notched material
US20160299046A1 (en) * 2014-09-25 2016-10-13 East China University Of Science And Technology A method of measurement and determination on fracture toughness of structural materials at high temperature
CN105928784A (en) * 2016-04-14 2016-09-07 华北水利水电大学 Method for measuring rupture toughness of hot-rolled carbon steel under plane stress
CN109991077A (en) * 2019-03-18 2019-07-09 重庆大学 A kind of prediction technique of composite material Mixed-Mode Delamination resistance curve
CN110907269A (en) * 2019-12-09 2020-03-24 大连理工大学 Titanium alloy fatigue life prediction method based on micro scratches

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
卿龙邦;聂雅彤;慕儒;程兰婷;王晓伟;: "定向钢纤维水泥基复合材料断裂理论分析及试验", 材料科学与工程学报, no. 02 *
管俊峰;钱国双;白卫峰;姚贤华;付金伟;: "岩石材料真实断裂参数确定及断裂破坏预测方法", 岩石力学与工程学报, no. 05 *

Also Published As

Publication number Publication date
CN113627012B (en) 2023-06-20

Similar Documents

Publication Publication Date Title
Gong et al. Delamination migration in multidirectional composite laminates under mode I quasi-static and fatigue loading
Hu et al. Low-velocity impact damage research on CFRPs with Kevlar-fiber toughening
Allegri et al. A new semi-empirical model for stress ratio effect on mode II fatigue delamination growth
Aoki et al. Damage propagation in CFRP laminates subjected to low velocity impact and static indentation
Ratcliffe Characterization of the edge crack torsion (ECT) test for mode III fracture toughness measurement of laminated composites
Li et al. Elastic and fracture behavior of three-dimensional ply-to-ply angle interlock woven composites: Through-thickness, size effect, and multiaxial tests
Sneddon et al. Sensitivity of material failure to surface roughness: A study on titanium alloys Ti64 and Ti407
Ji et al. Effects of bondline thickness on Mode-II interfacial laws of bonded laminated composite plate
Liu et al. Sliding of a diamond sphere on K9 glass under progressive load
Hutson et al. Characterization of fretting fatigue crack initiation processes in CR Ti–6Al–4V
Wallace et al. Fretting fatigue crack nucleation in Ti–6Al–4V
Kim et al. An indentation method for evaluation of residual stress: Estimation of stress-free indentation curve using stress-independent indentation parameters
Van Paepegem Fatigue testing methods for polymer matrix composites
Barnby et al. Crack propagation and compliance calibration in fibre-reinforced polymers
CN113627012B (en) Method for predicting fracture strength of carbon fiber/metal layered structure after surface scratch
Moller et al. Influence of the temperature on the fracture energy of a methacrylate adhesive for mining applications
Stefaniak et al. Chances and challenges in the application of fiber metal laminates
Cao et al. Measuring mechanical properties of micro-and nano-fibers embedded in an elastic substrate: theoretical framework and experiment
Nettles A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing Reference: Nettles, AT and Douglas, MJ,“A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing," Composite Materials: Testing, Design, and Acceptance Criteria, ASIM STP 1416, A. Zureick and AT Nettles, Eds.
Katerelos et al. Effect of off–axis matrix cracking on stiffness of symmetric angle-ply composite laminates
Oshima et al. High-resolution in situ characterization of micromechanisms in CFRP laminates under mode II loading
Wang et al. Experimental investigation of two-dimensional Mode-II delamination in composite laminates
Gathimba et al. Static ductility evaluation of corroded steel plates considering surface roughness characteristics
Nikbakht et al. 2D and 3D interlaminar fracture assessment under mixed-mode loading conditions
Xu et al. Measurements of through-thickness young's moduli of fibrous composite laminates using nanoindentation

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant