CN110595911A - Bending micro-stress detection method for performance degradation of fiber reinforced composite material - Google Patents
Bending micro-stress detection method for performance degradation of fiber reinforced composite material Download PDFInfo
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- CN110595911A CN110595911A CN201910705546.XA CN201910705546A CN110595911A CN 110595911 A CN110595911 A CN 110595911A CN 201910705546 A CN201910705546 A CN 201910705546A CN 110595911 A CN110595911 A CN 110595911A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N3/068—Special adaptations of indicating or recording means with optical indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0023—Bending
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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Abstract
The invention discloses a bending micro-stress detection method for performance degradation of a fiber reinforced composite material, which comprises the following steps: 1) placing the detected composite material test piece on a bending test device, applying a small bending load to cause the stress and elastic deformation of the composite material test piece without damage, and recovering the composite material test piece to an original state after the bending load is released; the bending load comprises uniformly distributed bending load and concentrated bending load; 2) detecting whether the in-plane displacement of the composite material test piece has ripples under bending load, and associating random normal distribution model parameters according to the amplitude and density of the ripplesζAnd obtaining the distribution statistical information of the mechanical property of the composite material test piece along the fiber main direction. The invention can quickly make effective prediction evaluation on the structure performance and the service behavior.
Description
Technical Field
The invention relates to a method for detecting performance degradation of a fiber reinforced composite material.
Background
The fiber reinforced composite material structure has the obvious advantages of high specific strength, large specific modulus, corrosion resistance, difficult fragment generation in damage and the like, is widely applied to the fields of aerospace, automobiles and naval vessels, constructional engineering, high-end sports equipment and the like, has good structural performance and light weight, can improve the anti-seismic performance while lightening the dead weight, can widely replace traditional metal industrial materials such as steel and the like in the future, and has wide development prospect.
The processing technology of the fiber reinforced composite material structure is complex, and in the processing process, the fiber reinforced composite material product has inevitable defects such as matrix holes, fiber folds and the like due to the changes of factors such as environmental temperature, humidity, fiber prestress, formula, curing temperature and the like.
The nondestructive detection of the defects of the composite material has important significance for the safety service, the residual strength prediction, the service life prediction and the like of the composite material structure. Previous defect detection methods have focused primarily on detecting and identifying the specific shape and size of defects, such as voids, present in composite materials and thereby further analyzing and evaluating the effect of the defects on material properties. However, due to the fact that the composite material structure has multiple internal defects, the defect characteristic sizes are dispersed, the defect damage severity is different, the specific position, shape and size of a single defect are tracked, and the effects of response analysis on the overall behavior of the composite material structure and life prediction are very limited.
How to integrally predict and evaluate the influence of the composite material structure defects on the structure service behavior and performance is a problem to be solved urgently in the prior art.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a novel bending micro-stress detection method for the performance degradation of a fiber reinforced composite material.
A bending micro-stress detection method for performance degradation of a fiber reinforced composite material comprises the following steps:
1) placing the detected composite material test piece on a bending test device, applying a small bending load to cause the stress and elastic deformation of the composite material test piece without damage, and recovering the composite material test piece to an original state after the bending load is released; the bending load comprises uniformly distributed bending load and concentrated bending load;
2) detecting whether the in-plane displacement of the composite material test piece has ripples under bending load, and associating random normal distribution model parameters according to the amplitude and density of the ripplesζObtaining the mechanical property of the composite material test piece along the main direction of the fiberStatistical information of the distribution of energy.
And 2) detecting whether the in-plane displacement of the composite material test piece has ripples or not by an optical method.
The optical method is a method for measuring full-field displacement in a designated area, and comprises laser interferometry, speckle interferometry and grating projection measurement.
The composite material test piece comprises a composite material laminated plate, a composite material beam, a composite material engine blade, a composite material propeller and a composite material wing.
The fiber reinforced composite material comprises artificial fibers and natural fibers, wherein the artificial fibers comprise carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, boron fibers and ultrahigh molecular weight polyethylene fibers.
The corrugation amplitude and density refer to the local distortion of the in-plane displacement of the composite material test piece, and the distortion degree and shape distribution of the composite material test piece.
SaidζThe value is the standard deviation of the macroscopic elastic constant and the average value of the composite material test piece along the fiber direction, and the associated random normal distribution model parametersζThe value is shown in formula (1):
in the formula (I), the compound is shown in the specification,E f which represents the elastic constant in the direction of the fiber,E f0 which represents the average value of the elastic constant,ζthe standard deviation is indicated.
The method has the advantages that the specific appearance and size of the defects possibly existing in the composite material are not detected one by one, but the overall distribution condition of the macroscopic mechanical property degradation of the composite material along the main direction of the fiber is directly detected through bending loading, so that the structure performance and the service behavior are effectively predicted and evaluated quickly.
Drawings
FIG. 1 is a schematic view of an inspection of a fiber reinforced composite laminate using the present invention;
figure 2 is a comparison of the in-plane displacement field of the laminate with no corrugation and with corrugation.
Detailed Description
For fibre-reinforced composites, the deterioration of the elastic properties in the main direction of the fibres is one of the most serious influences. Different types of defects may cause a decrease in the principal direction elastic modulus and strength of the fiber. The invention discovers that: when macroscopic elastic properties along the principal direction of the fibers deteriorate in certain local regions of the composite, the elastic modulus of the composite exhibits a dispersion that can be characterized approximately by a random normal distribution model. Due to the anisotropic property of the composite material, under a given bending load, the elastic modulus dispersity causes the in-plane displacement of the composite material test piece in a specific direction to generate special ripples, and the amplitude and the density of the ripples are directly related to the parameters of the random normal distribution model. Whereas out-of-plane displacements and in-plane displacements in other directions do not produce such special corrugations. Therefore, under the bending load, only the in-plane displacement in a specific direction of the composite material test piece is detected, but not the common corner displacement corresponding to the bending load, so that the distribution statistical information of the mechanical property degradation of the composite material test piece along the main direction of the fiber can be obtained.
In actual detection, a specific bending load is applied to a specific test piece, and whether the in-plane displacement of the composite material test piece in a specific direction has ripples or not can be detected by an optical detection method. According to the degree and density of the corrugation, the distribution statistical information of the mechanical property of the composite material test piece along the fiber main direction can be obtained. The applied bending load is small, the stress generated on the structure is low, the generated deformation is elastic deformation, the load is released after the detection is finished, the stress and the deformation are released immediately, and the structure cannot be damaged.
Based on the above findings, we propose a bending micro-stress detection method for performance degradation of fiber reinforced composite material, comprising the following steps:
1) placing the detected composite material test piece on a bending test device, applying a small bending load to cause the stress and elastic deformation of the composite material test piece without damage, and recovering the composite material test piece to an original state after the bending load is released; the bending load comprises uniformly distributed bending load and concentrated bending load;
2) detecting whether the in-plane displacement of the composite material test piece has ripples under bending load, and associating random normal distribution model parameters according to the amplitude and density of the ripplesζAnd obtaining the distribution statistical information of the mechanical property of the composite material test piece along the fiber main direction.
And 2) detecting whether the in-plane displacement of the composite material test piece has ripples or not by an optical method.
The optical method is a method for measuring full-field displacement in a designated area, and comprises laser interferometry, speckle interferometry and grating projection measurement.
The composite material test piece comprises a composite material laminated plate, a composite material beam, a composite material engine blade, a composite material propeller and a composite material wing.
The fiber reinforced composite material comprises artificial fibers and natural fibers, wherein the artificial fibers comprise carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, boron fibers and ultrahigh molecular weight polyethylene fibers.
The corrugation amplitude and density refer to the local distortion of the in-plane displacement of the composite material test piece, and the distortion degree and shape distribution of the composite material test piece.
SaidζThe value is the standard deviation of the elastic constant and the mean value of the composite material test piece along the fiber direction, and the associated random normal distribution model parametersζThe values are shown in particular in the following formula:
in the formula (I), the compound is shown in the specification,E f which represents the elastic constant in the direction of the fiber,E f0 which represents the average value of the elastic constant,ζthe standard deviation is indicated.
Examples
When the macroelastic properties of the fiber decrease, the structure will exhibit an unusual specific response pattern under a particular load.Taking a composite laminate as an example, as shown in FIG. 1, the specific load is a bending loadM y0。
When the strength of the laminated board along the main direction of the fiber is damaged, the bending load is applied to the laminated boardM y0The laminated plate edgeyThe in-plane displacement in the axial direction generates ripples, and the denser the ripples, the larger the ripple amplitude, which indicates that the strength in the main direction of the fiber is more impaired. For ease of comparison, FIG. 2 shows a comparison, FIG. 2ζThe value is the standard deviation of the elastic constant associated with the principal direction of the fiber from its mean.ζ=0 represents an ideal material without any degradation of properties.ζThe larger the value, the more severe the effect of the defect on the mechanical properties.
When the composite laminate has a loss of principal fiber strength, a bending load is applied to the laminate and the composite laminate is tested along the directionyAnd (3) obtaining the reduction of the elastic performance and the strength damage degree of the composite laminated board along the main direction of the fiber according to the density and the amplitude of the corrugation of the in-plane displacement in the axial direction.
The bending load comprises uniformly distributed bending load and concentrated bending load.
The generated corrugation is an elastic response, so that only a small bending load needs to be applied to the structure, and the full-field distribution condition of the corrugation can be obtained through an optical detection method. The stress generated in the structure by the method is very low, and the load is released after the detection is finished, so that the structure cannot be subjected to residual stress or damage.
And during the conventional mechanical property test, when a bending load is applied, the displacement, such as deflection and corner, of the test piece corresponding to the bending load is observed and recorded, and the mechanical property of the test piece is evaluated according to the displacement. The present invention differs from conventional bend detection in that: the invention discovers that due to the anisotropic property of the composite material, when the mechanical property of the composite material along the fiber direction is degraded, under the bending load, the in-plane displacement of the composite material test piece in the specific direction generates special ripple response, and the displacement corresponding to the bending, including deflection and corner, is not influenced by the performance degradation, and the special response of the ripple is not generated. Therefore, under a given bending load, by measuring the situation that the in-plane displacement generates ripples, the distribution statistical information of the mechanical property degradation along the fiber direction can be obtained, and the method has an unexpected effect.
Claims (7)
1. A bending micro-stress detection method for performance degradation of a fiber reinforced composite material is characterized by comprising the following steps:
1) placing the detected composite material test piece on a bending test device, applying a small bending load to cause the stress and elastic deformation of the composite material test piece without damage, and recovering the composite material test piece to an original state after the bending load is released; the bending load comprises uniformly distributed bending load and concentrated bending load;
2) detecting whether the in-plane displacement of the composite material test piece has ripples under bending load, and associating random normal distribution model parameters according to the amplitude and density of the ripplesζAnd obtaining the distribution statistical information of the mechanical property of the composite material test piece along the fiber main direction.
2. The method according to claim 1, wherein the step 2) optically detects whether the in-plane displacement of the composite material test piece is rippled.
3. The method of claim 2, wherein the optical method is a method for measuring full field displacement in the designated area, and comprises laser interferometry, speckle interferometry, and grating projection measurement.
4. The method of claim 1, wherein the composite test pieces comprise composite laminates, composite beams, composite engine blades, composite propellers, and composite airfoils.
5. The method of claim 1, wherein the fiber-reinforced composite material comprises artificial fibers and natural fibers, and the artificial fibers comprise carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, boron fibers, and ultra-high molecular weight polyethylene fibers.
6. The method of claim 1, wherein the waviness amplitude and density refer to local distortion of the in-plane displacement of the composite test piece, and the degree and shape distribution of the distortion.
7. The method of claim 1, wherein said step of removing is performed by a laserζThe value is the standard deviation of the macroscopic elastic constant and the average value of the composite material test piece along the fiber direction, and the associated random normal distribution model parametersζThe value is shown in formula (1):
in the formula (I), the compound is shown in the specification,E f which represents the elastic constant in the direction of the fiber,E f0 which represents the average value of the elastic constant,ζthe standard deviation is indicated.
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| US5419200A (en) * | 1994-06-14 | 1995-05-30 | The United States Of America As Represented By The Secretary Of The Army | Method for assessing the effects of loading forces on a composite material structure |
| US6043870A (en) * | 1996-07-01 | 2000-03-28 | Cybernet Systems Corporation | Compact fiber optic electronic laser speckle pattern interferometer |
| CN1556371A (en) * | 2004-01-02 | 2004-12-22 | 清华大学 | Multifunctional 3D Displacement Laser Interferometry System |
| CN101545849A (en) * | 2009-05-08 | 2009-09-30 | 中国科学院化学研究所 | Method for quantitatively analyzing material interface properties by combining non-destructive testing and definite element modelling |
| CN101672749A (en) * | 2009-09-28 | 2010-03-17 | 北京航空航天大学 | Test device for surface deformation and material and test method thereof |
| CN102505068A (en) * | 2011-09-30 | 2012-06-20 | 上海交通大学 | Method for improving surface performance of titanium-based composite material by pre-stress shot blasting |
| CN107742005A (en) * | 2017-09-01 | 2018-02-27 | 杭州健途科技有限公司 | A kind of fiber-reinforced composite materials structures mechanical properties prediction and control method |
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2019
- 2019-08-01 CN CN201910705546.XA patent/CN110595911A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5419200A (en) * | 1994-06-14 | 1995-05-30 | The United States Of America As Represented By The Secretary Of The Army | Method for assessing the effects of loading forces on a composite material structure |
| US6043870A (en) * | 1996-07-01 | 2000-03-28 | Cybernet Systems Corporation | Compact fiber optic electronic laser speckle pattern interferometer |
| CN1556371A (en) * | 2004-01-02 | 2004-12-22 | 清华大学 | Multifunctional 3D Displacement Laser Interferometry System |
| CN101545849A (en) * | 2009-05-08 | 2009-09-30 | 中国科学院化学研究所 | Method for quantitatively analyzing material interface properties by combining non-destructive testing and definite element modelling |
| CN101672749A (en) * | 2009-09-28 | 2010-03-17 | 北京航空航天大学 | Test device for surface deformation and material and test method thereof |
| CN102505068A (en) * | 2011-09-30 | 2012-06-20 | 上海交通大学 | Method for improving surface performance of titanium-based composite material by pre-stress shot blasting |
| CN107742005A (en) * | 2017-09-01 | 2018-02-27 | 杭州健途科技有限公司 | A kind of fiber-reinforced composite materials structures mechanical properties prediction and control method |
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