Method for detecting and evaluating surface state of low-density porous fiber reinforced composite material

Abstract

A method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material relates to the field of characterization evaluation of low-density fiber-reinforced heat-proof materials, and comprises the following steps: detecting the detected surface of the low-density porous fiber-reinforced heat-proof material by using a handheld visual profilometer which comprises an equipment body and a detection probe, a measurement contact medium of the detection probe is made of a material with elastic and flexible characteristics; a measurement contact medium of the detection probe is in contact with a measured surface, the surface of the measurement contact medium correspondingly deforms along with the change of the height of a surface bulge, and a detection element arranged in the detection probe captures the deformation of the measurement contact medium and feeds the deformation back to detection software of the equipment body; acquiring a surface state image and an analysis value of the detection part; and according to the surface state image and the analysis numerical value, obtaining the height of each bulge of the measured surface. The problem of surface state detection and evaluation of low-density weak-rigidity fiber reinforced composite materials such as low-density fiber reinforced heat-proof materials is solved.

Description

Technical Field

[0001] The invention belongs to a characterization and evaluation technology for low-density fiber-reinforced heat-resistant materials, and is applied to the development and evaluation of fiber-reinforced heat-resistant materials and composite material structure products. Background Art

[0002] With the rapid development of efficient thermal protection technology for spacecraft in the field of space exploration, the thermal flow environment and flight time experienced by spacecraft during space flight or re-entry have become more severe, which puts higher requirements on the weight, ablation and thermal control performance of thermal protection materials. At present, advanced ablative thermal protection materials at home and abroad mainly include three categories: high-density phenolic / glass reinforced plastic thermal protection materials, honeycomb reinforced functional resin thermal protection materials and fiber preformed structure composite functional resin thermal protection materials. High-performance thermal protection materials serve as thermal protection structure outer shells to ensure the safety and reliability of spacecraft missions.

[0003] At present, there are significant differences in the molding characteristics and material properties of the three types of heat-resistant materials, which have different impacts on subsequent processing, interface state, function addition and other engineering implementation and performance control. The material combination and molding process methods of high-density phenolic / glass fiber-reinforced plastic heat-resistant materials and honeycomb reinforced functional resin heat-resistant materials make the surface state of the materials dense and flat. The subsequent surface functional requirements can be directly implemented or directly polished and cleaned on the surface of this material system. However, for fiber preformed structure composite functional resin heat-resistant materials, this material is a low-density porous fiber reinforced composite material. There are a large number of fiber tufts on the surface of the material or on the surface after polishing. There is a problem that direct implementation on the surface cannot meet the interface bonding requirements and functional requirements, which brings new challenges to the implementation of heat-resistant structure engineering: how to effectively evaluate and detect the surface state of low-density porous fiber reinforced heat-resistant composite materials. At present, metal materials, fiberglass and other high-density rigid materials use contour indicators to detect and evaluate their material surface conditions. Their detection standards and detection methods have standards or bases. However, the above-mentioned metal material surface condition detection and evaluation methods are not applicable to low-density porous fiber reinforced heat-resistant materials and other weakly rigid low-density composite materials, which have surface unevenness at the level of hundreds of microns and are very easy to detect surface micro-deformations. There is no ready-made and effective surface detection method for the surface condition of such heat-resistant materials, which affects the implementation of subsequent surface additional function projects. Summary of the invention

[0004] The technical problem solved by the present application is: to overcome the shortcomings of the prior art, to provide a method for detecting and evaluating the surface state of low-density porous fiber-reinforced composite materials, and to solve the problem of detecting and evaluating the surface state of low-density weak-rigidity fiber-reinforced composite materials such as low-density fiber-reinforced heat-resistant materials.

[0005] According to the surface state characteristics and process features of weakly rigid porous composite materials such as low-density porous fiber-reinforced heat-proof materials, the present invention provides a surface state evaluation and detection method for such heat-proof composite materials, which enhances the molding control capability of the heat-proof composite materials and improves and perfects the process technology of new heat-proof structures.

[0006] The technical solutions provided by this application are as follows:

[0007] A method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material comprises: using a handheld visual profilometer to detect the surface of a low-density porous fiber-reinforced heat-resistant material to be detected, the handheld visual profilometer comprising a device body and a detection probe, the measurement contact medium of the detection probe adopts a material with elastic and soft characteristics; the measurement contact medium of the detection probe is brought into contact with the surface to be detected, the surface of the measurement contact medium undergoes corresponding deformation as the height of the surface protrusion changes, the detection element built into the detection probe captures the deformation of the measurement contact medium and feeds the deformation back to the detection software of the device body, and obtains a surface state image and analysis value of the detection part; and according to the surface state image and the analysis value, obtains the height of each protrusion on the surface to be detected.

[0008] The Shore hardness of the measuring contact medium of the detection probe is 10 degrees to 20 degrees.

[0009] The material of the measuring contact medium of the detection probe is a silica gel material containing silicon-oxygen segments or an organic resin material.

[0010] The test collection surface of the detection probe for measuring the contact medium has the same curvature as the surface to be measured, so that the test collection surface is in vertical contact with the surface to be measured.

[0011] According to the height of each protrusion on the surface of the low-density porous fiber reinforced heat-resistant material, the measuring contact medium of the detection probe is used to measure the position of the measured surface as the test collection surface, and the highest point value in each test collection surface is selected as the result of characterizing the state of the measured surface.

[0012] According to the heights of the protrusions on the surface of the low-density porous fiber reinforced heat-resistant material, 5 to 20 protrusion heights are randomly selected and the standard deviation is calculated as a result of characterizing the state of the measured surface.

[0013] According to the heights of the protrusions on the surface of the low-density porous fiber reinforced heat-resistant material, all the protrusion height values ​​in all the test collection surfaces are selected and the standard deviation is calculated as the result of characterizing the state of the tested surface.

[0014] The density of the low-density porous fiber reinforced heat-proof material is 0.20-0.90 g / cm 3 .

[0015] The low-density porous fiber-reinforced heat-resistant material is composite-molded by a fiber preform structure and a porous structure functional resin. The fiber preform is generally a short-cut fiber needle-punched structure, a weft-free cloth or a fiber woven structure, and the resin functional structure is an ablative, heat-insulating, wave-absorbing or wave-transmitting functional resin. The composite is formed by vacuum-assisted dipping, infusion or hot pressing.

[0016] In summary, this application at least includes the following beneficial technical effects:

[0017] The fiber preformed structure composite functional resin type heat-proof material according to the present invention is a type of low-density porous composite material. The surface of the material has significant differences from the surface of high-density metal or fiberglass and other rigid and dense materials: the surface is uneven and protruding at the level of hundreds of microns (>0.3mm~2.0mm), and the surface strength is weak (strength is less than 1MPa). The point probe detection method of the traditional metal surface profile detector cannot characterize the surface flatness state of this type of composite material, and the metal probe can easily cause the fiber fabric to deform and distort or "sink" into the porous structure during the detection process and cannot be measured or the high-precision probe is deformed and damaged. At the same time, the non-contact three-dimensional scanning test method cannot clearly identify and characterize the protruding features of the hundreds of microns of fibers or tufts. Therefore, it is a technical difficulty of the present invention to realize the surface state evaluation and detection of a low-density porous fiber-reinforced heat-proof composite material to meet the subsequent additional function design and process implementation of the heat-proof material.

[0018] The present invention proposes a new surface state detection and evaluation method for low-density porous fiber reinforced heat-resistant composite materials, and points out that the use of surface protrusion height as a surface state evaluation index is significantly innovative, and proposes a surface detection and evaluation method that is completely different from the traditional metal material surface roughness detection method. The invention is based on the contact measurement principle, and adopts a special silicone material containing silicon-oxygen segments with elastic and soft characteristics or an organic resin material with equivalent hardness as the test contact medium, which can sensitively and accurately obtain weak rigid fiber or surface protrusion information, and establishes corresponding data collection methods and detection and interpretation principles to achieve visualization and quantifiable detection of the surface state of this type of heat-resistant material, and realizes the surface state detection and evaluation of weak rigid heat-resistant materials with a height change of hundreds of microns for the first time. The invention can be extended to the surface state detection of different low-density porous fiber reinforced composite materials, has strong applicability, and has significant engineering practice value in the field of composite material design and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the detection signal of the detection method of the present invention.

[0020] Figure 2 It is a schematic diagram of the surface state detection and evaluation principle of the present invention. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] The present application embodiment discloses a method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material. Figure 1 and Figure 2 As shown, the following steps are included:

[0023] Step 1: The low-density porous fiber reinforced heat-resistant material is composited by a fiber preform structure and a porous structure functional resin. The fiber preform is generally a short-cut fiber needle-punched structure, a non-woven fabric or a fiber woven structure, and the resin functional structure is ablative, heat-insulating, wave-absorbing or wave-transmitting functional resin. It is composited by vacuum-assisted impregnation, infusion or hot pressing. The density of the low-density porous fiber reinforced heat-resistant material is 0.20-0.90 g / cm 3 ;

[0024] Step 2: The test piece or product configuration of the low-density porous fiber-reinforced composite material includes: generally a plane structure, a curved surface structure, a spherical cap structure, a cone section structure, a rotating body structure, etc. The size of the test piece or product is not limited;

[0025] Step 3: The surface state of this type of heat-resistant material is characterized by hundreds of micrometers. Traditional non-contact 3D scanning tests cannot accurately collect and characterize it. Therefore, a contact principle with clear and intuitive identification features is used for detection and evaluation;

[0026] Step 4: The surface state detection and evaluation method adopts a handheld visual profilometer for detection. The handheld visual profilometer includes a device body and a detection probe connected to the device body. The contact measurement contact medium of the detection probe adopts a material with elastic and soft characteristics as the detection medium to contact the surface of the low-density weak rigidity heat-resistant material. The detection medium has extremely weak resistance to deformation and is highly sensitive to the slight height changes and differences of the detection surface. The height of the detection surface is reflected by the deformation of the contact medium plane. The contact medium of the detection probe is a silicone material containing silicon oxide segments or an organic resin material of equivalent hardness. The Shore hardness of the contact medium of the test probe is controlled between 10 and 20 degrees.

[0027] Step 5: After the detection probe contacts the material surface, the surface of the measuring medium deforms accordingly as the height of the surface protrusion changes. The built-in detection element captures the deformation of the measuring medium and feeds the medium deformation back to the detection software to obtain the surface state image and analysis value of the detection part;

[0028] Step 6: Depending on the surface size of the test product, the test collection method is random collection or full coverage collection;

[0029] Among them, large-sized flat, curved or rotating products are randomly collected, where large size generally means that the surface to be tested is more than 50 times the coverage area of ​​a single detection probe collection;

[0030] Random sampling includes determining the single detection probe coverage area and the detection plane configuration, and then conducting the test: for flat or curved parts, the test is carried out in the horizontal and vertical directions, and the sampling interval is generally more than 1 times the single detection probe coverage area; for rotating structures, the test is divided into quadrants and carried out along the busbar direction, where the quadrants are divided into at least four quadrants, I, II, III and IV, and can also be divided into 8 and 16 equal parts. The busbar direction is generally fully covered by the detection probe, and interval sampling can also be carried out, and the sampling interval is generally more than 1 times the single detection probe coverage area.

[0031] For small-sized flat panels or special-shaped products, full coverage acquisition is adopted. Small size generally means that the measured surface is less than 50 times the acquisition area of ​​a single lens.

[0032] Full coverage acquisition includes using the measuring contact medium of the detection probe to contact the different positions of the measured surface to obtain the measurement results of the entire measured surface.

[0033] Step 7: Detection method: The detection size of the surface detection probe is 60*60mm~120*120mm, and the test area (soft silicone contact medium area) is 30mm~90mm. The detection probe is generally a plane, and can also be designed and customized as a curved surface with a curvature similar to or consistent with the detection plane to ensure that the detection contact surface is in vertical contact with the detection plane to the greatest extent;

[0034] Step 8: Detection contact principle: The tester touches the probe to the surface during the test. When the test software interface displays the image of the entire contact area, the surface state acquisition is completed.

[0035] Step 9: The detection method of the invention can realize image signals and data signals. The image signal directly feeds back the surface state of the heat-resistant material. The data signal is to quantify and statistically analyze the convex height of the detection surface. Two methods are used: the first is to select the highest point value in the test collection surface from multiple convex heights in the test collection surface; the second method is to select 5 to 20 convex height values ​​and calculate the standard deviation; or when higher data accuracy is required, select all convex height values ​​in all test collection surfaces and calculate the standard deviation. One or both can be used as needed to finally obtain a visible and quantifiable material surface state result.

[0036] like Figure 1 As shown in Table 1, in order to illustrate the application effect of the present invention, the surface state of low-density weak-rigidity heat-proof materials was tested. The results show that the present invention can effectively evaluate the surface state of such heat-proof materials.

[0037] Table 1 Examples of surface condition detection of heat-resistant materials using the present invention for detection and evaluation

[0038] Test piece Raised height (mm) 1# 0.312 2# 0.027 3# 0.276 4# 0.059 5# 0.048

[0039] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0040] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material, characterized in that: include: A handheld visual profilometer is used to detect the surface of the low-density porous fiber-reinforced heat-resistant material. The handheld visual profilometer includes a device body and a detection probe. The measurement contact medium of the detection probe is made of a material with elastic and soft characteristics. The measuring contact medium of the detection probe is brought into contact with the surface to be measured. The surface of the measuring contact medium deforms accordingly as the height of the surface protrusion changes. The detection element built into the detection probe captures the deformation of the measuring contact medium and feeds the deformation back to the detection software of the device body, thereby obtaining the surface state image and analysis value of the detection part. According to the surface state image and analysis value, the height of each protrusion on the measured surface is obtained.

2. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: The Shore hardness of the measuring contact medium of the detection probe is 10 degrees to 20 degrees.

3. A method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 2, characterized in that: The material of the measuring contact medium of the detection probe is a silica gel material containing silicon-oxygen segments or an organic resin material.

4. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: The test collection surface of the detection probe for measuring the contact medium has the same curvature as the surface to be measured, so that the test collection surface is in vertical contact with the surface to be measured.

5. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: According to the height of each protrusion on the surface of the low-density porous fiber reinforced heat-resistant material, the measuring contact medium of the detection probe is used to measure the position of the measured surface as the test collection surface, and the highest point value in each test collection surface is selected as the result of characterizing the state of the measured surface.

6. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: According to the heights of the protrusions on the surface of the low-density porous fiber reinforced heat-resistant material, 5 to 20 protrusion heights are randomly selected and the standard deviation is calculated as a result of characterizing the state of the measured surface.

7. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: According to the heights of the protrusions on the surface of the low-density porous fiber reinforced heat-resistant material, all the protrusion height values ​​in all the test collection surfaces are selected and the standard deviation is calculated as the result of characterizing the state of the tested surface.

8. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: The density of the low-density porous fiber reinforced heat-proof material is 0.20-0.90 g / cm 3 .

9. The method for detecting and evaluating the surface state of a low-density porous fiber-reinforced composite material according to claim 1, characterized in that: The low-density porous fiber-reinforced heat-resistant material is composite-molded by a fiber preform structure and a porous structure functional resin. The fiber preform is generally a short-cut fiber needle-punched structure, a weft-free cloth or a fiber woven structure, and the resin functional structure is an ablative, heat-insulating, wave-absorbing or wave-transmitting functional resin. The composite is formed by vacuum-assisted dipping, infusion or hot pressing.

Images