Design method and weaving method of three-dimensional woven preform defect test piece

Abstract

The invention discloses a design method and a weaving method of a three-dimensional woven preform defect test piece. The design method comprises the following steps: analyzing defect types; carrying out full-type defect pre-embedding by adopting a flat plate prefabricated body, and carrying out preliminary screening on defect types; and designing a target preform defect test piece: designing the number, the position and the implementation form of the screened defect types which are not easy to identify, and designing characteristic parameters of each defect which is not easy to identify. The weaving method comprises the steps of weaving the prefabricated body, pre-burying defects before weaving and in the weaving process, and verifying after the weaving is finished. Compared with the prior art, the method has the advantages that defect design and prefabricated body weaving are combined, the product defect tolerance is obtained through the technical means of 100% full-line CT detection on prefabricated body defect test pieces in the early stage, scientific basis and data support are provided for efficient final inspection, the overall delivery efficiency is improved on the premise that the final use safety of the product is guaranteed, and the production cost is reduced. And meanwhile, the detection cost is saved.

Description

A design method and weaving method for a three-dimensional woven preform defect test specimen Technical Field

[0001] This invention relates to the field of advanced manufacturing of three-dimensional woven fabrics, specifically to a design method and weaving method for a three-dimensional woven preform defect test piece. Background Technology

[0002] Three-dimensional woven preforms, as a type of composite material reinforcement, are one of the key materials driving the development of major projects in cutting-edge fields such as aerospace, rail transportation, and military equipment. Because the application scenarios for preformed composite materials are often quite demanding, the presence of defects in the preforms may affect the performance of the final product, potentially causing significant personal injury and property damage.

[0003] Three-dimensional woven prefabricated structures are typically inspected for defects using conventional testing methods, such as X-ray inspection. These methods have short inspection cycles and provide immediate results, allowing for rapid delivery and circulation of the prefabricated structures. However, they cannot detect all types of defects, and some difficult-to-detect defects may exist within the prefabricated structures, posing a risk.

[0004] Relatively comprehensive defect detection methods, such as industrial CT inspection, have long scanning and data processing times, making them unsuitable for 100% online full inspection. They are even less desirable for inspecting large-sized, complex prefabricated structures, as they severely impact product delivery schedules and are generally not used as final inspection defect detection methods.

[0005] Defect pre-embedding techniques and test specimens have been applied in the field of composite materials for defect detection in composite components. However, commonly used composite test specimens are mostly plywood flat sheets with simple and uniform structures. Complex three-dimensional woven preforms have complex process parameters and multiple defect types. Currently, there is no design for defect test specimens for woven preforms, resulting in a lack of verification of the accuracy of woven pre-embedding techniques and a lack of accumulated data on preform defect tolerance. This makes it difficult to guarantee product safety and seriously affects the delivery process of woven composite materials for major engineering projects. Summary of the Invention

[0006] The purpose of this invention is to provide a design method and weaving method for a three-dimensional woven precast defect test piece. By analyzing and designing defect types that are difficult to detect in the precast, these types of defects are pre-embedded into the precast test piece through weaving. Then, the defects are verified and characterized. Furthermore, by testing the test piece, the types and quantities of defects that do not affect product quality are determined, forming a defect tolerance limit. This provides a basis for subsequent defect type identification and reference data for final product defect inspection and release.

[0007] Defect tolerance: The maximum number and types of defects that a preform can tolerate without affecting the performance testing of composite products; that is, what types and quantities of defects the product can tolerate without affecting safety.

[0008] The technical solution to achieve the purpose of this invention is: a design method for a three-dimensional woven preform defect test specimen, the specific steps of which are as follows:

[0009] Step 1, Defect Type Analysis: After determining the raw materials for preform production, analyze the types of defects that may occur based on the production environment and weaving process of the three-dimensional woven preform product.

[0010] Step 2, Preliminary screening of defect types: Pre-embed all types of defects using flat precast bodies to conduct preliminary screening of defect types;

[0011] Step 3: Design of the target preform defect test specimen: Design the number, location and realization form of the difficult-to-identify defect types, and design the characteristic parameters for each difficult-to-identify defect.

[0012] A weaving method for a three-dimensional woven preform defect test specimen, comprising the following specific steps:

[0013] Defect realization form determination and warning location setting: The defect preform is woven using three-dimensional weaving equipment. The defect is controlled by weaving program or manual operation according to the type of defect, and the alarm position is set according to the defect design location.

[0014] Pre-weaving defect embedding: missing warp yarns, missing warp strands, and abnormal raw material inclusions need to be embedded manually before weaving;

[0015] Weave program settings: The weave program controls the movement of the yarn and the action signals of various functions; the types of weave program control are: mis-weave, missing weft yarn, missing weft strands, and uneven weft density; at the mis-weave design position, the weave pattern used by the weave program is locally modified to form an incorrect heald; at the corresponding missing weft yarn position, the weft insertion signal is eliminated to generate a missing weft yarn; at the missing weft strand position, the number of selected weft strands is reduced; at the uneven weft density position, the traction amount is changed;

[0016] Pre-embedding of defects in the weaving process: Types of defects in the weaving process include: yarn breakage and foreign object inclusion caused by human operation, as well as misweaving, missing weft yarns, missing weft strands, and uneven weft density achieved by the weaving program control.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] (1) The design method and weaving method of the preform defect test piece disclosed in this invention, by actively and accurately introducing a pre-set type of defect at a specific location of the preform in a specific shape and size, realizes the controllability, reproducibility and standardized introduction of defects, and opens up the process path from "defect design" to "solid weaving".

[0019] (2) Before designing the test piece for defects in the prefabricated body, the technical means of screening defect types using flat prefabricated body was adopted to maximize the simulation of various defect situations that may occur in actual production. Conventional detection methods were used to conduct preliminary screening of easily identifiable defects, which improved the efficiency of the test and the comprehensiveness of the data, and avoided blind spots in the research.

[0020] (3) In the verification stage of the prefabricated defect test piece, the technical means of introducing high contrast marking was adopted to solve the engineering problem of rapid and accurate positioning of defects after industrial CT scanning, which greatly improved the efficiency of data extraction and analysis and ensured the accuracy of subsequent comparative verification.

[0021] (4) By using the technical means of 100% full-line CT inspection of prefabricated defect test pieces, the product defect tolerance limit is obtained, avoiding the delivery bottleneck caused by using time-consuming inspection for all products. Without sacrificing product quality, the overall delivery efficiency is significantly improved, providing a scientific basis and data support for efficient final inspection.

[0022] (5) For defect detection, proactive and preventive quality management techniques are adopted to shift the focus of quality control from "post-event full screening" to "pre-event risk awareness and standard definition", thereby improving the quality control level of the entire manufacturing system and forming a closed-loop quality control system that links "R&D-standards-production".

[0023] (6) By utilizing the full-line testing technology that transforms large-scale production into small-scale, one-time R&D activities, the testing time and economic costs in subsequent large-scale production are greatly saved. Attached Figure Description

[0024] Figure 1 is an overall flowchart of the design method for the three-dimensional woven preform defect test specimen of the present invention;

[0025] Figure 2 is an overall flowchart of the weaving method for the three-dimensional woven preform defect test specimen of the present invention;

[0026] Figure 3 is a schematic diagram of a missing yarn layer in the middle position of the warp yarn;

[0027] Figure 4 is a schematic diagram of a missing yarn layer in the middle position of the weft yarn;

[0028] Figure 5 is a schematic diagram of the surface staggered weave along the warp yarn movement path;

[0029] Figure 6 is a schematic diagram of the internal staggered weave of the warp yarns along their movement path;

[0030] Figure 7 is a flowchart of the specific steps of "weaving the preform defect test piece" in Figure 2;

[0031] Figure 8 is a flowchart of the specific steps in the "Verification of Precast Defect Test Specimen" step in Figure 2;

[0032] Figure 9 is an outer contour view of the preform in Embodiment 1 of the present invention;

[0033] Figure 10 is a diagram showing the staggered positions of the preform in Embodiment 1 of the present invention;

[0034] Figure 11 is a diagram showing the location of yarn breakage in the preform in Embodiment 1 of the present invention;

[0035] Figure 12 is a schematic diagram of the setting method for the mis-weave defect pattern program;

[0036] Figure 13 is a schematic diagram of warp yarn breakage in Embodiment 1 of the present invention.

[0037] Figure 14 is an outer contour view of the preform in Embodiment 2 of the present invention;

[0038] Figure 15 is a diagram showing the staggered positions of the preform in Embodiment 2 of the present invention;

[0039] Figure 16 shows the locations of broken yarns and missing strands in the preform in Embodiment 2 of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to Figures 1-16. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] This invention discloses a design method for a three-dimensional woven preform defect test specimen, the specific steps of which are as follows:

[0042] Step 1, Defect Type Analysis:

[0043] After determining the raw materials for preform production, the possible types of defects are analyzed based on the production environment and weaving process of the three-dimensional woven preform product.

[0044] Among them, the main type of defect in the production environment is foreign matter inclusion, which includes metal inclusion, fiber clump inclusion, dust inclusion, tape inclusion, etc.

[0045] Defects that may occur during the weaving process include missing yarn, broken yarn, mis-weaving, missing ply, and uneven density.

[0046] Step 2: Preliminary screening of defect types:

[0047] Flat prefabricated bodies are used for pre-embedding all types of defects. The defect types are initially screened, and the types of defects to be pre-embedded should cover as many defect types as possible that are analyzed in the production environment and weaving process of the product. There should be at least one defect of each type, and the pre-embedding location is random. After the flat prefabricated bodies are prepared, they are quickly tested using conventional testing methods. If the defects can be detected and identified, it means that the subsequent delivery and circulation of prefabricated bodies containing such defects are controllable, so they will not be pre-embedded again in subsequent prefabricated defect test pieces. Defects that are not detected and identified are screened out and pre-embedded again in prefabricated defect test pieces for subsequent verification.

[0048] The weaving parameters of the flat preform are consistent with those of the target preform defect test piece, such as fiber raw materials and warp and weft density. The flat preform is woven using three-dimensional weaving equipment, and its structural parameters are singular, such as warp and weft density and weave structure, all using unique values. It also has no complex features such as variable thickness or delamination, and its size is random and controllable, resulting in high preparation efficiency. This makes it the most scientific and efficient method for preliminary defect screening.

[0049] The conventional testing methods mentioned refer to the defect detection methods commonly used in this industry, which are characterized by being fast, efficient, and non-destructive, such as X-ray inspection, visual inspection, and ultrasonic testing.

[0050] Step 3: Design of the test specimen for defects in the target precast body:

[0051] (1) First, the design of the prefabricated body with embedded defects is carried out. The design parameters include information on the structure, number of warp and weft yarn layers, warp and weft density, and warp and weft yarn specifications.

[0052] (2) Next, design the number, location and implementation form of the defect types that are not easy to identify. Based on the defect types obtained in step 2 and the maximum number of each defect counted in previous weaving experience, design the location of each defect and the implementation form of each defect.

[0053] The location of each defect is randomly generated, or a location with a high probability of occurrence is selected based on experience data, or the location with the most severe impact is selected; the location information includes the number of warp rows, the number of warp layers, the number of weft rows, and the number of weft layers.

[0054] The implementation of each type of defect can be categorized into two forms based on the defect type: implementation controlled by the weaving program and implementation controlled by human operation. Preferably, the defect implementation should be controlled by the weaving program to avoid the risks associated with human operation. Defect implementation controlled by human operation is typically used when the weaving program cannot achieve the desired result, such as defects like foreign matter inclusions, missing yarn, or broken yarn.

[0055] The weaving program is a set of instructions for controlling the movement of the yarn, which includes the corresponding weaving actions and signal information caused by defects.

[0056] (3) Design characteristic parameters for each type of defect that is difficult to identify;

[0057] Depending on the type of defect, the characteristic parameters for its design will differ. The characteristic parameters include: missing ply design should include the number of missing plies; mis-weave design should include the pattern of the mis-weave location; broken yarn design should include the length of the broken yarn and perform splicing treatment at the corresponding length; uneven density design should include the density information of warp and weft yarns and the size of the area where unevenness occurs; foreign object inclusion design should include the type and size of foreign objects and assess their impact on weaving feasibility.

[0058] The length of a broken warp yarn is usually recorded by the weft number, column number, or length value. For example, if the length of a broken warp yarn is 0 weft, it means that a splicing operation is performed immediately after the yarn breaks, forming a broken end and not a missing yarn. If the length of a broken warp yarn is greater than 0 weft, it forms a partial missing yarn. Broken weft yarn is similar to broken warp yarn, but broken weft yarn rarely occurs. If it does occur, the weft is reintroduced to avoid breaking the yarn.

[0059] A method for weaving a three-dimensional woven precast defect test specimen, comprising weaving the precast defect test specimen using three-dimensional weaving equipment and pre-embedding defects during the weaving process, the specific steps of which are as follows:

[0060] Step 1, Weaving of precast defect test specimens:

[0061] (1) Determination of defect implementation form and setting of warning location:

[0062] Three-dimensional weaving equipment is used to weave the defect preform. The weaving process is controlled by a weaving program or manual operation according to the type of defect. The preform is woven and the defect is pre-embedded according to the design position.

[0063] Among them, the weaving process can pre-embed defects such as missing weft yarns, misweaving, missing weft yarn strands, and uneven density, while manual operation can pre-embed defects such as missing warp yarns, missing warp yarn strands, broken warp yarns, broken weft yarns, and foreign matter inclusions.

[0064] During the weaving process, alarms are set at locations where manual operations are performed to prevent human error from causing defects to be missed in the correct locations; the alarms are sound or color warnings issued by the system.

[0065] There can be multiple weaving programs, but preferably, there is one weaving program.

[0066] When there are multiple weaving programs, an alarm reminder must be set when changing the program position to ensure that the position change is accurate.

[0067] (2) Pre-embedding defects before weaving:

[0068] The aforementioned pre-embedding of defects refers to defects that occur during the preparation of raw materials and the installation of warp yarns. Typically, defects such as missing warp yarns, missing warp strands, and abnormal raw material inclusions need to be pre-embedded manually before weaving.

[0069] (3) Weaving program settings:

[0070] The weaving program controls the movement of the yarn and the action signals of various functions; the defect types controlled by the weaving program are: misweaving, missing weft yarn, missing weft strands, and uneven weft density.

[0071] In this case, the pattern used in the weaving process is partially modified at the location of the mis-woven design, resulting in an incorrect heddle and causing the mis-woven defect. Mis-woven defects usually involve changing the warp point to the weft point or vice versa.

[0072] Eliminate the weft insertion signal at the corresponding weft yarn shortage location to generate a weft yarn shortage;

[0073] At the location where the weft yarn is missing a strand, the weft selection signal is changed, the weft selection port is replaced, and the number of strands is reduced;

[0074] At locations with uneven weft density, the traction amount is changed by the weft density signal.

[0075] (4) Pre-embedding defects during the weaving process:

[0076] Defects in the weaving process include: yarn breakage and foreign object inclusion caused by human operation, as well as misweaving, missing weft yarns, missing weft strands, and uneven weft density caused by the weaving program.

[0077] The conventional prefabricated weaving process includes: shedding, weft insertion, weft beat-up, and traction. The above-mentioned defect types may occur in one or two weaving steps. For example, missing weft yarns occur during the weft insertion process, uneven weft density occurs during the traction process, and mis-weaving occurs in the shedding and weft insertion steps.

[0078] Step 2, Verification of precast defect test specimens:

[0079] Industrial CT scanning is used to verify defects in precast test pieces. Compared with other methods such as ultrasound and X-rays, its core advantages lie in its three-dimensional, quantitative, and visualization capabilities. It verifies the accuracy of defect design and pre-embedded locations through CT image output, verifies the accuracy of defect quantity, ensures the completeness and accuracy of defect types, and accumulates characterization forms of various defects, providing a reference for subsequent defect detection and location. Although industrial CT inspection has a longer scanning and data processing time, it is the most accurate and suitable method for detecting and characterizing small batches of defect verification pieces. CT scans can verify the three-dimensional location of defects, characterize the yarn movement path of the internal structure of the precast, and verify all types of defects.

[0080] (1) Mark the surface column or weft number or the intersection of column and weft of the preform defect test piece and perform CT scan to facilitate the CT scan to quickly find the location of the defect; metal wire, other fibers or other materials with a large density difference from the raw material can be used for marking, and the marking appears in the CT output image in a highlighted form to facilitate quick search.

[0081] (2) Compare and verify the defect results of CT scan with the design defect form. After comparison and verification, the precast defect test piece is composite molded and strength test is performed. After the strength test is passed, it is shown that the existence of defects has no impact on product quality. The quantity and type of pre-embedded defects are the defect tolerance of this type of product. Data is accumulated to provide a basis for the final inspection and release of precast defects.

[0082] If the strength verification test fails, the defect data cannot be used as the product defect tolerance. A new round of design and verification of the preform defect test piece is required. At the same time, the controllability of the new round of defect types and quantities in the actual weaving process must be evaluated. After the strength verification test passes again, it can be used as the final inspection and release standard for this preform.

[0083] Example 1:

[0084] In this embodiment, the preform with large variable thickness defect test piece (Figure 9) is designed and woven. The preform has 6-25 layers and is woven using a three-dimensional preform weaving equipment with discontinuous warp yarns, with the warp yarns tied at fixed lengths. The design method for the preform with large variable thickness defect test piece is as follows:

[0085] Step 1, Defect Type Analysis:

[0086] Using carbon fiber as raw material, through analysis of the production environment and weaving process, the types of defects that may occur include metal and tape inclusions, missing yarns, broken yarns, misweaving, and uneven weft density.

[0087] Step 2: Preliminary screening of defect types:

[0088] A 100mm×100mm flat preform was used to weave and embed defects of all types. Other specifications and parameters should be kept as consistent as possible with the defect test piece of the preform with large variation thickness. The location of the defects was randomly generated. One 3mm×3mm tape inclusion, one 1mm×1mm metal inclusion, one missing warp and one missing weft yarn, one broken warp yarn, three mis-woven areas, and one area of ​​uneven weft density were embedded. After weaving, the flat preform was subjected to X-ray inspection. The results showed that the foreign object inclusion defect and uneven weft density were clearly visible. The three types of defects, namely missing yarn, broken yarn, and mis-woven areas, were not observed. Therefore, it was determined that these three types of defects could not be identified by X-ray inspection and might be transferred to the preform forming stage, affecting the product. Therefore, subsequent defect embedding and verification were carried out.

[0089] Step 3: Design of precast defect test specimens:

[0090] (1) Complete the design of the large-thickness prefabricated body according to the conventional design process, and obtain its organizational structure information, warp and weft yarn layer information, warp and weft density information, warp and weft yarn specification information, etc.

[0091] (2) Based on the experience accumulated from previous testing data of prefabricated structures with large variations in thickness, the yarn breakage defect rate was 0.2%, the surface misweaving rate was <0.5%, internal misweaving and missing yarn defects were not detected. After evaluation, 40 misweaving defects were designed, including 15 front misweaving defects (circular), 15 back misweaving defects (square), and 10 internal misweaving defects (triangle) (Figure 10), 3 warp yarn missing (QJ), 5 weft yarn missing (QW), and 2 warp yarn breakage defects (DJ). The planar positions were evenly distributed (Figure 11). Detailed two-dimensional position information was determined by the number of warp yarn rows and the number of weft yarn layers. The above number of defects can be used as the maximum number of defects after evaluation.

[0092] The layer information for internal misweaving, broken yarns, and missing yarns is all in the middle position layer. If the layer number is odd, it is in the exact middle position; if the layer number is even, it is in the lower middle layer. The middle layer is where the yarn shortage condition is most severe, with the longest yarn shortage position and the most serious impact. The three types of defects are implemented using both weaving program control and task operation.

[0093] (3) The length of the broken yarn at point 2 is 0 weft, that is, the yarn is immediately spliced ​​after the yarn breaks, and no yarn is missing; the warp yarn missing yarn is the whole yarn missing yarn, and the weft yarn missing yarn is the whole weft yarn missing yarn; the 40 mis-woven points are all mis-woven patterns formed by the exchange of warp and weft yarn structures at a single interlacing point.

[0094] The weaving method for defect test specimens of precast bodies with large variations in thickness, and its specific steps are as follows:

[0095] Step 1, Weaving of precast defect test specimens:

[0096] (1) Determination of defect implementation form and setting of warning location:

[0097] There are three types of defects: mis-weave, broken yarn, and missing yarn. Missing warp yarn (QJ) and broken warp yarn are controlled manually, while mis-weave and missing weft yarn (QW) are controlled by the weave program. Two system alarms are set for broken warp yarn (DJ). The weave display corresponding to the broken yarn location is input into the equipment control system to ensure that an alarm is issued at the corresponding weave location.

[0098] (2) Pre-embedding defects before weaving:

[0099] The warp yarn missing (QJ) defect needs to be pre-embedded by manual operation before weaving. The specific operation method is to not lay the middle layer of warp yarns in the warp row corresponding to the missing yarn design position, while laying the yarn normally in other positions. The total number of warp yarns is missing one, forming a warp yarn missing (QJ).

[0100] (3) Weaving program settings:

[0101] Misweaving and missing weft yarn (QW) are controlled by the weaving program. At the misweaving design position, the weaving pattern used by the weaving program is locally modified, changing the warp point to the weft point or the weft point to the warp point (Figure 12), forming an incorrect heald lift, which leads to the misweaving defect; at the corresponding missing weft yarn (QW) position, the weft insertion signal is eliminated to generate missing weft yarn (QW).

[0102] (4) Pre-embedding defects during the weaving process:

[0103] The prefabricated body is woven normally using the weaving program set in step (3). The weaving program controls the pre-embedding of defects such as misweaving and missing weft yarn (QW). During the weaving process, defects requiring manual operation are pre-embedding. When the system issues a buzzer alarm, the yarn in the middle layer of the warp column corresponding to the warp yarn breakage (DJ) design position is cut to form a warp yarn breakage. At the same time, the yarn splicing is performed at this position, and the warp yarn is replaced with a yarn of the same specification. The length of the yarn should be 5-10cm longer than the original remaining warp yarn, so that the warp yarn breakage can be woven and fixed in the next weft (Figure 13).

[0104] Step 2, Verification of the defective specimen:

[0105] (1) Determine the specific location of the warp yarn row number or weft yarn number based on the location information of the defect design, place the metal sheet on the front and back surfaces of the preform and mark the defect location, and use a CT scanning device to scan the preform defect test piece.

[0106] (2) After scanning, obtain the three-dimensional view of the preform and locate each defect one by one. Verify the defects using the warp movement path cross-section diagram to check whether the yarn misweaving path is consistent with the theoretical design, whether the number of misweaving is 40, and whether the location and number of broken and missing yarns are consistent with the design. Save the morphology screenshot of each defect for reference in subsequent defect characterization. After verification, the defect test piece can continue to be transferred for composite material molding. Finally, a strength test is conducted for verification. After verification, the defect type and number of the defect test piece of the large-thickness preform are used as the product defect tolerance limit, which serves as the basis and standard for final inspection and release of subsequent delivered parts.

[0107] Example 2

[0108] In this embodiment, a large-size three-dimensional cylindrical thin-layer prefabricated defect test specimen (Figure 14) is designed and woven. The prefabricated prefabricated prefabricated prefabricated prefabricated prefabricated with three warp layers, using a continuous three-dimensional weaving prefabricated prefabricated prefabricated equipment, allowing for an unlimited supply of warp yarns. The design method for the large-size three-dimensional cylindrical thin-layer prefabricated defect test specimen is as follows:

[0109] Step 1, Defect Type Analysis:

[0110] Using glass fiber as raw material, through analysis of the production environment and weaving process, the types of defects that may occur include metal and carbon fiber tufts, missing yarn, broken yarn, mis-weaving, uneven weft density, and missing weft yarn strands.

[0111] Step 2: Preliminary screening of defect types:

[0112] A flat preform with all types of defects was prepared using glass fiber. The preform size was 120mm × 120mm. The weaving parameters were basically the same as those for the large-size three-dimensional cylindrical thin-layer preform defect test piece. The pre-embedded defect types included one 1mm × 1mm metal inclusion, one carbon fiber tuft inclusion, one missing warp and one missing weft yarn, one broken warp yarn, two mis-weaving areas, one area of ​​uneven weft density, one missing weft strand, and one localized missing warp yarn. The defect locations were randomly set. After weaving, the flat preform was subjected to X-ray inspection. The results showed that foreign object inclusion defects, uneven weft density, missing warp and weft yarns, and localized missing warp yarns were all clearly visible. Weft strand missing, broken yarn, and mis-weaving defects were not observed. Analysis showed that the fewer yarn layers, the more obvious the defects were, thus increasing the types of defects that could be detected. The three defects of missing weft strand, broken yarn, and mis-weaving were further investigated for subsequent defect pre-embedding and verification.

[0113] Step 3: Design of precast defect test specimens:

[0114] (1) Complete the design of large-size three-dimensional cylindrical thin-layer prefabricated body according to the conventional design process, and obtain its organizational structure information, warp and weft yarn layer information, warp and weft density information, warp and weft yarn specification information, etc.

[0115] (2) Defect Prefabricated Design: Based on weaving experience, it is known that each product has 1 to 2 broken warp yarns, and the surface (front and back) misweaving occurs less than 3 times, and missing strands cannot be detected. Therefore, this design includes 10 misweaving locations, including 3 misweaving locations in the first layer (circular), 3 misweaving locations in the third layer (square), and 4 misweaving locations in the second layer (inner) (triangle) (Figure 15), 6 broken warp yarns (DJ) (Figure 16), two of which are on the same warp yarn, distributed in each warp layer. In addition, 2 missing weft strands (QG) are set. The above number of defects is evaluated as the number of defects.

[0116] (3) The yarn breakage length at point 6 is 0 weft, that is, the yarn is immediately spliced ​​after the yarn breakage, and no yarn loss is formed; the number of strands missing in the weft yarn is 1 strand; the 10 mis-woven patterns are all mis-woven patterns formed by the exchange of warp and weft yarns at a single interlacing point.

[0117] The weaving method for large-size three-dimensional cylindrical thin-layer precast defect test specimens, with the following specific steps:

[0118] Step 1, Weaving of precast defect test specimens:

[0119] (1) Determination of defect implementation form and setting of warning location:

[0120] There are three types of defects: mis-weave, broken yarn, and missing ply. Warp yarn breakage (DJ) is controlled manually, while mis-weave and missing ply (QG) are controlled by the weave program. Six system alarms are set for warp yarn breakage (DJ), and the weave display corresponding to the breakage location is input into the equipment control system to ensure that an alarm is issued at the corresponding weave location.

[0121] (2) Pre-embedding defects before weaving: This embodiment does not involve pre-embedding defects before weaving.

[0122] (3) Weaving program settings:

[0123] Misalignment and QG (Quick Grow) are achieved using weave program control. At the misalignment location, the weave program pattern is partially modified to generate a misalignment signal; at the QG location, the weft selection signal is changed, changing the 3-strand weft selection port to a 2-strand weft selection port, thus forming a QG.

[0124] (4) Pre-embedding defects during the weaving process:

[0125] The prefabricated body is woven normally using the weaving program set in step (3). The weaving program controls the pre-embedding of defects such as misweaving and missing weft yarn (QG). During the weaving process, defects requiring manual operation are pre-embedding. When the system issues a buzzer alarm, the yarn in the corresponding layer of the warp column at the warp yarn breakage (DJ) design position is cut to form a warp yarn breakage. At the same time, yarn splicing is performed at this position. The cut warp yarn is manually stretched and fixed to the prefabricated body to continue weaving until the yarn is woven into the prefabricated body, thus completing the yarn splicing.

[0126] Step 2, Verification of precast defect test specimens:

[0127] (1) Based on the design location, find the corresponding defect location on the surface of the precast body, attach the tape block to the surface of the precast body to mark the approximate location of the defect, and use CT scanning equipment to verify the defect.

[0128] (5) Using three-dimensional images, locate each defect one by one, and save the appearance of each type of defect in the form of images. Check whether the defect type, quantity and appearance are consistent with the design. After verification, the precast defect test piece can be used for subsequent molding and strength test verification. After verification, the defect type and quantity of the large-size three-dimensional cylindrical thin-layer precast defect test piece will be used as the defect tolerance of this product, and will be used as the basis and standard for final inspection and release of subsequent delivered parts.

[0129] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for designing a three-dimensional woven precast defect test specimen, characterized in that, The specific steps are as follows: Step 1, Defect type analysis: After determining the raw materials for prefabricated body production, analyze the defect types that appear based on the production environment and weaving process of the three-dimensional woven prefabricated body product; Step 2, Preliminary screening of defect types: Use flat prefabricated bodies to pre-embed all types of defects and conduct preliminary screening of defect types; Step 3, Design of target prefabricated body defect test pieces: Design the number, location, and realization form of defect types that are not easy to identify, and design the characteristic parameters for each type of defect that is not easy to identify.

2. The design method for a three-dimensional woven precast defect test specimen according to claim 1, characterized in that, In step 1, the main type of defect in the production environment is foreign matter inclusion, which includes metal inclusion, fiber clump inclusion, dust inclusion, and tape inclusion; the types of defects that may occur during the weaving process include missing yarn, broken yarn, mis-weaving, missing strands, and uneven density.

3. The design method for a three-dimensional woven precast defect test specimen according to claim 1, characterized in that, In step 2, when pre-embedding defects in the flat preform, the types of defects to be pre-embedded should cover all defect types analyzed in the production environment and weaving process of the product, with at least one of each type of defect, and the pre-embedding location should be random. After the flat preform is prepared, it is quickly tested using conventional testing methods. If a defect is detected and identified, it indicates that the preform containing such a defect will be delivered and transferred in the future, so it will not be pre-embedded again in the subsequent preform defect test pieces. Defects that are not detected and identified are screened out and pre-embedded again in the preform defect test pieces.

4. The design method for a three-dimensional woven precast defect test specimen according to claim 1, characterized in that, The specific steps of step 3 are as follows: (1) Design of the prefabricated defect test piece. The design parameters include information on the structure, number of warp and weft yarn layers, warp and weft density, and warp and weft yarn specifications; (2) Design of the number, location, and implementation form of the defect types that are not easy to identify. The location of each defect is randomly generated or selected based on experience data, and then the location with the most serious impact is selected. The implementation form of each defect is divided into implementation controlled by the weaving program and implementation controlled by human operation. The preferred implementation form of the defect is implementation controlled by the weaving program. The implementation form of the defect controlled by human operation is usually applied when the weaving program cannot be implemented; (3) Design of characteristic parameters for each type of defect that is not easy to identify: the characteristic parameter information is different depending on the type of defect. The characteristic parameter information includes: missing ply design should include the number of missing plies; mis-weave design should include the pattern of the mis-weave position; broken yarn design should include the length of the broken yarn and perform splicing treatment at the corresponding length; uneven density design should include the density information of warp and weft yarns and the size of the area where unevenness occurs; foreign object inclusion design should include the type and size of foreign objects and assess their impact on weaving.

5. A method for weaving a three-dimensional woven preform defect test specimen, applicable to the design method of the three-dimensional woven preform defect test specimen according to any one of claims 1-4, characterized in that, The specific steps are as follows: Determination of defect implementation form and setting of warning position: The prefabricated defect test piece is woven using a three-dimensional weaving machine. The defect type is controlled by a weaving program or manual operation, and alarm positions are set according to the defect design location; Pre-weaving defect embedding: Warp yarn shortage, warp yarn shortage, and abnormal raw material inclusions need to be pre-embedded manually before weaving; Weaving program setting: The weaving program controls the movement of the yarn and the action signals of each function; The types controlled by the weaving program are: misweaving, weft yarn shortage, weft yarn shortage, and uneven weft density; At the misweaving design location, the weaving pattern used by the weaving program is locally modified to form an incorrect heald; At the corresponding weft yarn shortage location, the weft insertion signal is eliminated to generate a weft yarn shortage; At locations where weft yarn is missing strands, the number of weft strands will be reduced; at locations where weft density is uneven, the traction amount will be changed; weaving process defect pre-embedding: Weaving process defect types include: yarn breakage and foreign object inclusion caused by manual operation, as well as misweaving, missing weft yarn, missing weft strands, and uneven weft density achieved through weaving program control.

6. The weaving method for the three-dimensional woven preform defect test specimen according to claim 5, characterized in that, During the weaving process, alarms are set at locations where manual operations are performed to prevent human error from causing defects to be missed in the correct locations; the alarms are sound or color warnings issued by the system.

7. The weaving method for the three-dimensional woven preform defect test specimen according to claim 5, characterized in that, After the prefabricated defect test piece is woven, defect verification is required. Specifically, the surface column or weft number of the prefabricated defect test piece is marked, and then CT scanning is used for defect inspection. The defect results of the CT scan are compared and verified with the design defect type. After the comparison and verification, the prefabricated defect test piece is composite molded and subjected to a strength test. If the strength test is passed, it indicates that the existence of defects has no impact on product quality. The quantity and type of pre-embedded defects are then used as the defect tolerance limit for this type of product. Data is accumulated to provide a basis for the final inspection and release of prefabricated defects.

8. The weaving method for the three-dimensional woven preform defect test specimen according to claim 5, characterized in that, When weaving a three-dimensional cylindrical thin-layer prefabricated defect test piece, the types of defects are mis-weave, broken yarn, and missing strands; broken warp yarns are controlled by manual operation, while mis-weave and missing weft yarns are controlled by the weaving program.

9. The weaving method for the three-dimensional woven preform defect test specimen according to claim 5, characterized in that, When weaving the defect test piece of the variable thickness preform, the types of defects are mis-weave, broken yarn, and missing yarn; missing warp yarn and broken warp yarn are controlled by manual operation, while mis-weave and missing weft yarn are controlled by the weaving program.

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