Shrinkage detection method for skin-core type composite fiber fabric

Abstract

The invention discloses a shrinkage detection method of a sheath-core type composite fiber fabric. The method comprises the following steps: acquiring an image and measuring an initial distance; carrying out damp-heat circulation treatment; calculating the shrinkage rate; calibrating a skin-core coupling coefficient; analyzing theoretical shrinkage and deviation; and evaluating the cyclic stability for multiple times. The method overcomes the technical limitation that the existing general detection method can only measure the overall size change and cannot analyze the complex interaction effect of the skin-core structure, realizes the non-contact accurate measurement of the fabric shrinkage rate by introducing the high-precision image marking and full-field strain analysis technology, can identify the local deformation abnormity, and has the advantages of high accuracy and high accuracy. An effective means is provided for positioning potential defects of the skin-core interface; according to the method, a dimensional stability evaluation system oriented to an actual use scene is constructed through multiple times of damp-heat cyclic treatment and combination of variation coefficient evaluation, and the repeated damp-heat stress process of the fabric in the wearing and washing process is effectively simulated.

Description

Technical Field

[0001] This invention relates to the field of textile testing technology, and more specifically, to a method for detecting the shrinkage of core-sheath composite fiber fabrics. Background Technology

[0002] Core-sheath composite fiber fabrics achieve functional complementarity by combining fibers with different properties in the same yarn. For example, the core layer uses porous polyester to provide moisture-wicking channels, while the sheath layer uses viscose fiber for skin-friendly comfort. During wear and washing, these fabrics are prone to problems such as dimensional instability, wrinkling, and delamination due to the differences in heat and moisture shrinkage properties between the core and sheath layers. Existing shrinkage testing methods primarily measure the overall dimensional changes of the fabric and cannot reveal potential defects caused by the interaction between the core and sheath layers.

[0003] Therefore, a new solution is needed to address this problem. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for detecting the shrinkage of core-sheath composite fiber fabrics.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for detecting the shrinkage rate of a core-sheath composite fiber fabric, wherein the fabric is woven from core fibers and sheath fibers through blending to form a core-sheath structure yarn, includes the following steps:

[0007] Step S1: Create a grid of marker points on the surface of the fabric to be tested, acquire an initial image, obtain the initial coordinates of each marker point, and calculate the initial distance between adjacent marker point pairs in the warp and weft directions;

[0008] Step S2: Perform multiple wet and hot cycle treatments on the fabric, and acquire an image after each cycle to obtain the coordinates of each marked point after processing, and calculate the processed distance between adjacent marked point pairs in the warp and weft directions.

[0009] Step S3: Based on the initial distance and the processed distance, calculate the shrinkage rate of each pair of marked points after multiple cycles, and then calculate the average shrinkage rate of the fabric in the warp and weft directions after multiple cycles.

[0010] Step S4: Calculate the ideal weighted shrinkage rate based on the material property parameters of the core fiber and the sheath fiber, and calibrate the core-sheath coupling coefficient using the average shrinkage rate after the first cycle.

[0011] Step S5: Based on the calibrated core-skin coupling coefficient and the ideal weighted shrinkage rate, calculate the theoretical shrinkage rate, and calculate the deviation between the actual average shrinkage rate and the theoretical shrinkage rate in the longitudinal and latitudinal directions after multiple cycles.

[0012] Step S6: Calculate the coefficients of variation in the warp and weft directions based on the average shrinkage rate after multiple cycles to evaluate the dimensional stability of the fabric.

[0013] Furthermore, in step S2, the damp heat cycle treatment includes:

[0014] Soak in warm water at 40±2℃ for 30 minutes with a bath ratio of 1:30, stirring gently during soaking;

[0015] Centrifuge for 1 minute at 500 rpm to dehydrate;

[0016] Spread out and dry in an oven at 80±2℃ for 60 minutes;

[0017] After 24 hours of humidification under standard atmospheric conditions, image acquisition and the next cycle will be performed.

[0018] Furthermore, in step S3, the formula for calculating the shrinkage rate is:

[0019]

[0020] In the formula, For the first After the nth iteration A pair of marker points in the direction The shrinkage rate on; For the initial state, the first A pair of marker points in the direction Distance on; For the first After the nth iteration A pair of marker points in the direction Distance on; Indicates the direction of longitude or latitude;

[0021] The formula for calculating the average shrinkage rate is:

[0022]

[0023] In the formula, For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction The total number of marked points on the map.

[0024] Furthermore, in step S4, the material performance parameters of the core fiber and the sheath fiber include the measured shrinkage rates of the pure core fabric and the pure sheath fabric under the same humid heat treatment conditions, as well as the core-sheath mass ratio.

[0025] Furthermore, in step S4, the formula for calculating the ideal weighted scaling factor is:

[0026]

[0027] In the formula, For ideal weighted scaling; The measured shrinkage rate of the pure core layer fabric under the same humid heat treatment conditions; The measured shrinkage rate of pure leather fabric under the same humid heat treatment conditions; The ratio of skin to core mass;

[0028] The calibration formula for the core-skin coupling coefficient is:

[0029]

[0030] In the formula, The core-skin coupling coefficient; This represents the average shrinkage rate after the first cycle.

[0031] Furthermore, in step S5, the formula for calculating the theoretical shrinkage rate is:

[0032]

[0033] In the formula, This is the theoretical reduction ratio; The core-skin coupling coefficient; For ideal weighted scaling;

[0034] The formula for calculating the theoretical shrinkage deviation is:

[0035]

[0036] In the formula, For the first Direction after the second cycle The deviation between the actual average shrinkage rate and the theoretical shrinkage rate; For the first After the second cycle, the fabric is in the direction The average shrinkage rate.

[0037] Furthermore, in step S6, the formula for calculating the coefficient of variation is:

[0038]

[0039] In the formula, For direction coefficient of variation; This represents the total number of loops. For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction superior The average of the average shrinkage rate over each cycle.

[0040] Furthermore, it also includes full-field strain analysis of the images acquired in steps S1 and S2: the initial image and the image after cyclic processing are divided into several sub-regions, and the displacement of each sub-region is obtained through digital image correlation matching, thereby constructing the strain fields in the longitudinal and latitudinal directions; the strain value of each point in the strain field is compared with twice the average shrinkage rate in the corresponding direction, and the area where the strain value is greater than twice the average shrinkage rate is identified as the strain concentration area, which is used to warn of core-skin delamination or local defects.

[0041] Furthermore, the core fiber is a porous polyester filament, and the sheath fiber is a viscose fiber.

[0042] The beneficial effects of this invention are:

[0043] 1. This invention overcomes the technical limitations of existing general detection methods, which can only measure overall size changes and cannot analyze the complex interaction of the core-sheath structure. By introducing high-precision image marking and full-field strain analysis technology, it realizes non-contact and accurate measurement of fabric shrinkage and can identify local deformation anomalies, providing an effective means to locate potential defects at the core-sheath interface.

[0044] 2. This invention decomposes the shrinkage problem of core-sheath structure fabrics into the superposition of the independent contributions of core fibers and sheath fibers and the interfacial coupling effect, and constructs a theoretical prediction model. By setting pure core and pure sheath fabrics as control references, the intrinsic shrinkage characteristics of single-component materials are obtained, and then an ideal weighted shrinkage model is constructed. Furthermore, the core-sheath coupling coefficient is introduced to quantify the influence of interfacial interaction on the overall shrinkage, thus realizing the leap from empirical estimation to mechanism modeling.

[0045] 3. This invention constructs a dimensional stability assessment system for practical use scenarios by performing multiple wet and heat cycles and combining them with coefficient of variation evaluation. It effectively simulates the repeated wet and heat stress process of fabrics during wearing and washing, and reflects the dimensional fluctuations over time through the coefficient of variation, providing a more comprehensive quality evaluation basis for products such as pantyhose that have high requirements for dimensional stability. Attached Figure Description

[0046] Figure 1 This is a flowchart of a shrinkage detection method for core-sheath composite fiber fabrics in this embodiment. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0048] Example: A method for detecting the shrinkage rate of a core-sheath composite fiber fabric, comprising the following steps:

[0049] Step S1, Image Acquisition and Initial Distance Measurement: Create a grid of marker points on the surface of the fabric to be tested, acquire the initial image, obtain the initial coordinates of each marker point, and calculate the initial distance between adjacent marker point pairs in the warp and weft directions.

[0050] The fabric under test is made by blending core and outer fibers to form a core-sheath structure yarn (i.e., the outer fibers are twisted and tightly wrapped around the surface of the core fibers), and then weaving it. The core fibers are porous polyester filaments, and the outer fibers are viscose fibers. In the woven fabric, after the viscose fibers in the outer layer absorb sweat from the skin surface, the sweat is quickly guided into the core channels due to the stronger capillary effect of the porous polyester core, and then conducted longitudinally along the fibers to the outer surface of the fabric, achieving a rapid drying process of "sweat absorption-conduction-evaporation". At the same time, the outer viscose fiber ensures the soft and skin-friendly feel of the fabric, while the inner polyester filament provides a strong skeleton. This fabric can be used in quick-drying pantyhose products.

[0051] Before shrinkage testing, the fabric to be tested is conditioned for 24 hours under standard atmospheric conditions to eliminate the influence of internal stress and moisture differences on the initial measurement. After conditioning, a grid of markings is created on the surface of the fabric using water- and heat-resistant inks (such as epoxy-based heat-resistant inks or thermosetting screen printing inks) to ensure that the markings do not fall off or become blurred during subsequent soaking and drying processes. The diameter of the markings is set to no more than 1 mm, and the spacing between the markings is preferably 5-20 mm, with the specific spacing determined according to the fabric size.

[0052] After the marker matrix is ​​prepared, lay the fabric flat under a scanner or high-resolution digital camera, ensuring the fabric is flat and wrinkle-free, and that the image acquisition plane is parallel to the fabric surface. Acquire an image in the initial state and extract the coordinates of each marker point in the image. Then calculate the initial distance between adjacent marker point pairs in the warp and weft directions, and record them as the initial warp distance and the initial weft distance, respectively. The number of marker point pairs in each direction should be no less than 30 to ensure statistical representativeness.

[0053] Step S2, Humidity and Heat Cycling Treatment: The fabric undergoes multiple humidity and heat cycling treatments to simulate actual wearing and washing processes. The humidity and heat cycling treatment includes soaking, dehydration, and drying, specifically:

[0054] Soaking: Place the fabric in warm water at 40±2℃ with a bath ratio of 1:30 and soak for 30 minutes. Stir gently every 5 minutes during this time to ensure that the water fully wets the fibers, activates the water absorption and expansion of the porous fibers and releases the stress at the core-sheath interface.

[0055] Dehydration: Remove the fabric and dehydrate it for 1 minute at 500 rpm using a centrifugal dehydrator to shorten the subsequent drying time;

[0056] Drying: Lay the dehydrated fabric flat in an oven at 80±2℃ and dry for 60 minutes. This temperature was chosen to take into account the glass transition temperature of porous polyester and the temperature resistance of the composite film, which can effectively induce heat shrinkage without damaging the fiber structure.

[0057] Conditioning: Remove the dried fabric and place it under standard atmospheric conditions for 24 hours to allow it to return to equilibrium before taking measurements.

[0058] After each wet heat cycle is completed, an image is acquired to obtain the coordinates of each marked point after processing, and the processed distance between adjacent marked point pairs in the longitudinal and latitudinal directions is calculated; the number of cycles can be set according to product standards or requirements.

[0059] Step S3, Shrinkage Calculation: Based on the initial distance obtained in step S1 and the processed distance obtained in step S2, calculate the shrinkage of each pair of marked points after multiple cycles, and then calculate the average shrinkage of the fabric in the warp and weft directions after multiple cycles.

[0060] The formula for calculating the shrinkage rate is as follows:

[0061]

[0062] In the formula, For the first After the nth iteration A pair of marker points in the direction The shrinkage rate on; For the initial state, the first A pair of marker points in the direction Distance on; For the first After the nth iteration A pair of marker points in the direction The distance on.

[0063] The formula for calculating the average shrinkage rate is:

[0064]

[0065] In the formula, For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction The total number of marked points on the map.

[0066] It should be noted that, It can be expressed as longitudinal or latitudinal, that is, the reduction rate and average reduction rate in longitudinal and latitudinal directions are calculated respectively.

[0067] Step S4, core-sheath coupling coefficient calibration: Based on the material performance parameters of the core fiber and the sheath fiber, including the measured shrinkage rates of pure core fabric and pure sheath fabric under the same humid heat treatment conditions, and the core-sheath mass ratio, calculate the ideal weighted shrinkage rate, and use the average shrinkage rate after the first cycle to calibrate the core-sheath coupling coefficient.

[0068] Pure core layer fabric refers to a fabric woven with the same core layer fibers (i.e., porous polyester filaments) and specifications as the fabric under test; pure lining fabric refers to a fabric woven with the same lining fibers (i.e., viscose fibers) and specifications as the fabric under test. Both reference fabrics are subjected to the same wet-heat cycling treatment in step S2 (only the first cycle is required), and their average shrinkage rates are measured, recorded as pure core layer shrinkage rate and pure lining layer shrinkage rate, respectively.

[0069] The sheath-core weight ratio refers to the ratio of the weight of the sheath fibers to the weight of the core fibers, which can be calculated or measured using yarn specifications.

[0070] Assuming there are no mutual constraints between the core and the sheath, the ideal weighted shrinkage rate is:

[0071]

[0072] In the formula, For ideal weighted scaling; The measured shrinkage rate of the pure core layer fabric under the same humid heat treatment conditions; The measured shrinkage rate of pure leather fabric under the same humid heat treatment conditions; The ratio of skin to core mass.

[0073] Next, the core-sheath coupling coefficient is calibrated using the ratio of the average shrinkage (average of warp and weft) after the first cycle of the fabric under test to the ideal weighted shrinkage. The calculation formula is as follows:

[0074]

[0075]

[0076] In the formula, The core-skin coupling coefficient; This represents the average shrinkage rate after the first cycle; and These are the average shrinkage rates of the fabric in the warp and weft directions after the first cycle, respectively.

[0077] The core-skin coupling coefficient reflects the degree of influence of core-skin interface interaction on shrinkage. When the coefficient is greater than 1, it indicates that the core and skin restrain each other, which intensifies shrinkage; when the coefficient is less than 1, it indicates that the core and skin inhibit each other, which weakens shrinkage.

[0078] Step S5, Theoretical shrinkage and deviation analysis: Based on the calibrated core-skin coupling coefficient and ideal weighted shrinkage, calculate the theoretical shrinkage, and calculate the deviation between the actual average shrinkage in the meridional and latitudinal directions and the theoretical shrinkage after multiple cycles.

[0079] The theoretical shrinkage rate represents the expected shrinkage rate that the fabric should achieve under the current core-sheath bonding condition, and its calculation formula is as follows:

[0080]

[0081] In the formula, This is the theoretical reduction ratio; The core-skin coupling coefficient; The ideal weighted reduction ratio.

[0082] Deviation is used to determine whether a dimension deviates from the expected value; its calculation formula is:

[0083]

[0084] In the formula, For the first Direction after the second cycle The deviation between the actual average shrinkage rate and the theoretical shrinkage rate; For the first After the second cycle, the fabric is in the direction The average shrinkage rate.

[0085] Step S6, Multiple Cycle Stability Evaluation: Based on the average shrinkage rate after multiple cycles, calculate the coefficients of variation in the warp and weft directions to evaluate the dimensional stability of the fabric.

[0086] The formula for calculating the coefficient of variation is as follows:

[0087]

[0088]

[0089] In the formula, For direction coefficient of variation; This represents the total number of loops. ; For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction superior The average of the average shrinkage rate over each cycle.

[0090] coefficient of variation The smaller the value, the more stable the fabric's size changes and the smaller the fluctuations after multiple washes.

[0091] To further evaluate the deformation of the fabric, a digital image correlation algorithm can be used to perform full-field strain analysis on the acquired images, specifically:

[0092] Step 1: Convert the initial image acquired in step S1 and the deformed image acquired in step 2 after the damp heat cycle processing into grayscale images, and perform enhancement processing if necessary.

[0093] Step 2: Define the detection region in the initial image and divide the detection region into several small sub-regions. Each sub-region contains a certain number of pixels and should contain sufficient grayscale features to ensure the accuracy of matching.

[0094] Step 3: For each sub-region in the initial image, search for the sub-region with the most similar gray-level distribution in the deformed image. The similarity measure adopts the normalized cross-correlation function, and the sub-pixel displacement of the sub-region center point is obtained through sub-pixel interpolation and iterative optimization algorithm.

[0095] Step 4: Combine the displacements of all sub-region center points to form the longitudinal and latitudinal displacement fields of the entire field;

[0096] Step 5: After smoothing the displacement field, the displacement plane is fitted using the local least squares method, and then the derivative is calculated to obtain the meridional and zonal strain values ​​at each point. The strain values ​​reflect the degree of local contraction at that point.

[0097] Step 6: Compare the meridional strain value at each point with the average meridional shrinkage after the kth cycle. If the meridional strain value at a certain point... Greater than the average meridional shrinkage twice as much as Then this point is marked as the meridional strain concentration point. express The location is in the direction The strain values ​​in the upper direction are analyzed; the same applies to the latitudinal direction. The collection of these points constitutes a strain concentration area, suggesting possible core-skin delamination, localized debonding, or material damage, requiring further investigation.

[0098] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting the shrinkage rate of a core-sheath composite fiber fabric, wherein the fabric is woven from core fibers and sheath fibers blended to form a core-sheath structure yarn, characterized in that... Includes the following steps: Step S1: Create a grid of marker points on the surface of the fabric to be tested, acquire an initial image, obtain the initial coordinates of each marker point, and calculate the initial distance between adjacent marker point pairs in the warp and weft directions; Step S2: Perform multiple wet and hot cycle treatments on the fabric, and acquire an image after each cycle to obtain the coordinates of each marked point after processing, and calculate the processed distance between adjacent marked point pairs in the warp and weft directions. Step S3: Based on the initial distance and the processed distance, calculate the shrinkage rate of each pair of marked points after multiple cycles, and then calculate the average shrinkage rate of the fabric in the warp and weft directions after multiple cycles. Step S4: Calculate the ideal weighted shrinkage rate based on the material property parameters of the core fiber and the sheath fiber, and calibrate the core-sheath coupling coefficient using the average shrinkage rate after the first cycle. Step S5: Based on the calibrated core-skin coupling coefficient and the ideal weighted shrinkage rate, calculate the theoretical shrinkage rate, and calculate the deviation between the actual average shrinkage rate and the theoretical shrinkage rate in the longitudinal and latitudinal directions after multiple cycles. Step S6: Calculate the coefficients of variation in the warp and weft directions based on the average shrinkage rate after multiple cycles to evaluate the dimensional stability of the fabric.

2. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, In step S2, the wet heat cycle treatment includes: Soak in warm water at 40±2℃ for 30 minutes with a bath ratio of 1:30, stirring gently during soaking; Centrifuge for 1 minute at 500 rpm to dehydrate; Spread out and dry in an oven at 80±2℃ for 60 minutes; After 24 hours of humidification under standard atmospheric conditions, image acquisition and the next cycle will be performed.

3. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, In step S3, the formula for calculating the shrinkage rate is: In the formula, For the first After the nth iteration A pair of marker points in the direction The shrinkage rate on; For the initial state, the first A pair of marker points in the direction Distance on; For the first After the nth iteration A pair of marker points in the direction Distance on; Indicates the direction of longitude or latitude; The formula for calculating the average shrinkage rate is: In the formula, For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction The total number of marked points on the map.

4. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, In step S4, the material performance parameters of the core fiber and the sheath fiber include the measured shrinkage rates of the pure core fabric and the pure sheath fabric under the same humid heat treatment conditions, as well as the core-sheath mass ratio.

5. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 4, characterized in that, In step S4, the formula for calculating the ideal weighted scaling factor is: In the formula, For ideal weighted scaling; The measured shrinkage rate of the pure core layer fabric under the same humid heat treatment conditions; The measured shrinkage rate of pure leather fabric under the same humid heat treatment conditions; The ratio of skin to core mass; The calibration formula for the core-skin coupling coefficient is: In the formula, The core-skin coupling coefficient; This represents the average shrinkage rate after the first cycle.

6. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, In step S5, the formula for calculating the theoretical shrinkage rate is: In the formula, This is the theoretical reduction ratio; The core-skin coupling coefficient; For ideal weighted scaling; The formula for calculating the theoretical shrinkage deviation is: In the formula, For the first Direction after the second cycle The deviation between the actual average shrinkage rate and the theoretical shrinkage rate; For the first After the second cycle, the fabric is in the direction The average shrinkage rate.

7. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, In step S6, the formula for calculating the coefficient of variation is: In the formula, For direction coefficient of variation; This represents the total number of loops. For the first After the second cycle, the fabric is in the direction The average shrinkage rate; For direction superior The average of the average shrinkage rate over each cycle.

8. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, It also includes full-field strain analysis of the images acquired in steps S1 and S2: the initial image and the image after cyclic processing are divided into several sub-regions, and the displacement of each sub-region is obtained through digital image correlation matching, thereby constructing the strain fields in the longitudinal and latitudinal directions; the strain value of each point in the strain field is compared with twice the average shrinkage in the corresponding direction, and the area where the strain value is greater than twice the average shrinkage is identified as the strain concentration area, which is used to warn of core-skin delamination or local defects.

9. The shrinkage detection method for a core-sheath composite fiber fabric according to claim 1, characterized in that, The core fiber is a porous polyester filament, and the sheath fiber is a viscose fiber.

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