CN-122016938-A - Device for testing radial resistance of composite fiber monofilaments and resistivity calculation method

CN122016938ACN 122016938 ACN122016938 ACN 122016938ACN-122016938-A

Abstract

The invention discloses a device for testing radial resistance of composite material fiber monofilaments and a resistivity calculation method, and belongs to the technical field of composite material performance testing and structural health monitoring. The device comprises a base, a cross beam, a spiral micrometer push rod and a plate electrode. The cross beam is an elastic component, two ends of the cross beam are arranged on the upright post of the base, and the plate-shaped electrodes on the cross beam can move in parallel and opposite directions through the driving of the push rod, so that the fiber monofilaments can be clamped in parallel and in a non-destructive manner. The base is provided with a monofilament fixing mechanism for straightening and fixing the fibers. When in testing, after the fiber monofilaments are straightened and aligned, the plate-shaped electrode is used for clamping the section to be tested in parallel, constant current is conducted, voltage drop is measured, and radial resistance is calculated. Further, based on the measured resistance value, a finite element model with a corresponding size is established, and the radial conductivity of the fiber is inverted by adopting a binary iteration method. The invention solves the difficult problem that the radial resistance of the micron-sized fiber monofilament is difficult to accurately measure, has simple structure, convenient operation, low cost and accurate and reliable measurement result, and provides a key parameter acquisition means for modeling of the composite material microscopic conductive network and structural health monitoring.

Inventors

LI JIAMING
YU GUOQIANG
Xue beichen
SONG YINGDONG
MA WENBING
NI ZHENG
GAO XIGUANG

Assignees

南京航空航天大学

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (8)

1. The device for testing the radial resistance of the composite fiber monofilaments is characterized by comprising a base (1), a cross beam (4), a spiral micrometer push rod (2) and a plate electrode (3); a plurality of upright posts (11) and push rod mounting seats (12) are arranged on the base (1); the cross beams (4) are elastic members, two ends of each cross beam are detachably arranged on the upright posts (11), and the two cross beams (4) are parallel to each other and positioned on two sides of the fiber monofilaments (7); the plate-shaped electrode (3) is arranged on the mounting structure of the cross beam (4), and the plate surface of the plate-shaped electrode (3) is parallel to the cross beam (4); The spiral micrometer push rod (2) is arranged on the push rod mounting seat (12), and the telescopic end of the spiral micrometer push rod acts on the cross beams (4) and is used for pushing the two cross beams (4) to bend in parallel in opposite directions so that the two plate-shaped electrodes (3) clamp the fiber monofilaments (7) in parallel; The base (1) is also provided with a monofilament fixing mechanism for fixing two ends of the fiber monofilament to be detected, so that the fiber monofilament is straightened and positioned at the center line position between the two plate-shaped electrodes (3).
2. The composite fiber monofilament radial resistance testing device according to claim 1, wherein the top ends of the upright posts (11) are provided with T-shaped mounting grooves (13), two ends of the cross beam (4) are of T-shaped structures matched with the T-shaped mounting grooves (13), and the mounting and positioning of the cross beam (4) are realized through T-shaped matching.
3. The composite fiber monofilament radial resistance testing device according to claim 1, wherein the plate-shaped electrode (3) is a copper electrode, one end of the plate-shaped electrode is provided with an electrode column perpendicular to the plate surface, the middle mounting structure of the cross beam (4) is a sleeve matched with the electrode column, and the plate-shaped electrode (3) is mounted by the plug-in matching of the electrode column and the sleeve.
4. The device for testing the radial resistance of the composite fiber monofilaments according to claim 1, wherein the monofilament fixing mechanism comprises at least two threaded holes arranged on the base (1), a bolt (5) matched with the threaded holes, and a threaded gasket (6) sleeved on the bolt (5) and matched with the threads of the bolt, and the fiber monofilaments are tightly fixed on the base (1) through the screwed threaded gasket (6).
5. A method for testing radial resistance of composite fiber monofilaments, characterized in that a device for testing radial resistance of composite fiber monofilaments according to any of claims 1-4 is used, comprising the steps of: s1, mounting a plate-shaped electrode (3) on a cross beam (4), mounting the cross beam (4) on a base (1), and mounting a micrometer push rod (2) on the base (1); s2, straightening the fiber monofilaments (7), and fixing the two ends of the fiber monofilaments to the base (1) by utilizing a monofilament fixing mechanism so that the fiber monofilaments (7) are aligned with the central lines of the two plate-shaped electrodes (3); S3, connecting a measuring wire to the two plate-shaped electrodes (3) and accessing a resistance measuring device; S4, operating a spiral micrometer push rod (2), pushing a cross beam (4) to bend, enabling two plate-shaped electrodes (3) to clamp the fiber monofilaments (7) in parallel, and cutting off redundant fiber monofilaments outside the electrodes; and S5, applying constant current I to the two plate-shaped electrodes (3) through a resistance measuring device, measuring voltage drop V between the two electrodes, and calculating to obtain the radial resistance value r=V/I of the clamping section of the fiber monofilament between the two electrodes.
6. The method for testing the radial resistance of the composite fiber monofilaments of claim 5, wherein the fiber monofilaments are silicon carbide fiber monofilaments or carbon fiber monofilaments.
7. The method for calculating the radial conductivity of the composite fiber monofilaments is characterized by comprising the following steps of: P1, based on the radial resistance r of the fiber monofilament measured by the radial resistance testing method of the composite fiber monofilament according to claim 5, establishing a cylindrical finite element model consistent with the geometric dimension of the clamped section of the measured fiber monofilament; p2, applying constant current I which is the same as actual measurement as excitation in a region of the finite element model corresponding to the contact position of the plate electrode (3), and setting a grounding boundary condition at the other end of the model; The method comprises the steps of P3, calculating radial conductivity of the fiber monofilaments by adopting a bipartite iteration method, namely setting a conductivity search interval [ A, B ] to enable a model calculation resistance value a, B corresponding to the interval to meet r E [ a, B ], taking a midpoint conductivity value C= (A+B)/2 in the interval to calculate to obtain a model resistance value C, enabling B=C if C is smaller than r, enabling A=C if the B=C otherwise, repeating the iteration process until errors of the calculation resistance value C and an actually measured resistance value r meet a preset standard, and enabling the corresponding conductivity C to be the radial conductivity of the fiber monofilaments.
8. The method for calculating the radial conductivity of the composite fiber monofilaments according to claim 7, wherein in the step P1, the finite element model is a cylinder with the same diameter as the fiber monofilaments and the length equal to the distance between the clamping points of the two plate-shaped electrodes (3).

Description

Device for testing radial resistance of composite fiber monofilaments and resistivity calculation method Technical Field The invention belongs to the field of composite material structure health monitoring, and particularly relates to a fiber monofilament radial resistance testing device and a resistivity calculating method. Background Fiber reinforced composites have found wide application in various fields due to their superior properties, such as high strength, high modulus, and low density. At the same time, however, the harsh operating environment can lead to extremely complex damage patterns. Failure during operation can have catastrophic consequences if the damage cannot be identified and evaluated in a timely manner after it has occurred. It is important how to detect the health of fiber reinforced composite related components and predict failure. The fiber reinforced composite material has conductivity, and the resistance response is closely related to various factors such as temperature, load and failure mode, so the fiber reinforced composite material can be used as the working temperature and load of a sensor in-situ feedback component and provides basis for reliability evaluation and failure prediction. The anisotropy of the fiber reinforced composite material is not only reflected in mechanical properties, but also remarkable in electrical properties, so that the establishment of the overall model by resistivity parameters in different directions is particularly important. The axial resistivity is easier to measure, while the radial resistivity is more difficult to measure and the resistivity is less derivable. At present, only the measuring device and the measuring method of the transverse resistivity of the fiber bundle are invented by the university of aviation aerospace in south Beijing, liu Wei and the like, and the measurement of the transverse resistivity of the fiber bundle is realized (the measuring device and the measuring method of the transverse resistivity of the fiber bundle, CN 116338312). However, the form of the filaments inside the fiber bundle is extremely complex, the filaments are not in an ideal parallel contact state, and the resistance network is not in a simple parallel relation, so that macroscopic transverse resistance parameters measured on the basis of the fiber bundle cannot be directly applied to the dimensions of the filaments, and the transverse resistance (radial resistance) of the filaments is a critical parameter when constructing a microscopic conductive network of the composite material. While the fiber filaments are smaller in size, conventional resistance measurement methods are not capable of measuring the exact transverse resistance of the fiber filaments. Therefore, it is necessary to design a device for measuring the transverse resistance of the fiber monofilaments, so as to solve the problem of measuring the transverse resistance of the monofilaments and provide accurate parameters for establishing a composite material microscopic conductive network for the subsequent combination of the internal forms of the fiber bundles. Disclosure of Invention The invention provides a device for testing radial resistance of composite fiber monofilaments and a method for calculating resistivity, aiming at the defects of the prior art. In order to achieve the technical purpose, the invention adopts the following technical scheme: The composite fiber monofilament radial resistance testing device comprises a base, a cross beam, a spiral micrometer push rod and a plate electrode; the base is provided with a plurality of upright posts and push rod mounting seats; The cross beams are elastic members, two ends of the cross beams are detachably arranged on the upright posts, and the two cross beams are parallel to each other and positioned on two sides of the fiber monofilaments; the plate-shaped electrode is arranged on the mounting structure of the cross beam, and the plate surface of the plate-shaped electrode is parallel to the cross beam; The spiral micrometer push rod is arranged on the push rod mounting seat, the telescopic end of the spiral micrometer push rod acts on the cross beams and is used for pushing the two cross beams to bend in parallel in opposite directions, so that the two plate-shaped electrodes clamp the fiber monofilaments in parallel; The base is also provided with a monofilament fixing mechanism for fixing two ends of the fiber monofilament to be detected, so that the fiber monofilament is straightened and positioned at the center line position between the two plate-shaped electrodes. In order to optimize the technical scheme, the specific measures adopted further comprise: t-shaped mounting grooves are formed in the top ends of the stand columns, T-shaped structures matched with the T-shaped mounting grooves are arranged at the two ends of the cross beam, and the cross beam is mounted and positioned through T-shaped matching. The plate-shaped el