A test method and apparatus for evaluating the load-bearing capacity of laminated glass.

Abstract

This invention belongs to the field of glass performance testing technology, and relates to a test method and apparatus for evaluating the load-bearing capacity of laminated glass. The test method involves placing a laminated glass sample with an adhesively bonded edge connection structure, after curing, onto the movable part of the testing apparatus. Bolts are used to fix the edge connection structure of the sample, and then tightened with a torque wrench. A loading speed is set, causing the loading part to displace downwards to apply a compressive load to the sample until the sample fails. The test automatically stops. The maximum load data of the indenter is collected by a pressure sensor, and a calculation formula applicable to the load-bearing capacity of laminated glass samples is proposed. The test apparatus of this invention is simple and feasible, and suitable for assessing the load-bearing capacity of laminated glass used for windshields.

Description

Technical Field

[0001] This invention belongs to the field of glass performance testing technology, and relates to a test method and test apparatus for load-bearing capacity, specifically, a test method and apparatus for evaluating the load-bearing capacity of laminated glass. Background Technology

[0002] Aircraft windshields are typically laminated structures composed of multiple layers of silicate glass and an intermediate layer material. Due to significant differences in mechanical properties, silicate glass and the fuselage metal frame cannot be directly connected. A composite material frame is usually added to the edges of the silicate glass, and the two are connected using adhesives. Holes are then drilled in the composite material frame, and bolts are used to connect it to the fuselage metal frame. The performance differences between the edge composite material and silicate glass are substantial, and different interface treatments and types of adhesives greatly affect the load-bearing capacity of the laminated glass. The load-bearing capacity of the laminated glass has a significant impact on the reliable service of the windshield and is directly related to the safety of the aircraft and pilots. Therefore, a reliable and convenient device and testing method for evaluating the load-bearing capacity of laminated glass is needed.

[0003] GB / T 34171-2017 provides methods for assessing the load-bearing capacity of glass, but this standard only tests the bending strength of thin and ultra-thin monolithic glass with a thickness of less than 3 mm. JC / T 676-1997 can be used to test the bending strength of glass and microcrystalline materials, but it is also limited to monolithic glass and not applicable to laminated glass. CN 1512161A invented a test method for testing the bonding strength of solid materials, which can be used to test the bonding strength between ceramics and ceramics, and between ceramics and metals. It requires processing the two materials to be bonded to the required dimensions and then bonding them in a cross shape. By applying force to the specimen in the vertical direction, the shear stress at the bonding interface is generated under pressure, thereby testing the shear strength at the time of cracking. CN 109142214 A invented a test method for the bonding strength of rubber and composite material interfaces. By applying force along the bonding interface on the bonded test specimen, the maximum shear strength at the time of peeling of the bonding interface is obtained. CN 113029942 A discloses a single-interface adhesive strength evaluation test method, which obtains the maximum load at which the adhesive interface fails by subjecting the cured adhesive sample to bending load. The paper "Performance Study of Polyurethane Adhesives for Cockpit Edge Connections" evaluates the tensile shear strength of polyurethane adhesives at different temperatures. These methods all assess the bending strength of a single layer of glass or the adhesive strength of a single interface. The sample structure differs significantly from the actual structure of windshields, and the reference value of their assessment results for the load-bearing capacity of windshields needs further investigation.

[0004] To address the above issues, this patent presents a device and test method for assessing the load-bearing capacity of laminated glass for windshields. The test sample adopts the same lamination structure and edge connection form as aircraft windshields, which can more intuitively reflect the load-bearing capacity of laminated glass for windshields. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and test method for evaluating the load-bearing capacity of laminated glass for windshields.

[0006] To solve this technical problem, the technical solution of the present invention is as follows:

[0007] On the one hand, a test method for evaluating the load-bearing capacity of laminated glass is provided. The method involves placing a laminated glass sample with an edge connection structure glued on and cured on the movable part of a test device, fixing the edge connection structure of the sample with bolts, tightening it with a constant force wrench, setting a loading speed, causing the loading part to move downward to apply a compressive load to the sample until the sample is damaged, and the test automatically stops. The maximum load data of the indenter is collected by a pressure sensor.

[0008] The load-bearing capacity of the laminated glass sample is calculated using the following formula:

[0009]

[0010] In the formula, S: fracture modulus, MPa; P: failure load, i.e., the maximum load data of the pressure head collected by the pressure sensor, N; a: moment arm, i.e., the distance between adjacent support sides and loading sides, mm; b: sample width, mm; d1: glass thickness, mm; d2: original film thickness, mm.

[0011] The laminated glass sample is a composite structure of silicate glass and film, and the silicate glass is annealed glass or prestressed glass. The calculation formula is applicable to samples of the following sizes:

[0012] For single-layer or multi-layer polyurethane films with a film thickness between 1mm and 10mm, the sample length is 250±3mm and the width is 38±3mm; multi-layer polyurethane films can be multi-layered, with a total thickness between 1mm and 10mm.

[0013] During the application of compressive load, the first drop in load may indicate damage to the edge connection structure of the specimen. Therefore, the maximum load corresponding to the final automatic stop of the test should be used as the load for calculating the bearing capacity.

[0014] The laminated glass samples in each group consist of 10-15 pieces, and the load-bearing capacity is taken as the arithmetic mean of the test results of all samples.

[0015] The edge connection structure refers to a structure made of materials such as polyester steel, fiberglass, and aluminum alloy, with the same width as the laminated glass sample and a 10mm-20mm wide stepped area, capable of covering both ends of the laminated glass sample with adhesive. This structure, used to simulate the installation state of laminated glass and capable of covering both ends of the laminated glass sample with adhesive, realistically simulates the usage environment of laminated glass.

[0016] The tightening torque using a constant torque wrench is 1.0 N·m - 6.0 N·m.

[0017] On the other hand, an apparatus for evaluating the load-bearing capacity of laminated glass is provided, employing the test method for evaluating the load-bearing capacity of laminated glass. The apparatus comprises a support section, a movable section, and a loading section. The movable section has two left and right modules, each bolted to a slide rail on the support section. The distance between the two movable sections is adjustable. Two bolt holes are drilled in each movable section for fixing a laminated glass sample with an edge-connected structure. The edge of the movable section in contact with the sample should be rounded. The loading section can be controlled by sensors to move up and down and apply loads.

[0018] The elastic modulus of the loading part must be greater than 200 GPa; the elastic modulus of the material used for the moving part must be greater than 200 GPa.

[0019] The radius of the edge in contact with the sample is 3mm ± 0.1mm.

[0020] The bolt holes have a diameter of 3mm-10mm, and the four bolt holes on the movable parts at both ends form a rectangle.

[0021] The beneficial effects of this invention are as follows: The process of this invention is simple and suitable for assessing the load-bearing capacity of laminated glass, especially for windshields. The testing device of this invention is simple to operate and facilitates sample acquisition. Using this device, the load-bearing capacity indicators of laminated glass can be obtained conveniently and quickly. Within the sample size requirements of this invention, the calculation formula proposed in this invention can closely approximate the actual load-bearing capacity results of laminated glass for windshields, making it very convenient to obtain the modulus of rupture of laminated glass without the need for laborious testing. The calculation formula of this invention can calculate the load-bearing capacity of laminated glass by simply measuring the thickness of the glass and film in the sample, and the destructive load data collected during the test, without needing to obtain the load-bearing capacity of the laminated sample by attaching strain gauges to the sample surface and using an additional dynamic signal testing and analysis system, thus simplifying the operation considerably. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the examples of the present invention will be briefly explained below.

[0023] Figure 1This is a schematic diagram of a test device for the load-bearing capacity of laminated glass;

[0024] Among them, 1-loading part; 2-moving part; 3-supporting part. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. 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.

[0026] The following describes a specific embodiment of the apparatus and test method for evaluating the load-bearing capacity of laminated glass according to the present invention, with reference to the accompanying drawings.

[0027] The testing device of the present invention:

[0028] See attached diagram for a device used to evaluate the load-bearing capacity of laminated glass. Figure 1 It includes a support part 3, a movable part 2, and a loading part 1. The movable part 2 is divided into two modules, left and right, which are fixed to the slide rail of the support part 3 by bolts. The distance between the two movable parts 2 is adjustable. There are two bolt holes drilled on the movable part to fix the laminated glass sample with edge connection structure. The edge of the movable part 2 in contact with the sample should be arc. The loading part 1 can be controlled by a sensor to move up and down and apply load. The distance between the two pressure heads of the loading part is 100mm.

[0029] Example 1

[0030] The movable part is made of a metal material with an elastic modulus of 210 GPa and is divided into two modules, left and right, which are fixed to the slide rail of the support part by bolts. The distance between the two movable parts is adjustable. There are two bolt holes with a diameter of 7 mm drilled on the movable part to fix the laminated glass sample with edge connection structure. The edge of the movable part in contact with the sample is an arc with a radius of 3 mm. The loading part is made of a metal material with an elastic modulus of 210 GPa and can be controlled by sensors to move up and down and apply loads.

[0031] Aluminosilicate glass with surface prestress and a film are laminated into a composite structure with a sample size of 250mm × 38mm. Polyester steel edge connection structures are glued to both sides of the laminated glass sample, with a polyester steel step area width of 20mm. After the adhesive cures, the sample is placed on the movable part of the testing device, and the edge connection structure of the sample is fixed with bolts. The bolts are tightened with a constant torque wrench to a torque of 2.5 N·m. The loading speed is set to 5mm / min, and the loading part is displaced downward to apply a compressive load to the sample until the sample is damaged. The test stops automatically, and the maximum load data of the indenter is collected by a pressure sensor.

[0032] Ten specimens were used, and the calculated load-bearing capacities are shown in Table 1. The calculated values ​​in Table 1 were obtained using the calculation formula of this invention.

[0033]

[0034] In the formula, S: fracture modulus, MPa; P: failure load, i.e., the maximum load data of the indenter collected by the pressure sensor for each sample, N; a: moment arm, i.e., the distance between adjacent support sides and loading sides, which is 87.5 mm; b: sample width, which is 38 mm; d1 = 3.6 mm, which is the glass thickness; d2 = 1.8 mm, which is the original thickness of the film.

[0035] Table 1. Sample load-bearing capacity

[0036]

[0037]

[0038] Example 2

[0039] The movable part is made of a metal material with an elastic modulus of 200 GPa and is divided into two modules, left and right, which are fixed to the slide rail of the support part by bolts. The distance between the two movable parts is adjustable. There are two bolt holes with a diameter of 9 mm drilled on the movable part to fix the laminated glass sample with edge connection structure. The edge of the movable part in contact with the sample is an arc with a radius of 3 mm. The loading part is made of a metal material with an elastic modulus of 200 GPa and can be controlled by sensors to move up and down and apply loads.

[0040] Aluminosilicate glass with surface prestress and a film are laminated into a composite structure with a sample size of 250mm × 38mm. Fiberglass edge connection structures are glued to both sides of the laminated glass sample, with a fiberglass step area width of 10mm. After the adhesive cures, the sample is placed on the movable part of the testing device, and the edge connection structure is fixed with bolts. A torque wrench is used to tighten the bolts to a torque of 6.0 N·m. The loading speed is set to 8mm / min, causing the loading part to move downwards to apply a compressive load to the sample until the sample fails. The test automatically stops, and the maximum load data of the indenter is collected by a pressure sensor.

[0041] The number of test specimens was 15, and the calculated load-bearing capacity of the specimens is shown in Table 2.

[0042] Table 2. Sample load-bearing capacity

[0043]

[0044]

[0045] From the above embodiments, it can be concluded that the deviation between the load-bearing capacity of the laminated specimen obtained by the test method and apparatus of the present invention and the load-bearing capacity obtained by the stress-strain tester in a single test is less than 10%. When repeated tests are performed 10 to 15 times, the error is basically controlled at about 1% after taking the arithmetic mean, indicating good repeatability. The test apparatus of the present invention is simple and easy to calculate, and does not require separate strain gauges or an additional dynamic signal test and analysis system to test the load-bearing capacity.

[0046] Although the present invention has been specifically described with reference to the above embodiments, it should be understood by those skilled in the art that modifications or improvements can be made based on the disclosure of the present invention without departing from the spirit and scope of the present invention, and such modifications and improvements are all within the spirit and scope of the present invention.

Claims

1. A test method for evaluating the load-bearing capacity of laminated glass, characterized in that: The test method involves placing a laminated glass sample with an edge connection structure glued on and cured onto the movable part of the test device, fixing the edge connection structure of the sample with bolts, tightening it with a constant force wrench, setting the loading speed, and causing the loading part to move downward to apply a compressive load to the sample until the sample is destroyed. The test then stops automatically, and the maximum load data of the indenter is collected by a pressure sensor. The load-bearing capacity of the laminated glass sample is calculated using the following formula: In the formula, S : Modulus of fracture, MPa; P : Destructive load, i.e., the maximum load data of the pressure head collected by the pressure sensor, in N; a : Rectangular arm, i.e., the distance between adjacent support edges and loading edges, in mm; b Sample width, mm; d 1: Glass thickness, mm; d 2: Original film thickness, mm; The laminated glass sample is a composite structure of silicate glass and film, and the silicate glass is annealed glass or prestressed glass. The calculation formula is applicable to samples of the following sizes: A single-layer or multi-layer polyurethane film with a film thickness between 1mm and 10mm, with a sample length of 250±3mm and a width of 38±3mm.

2. The test method for evaluating the load-bearing capacity of laminated glass according to claim 1, characterized in that: During the application of compressive load, the maximum load corresponding to the final automatic stop of the test is used as the load for calculating the bearing capacity.

3. The test method for evaluating the load-bearing capacity of laminated glass according to claim 1, characterized in that: The laminated glass samples consist of 10-15 pieces per group, and the load-bearing capacity is the arithmetic mean of the test results of all samples.

4. The test method for evaluating the load-bearing capacity of laminated glass according to claim 1, characterized in that: The edge connection structure refers to a structure made of polyester steel, fiberglass, or aluminum alloy, with the same width as the laminated glass sample and a 10mm-20mm wide step area, which can cover both ends of the laminated glass sample with adhesive.

5. The test method for evaluating the load-bearing capacity of laminated glass according to claim 1, characterized in that: The torque for tightening using a constant torque wrench is 1.0 N·m to 6.0 N·m.

6. An apparatus for evaluating the load-bearing capacity of laminated glass, employing the test method for evaluating the load-bearing capacity of laminated glass as described in claim 1, characterized in that: The device includes a support section, a movable section, and a loading section. The movable section consists of two modules, left and right, which are respectively fixed to the slide rail of the support section by bolts. The distance between the two movable sections is adjustable. Two bolt holes are drilled on the movable section to fix the laminated glass sample with edge connection structure. The edge of the movable section in contact with the sample should be arc-shaped. The loading section can be controlled by a sensor to move up and down and apply load.

7. The apparatus for evaluating the load-bearing capacity of laminated glass according to claim 6, characterized in that: The elastic modulus of the loading part and the elastic modulus of the material used for the moving part must be greater than 200 GPa.

8. The apparatus for evaluating the load-bearing capacity of laminated glass according to claim 6, characterized in that: The radius of the edge in contact with the sample is 3mm ± 0.1mm.

9. The apparatus for evaluating the load-bearing capacity of laminated glass according to claim 6, characterized in that: The bolt holes have a diameter of 3mm-10mm, and the four bolt holes on the movable parts at both ends form a rectangle.

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