Hardness Detection Device and Method for Fiber Reinforced Sheet Molding Compound

Abstract

The present invention discloses a hardness detection device and method for fiber-reinforced sheet molding compound. The detection device includes a support member, a bearing member, and an upper pressing member. The bearing member includes a bearing bottom plate, a left bearing frame, a right bearing frame, an upper pressing strip, and a lower bearing strip. Two lower bearing strips are arranged on the bearing bottom plate. The left bearing frame and the right bearing frame are arranged oppositely, and parallel front bearing plates and rear bearing plates are also installed between the left bearing frame and the right bearing frame. A cavity is left between the left bearing frame and the front bearing plate and the rear bearing plate, and another cavity is left between the right bearing frame and the front bearing plate and the rear bearing plate. And a test piece to be tested is placed in each cavity. An upper pressing strip is also arranged above the test piece to be tested. The beneficial effect of the present invention is that the detection device is novel in design, reasonable in structural design, low in manufacturing cost. Using this detection device to detect the hardness of sheet molding compound is convenient in operation and accurate in test results.

Description

Technical Field

[0001] The present invention relates to the technical field of sheet molding compound detection, and particularly to a hardness detection device and method for fiber-reinforced sheet molding compound. Background Art

[0002] Sheet molding compound is a sheet-shaped composite composed of thickenable resin, chopped (and / or continuous) glass fiber reinforcing material, filler, additives and other materials, with load-bearing films covering both the upper and lower surfaces.

[0003] The hardness of the sheet molding compound needs to be tested after curing and before pressing. The usual test method is GB3398.1 "Determination of Hardness of Plastics", which is applicable to the testing of thermoplastic plastics. However, sheet molding compound belongs to the intermediate of thermosetting plastics, and the existing problems are as follows:

[0004] 1. The sheet molding compound has certain viscoelasticity. If the four sides of the test sample of the sheet molding compound cannot be fixed, it is difficult to obtain the correct test value of the indentation value.

[0005] 2. The maximum thickness of the test sample is 30 mm, and the test sample is in a free state. If an indentation test is carried out, the laminated samples will move freely, resulting in distorted test data.

[0006] 3. The test sample size is too small, with a sample size of 20×20 mm and a recommended thickness of 4 mm. In this case of sample size and thickness, the hardness state of the sheet molding compound cannot be correctly evaluated. Summary of the Invention

[0007] In order to solve the technical problem that the hardness of the sheet molding compound cannot be accurately tested, the present invention discloses a hardness detection device and method for fiber-reinforced sheet molding compound.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A hardness detection device for fiber-reinforced sheet molding compound, comprising a support member, a load-bearing member fixedly installed on the support member, and an upper pressing member for applying a load. The load-bearing member includes a load-bearing bottom plate, a left load-bearing frame, a right load-bearing frame, an upper pressing strip and a lower load-bearing strip. Two lower load-bearing strips are arranged on the load-bearing bottom plate. The left load-bearing frame and the right load-bearing frame are arranged oppositely, and a front load-bearing plate and a rear load-bearing plate are installed between the left load-bearing frame and the right load-bearing frame. A cavity is left between the left load-bearing frame and the front load-bearing plate and the rear load-bearing plate, and another cavity is left between the right load-bearing frame and the front load-bearing plate and the rear load-bearing plate. A test piece to be tested is placed in each cavity, and an upper pressing strip is further arranged above the test piece to be tested.

[0010] As a further preference of the present invention, the specimen to be tested is rectangular and made by stacking a plurality of sheet molding compounds after removing the films.

[0011] As a further preference of the present invention, the upper pressing strip and the lower pressing strip have the same size, and the lengths of the upper pressing strip and the lower pressing strip are both greater than the length of the specimen to be tested. The widths of the upper pressing strip and the lower pressing strip are adapted to the width of the cavity.

[0012] As a further preference of the present invention, the bearing bottom plate is fixedly connected to the bottoms of the left bearing frame and the right bearing frame, and the bearing bottom plate is fixedly connected to two lower bearing strips.

[0013] As a further preference of the present invention, the left bearing frame and the right bearing frame have the same structure, both being U-shaped structures.

[0014] As a further preference of the present invention, the bottom of the upper pressing member is a semi-spherical structure, and the radius R of the spherical ball is 17.4 - 17.6 mm.

[0015] Another object of the present invention is to disclose a method for detecting the hardness of a fiber-reinforced sheet molding compound. Using the above test device, it specifically includes the following steps:

[0016] (1) Fabricate the specimen to be tested and check its appearance;

[0017] (2) Adjust the state of the specimen to be tested and assign a test number to the specimen after passing the inspection;

[0018] (3) Use four clamping springs to connect the upper pressing strip and the lower bearing strip, and measure the distances h1, h2, h3, h4 between the upper pressing strip and the lower bearing strip at four places, that is, the thickness of the specimen to be tested is

[0019] (4) When measuring the relative hardness of the sheet molding compound, set the constant load P of the universal tensile testing machine to 500 N, and set the load duration t to 5 s; set the test speed V: the conventional test speed is 10 mm / min, and the arbitration test speed is 2 mm / min;

[0020] (5) Measure the strain distance C of the relative hardness, that is, the strain distance from the start of recording the initial load to the constant load of 500 N after 5 s of constancy.

[0021] Further, the relative thickness of the average single-layer sheet thickness is: where n is the number of stacked sheet layers.

[0022] Further, the calculation formula for the relative hardness of the fiber-reinforced sheet molding compound is:

[0023] where:

[0024] Z-shaped molding relative hardness, unit HZa;

[0025] C - maximum strain distance under constant load, unit is millimeter (mm);

[0026] h0 - average single-layer sheet thickness, unit is millimeter (mm).

[0027] The beneficial effects of the present invention are as follows

[0028] 1. The detection device is novel in design, reasonable in structural design, and low in manufacturing cost. Using this detection device to detect the hardness of sheet molding compound is convenient to operate and the test results are accurate.

[0029] 2. Set up using a general universal tensile testing machine, making the test more convenient.

[0030] 3. Re-evaluated the influence of the number of plies on the indentation hardness, introduced the concept of relative hardness, which has practical significance for guiding the production of sheet molding compound. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the overall structure of the detection device in the present invention;

[0032] Figure 2 It is Figure 1 front view;

[0033] Figure 3 It is Figure 1 rear view.

[0034] Figure 4 It is Figure 1 top view;

[0035] Among them, 1 - upper pressing member; 2 - supporting member; 3 - left bearing frame; 4 - right bearing frame; 5 - front bearing plate; 6 - rear bearing plate; 7 - upper pressing strip; 8 - lower bearing strip; 9 - specimen to be tested; 10 - bearing bottom plate. Detailed Embodiments

[0036] Next, the technical solutions of the present invention will be described clearly and completely in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0039] As shown in the figure, a hardness testing device for fiber-reinforced sheet molding compound includes a support member 2, a load-bearing member fixedly installed on the support member 2, and an upper pressing member 1 for applying a load. The above load-bearing member includes a load-bearing bottom plate 10, a left load-bearing frame 3, a right load-bearing frame 4, an upper pressing strip 7, and a lower load-bearing strip 8. Two lower load-bearing strips 8 are provided on the above load-bearing bottom plate 10. The above left load-bearing frame 3 and right load-bearing frame 4 are arranged oppositely, and a front load-bearing plate 5 and a rear load-bearing plate 6 are installed between the left load-bearing frame 3 and the right load-bearing frame 4. A cavity is left between the above left load-bearing frame 3 and the front load-bearing plate 5 and the rear load-bearing plate 6. Another cavity is left between the above right load-bearing frame 4 and the front load-bearing plate 5 and the rear load-bearing plate 6. And a test specimen 9 to be tested is placed in each cavity. An upper pressing strip 7 is further provided above the above test specimen 9 to be tested.

[0040] Specifically, the above test specimen 9 to be tested is rectangular and is made by stacking several layers of sheet molding compound after removing the film.

[0041] In the present invention, the number of test specimens to be tested refers to Chapter 2 of GB 1446-83 "General Rules for Test Methods of Fiber Reinforced Plastics Properties".

[0042] The arbitration dimensions (unit: mm) of common test specimens to be tested are shown in Table 1 below:

[0043] Table 1

[0044] Single-layer thickness h0 of the sheet Number of stacked layers Stacked thickness 1＜h0≤2 30 30 - 60mm 2＜h0≤3 20 40 - 60mm 3＜h0≤4 15 45 - 60mm 4＜h0≤5 12 48 - 60mm

[0045] In the present invention, the length a of the test specimen 9 to be tested is 180 mm, the width b is 100 mm, the number of layers of sheet molding compound is 20, and the thickness c is 60 - 70 mm.

[0046] Specifically, the upper pressing strip 7 and the lower pressing strip have the same dimensions, and the lengths of the upper pressing strip 7 and the lower pressing strip are both greater than the length of the test specimen 9 to be tested. The widths of the upper pressing strip 7 and the lower pressing strip are adapted to the width of the cavity.

[0047] Specifically, the above-mentioned bearing bottom plate 10 is fixedly connected to the bottoms of the left bearing frame 3 and the right bearing frame 4, and the above-mentioned bearing bottom plate 10 is fixedly connected to two lower bearing strips 8.

[0048] Specifically, the left bearing frame 3 and the right bearing frame 4 have the same structure, both of which are U-shaped structures.

[0049] Specifically, the bottom of the above-mentioned upper pressing member 1 is a semi-spherical structure, and the radius R of the spherical ball is 17.4 - 17.6 mm.

[0050] When using this detection device for testing, the preparations before the test include:

[0051] 1. Test environmental conditions, referring to Chapter 3 of GB1446 - 83.

[0052] 2. The detection device uses a ball - press - type relative hardness tester. The main schematic diagram of its test instrument is shown in Figure 2 .

[0053] 3. Test instruments and equipment

[0054] 3.1 The testing machine shall comply with the provisions of Chapter 5 of GB / T1446 - 2005.

[0055] 3.2 After the relative hardness testing device is installed as Figure 2 shown.

[0056] 4. Test speed

[0057] When measuring the relative hardness of sheet molding compound, the test speed V is: the conventional test speed is 10 mm / min, and the arbitration test speed is 2 mm / min.

[0058] The present invention also discloses a method for detecting the hardness of fiber - reinforced sheet molding compound. Using the above - mentioned test device, it specifically includes the following steps:

[0059] (1) Fabricate the test specimen 9 to be tested and inspect its appearance, which is carried out in accordance with GB / T15568 - 2008, that is, the appearance should be flat, the color should be uniform, the fibers should be well impregnated, there should be no impurities, and the covering film should be intact.

[0060] (2) Adjust the state of the test specimen 9 to be tested, which is carried out in accordance with the provisions of 4.4 in GB / T1445 - 2005, and number the qualified test specimen 9 after inspection. Use Arabic numerals for numbering, such as 1, 2, 3.

[0061] (3) Connect the upper pressing strip 7 and the lower bearing strip 8 with four 50N clamping springs, and measure the distances h1, h2, h3, and h4 between the upper pressing strip 7 and the lower bearing strip 8 at four places, that is, the thickness of the specimen to be tested is

[0062] (4) When measuring the relative hardness of the sheet molding compound, set the constant load P of the universal tensile testing machine to 500N, and set the load duration t to 5s;

[0063] The loading speed is executed in accordance with the regulations of the test speed standard.

[0064] (5) Measure the strain distance C of the relative hardness, that is, the strain distance from the start of recording the initial load to the constant load of 500N after 5s of constancy.

[0065] Specifically, the relative thickness of the average single-layer sheet is:

[0066] Where n is the number of layers of the stacked sheets.

[0067] Specifically, the calculation formula for the relative hardness of the fiber-reinforced sheet molding compound is:

[0068] Where:

[0069] Z-shaped molding relative hardness, unit HZa;

[0070] C - the maximum strain distance under the constant load, unit is millimeter (mm);

[0071] h0 - the average single-layer sheet thickness, unit is millimeter (mm).

[0072] The number of tests conducted on the fiber-reinforced sheet molding compound of the same batch should be greater than 3 times. After the test is completed, complete the test report in accordance with the regulations of Chapter 7 of GB / T1446-2005.

[0073] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the substantial scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A hardness detection device for fiber-reinforced sheet molding compound, characterized in that, It includes a support member, a load-bearing member fixedly installed on the support member, and an upper pressing member for applying a load. The load-bearing member includes a load-bearing bottom plate, a left load-bearing frame, a right load-bearing frame, an upper pressing strip, and a lower load-bearing strip. Two lower load-bearing strips are provided on the load-bearing bottom plate. The left load-bearing frame and the right load-bearing frame are arranged oppositely, and opposite front load-bearing plates and rear load-bearing plates are installed between the left load-bearing frame and the right load-bearing frame. A cavity is left between the left load-bearing frame and the front load-bearing plate and the rear load-bearing plate. Another cavity is left between the right load-bearing frame and the front load-bearing plate and the rear load-bearing plate. And a test piece to be tested is placed in each cavity. An upper pressing strip is also provided above the test piece to be tested.

2. The hardness detection device for a fiber-reinforced sheet molding compound according to claim 1, wherein, The test piece to be tested is rectangular and is made by stacking several layers of sheet molding compounds after removing the film.

3. The hardness detection device for a fiber-reinforced sheet molding compound according to claim 1, characterized in that, The upper pressing strip and the lower pressing strip have the same size, and the lengths of the upper pressing strip and the lower pressing strip are both greater than the length of the test piece to be tested. The widths of the upper pressing strip and the lower pressing strip are adapted to the width of the cavity.

4. The hardness detection device for a fiber-reinforced sheet molding compound according to claim 1, characterized in that, The load-bearing bottom plate is fixedly connected to the bottoms of the left load-bearing frame and the right load-bearing frame, and the load-bearing bottom plate is fixedly connected to the two lower load-bearing strips.

5. The hardness detection device for a fiber-reinforced sheet molding compound according to claim 1, characterized in that, The left load-bearing frame and the right load-bearing frame have the same structure, both of which are U-shaped structures.

6. The hardness detection device for a fiber-reinforced sheet molding compound according to claim 1, characterized in that, The bottom of the upper pressing member is a semi-spherical structure, and the radius R of the spherical ball is 17.4 - 17.6 mm.

7. A method for detecting the hardness of a fiber-reinforced sheet molding compound, using the detection device as described in any one of claims 1-6, characterized in that, Specifically, it includes the following steps: (1) Manufacture the test piece to be tested and check its appearance. (2) Adjust the state of the test piece to be tested and assign a test number to the test piece to be tested after passing the inspection. (3) Connect the upper pressing strip and the lower bearing strip using four clamping springs, and measure the distances between the upper pressing strip and the lower bearing strip at four locations, h1, h2, h3, h4, that is, the thickness of the specimen to be tested is (4) When measuring the relative hardness of the sheet molding compound, set the constant load P of the universal tensile testing machine to 500 N, and set the load duration t to 5 s; Set the test speed V: the conventional test speed is 10 mm / min, and the arbitration test speed is 2 mm / min. (5) Measure the strain distance C for the relative hardness, that is, the strain distance from the start of recording the initial load to the constant load of 500 N and after 5 s of constancy. The relative hardness calculation formula of fiber-reinforced sheet molding compound is as follows: Where: Z-shaped molding relative hardness, unit HZa; C - the maximum strain distance under the constant load, unit mm; h0 - the average single-layer sheet thickness, unit mm.

8. The hardness detection method of a fiber-reinforced sheet molding compound according to claim 7, characterized in that The relative thickness of the average single-layer sheet thickness is as follows: where n is the number of layers of the stacked sheets.

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