CN114184467A - Test piece for fracture performance test and preparation method thereof - Google Patents
Test piece for fracture performance test and preparation method thereof Download PDFInfo
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- CN114184467A CN114184467A CN202010965650.5A CN202010965650A CN114184467A CN 114184467 A CN114184467 A CN 114184467A CN 202010965650 A CN202010965650 A CN 202010965650A CN 114184467 A CN114184467 A CN 114184467A
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- 238000012360 testing method Methods 0.000 title claims abstract description 101
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 238000011056 performance test Methods 0.000 title abstract description 13
- 239000000835 fiber Substances 0.000 claims abstract description 116
- 239000011347 resin Substances 0.000 claims abstract description 26
- 229920005989 resin Polymers 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 5
- 239000011159 matrix material Substances 0.000 abstract description 34
- 239000002131 composite material Substances 0.000 description 10
- 239000003292 glue Substances 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 3
- 244000025254 Cannabis sativa Species 0.000 description 1
- 235000012766 Cannabis sativa ssp. sativa var. sativa Nutrition 0.000 description 1
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- 235000005607 chanvre indien Nutrition 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000007656 fracture toughness test Methods 0.000 description 1
- 239000011487 hemp Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention provides a test piece for fracture performance test, which comprises a first part and a second part, wherein the first part and the second part are respectively used for receiving tensile load, the first part and the second part are respectively provided with a first side surface and a second side surface which are opposite in a load direction, and the first part and the second part are made of resin; the trial further includes a fiber bundle in which the body segment extends sandwiched between the first and second sides thereby connecting the first and second portions and the second end of the body segment is closer to an application location of the first portion for receiving a tensile load than the first end; the extension extends from the second end of the main body segment against the first portion, and the extension direction has a component in the load direction. The invention also provides a preparation method of the test piece for the fracture performance test. By adopting the test piece for testing the fracture performance, the fracture toughness of the interface between the fiber bundle and the matrix can be measured.
Description
Technical Field
The invention relates to a test piece for fracture performance testing and a preparation method thereof.
Background
Due to the excellent impact resistance of the woven composite material, the woven composite material is applied to fan blades and containing casings of aircraft engines, and the accurate prediction of the strength of the woven composite material becomes the key to the application. For the woven composite material, because the woven structure is changeable, the fiber bundles in the internal structure are mutually interwoven, so that the strength of the woven composite material is difficultly predicted. In tests, it was found that for woven composites, crack initiation generally occurs at the interface between the fiber bundle and the matrix or resin and crack propagation proceeds along the interface, and thus it is important to obtain the properties of the interface between the fiber bundle and the matrix, especially the resistance of the interface to crack propagation.
The inventor analyzes and considers that the layered composite material has obvious interlayer interfaces (macroscopic interfaces), and in the process of interface crack propagation, more obvious fiber bridging exists, and the obtained interface performance is not the real interface performance between the fiber bundles and the resin. The interface of the woven composite material is more complex, including the interface between the fiber bundle and the matrix, the interface between the fiber inside the fiber bundle and the matrix, and the like, the interface between the fiber inside the fiber bundle and the matrix belongs to a microscopic interface, and the strength performance of the interface between the fiber and the matrix is generally obtained through tests such as fiber extraction and the like. The interface between the fiber bundle and the matrix belongs to a microscopic interface, although the test method of the interface performance of partial fibers and the matrix can be used for reference, for measuring crack propagation performance such as fracture toughness and the like, the crack propagation in the test process may not be along the interface between the fiber bundle and the matrix but enter the fiber bundle and occur between the fibers and the matrix, so that the test difficulty of the performance of the measured performance fiber bundle and the matrix is increased.
The invention aims to provide a test piece for fracture performance test and a preparation method thereof, which can be used for measuring the fracture toughness of an interface between a fiber bundle and a matrix.
Disclosure of Invention
The invention aims to provide a test piece for fracture performance test, which can be used for measuring the fracture toughness of an interface between a fiber bundle and a matrix.
The invention also aims to provide a preparation method of the test piece for the fracture performance test, which can be used for preparing the test piece capable of measuring the fracture toughness of the interface between the fiber bundle and the matrix.
The invention provides a test piece for fracture performance test, which comprises a first part and a second part, wherein the first part and the second part are respectively used for receiving tensile load, the first part and the second part are respectively provided with a first side surface and a second side surface which are opposite in a load direction, and the first part and the second part are made of resin; the trial further includes a fiber bundle in which a body segment extends sandwiched between the first and second sides thereby connecting the first and second portions, and a second end of the body segment is closer to an application location of the first portion for receiving a tensile load than the first end; an extension extends from the second end of the main body segment against the first portion, and the extension direction of the extension has a component in the load direction.
In one embodiment, the first portion further has two end faces each perpendicular to the first side face, of which the second end face is closer to the force application site of the first portion than the first end face.
In one embodiment, a tail section of the extension extends along the load direction against the second end face.
In one embodiment, the first portion further has a first bevel connecting the first side surface and the second end surface, thereby forming a V-notch of the test piece in cooperation with the second portion; the extension extends against the first bevel and then against the second end face.
In one embodiment, the extension extends along the entire length of the second end face in the load direction, against the second end face.
In one embodiment, the main body segment extends along the entire length of the first side in a direction perpendicular to the load direction.
In one embodiment, the first side and the second side are both surfaces of undulating form, and the main body segments of the fiber bundle are adapted to undulate form.
The invention also provides a preparation method of the test piece for the fracture performance test, which comprises the following steps: providing a mould, wherein the lower surface of an upper mould is provided with an extended upper groove, the upper surface of a lower mould is provided with an extended lower groove, the mould is arranged so that the upper mould can cover the lower mould to form a mould cavity, and the upper groove corresponds to the lower groove; inserting a fiber bundle into a lower groove of the lower mold of the mold; enabling the upper die to cover the lower die to form a die cavity, and enabling the upper side part of the fiber bundle to be embedded into the upper groove of the upper die; and pouring resin into the die cavity, and curing and molding to obtain the test piece.
In one embodiment, the fiber bundle is modified in its extended form in the test piece by adjusting the extended form of the upper and lower grooves.
In one embodiment, one of the upper die and the lower die is provided with a surrounding boss which surrounds a containing cavity, and the containing cavity is sealed by the other contacting the boss surface of the surrounding boss, so that the containing cavity forms the die cavity.
In the above test piece for fracture performance test, the main body section of the fiber bundle is sandwiched between the first part and the second part of the resin to connect both, the interface between the fiber bundle and the matrix can be obtained, and by extending the extension section of the fiber bundle against the first part of the resin in the direction having a component in the load direction, it can be ensured that cracks occur at the interface between the fiber bundle and the matrix and that the cracks propagate along the interface between the fiber bundle and the matrix, so that the fracture toughness of the interface between the fiber bundle and the matrix can be measured.
The preparation method can prepare the test piece for the fracture performance test, and is used for measuring the fracture toughness of the interface between the fiber bundle and the matrix. Moreover, the preparation method can control the direction of the fiber bundle in the test piece, ensure that the direction of the fiber bundle is controllable, and obtain a stable and reliable test result.
Drawings
The above and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings, in which:
FIG. 1 is a front view of an exemplary compact tensile test specimen.
FIG. 2 is a side view of an exemplary compact tensile test specimen.
FIG. 3 is a schematic illustration of crack propagation for the test piece of FIG. 1.
Fig. 4 is a schematic view of an extended form of a fiber bundle of an exemplary test piece for compact tensile test.
FIG. 5 is a front view of an exemplary test piece for a dual cantilever test.
Fig. 6 is an exploded view of an exemplary mold.
Fig. 7 is a perspective view of an upper die of an exemplary mold.
Detailed Description
The present invention will be further described with reference to the following detailed description and the accompanying drawings, wherein the following description sets forth further details for the purpose of providing a thorough understanding of the present invention, but it is apparent that the present invention can be embodied in many other forms other than those described herein, and it will be readily apparent to those skilled in the art that the present invention may be embodied in many different forms without departing from the spirit or scope of the invention.
For example, a first feature described later in the specification may be formed over or on a second feature, and may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact. Further, when a first element is described as being coupled or coupled to a second element, the description includes embodiments in which the first and second elements are directly coupled or coupled to each other, as well as embodiments in which one or more additional intervening elements are added to indirectly couple or couple the first and second elements to each other.
Fig. 1 and 2 show one example configuration of a test piece 10a for fracture performance testing according to the present invention from different perspectives, respectively.
Referring to fig. 1 and 2, trial 10a includes a first portion 1a and a second portion 2a for receiving tensile loads F1a and F2a, respectively. The test rig may apply tensile loads F1a and F2a to the test piece 10a in opposite directions, and the tensile loads F1a and F2a may define a load direction DF that is not differentiated as to whether it is positive or negative, in other words, may include both positive and negative directions in that direction, as shown in fig. 1 and 2. Considering that the test piece 10a is changed during the test of the test piece 10a as shown in fig. 3, it is understood that the load direction DF means a load direction in an initial state when the test piece 10a is tested. It is to be understood that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
The first portion 1a and the second portion 2a have a first side surface 11a and a second side surface 21a, respectively, which are opposite in the load direction DF. In other words, the first portion 1a has a first side 11a and the second portion 2a has a second side 21a, the first side 11a and the second side 21a being disposed facing each other in the load direction DF.
In the test piece 10a, the first portion 1a and the second portion 2a were made of resin.
The fiber bundle 3a includes a main section 31a and an extension section 32 a. The main body segment 31a extends sandwiched between the first side 11a and the second side 21a, thereby connecting the first portion 1a and the second portion 2 a. In other words, in fig. 1, the upper edge of the main body segment 31a is connected to the first portion 1a, and the lower edge of the main body segment 31a is connected to the second portion 2a, so that the first portion 1a, the second portion 2a, and the fiber bundle 3a of the test piece 10a can be connected together.
The main body segment 31a of the fiber bundle 3a has a first end 311a and a second end 312 a. The second end 312a of the main body segment 31a is closer to the force application location Ha of the first portion 1a for receiving the tensile load F1a than the first end 311 a. In other words, in fig. 1, the force application position Ha of the first portion 1a for receiving the tensile load F1a is located at a position on the right side of the first portion 1a, the second end 312a of the main body segment 31a is a right end, and the first end 311a of the main body segment 31a is a left end. In fig. 1, the force application site H1a of the first portion 1a for receiving the tensile load F1a is a tensile hole, and correspondingly, the second portion 2a also has a force application site H1b for receiving the tensile load F2a, which is also a tensile hole, and can be connected with a testing device for applying a load.
The extension 32a of the fiber bundle 3a extends from the second end 312a of the main body segment 31a against the first portion 1 a. Also, the extension direction of the extension segment 32a has a component in the load direction DF, in other words, at least one segment of the extension segment 32a extends in a direction that is not perpendicular to the load direction DF, which may be referred to as a lateral direction DX, as shown in fig. 1.
Since the fiber bundle is formed by a plurality of fibers, cracks may occur at the interface between the fibers inside the fiber bundle and the matrix during testing, or the cracks may propagate along the interface between the fibers and the matrix inside the fiber bundle, so that the measured performance is not the interface between the fiber bundle and the matrix, and the measured data is not the performance between the fiber bundle and the matrix, and therefore, the result is misleading. Meanwhile, for the layering material, fiber bridging is easy to occur during the layering fracture toughness test, and the condition that the real performance of the interface between the fiber bundle and the matrix cannot be obtained is improved.
In the test piece 10a, one fiber bundle 3a is arranged between the two resin parts 1a and 2a, so that the condition of bridging between the fiber bundles does not occur, the extension section 32a which has a component in the extension direction in the load direction DF and extends along the resin part 1a is arranged, the conformal length of the fiber bundle 3a in the test piece 10a can be extended, the generation position and the propagation path of the crack can be controlled, the crack can be generated between the fiber bundle and the matrix and can propagate along the fiber bundle and the matrix, so that the fracture toughness of the interface between the fiber bundle and the matrix can be measured, and the real performance parameters of the interface between the fiber bundle and the matrix can be obtained. The test piece 10a does not need to be provided with a prefabricated crack or a prefabricated notch, and the preparation difficulty of the test piece can be greatly reduced.
In the embodiment shown in fig. 1, the first portion 1a may further have two end faces (left and right end faces in fig. 1) each perpendicular to the first side face 11 a. Of the two end surfaces, the second end surface 122a (the right end surface in fig. 1) is closer to the urging position H1a of the first portion 1a than the first end surface 121a (the left end surface in fig. 1).
In fig. 1, the tail section 322a of the extension section 32a may extend along the load direction DF against the second end face 122 a. In other words, the second end face 122a may extend along the load direction DF, and the tail section 322a of the extension 32a may extend against the second end face 122 a. In the embodiment of fig. 1, the extension 32a extends along the entire length of the second end face 122a in the load direction DF, against the second end face 122 a. In other words, the first portion 1a may also have a third side surface 13a opposite the first side surface 11a in the load direction DF, the first portion 1a being substantially rectangular in shape, the extension 32a extending along the second end surface 122a to the intersection of the second end surface 122a and the third side surface 13 a.
In the embodiment shown in fig. 1, the first portion 1a may further have a first inclined surface 14a connecting the first side surface 11a and the second end surface 122a, thereby forming a V-notch VS of the test piece 10a in cooperation with the second portion 2 a.
In the illustrated embodiment, the main body segment 31a of the fiber bundle 3a is located between the first portion 1a and the second portion 2a made of resin, and the second portion 2a may be symmetrically disposed with respect to the first portion 1a, and the properties and dimensions may be completely the same. The second part 2a may also have two end faces 221a, 222a, both perpendicular to the second side face 21a, wherein the end face 222a is closer to the force application position H1b of the second part 2a than the end face 221 a; the second portion 2a also has a bevel 24a connecting the second side face 21a and the end face 222 a. The bevels 14a and 24a may form a V-notch VS of the test piece 10 a. After the V-notch VS is preformed, the test piece 10a is more likely to break at the desired location.
The extension 32a of the fiber bundle 3a may extend against the first bevel 14a and then against the second end face 122 a. In other words, the extension 32a of the fiber bundle 3a includes a front section 321a extending against the first inclined surface 14a and a rear section 322a extending against the second end surface 122 a.
In the embodiment shown in fig. 1, the main body segment 31a of the fiber bundle 3a may extend along the full length of the first side 11a in a direction perpendicular to the load direction DF (i.e., the lateral direction DX). In other words, the main body segment 31a may extend from the intersection of the first side surface 11a and the first end surface 121a to the intersection of the first side surface 11a and the first inclined surface 14 a; in the absence of the first inclined surface 14a, the right end of the first side surface 11a is connected to the second end surface 122a, and at this time, the main body segment 31a may extend from the connection between the first side surface 11a and the first end surface 121a to the connection between the first side surface 11a and the second end surface 122 a.
The test piece 10a shown in fig. 1 and 2 is particularly suitable for compact tensile tests, also abbreviated to CT tests. As shown in fig. 3, in the compact tensile test, the test piece 10a is subjected to an opening load by tensile loads Fa, Fb of the two tensile holes, and a crack CS first occurs between the main body segment 31a of the fiber bundle 3a and the second portion 2a made of resin, and propagates along the interface between the main body segment 31a and the second portion 2a of the fiber bundle 3 a.
Preferably, the thickness ta of the resin portion (i.e., the first portion 1a and the second portion 2a) of the test piece 10a should not exceed the thickness of the fiber bundle 3 a. The fiber bundle 3a is wound substantially in the form of a hemp rope from a plurality of fibers, and its thickness may also be referred to as its diameter or width. In this way, more consistent test data can be obtained.
Fig. 4 schematically shows another embodiment of a test piece 10 a. In the test piece 10a of fig. 4, both the first side 11a of the first portion 1a and the second side 21a of the second portion 2a were surfaces of an undulating form, and the main body segments 31a of the fiber bundle 3a were adapted to the undulating form. In woven composites, the fiber bundles, in particular the warp yarns, often exhibit a regular undulating pattern, which can be better simulated by designing the main body section 31a of the fiber bundle 3a to have an undulating pattern to configure the interfaces of the undulating pattern.
Fig. 5 shows a test piece 10b as a modification of the test piece 10 a. The present embodiment follows the reference numerals and some contents of the elements of the previous embodiments, wherein similar reference numerals are used to indicate similar or similar elements, and the description of the same technical contents is optionally omitted. For the description of the omitted parts, reference may be made to the foregoing embodiments, and the description of the embodiments is not repeated.
The main difference from test piece 10a is that no V-notch was preformed in test piece 10 b. In the test piece 10b, taking the first portion 1b as an example, the first portion 1b is not rectangular but L-shaped, in other words, the third side surface 13a of the first portion 1b includes two horizontal surfaces 131a, 132a and a vertical surface 133a connecting the two horizontal surfaces 131a, 132a, and is substantially in the form of a stepped surface. This version of the test piece 10b is particularly suitable for a double cantilever test, which may be referred to as a DCB test for short.
In the embodiment shown in fig. 5, the extension 32b of the fiber bundle 3b extends along the load direction DF against the second end face 122b, but does not extend along the entire length of the second end face 122b, but stops extending along a portion of the second end face 122 b. It is to be understood that the variations of the different embodiments may be combined as appropriate.
In summary, the above test pieces can be used for fracture performance tests, including CT tests and DCB tests, to evaluate the fracture toughness of the interface between the fiber bundle and the matrix, or the resistance of the interface between the fiber bundle and the matrix to crack propagation. The influence of the body content on the fracture performance can be researched by obtaining test pieces for the fracture performance test of the body content of fibers in different fiber bundles.
The method for preparing the test piece for fracture property test will be described below with reference to fig. 6 and 7. Fig. 6 is an exploded view of the mold 20, and fig. 7 is a schematic structural view when the upper mold 6 of the mold 20 is placed upside down.
First, a mold 20 is provided, as shown in fig. 6 and 7. The mold 20 may include an upper mold 6 and a lower mold 4. The lower surface 61 of the upper die 6 is provided with an extended upper recess 6 a. The upper surface 41 of the lower die 4 is provided with an extended lower groove 4 a. The mold 20 is configured such that the upper mold 6 can be closed to the lower mold 4 to form the cavity S0, and the upper groove 6a corresponds to the lower groove 4 a.
Then, the fiber bundle 3 (which may represent the fiber bundle 3a in the aforementioned test piece 10a and the fiber bundle 3b in the test piece 10 b) is fitted into the lower groove 4a of the lower mold 4 of the mold 20.
Then, the upper mold 6 of the mold 20 is closed to the lower mold 4 to form the cavity S0, and the upper portion 31 of the fiber bundle 3 is fitted into the upper groove 6a of the upper mold 6.
A resin was poured into the cavity S0, and cured to obtain test pieces, such as the test pieces 10a and 10b described above.
The preparation method obtains the test piece through RTM molding, and can obtain the interface between the fiber bundle and the matrix in the woven composite material. By arranging or machining grooves 4a and 6a having a shape closer to the fiber bundle 3 at corresponding positions in the upper mold 6 and the lower mold 4 of the mold 20, the lower portion 32 of the fiber bundle 3 is embedded in the lower groove 4a, and the upper portion 31 is embedded in the upper groove 6a, so that the fiber bundle 3 can be positioned, and the fiber bundle 3 is ensured not to be washed away in the molding process. The fiber bundle 3 roughly divides the cavity S0 into two chambers, and the resin poured inside the two chambers can form the first portion 1a and the second portion 2a of the aforementioned test piece 10 a.
It will be appreciated that in practice, the fibre bundle 3 contains a plurality of fibres with voids between them, allowing resin to wet into the fibre bundle 3, which may better enable the first and second portions 1a, 2a to be connected to the fibre bundle 3. At the same time, the resin can flow between the two chambers through the fiber bundle 3, in particular the gap between the fiber bundle 3 and the grooves 4a, 6 a. It was found experimentally that the measured properties were those of the interface, not of the resin, as long as the resin above the upper part 31 and below the lower part 32 of the fiber bundle 3 was sufficiently low. In other words, the actual molding process may be allowed to result in a small amount of resin above or below the fiber bundle 3 in the test piece 10a, which may serve as an auxiliary connecting function for the first and second portions 1a and 2a of resin.
In the manufacturing method shown in fig. 6, the wedge 5 may be placed on the upper surface 41 of the lower mold 4 after the fiber bundle 3 is inserted into the lower groove 4a of the lower mold 4, the shape of the wedge 5 may be matched to the V-notch VS in the test piece 10a, and the thickness of the wedge 5 may be matched to the thickness of the cavity S0 formed when the upper mold 6 is closed to the lower mold 4. The wedge-shaped block 5 not only can help to fix the position of the fiber bundle 3, but also can facilitate the prefabrication of the V-shaped notch VS.
In the above-described manufacturing method, the extending form of the fiber bundle 3 in the test piece can be changed by adjusting the extending forms of the upper groove 6a and the lower groove 4 a. For example, the upper groove 6a and the lower groove 4a are designed in an undulating form, thereby forming the fiber bundle 3a in an undulating form as shown in fig. 4. Preferably, the wave pattern of the fiber bundle 3 or the grooves 6a, 4a is symmetrical along the middle of the test piece.
In the above manufacturing method, one of the upper mold 6 and the lower mold 4 (in fig. 5, the upper mold 6 is taken as an example of the one) may have the surrounding boss 6b surrounding the housing cavity S1, and the housing cavity S1 may be closed by the other (correspondingly, in fig. 5, the lower mold 4 is taken as an example of the other) contacting the boss surface 61b of the surrounding boss 6b, so that the housing cavity S1 constitutes the mold cavity S0. In other words, in fig. 5 and 6, the receiving cavity S1 surrounded by the surrounding boss 6b is closed by the upper surface 41 of the lower die 4 contacting the boss surface 61b of the surrounding boss 6b of the upper die 6, thereby constituting the die cavity S0. The thickness of the cavity S0 (i.e., the thickness ta of the test piece 10a, or the thickness of the first and second portions 1a and 2a of the resin, for example, with respect to the test piece 10 a) is ensured by the encircling projection 6b of the upper die 6, and the height of the encircling projection 6b is the thickness ta of the test piece 10 a.
Further, the other party (in fig. 5, that is, the lower die 4) may be made to have the containing cavity S2 so that the one party (in fig. 5, that is, the upper die 6) is positioned with respect to the other party by fitting the surrounding boss 6b to the containing cavity S2. The containing cavity S2 not only facilitates the positioning of the upper die 6 to the lower die 4, but also can play a further containing role in the die cavity S0, so that the internal resin is not easy to flow out.
In the illustrated embodiment, the upper mold 6 may be provided with the glue injection port 7, so that the fiber bundle 3 in the molded test piece can be prevented from being bent and deformed due to the scouring of the fiber bundle 3 caused by the glue injection pressure. In one embodiment, a glue injection opening 7 may be provided on the upper side of one of the two chambers into which the cavity S0 is divided by the fiber bundle 3, and a glue discharge opening may be provided on the lower side of the other of the two chambers (i.e., on the lower mold 4) to direct the flow of resin from one chamber to the other chamber through the aforementioned gap. In another embodiment, a glue injection port may be provided on each of the upper sides of the two chambers into which the fiber bundle 3 is divided in the cavity S0.
The preparation method can prepare the test piece which can easily measure the fracture toughness of the interface between the fiber bundle and the matrix, and ensure that cracks are generated at the interface between the fiber bundle and the matrix. In addition, the preparation method can easily control the direction of the fiber bundle according to the direction of the actual fiber bundle so as to design and prepare the test piece, can conveniently avoid the process of prefabricating cracks in the preparation process of the test piece, and ensures the stability of the test result. The preparation method is very convenient to implement, has low cost and is particularly suitable for batch preparation.
Although the present invention has been disclosed in terms of the preferred embodiment, it is not intended to limit the invention, and variations and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention. Therefore, any modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope defined by the claims of the present invention, unless the technical essence of the present invention departs from the content of the present invention.
Claims (10)
1. A test piece for fracture performance testing, comprising a first portion and a second portion for receiving a tensile load, respectively, the first portion and the second portion having a first side surface and a second side surface opposite in a load direction, respectively, characterized in that,
the first portion and the second portion are made of resin;
the test piece further includes a fiber bundle including:
a body segment extending between the first side and the second side, thereby connecting the first portion and the second portion, and a second end of the body segment being closer to an application location of the first portion for receiving a tensile load than the first end; and
an extension extending from the second end of the main body segment against the first portion, and the extension having a component in a direction of load.
2. The test piece of claim 1,
the first portion also has two end faces each perpendicular to the first side face, of which a second end face is closer to a force application site of the first portion than the first end face.
3. The test piece of claim 2,
a tail section of the extension section extends along the load direction against the second end face.
4. Test piece according to claim 3,
the first part is also provided with a first inclined surface connecting the first side surface and the second end surface, so that a V-shaped notch of the test piece is formed by matching with the second part;
the extension extends against the first bevel and then against the second end face.
5. Test piece according to any of claims 2 to 4,
the extension extends along the entire length of the second end face in the load direction, against the second end face.
6. The test piece of claim 1,
the main body segment extends along the entire length of the first side surface in a direction perpendicular to the load direction.
7. The test piece of claim 1,
the first side and the second side are both surfaces of undulating form, and the main body segments of the fiber bundle are adapted to undulate form.
8. A preparation method of a test piece for fracture performance testing is characterized by comprising the following steps:
providing a mold, the mold comprising:
the lower surface of the upper die is provided with an extended upper groove; and
the upper surface of the lower die is provided with an extended lower groove;
the upper die can cover the lower die to form a die cavity, and the upper groove corresponds to the lower groove;
inserting a fiber bundle into a lower groove of the lower mold of the mold;
enabling the upper die to cover the lower die to form a die cavity, and enabling the upper side part of the fiber bundle to be embedded into the upper groove of the upper die; and
and pouring resin into the die cavity, and curing and molding to obtain the test piece.
9. The method according to claim 8,
and changing the extending form of the fiber bundle in the test piece by adjusting the extending forms of the upper groove and the lower groove.
10. The method according to claim 8,
one of the upper die and the lower die is provided with a surrounding boss which surrounds an accommodating cavity, and the accommodating cavity is sealed by the contact of the other one of the upper die and the lower die with the boss surface of the surrounding boss, so that the accommodating cavity forms the die cavity.
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