AU2021103814A4 - Method for improving interlaminar strength effect of z-pin reinforced composite - Google Patents

Method for improving interlaminar strength effect of z-pin reinforced composite Download PDF

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AU2021103814A4
AU2021103814A4 AU2021103814A AU2021103814A AU2021103814A4 AU 2021103814 A4 AU2021103814 A4 AU 2021103814A4 AU 2021103814 A AU2021103814 A AU 2021103814A AU 2021103814 A AU2021103814 A AU 2021103814A AU 2021103814 A4 AU2021103814 A4 AU 2021103814A4
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pin
reinforced
twisting
composite
laminated member
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AU2021103814A
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Wei Chen
Yunyong Chen
Yunyong Cheng
Xiangqian Li
Weiwei Liu
Bin YAN
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Northwestern Polytechnical University
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Northwestern Polytechnical University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/56—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using mechanical means or mechanical connections, e.g. form-fits
    • B29C65/562—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using mechanical means or mechanical connections, e.g. form-fits using extra joining elements, i.e. which are not integral with the parts to be joined
    • B29C65/564—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using mechanical means or mechanical connections, e.g. form-fits using extra joining elements, i.e. which are not integral with the parts to be joined hidden in the joint, e.g. dowels or Z-pins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
    • B29C66/721—Fibre-reinforced materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/739—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/7392—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/06—Fibrous reinforcements only
    • B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
    • B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
    • B29C70/24—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in at least three directions forming a three dimensional structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/50—Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
    • B29C70/52—Pultrusion, i.e. forming and compressing by continuously pulling through a die
    • B29C70/521—Pultrusion, i.e. forming and compressing by continuously pulling through a die and impregnating the reinforcement before the die
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/08—Interconnection of layers by mechanical means

Abstract

The invention discloses a method for improving the interlaminar strength effect of a Z-pin reinforced composite, comprising the following steps: step 1, preparing a composite laminated member preform which is a cube with a laminated structure; a region to be reinforced is selected on the composite laminated member preform, and determining an implantation point to be reinforced in the region to be reinforced; step 2, preparing a twisting Z-pin member which is a strip-shaped twisting fiber section; and step 3, implanting a plurality of twisting Z-pin members in the step 2 perpendicularly into the composite laminated member preform from corresponding implantation points to obtain a reinforced composite laminated member preform; the length of each twisting Z-pin member is the thickness at the implantation point to be reinforced minus the amount of cure shrinkage of the composite laminated member preform. The interlaminar strength of the composite laminated member can be better improved by the twisting Z-pin member. The invention has simple and convenient operation and strong practicability. 1/6 FIG. 1

Description

1/6
FIG. 1
Method for improving interlaminar strength effect of Z-pin reinforced composite
Technical Field The invention belongs to the technical field of composite material Z-pin reinforcement, and particularly relates to a method for improving the interlaminar strength effect of a Z-pin reinforced composite.
Background Art Z-pin reinforcement technology is a new technology which can improve the interlaminar properties of composites. Z-pin can significantly improve the interlaminar fracture toughness, damage tolerance and lap strength of composites, and has been widely used in the reinforcement of various load-bearing structures. However, in the actual process of Z-pin pultrusion, it is found that defects with a large number of air holes are easily generated. When the Z-pin passes through a traction rod, the air holes are broken, fiber bundles are split and dispersed, and then the Z-pin cannot be implanted into a composite preform as a reinforcement, so that the interlayer reinforcement effect cannot be effectively realized. In addition, both industrial and scientific Z-pins are currently cylindrical structures with relatively smooth surfaces. According to the paper published by Sweeting (Sweeting R D, Thomson R S. The effect of thermal mismatch on z-pinned laminated composite structures[J]. Composite Structure, 2004), it indicates that the interface between Z-pin and laminate with smoother surface has larger thermal residual stress, and the smooth interface between Z-pin and laminate is prone to crack propagation. In order to solve the problem, the traditional method changes the bridging force by changing the parameters of the novel Z-pin groove shape, groove distribution density, groove depth and the like so as to achieve the effect of improving the interlayer strength of the laminated composite. However, this solution has defects. According to the analysis to the pore formation of composites during hot-press forming with the classical nucleation theory by Kardos (Kardos J L, Dudukovic M P, Dave R. Void growth and resin transport during processing of thermosetting matrix composites[M]. Berlin: Springer, 1986), it can be known that increasing the isostatic pressure intensity of resin can effectively inhibit the pore growth, while the processing technology of novel Z-pin does not increase the radial pressure of resin, the pore growth will still exist during the pultrusion of Z-pin. In addition, the preparation process flow of the Z-pin is too complicated. Different processing dies are required to be designed for the novel Z-pin with different groove shapes. The preparation time of the early-stage tooling is too long, and the processing efficiency is low, with too many factors affecting the reinforcing effect. It is difficult to guarantee the reliability of the reinforcing effect of the Z-pin in practical application, and it is not easy to research and predict the same.
Summary of the Invention The invention is directed to provide a method for improving the interlaminar strength effect of a Z-pin reinforced composite. The interlaminar strength of the composite laminated member can be better improved by the twisting Z-pin member. The invention has simple and convenient operation and strong practicability. The invention adopts the following technical solution: a method for improving the interlaminar strength effect of the Z-pin reinforced composite is provided, which comprises the following steps: step 1, preparing a composite laminated member preform (1), wherein the composite laminated member preform (1) is a cube with a laminated structure; a region to be reinforced is selected on the composite laminated member preform (1), and determining an implantation point to be reinforced in the region to be reinforced; step 2, preparing a twisting Z-pin member (2) which is a strip-shaped twisting fiber section; and step 3, implanting a plurality of twisting Z-pin members (2) in the step 2 perpendicularly into the composite laminated member preform (1) from corresponding implantation points to obtain a reinforced composite laminated member preform; the length of each twisting Z-pin member (2) is the thickness at the implantation point to be reinforced minus the amount of cure shrinkage of the composite laminated member preform (1). Furthermore, the twisting Z-pin member (2) implanted to the implantation point to be reinforced has a row/column spacing of 2-10 mm. Furthermore, the preparation method of the twisting Z-pin member (2) includes fully impregnating the nontwisting Z-pin fiber bundle (3) into resin, and pultrusion forming the same in a forming die; twisting and curing the nontwisting Z-pin fiber bundle (3) impregnated with the resin to obtain a long-strip-shaped twisting fiber bundle, and cutting the long-strip-shaped twisting fiber bundle into twisting fiber sections with required lengths to obtain the twisting Z-pin member (2). Further, the nontwisting Z-pin fiber bundle (3) has a material of carbon fiber, glass fiber or polyimide fiber and has a diameter of 00.1 mm- Imm. Furthermore, in the step 1, the process for determining the reinforcement implantation point includes dividing the surface of the region to be reinforced into a plurality of small squares, and the centers of the squares are the implantation points to be reinforced; wherein the sides of each of the small squares are parallel to the corresponding sides on the same side of the composite laminated member preform (1). Further, the composite laminated member preform (1) is formed by stacking fiber-reinforced resin-based composite prepregs. According to a second technical solution adopted by the invention, a strength-reinforced composite laminated member preform prepared by the method for improving the interlaminar strength effect of the Z-pin reinforced composite is provided, comprising: a composite laminated member preform (1) being a cube of a laminated structure formed by stacking fiber-reinforced resin-based composite prepregs; a region to be reinforced is selected on the composite laminated member preform (1); a plurality of implantation points to be reinforced are set in the region to be reinforced; and a twisting Z-pin member (2) being a strip-shaped twisting fiber section and implanted into the composite laminated member preform (1) perpendicularly from each implantation point to be reinforced, wherein the twisting Z-pin members (2) in a plurality of reinforcement implantation points have a row/column spacing of 2-10 mm. The invention has the following beneficial effects. 1. After the nontwisting Z-pin fiber bundle is pultruded in a forming die, a twisting process is added before a post-curing process, so that the fiber bundle can be fully impregnated with resin before the twisting, and the twisting Z-pin member with good surface quality can be obtained. 2. Fiber monofilaments are gathered towards the axis under the action of pulling force to generate an extrusion force by twisting an uncured nontwisting Z-pin fiber bundle impregnated with resin, and bubbles are discharged under the action of the extrusion force if the Z-pin fiber bundle contains the bubbles; and if the Z-pin fiber bundle contains more resin, the excess resin is extruded under the action of the extrusion force. 3. There are grooves on the surface of the Z-pin fiber bundle and are not smooth, and the extruded resin can fill these grooves to obtain better surface quality. 4. The interfacial properties formed by co-curing Z-pin members and composites directly affect the interlaminar strength of Z-pin reinforced composites, while the twisting Z-pin members can improve the interfacial properties, so higher interlaminar strength of composites can be obtained. 5. Since the length of the twisting Z-pin member which is finally implanted into the composite laminated member preform is obtained by subtracting the curing shrinkage of the composite laminated member preform from the thickness of the position where the twisting Z-pin member is to be implanted, which is predefined on the composite laminated member preform, it is ensured that the twisting Z-pin member does not protrude out of the surface of the composite laminated member preform without any additional trimming process; and the surface is flat, the processes are reduced, and the Z-pin deflection problem caused by cutting after implantation is avoided. 6. The invention has wide application range, strong practicability, and can be used for Z-pin fiber bundles with different materials and diameters.
Brief Description of the Drawings Fig. 1 is a schematic view of a composite laminated member preform and a distribution of implantation positions; Fig. 2 is a schematic view of a twisting Z-pin member;
Fig. 3 is a schematic view of a process flow for preparing the twisting Z-pin member;
Fig. 4 is a schematic view of the spatial morphology of fiber monofilaments in an ideal twisting fiber
bundle;
Fig. 5 is a schematic view of a nontwisting Z-pin member;
Fig. 6 is a schematic view of a test piece of a composite laminate member in a validation test;
In the drawings, 1. a composite laminated member preform; 2. a twisting Z-pin member; 3. a nontwisting
Z-pin fiber bundle; 4. a gumming tank; 5. a forming die; 6. an elongated nontwisting Z-pin member; 7. a
long twisting Z-pin member; 8. a curing device; 9. a fiber monofilament; 10. a nontwisting Z-pin member;
11. a test piece of a composite laminate member.
Detailed Description of the Invention The present invention will now be described in detail with reference to the accompanying drawings and
detailed description.
According to the analysis to the pore formation of composites during hot-press forming with the classical
nucleation theory and the conclusion is obtained that increasing the isostatic pressure intensity of resin can
effectively inhibit the pore growth, a method for further improving the interlaminar strength effect of a
polyimide Z-pin reinforced carbon fiber reinforced resin-based composite laminate is provided.
The embodiment of the invention discloses a method for improving the interlaminar strength effect of the
Z-pin reinforced composite, comprising the following steps:
a method for improving the interlaminar strength effect of a Z-pin reinforced composite is provided,
comprising the following steps: step 1, preparing a composite laminated member preform 1, which is a
cube with a laminated structure; a region to be reinforced is selected on the composite laminated member
preform 1, and determining an implantation point to be reinforced in the region to be reinforced; A plurality
of implant points to be reinforced have a row/column spacing of 2 mm-10 mm. The composite laminated
member preform 1 is formed by stacking fiber-reinforced resin-based composite prepregs.
The process for determining the reinforcement implantation point includes dividing the surface of the
region to be reinforced into a plurality of small squares, and the centers of the squares are the implantation
points to be reinforced; wherein the sides of each of the small squares are parallel to the corresponding
sides on the same side of the composite laminated member preform 1.
Step 2, preparing a twisting Z-pin member (2) which is a strip-shaped twisting fiber section. The twisting
Z-pin member 2 is prepared by the following method including: fully impregnating the nontwisting Z-pin
fiber bundle 3 into resin, and pultrusion forming the same in a forming die; twisting and curing the
nontwisting Z-pin fiber bundle 3 impregnated with the resin to obtain a long-strip-shaped twisting fiber
bundle, and cutting the long-strip-shaped twisting fiber bundle into twisting fiber sections with required
lengths to obtain the twisting Z-pin member 2. The nontwisting Z-pin fiber bundle 3 has a material of carbon fiber, glass fiber or polyimide fiber and has a diameter of (0.1 mm-D Imm. Step 3, implanting a plurality of twisting Z-pin members 2 in the step 2 perpendicularly into the composite laminated member preform (1) from corresponding implantation points to obtain a reinforced composite laminated member preform; the length of each twisting Z-pin member 2 is the thickness at the implantation point to be reinforced minus the amount of cure shrinkage of the composite laminated member preform 1. The invention also discloses a strength-reinforced composite laminated member preform prepared by the method for improving the interlaminar strength effect of the Z-pin reinforced composite is provided, comprising: a composite laminated member preform 1 being a cube of a laminated structure formed by stacking fiber-reinforced resin-based composite prepregs; a region to be reinforced is selected on the composite laminated member preform 1; a plurality of implantation points to be reinforced are set in the region to be reinforced; and a twisting Z-pin member 2 being a strip-shaped twisting fiber section and implanted into the composite laminated member preform 1 perpendicularly from each implantation point to be reinforced, wherein the twisting Z-pin members 2 in a plurality of reinforcement implantation points have a row/column spacing of 2-10 mm. Embodiment 1 A method for improving the interlaminar strength effect of a Z-pin reinforced composite comprises the following steps: Step 1, a composite laminated member preform 1 is prepared by using a carbon fiber-reinforced resin-based composite prepreg tape, and the position of a twisting polyimide fiber Z-pin member 2 to be implanted is defined according to a row/column spacing of 3 mm. The composite laminated member preform 1 is formed by compositing four square single-layer plates with the thickness of t = 0.25 mm and the length of 200 mm, the laying angles of each layer are respectively 45, 0, 00 and 450, and the laying layers are symmetrically laid up and down. Step 2, the nontwisting polyimide Z-pin fiber bundle 3 is impregnated with resin in an gumming tank 4, and then pultrusion is performed on the same by a pre-designed molding die 5 to obtain a longer nontwisting Z-pin member 6; and then the long nontwisting Z-pin member 6 impregnated with the resin is twisted according to 80-100 twists per meter, and fed into a curing device 8 for high-temperature pressurization curing, finally cutting to obtain a long strip-shaped twisting fiber bundle with the length of 1 m; and a twisting fiber Z-pin member 2 which is made of polyimide is obtained by the cutting, as shown in Fig. 3. Step 3, the curing shrinkage of the carbon fiber-reinforced resin-based composite laminated member preform 1 is subtracted from the thickness of the position where the twisting Z-pin member 2 is to be implanted, which is predefined on the carbon fiber-reinforced resin-based composite laminated member preform 1, to obtain a length of the twisting Z-pin member 2 to be implanted and a twisting fiber section with the length of 10 mm.
Step 4, the twisting fiber section is implanted into the composite laminated member preform 1 according to
the predefined position to ensure that the twisting polyimide fiber Z-pin member 2 does not protrude out of
the surface of the carbon fiber-reinforced resin-based composite laminated member preform 1.
Embodiment 2
In order to verify that the method can achieve the effect of improving the interlaminar strength of the Z-pin
reinforced composite material, a verification test for interlaminar strength of a polyimide Z-pin reinforced
carbon fiber reinforced resin-based composite laminate is designed according to the requirement of the
GBT1449-2005 on the fiber reinforced plastic bending performance test method, and the test steps are as
follows:
Step 1, a composite laminated member test piece 11 is prepared by using a carbon fiber-reinforced
resin-based composite prepreg tape, with a specification of 250 mm in length x 25 mm in width x 3.6 mm
in thickness and a Z-pin to-be-implanted region of 112.5 mm x 25 mm, and the Z-pin member
to-be-implanted position is defined according to a row/column spacing of 2.5 mm, as shown in Fig. 6. The
composite laminated member test pieces 11 are divided into three groups, namely groups A, B and C,
wherein each group has five test pieces.
Step 2, the nontwisting polyimide Z-pin fiber bundle 3 is impregnated with epoxy resin in an gumming
tank 4, and then pultrusion is performed on the same by a pre-designed molding die 5 to obtain a longer
nontwisting Z-pin member 6; and then a part of the long nontwisting Z-pin member 6 impregnated with the
epoxy resin is twisted according to 80 twists per meter, and then fed into a curing device 8 for
high-temperature pressurization curing, and finally cut to obtain a long twisting Z-pin member 7 with the
length of 1 m;
Step 3, the curing shrinkage of the carbon fiber-reinforced resin-based composite laminated member test
piece 11 is subtracted from the thickness of the position where the Z-pin member is to be implanted, which
is predefined on the carbon fiber-reinforced resin-based composite laminated member test piece 11, to
obtain the length of the twisting polyimide fiber Z-pin member 2 to be implanted, and the cutting is made
according to the length to obtain a twisting fiber section with a proper length; similarly, a nontwisting
polyimide fiber Z-pin member 10 of suitable length is obtained in this manner.
Step 4, Z-pin implantation operations are performed on the composite laminated member test pieces 11
marked with group A, group B and group C, wherein the implantation operations of the three groups are
respectively as follows:
the group A is a blank group, with no implantation operation;
a nontwisting fiber Z-pin member 10 made of polyimide material is implanted at the predefined position
into a composite laminated member test piece 11, group B, and it is ensured that the nontwisting polyimide
fiber Z-pin member 10 does not protrude out of the surface of the carbon fiber reinforced resin-based
composite laminated member test piece 11, as shown in Fig. 5.
A twisting fiber Z-pin member 2 is implanted at a predefined position into a composite laminate member
test piece 11, group C, and it is ensured that the twisting fiber Z-pin member 2 does not protrude out of the
surface of the carbon fiber-reinforced resin-based composite laminate member test piece 11, as shown in
Fig. 6.
Step 5, after implantation is finished, the three groups of composite laminated member test pieces 1 marked
as A, B and C are put into a designed special curing mold, the special curing mold is fed into a curing
device 8, and the curing is performed according to the designed curing process flow.
Step 6, preparation pieces cured in the groups A, B and C are selected as test pieces, the test pieces are
mounted and fixed strictly according to the requirement of the GBT1449-2005 on the fiber reinforced
plastic bending performance test method, and it is ensured that the test pieces fail due to pure bending in
the load destroying process. Groups A, B and C are each treated for 5 times, each identified by a number
below.
The test data are collected during the test, and the experimental data are processed after the completion of
the experiment, as shown in Table 1:
Table 1 Test Maximum Average Increase ratio Bending Average Increase ratio piece load (N) marks Load (N) (%) strength strength or (%)
or (MPa) (MPa)
Al 2496.54 2579.33 1088.72 1131.37
A2 2367.35 1044.27
A3 2944.75 1261.14
A4 2431.94 1066.49
A5 2656.05 1174.93
BI 1923.07 2763.34 6.16 827.29 1193.59 5.50 B2 2971.69 1289.42 B3 3098.67 1329.31 B4 3176.99 1382.26 B5 2646.28 1139.70 C1 2919.73 2988.20 14.80 1229.20 1289.05 13.94 C2 2997.08 1312.34 C3 2963.52 1284.58 C4 3240.29 1403.14 C5 2820.36 1215.96
As can be known from analyzing the experimental data, compared with group A (without Z-pin implantation), the average bending strength of group B (without Z-pin implantation) is only increased by
5.50%, and the average bending strength of group C (with Z-pin implantation) is increased by 13.94%. It
can be seen therefrom that the twisting polyimide Z-pin has an obvious effect on the bending strength of
carbon fiber-reinforced resin-based composite laminates, i.e. a method for improving the interlaminar
strength of the Z-pin reinforced composite is experimentally verified.

Claims (7)

Claims
1. A method for improving the interlaminar strength effect of a Z-pin reinforced composite, characterized
by comprising the following steps:
step 1, preparing a composite laminated member preform (1), wherein the composite laminated member
preform (1) is a cube with a laminated structure; a region to be reinforced is selected on the composite
laminated member preform (1), and determining an implantation point to be reinforced in the region to be
reinforced;
step 2, preparing a twisting Z-pin member (2) which is a strip-shaped twisting fiber section; and
step 3, implanting a plurality of twisting Z-pin members (2) in the step 2 perpendicularly into the composite
laminated member preform (1) from corresponding implantation points to obtain a reinforced composite
laminated member preform; the length of each twisting Z-pin member (2) is the thickness at the
implantation point to be reinforced minus the amount of cure shrinkage of the composite laminated member
preform (1).
2. The method for improving the interlaminar strength effect of the Z-pin reinforced composite according
to claim 1, characterized in that the twisting Z-pin member (2) implanted to the implantation point to be
reinforced has a row/column spacing of 2-10 mm.
3. The method for improving the interlaminar strength effect of the Z-pin reinforced composite according
to claim 1 or 2, characterized in that the preparation method of the twisting Z-pin member (2) includes fully
impregnating the nontwisting Z-pin fiber bundle (3) into resin, and pultrusion forming the same in a
forming die; twisting and curing the nontwisting Z-pin fiber bundle (3) impregnated with the resin to obtain
a long-strip-shaped twisting fiber bundle, and cutting the long-strip-shaped twisting fiber bundle into
twisting fiber sections with required lengths to obtain the twisting Z-pin member (2).
4. The method for improving the interlaminar strength effect of the Z-pin reinforced composite according
to claim 3, characterized in that the nontwisting Z-pin fiber bundle (3) has a material of carbon fiber, glass
fiber or polyimide fiber and has a diameter of (0.1 mm-$l mm.
5. The method for improving the interlaminar strength effect of the Z-pin reinforced composite according
to claim 3, characterized in that in the step 1, the process for determining the reinforcement implantation
point includes dividing the surface of the region to be reinforced into a plurality of small squares, and the
centers of the squares are the implantation points to be reinforced; wherein the sides of each of the small
squares are parallel to the corresponding sides on the same side of the composite laminated member
preform (1).
6. The method for improving the interlaminar strength effect of the Z-pin reinforced composite according
to claim 1 or 5, characterized in that the composite laminated member preform (1) is formed by stacking fiber-reinforced resin-based composite prepregs.
7. A strength-reinforced composite laminated member preform prepared by the method for improving the interlaminar strength effect of the Z-pin reinforced composite according to any one of claims 1 to 6, characterized by comprising: a composite laminated member preform (1) being a cube of a laminated structure formed by stacking fiber-reinforced resin-based composite prepregs; a region to be reinforced is selected on the composite laminated member preform (1); a plurality of implantation points to be reinforced are set in the region to be reinforced; and a twisting Z-pin member (2) being a strip-shaped twisting fiber section and implanted into the composite laminated member preform (1) perpendicularly from each implantation point to be reinforced, wherein the twisting Z-pin members (2) in a plurality of reinforcement implantation points have a row/column spacing of 2-10 mm.
* 1/6
/
FIG. 1 ： t
1 *
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4201653A1 (en) * 2021-12-16 2023-06-28 Rolls-Royce plc Z-pin for increasing delamination resistance

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4201653A1 (en) * 2021-12-16 2023-06-28 Rolls-Royce plc Z-pin for increasing delamination resistance
US11840613B2 (en) 2021-12-16 2023-12-12 Rolls-Royce Plc Z-pin for increasing delamination resistance

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