Gradient cure bonding method for ceramic matrix composite tensile specimen stiffeners

Abstract

The application discloses a gradient curing bonding method for a ceramic matrix composite material tensile specimen reinforcing sheet and belongs to the technical field of material mechanical property testing. The bonding method comprises the following steps: (1) performing surface pretreatment on the ceramic matrix composite material tensile specimen, forming an interlaced groove array in a bonding area of the specimen, performing surface modification by using a silane coupling agent, performing oil dirt removal treatment after drying, then performing dry and wet polishing, and storing after cleaning and drying; (2) coating a glue layer on the bonding area surface of the ceramic matrix composite material tensile specimen treated in the step (1) in sequence to form a gradient glue layer structure; and (3) performing stage curing on the ceramic matrix composite material tensile specimen treated in the step (2). The gradient glue layer curing design realizes smooth transition of the tensile modulus from the specimen to the reinforcing sheet, the tensile specimen treated by the method breaks down uniformly for effective testing, the CMC tensile test loss is greatly reduced, and the test cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of material mechanical property testing technology, specifically relating to a gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens. Background Technology

[0002] Ceramic matrix composites (CMCs) are characterized by high strength and brittleness. During room temperature tensile testing, there is a risk of the specimens being crushed by the testing machine grips. To prevent this, reinforcing sheets of a certain thickness are bonded to both ends of the specimen to protect it and transfer the load. However, existing methods of bonding CMCs to these reinforcing sheets have the following problems:

[0003] Due to its high brittleness and low interlaminar shear strength, CMC is prone to premature fracture at the end of the reinforcing sheet in tensile tests due to stress concentration.

[0004] The poor adhesion of general-purpose reinforcing sheets to composite materials and their frequent detachment lead to an increase in invalid room temperature tensile tests, which reduces test efficiency and increases test costs. The bonding quality of the reinforcing sheets directly affects the failure mode of the test specimens and the validity of the test data.

[0005] Traditional epoxy resin bonding processes suffer from uneven adhesive layer thickness and stress concentration during curing. If high-temperature curing adhesives (such as polyimide) are used, the large difference in thermal expansion coefficients between the high-temperature curing adhesive and CMC can easily lead to delamination at the interface. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, which solves the problems of poor reinforcing sheet compatibility, low precision, and poor effective tensile test results in traditional reinforcing sheet bonding methods, reduces the interference of specimen deformation and mechanical properties, and ensures the bonding quality of the reinforcing sheet.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, specifically including the following steps:

[0009] (1) The surface of the ceramic matrix composite tensile specimen is pretreated to form an array of staggered grooves in the bonding area of ​​the specimen, and the surface is modified with silane coupling agent. After drying, the specimen is degreased, then dry and wet polished, cleaned, dried and stored.

[0010] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a gradient adhesive layer structure;

[0011] (3) The ceramic matrix composite tensile specimens treated in step (2) are cured in stages.

[0012] Furthermore, in step (1), the ceramic matrix composite material is a SiCf / SiC ceramic matrix composite material;

[0013] The silane coupling agent is a KH550, KH792 or KH602 silane coupling agent containing nano-SiO2 particles.

[0014] Furthermore, the content of nano-SiO2 particles is 30 wt.%, and the particle size is 20 nm-50 nm.

[0015] Further, in step (1), laser microtexturing technology is used to process an interlaced groove array in the bonding area of ​​the sample. The groove width of the interlaced groove array is 50μm-100μm, the depth is 200μm-300μm, and the spacing is 1.5 times to 2 times the groove width.

[0016] Further, step (1) degreasing is done by blowing away dust and then wiping clean with degreased cotton soaked in cleaning agent; dry polishing is done by polishing with gauze along the fiber direction in a straight line; wet polishing is done by polishing with wet sandpaper under running water; cleaning is done by rinsing with volatile polar solvent and then wiping; drying is done by drying in an oven and then cooling naturally; storage is done by wrapping with neutral packaging paper for moisture and dust protection.

[0017] Furthermore, in step (2), the gradient adhesive layer structure is a sandwich adhesive layer structure consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive.

[0018] Furthermore, the bottom flexible epoxy adhesive is 70wt.% E-51 epoxy resin + 30wt% polysulfide rubber, with a modulus ≤1GPa;

[0019] The carbon fiber in the intermediate carbon fiber reinforced epoxy resin is T300 fiber, with a volume fraction of 15% and a length of 3mm;

[0020] The modulus of the cyanate ester adhesive in the surface layer is ≥3 GPa.

[0021] Furthermore, the thickness of the flexible epoxy coating on the bottom layer is 100±10μm;

[0022] The thickness of the intermediate layer coated with carbon fiber reinforced epoxy adhesive is 150±10μm;

[0023] The thickness of the surface coating with high-temperature cyanate ester adhesive is 50±5μm.

[0024] Further, step (3) involves three stages of curing: the first stage is heat preservation and pressure curing, the second stage is step heating followed by heat preservation and pressure curing, and the third stage is natural cooling followed by heat preservation and pressure curing.

[0025] Furthermore, the first stage curing temperature is 60℃-65℃, the surface pressure is 0.5MPa, and the curing time is 1h-1.5h;

[0026] The second stage of curing involves a stepped temperature increase to 120℃-125℃ at a rate of 2℃ / min, with a surface pressure of 1MPa and a curing time of 2h-2.5h.

[0027] The third stage involves natural cooling to 50°C, with a surface pressure of 1 MPa and a curing time of 30 minutes.

[0028] Advantages and effects of the present invention:

[0029] 1. Improve the interfacial mechanical interlocking at the clamping end of CMC tensile specimens through the synergistic effect of surface microtexturing and nano-modification;

[0030] 2. The gradient adhesive layer curing design achieves a smooth transition of tensile modulus from the sample to the reinforcing sheet;

[0031] 3. All tensile specimens treated by the bonding method of this invention underwent valid fracture tests.

[0032] 4. It can be extended to the application of bonding and curing of tensile test specimen reinforcement sheets for other brittle materials such as composite materials;

[0033] 5. Significantly reduces CMC tensile test losses. Due to the high cost of CMC materials, the loss of specimens caused by tensile test failures is relatively high. After improving the reinforcing sheet bonding process through this invention, the test losses are greatly reduced, and the tensile test cost is reduced by RMB 17,500 per batch. Attached Figure Description

[0034] Figure 1 These are schematic diagrams of gradient curing bonding of reinforcing sheets for tensile specimens of ceramic matrix composites in Examples 1 to 7. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0036] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0037] (1) The tensile specimens of SiCf / SiC ceramic matrix composites were pretreated on the surface. A staggered groove array was fabricated in the bonding area of ​​the specimens using laser microtexturing technology. The groove width of the staggered groove array was 50μm-100μm, the depth was 200μm-300μm, and the spacing was 1.5-2 times the groove width. The surface was modified using KH550, KH792 or KH602 series silane coupling agents containing nano-SiO2 particles. The content of nano-SiO2 particles was 30wt.%, and the particle size was 20nm-50nm. nm, after drying, undergo degreasing treatment by blowing away dust and dirt, then wipe with degreased cotton soaked in acetone and / or ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sand with 28# gauze along the fiber direction in a straight line, and then wet sand with 35# sandpaper under a small stream of water. Neither dry nor wet sanding should remove the fiber interface layer. After rinsing with acetone and / or ethanol, wipe with silk cloth until the silk cloth is free of marks, dry in an oven at 90℃-100℃ for 2 hours, cool naturally, and wrap with neutral packaging paper to prevent moisture and dust. If left for more than 24 hours, clean with ethanol.

[0038] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70wt.% E-51 epoxy resin + 30wt.% polysulfide rubber with a modulus ≤1GPa and a coating thickness of 100±10μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3mm, and a coating thickness of 150±10μm; the top layer adhesive is cyanate ester adhesive with a modulus ≥3GPa and a coating thickness of 50±5μm.

[0039] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 60℃-65℃, surface pressure of 0.5MPa, cured for 1h-1.5h; second stage: stepped temperature increase to 120℃-125℃, heating rate of 2℃ / min, surface pressure of 1MPa at 120℃, cured for 2h-2.5h; third stage: natural cooling to 50℃, surface pressure of 1MPa at 50℃, cured for 30min.

[0040] like Figure 1As shown, each embodiment of the present invention uses an aluminum sheet with a thickness of 2mm-3mm, processed into a shape with a chamfer of 15±1°, a length of 31.8±0.1mm, and a width of 10±0.1mm. The aluminum sheet is bonded to the upper and lower surfaces of the left and right ends of the specimen using the gradient curing bonding method of the present invention for reinforcing sheets of ceramic matrix composite tensile specimens. The parallelism error of the upper and lower surfaces of the specimen does not exceed 0.05mm, and the symmetry error between the specimen surface and the reference plane A does not exceed 0.05mm, thus obtaining a standard reinforcing sheet for ceramic matrix composite tensile specimens for tensile testing. The comparative example of a standard reinforcing sheet for tensile testing of ceramic matrix composite tensile specimens differs from the embodiments only in the bonding method.

[0041] Example 1

[0042] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0043] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 50μm, a depth of 200μm, and a spacing of 1.5 times the groove width; spray with KH550 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 20nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks, dry in an oven at 90℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0044] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1 GPa and a coating thickness of 90 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 140 μm; the top layer adhesive is 502 cyanate ester adhesive with a modulus of 3 GPa and a coating thickness of 45 μm.

[0045] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 60℃, surface pressure of 0.5MPa, cured for 1h; second stage: stepped temperature increase to 120℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0046] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 1 of this paper were subjected to tensile tests, and all of them were valid tests.

[0047] Example 2

[0048] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0049] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 80μm, a depth of 250μm, and a spacing of 1.5 times the groove width; spray with KH792 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 35nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks. Dry in an oven at 95℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0050] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 0.9 GPa and a coating thickness of 100 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 150 μm; the top layer adhesive is 502 cyanate ester adhesive with a modulus of 3.2 GPa and a coating thickness of 50 μm.

[0051] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 63℃, surface pressure of 0.5MPa, cured for 1.2h; second stage: stepped temperature increase to 123℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.2h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0052] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 2 of this paper were subjected to tensile tests, and all of them were valid tests.

[0053] Example 3

[0054] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0055] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 100μm, a depth of 300μm, and a spacing of twice the groove width; spray with KH602 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 50nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks. Dry in an oven at 100℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0056] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 0.8 GPa and a coating thickness of 110 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 160 μm; the top layer adhesive is 502 cyanate ester adhesive with a modulus of 3.5 GPa and a coating thickness of 55 μm.

[0057] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 65℃, surface pressure of 0.5MPa, cured for 1.5h; second stage: stepped temperature increase to 125℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.5h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0058] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 3 of this paper were subjected to tensile tests, and all of them were valid tests.

[0059] Example 4

[0060] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0061] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 60μm, a depth of 210μm, and a spacing of 1.5 times the groove width; spray with KH550 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 25nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks. Dry in an oven at 92℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0062] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1 GPa and a coating thickness of 95 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 145 μm; the top layer adhesive is 502 cyanate ester adhesive with a modulus of 3 GPa and a coating thickness of 48 μm.

[0063] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 60℃, surface pressure of 0.5MPa, cured for 1.3h; second stage: stepped temperature increase to 121℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.1h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0064] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 4 of this paper were subjected to tensile tests, and all of them were valid tests.

[0065] Example 5

[0066] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0067] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 90μm, a depth of 240μm, and a spacing of twice the groove width; spray with KH602 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 40nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks, dry in an oven at 96℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0068] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 0.8 GPa and a coating thickness of 98 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 150 μm; the top layer adhesive is triphenylmethane triisocyanate adhesive with a modulus of 3.1 GPa and a coating thickness of 50 μm.

[0069] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 65℃, surface pressure of 0.5MPa, cured for 1.5h; second stage: stepped temperature increase to 123℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.4h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0070] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 5 of this paper were subjected to tensile tests, and all of them were valid tests.

[0071] Example 6

[0072] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0073] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 100μm, a depth of 270μm, and a spacing of 1.7 times the groove width. Surface modification is achieved by spraying with KH550 silane coupling agent containing nano-SiO2 particles (30wt.% content, 45nm particle size), followed by drying at 80℃. Degreasing is performed by blowing away dust, then wiping with cotton soaked in ethanol wrapped in silk until no black marks remain. Next, use 28# gauze to sand along the fiber direction in a straight line, followed by wet sanding with 35# wet sandpaper under a low water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol, then wipe with silk until no marks remain. Dry in an oven at 98℃ for 2 hours, allow to cool naturally, and wrap in neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0074] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1 GPa and a coating thickness of 108 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 160 μm; the top layer adhesive is 502 cyanate ester adhesive with a modulus of 3.5 GPa and a coating thickness of 52 μm.

[0075] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: cured for 1 h at 60 °C with a surface pressure of 0.5 MPa; second stage: the temperature was gradually increased to 124 °C at a rate of 2 °C / min, and cured for 2.5 h at 124 °C with a surface pressure of 1 MPa; third stage: the temperature was naturally cooled to 50 °C, and cured for 30 min at 50 °C with a surface pressure of 1 MPa.

[0076] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 6 of this paper were subjected to tensile tests, and all of them were valid tests.

[0077] Example 7

[0078] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens specifically includes the following steps:

[0079] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 50μm, a depth of 280μm, and a spacing of twice the groove width; spray with KH602 silane coupling agent containing nano-SiO2 particles for surface modification, with a nano-SiO2 particle content of 30wt.% and a particle size of 50nm, and dry at 80℃; perform degreasing treatment by blowing away dust and dirt, then wiping with degreased cotton soaked in ethanol wrapped in silk cloth until the silk cloth is free of black marks, then sanding in a straight line along the fiber direction with 28# gauze, and then wet sanding with 35# wet sandpaper under a small water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol and wipe with silk cloth until the silk cloth is free of marks, dry in an oven at 99℃ for 2 hours, cool naturally, and wrap with neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0080] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 0.7 GPa and a coating thickness of 110 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 140 μm; the top layer adhesive is triphenylmethane triisocyanate adhesive with a modulus of 3 GPa and a coating thickness of 53 μm.

[0081] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 65℃, surface pressure of 0.5MPa, cured for 1.2h; second stage: stepped temperature increase to 125℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.2h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0082] Five sets of tensile specimens obtained using the gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens in Example 7 of this paper were subjected to tensile tests, and all of them were valid tests.

[0083] Comparative Example 1

[0084] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, specifically including the following steps:

[0085] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 The process involves fabricating an interlaced groove array with a groove width of 48 μm, a depth of 190 μm, and a spacing of twice the groove width. Surface modification is achieved by spraying with KH550 silane coupling agent containing nano-SiO2 particles (30 wt.% content, 18 nm particle size), followed by drying at 80°C. Degreasing is then performed by blowing away dust, followed by wiping with cotton soaked in ethanol wrapped in silk until no black residue remains. Next, the fabric is sanded in a straight line along the fiber direction using 28# gauze, and then wet-sanded with 35# sandpaper under a low water flow. Neither dry nor wet sanding should remove the fiber interface layer. After rinsing with acetone or ethanol, the fabric is wiped clean with silk until no residue remains. The fabric is then dried in an oven at 85°C for 2 hours, allowed to cool naturally, and wrapped in neutral packaging paper for moisture and dust protection. If left for more than 24 hours, it should be cleaned with ethanol.

[0086] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1 GPa and a coating thickness of 85 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 135 μm; the top layer adhesive is 502 isocyanate adhesive with a modulus of 3 GPa and a coating thickness of 43 μm.

[0087] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 58℃, surface pressure of 0.5MPa, cured for 1.3h; second stage: stepped temperature increase to 110℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 1.8h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0088] Five sets of tensile specimens obtained using the gradient curing bonding method of the ceramic matrix composite tensile specimen reinforcement sheet of Comparative Example 1 were subjected to tensile tests. Four sets of tests were invalid tests due to adhesive layer debonding, accounting for 80% of the tests.

[0089] Comparative Example 2

[0090] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, specifically including the following steps:

[0091] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 110μm, a depth of 350μm, and a spacing of twice the groove width. Surface modification is achieved by spraying with KH602 silane coupling agent containing nano-SiO2 particles (30wt.% content, 60nm particle size), followed by drying at 80℃. Degreasing is performed by blowing away dust, then wiping with cotton soaked in ethanol wrapped in silk until no black marks remain. Next, use 28# gauze to sand along the fiber direction in a straight line, followed by wet sanding with 35# wet sandpaper under a low water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol, then wipe with silk until no marks remain. Dry in an oven at 115℃ for 2 hours, allow to cool naturally, and wrap in neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0092] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1.2 GPa and a coating thickness of 125 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 150 μm; the top layer adhesive is triphenylmethane triisocyanate adhesive with a modulus of 2.8 GPa and a coating thickness of 65 μm.

[0093] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 80℃, surface pressure of 0.5MPa, cured for 2h; second stage: stepped temperature increase to 140℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 3.5h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0094] Five sets of tensile specimens obtained using the gradient curing bonding method of the ceramic matrix composite tensile specimen reinforcement sheet of Comparative Example 2 were subjected to tensile tests. Three sets of tests were invalid tests due to adhesive layer debonding, accounting for 60% of the tests.

[0095] Comparative Example 3

[0096] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, specifically including the following steps:

[0097] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 The process involves fabricating an interlaced groove array with a groove width of 103 μm, a depth of 310 μm, and a spacing of twice the groove width. Surface modification is achieved by spraying with KH602 silane coupling agent containing nano-SiO2 particles (30 wt.%, 52 nm diameter), followed by drying at 80°C. Degreasing is performed by blowing away dust, then wiping with cotton soaked in ethanol wrapped in silk until no black marks remain. Next, the fabric is sanded in a straight line along the fiber direction using 28# gauze, followed by wet sanding with 35# sandpaper under a low water flow. Neither dry nor wet sanding should remove the fiber interface layer. After rinsing with acetone or ethanol, the fabric is wiped clean with silk until no marks remain. The fabric is then dried in an oven at 105°C for 2 hours, allowed to cool naturally, and wrapped in neutral packaging paper for moisture and dust protection. If left for more than 24 hours, it should be cleaned with ethanol.

[0098] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 0.8 GPa and a coating thickness of 115 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 165 μm; the top layer adhesive is triphenylmethane triisocyanate adhesive with a modulus of 2.8 GPa and a coating thickness of 58 μm.

[0099] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 68℃, surface pressure of 0.5MPa, cured for 0.5h; second stage: stepped temperature increase to 130℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 2.8h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0100] Five sets of tensile specimens obtained using the gradient curing bonding method of the ceramic matrix composite tensile specimen reinforcement sheet of Comparative Example 3 were subjected to tensile tests. Four sets of tests were invalid tests due to adhesive layer debonding, accounting for 80% of the tests.

[0101] Comparative Example 4

[0102] A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, specifically including the following steps:

[0103] (1) The surface of the SiCf / SiC ceramic matrix composite tensile specimen was pretreated, and laser etching was performed on the bonding area of ​​the specimen (wavelength 1064nm, pulse energy 20J / cm). 2 Process an interlaced groove array with a groove width of 105μm, a depth of 320μm, and a spacing of twice the groove width. Surface modification is achieved by spraying with KH550 silane coupling agent containing nano-SiO2 particles (30wt.% content, 55nm particle size), followed by drying at 80℃. Degreasing is performed by blowing away dust, then wiping with cotton soaked in ethanol wrapped in silk until no black marks remain. Next, use 28# gauze to sand along the fiber direction in a straight line, followed by wet sanding with 35# sandpaper under a low water flow. Neither dry nor wet sanding should remove the fiber interface layer. Rinse with acetone or ethanol, then wipe with silk until no marks remain. Dry in an oven at 110℃ for 2 hours, allow to cool naturally, and wrap in neutral packaging paper for moisture and dust protection. If left for more than 24 hours, clean with ethanol.

[0104] (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich (gradient) structure adhesive layer consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive, and a top high temperature cyanate ester adhesive. The bottom flexible epoxy adhesive is 70 wt.% E-51 epoxy resin + 30 wt.% polysulfide rubber with a modulus of 1 GPa and a coating thickness of 120 μm; the middle layer adhesive is carbon fiber reinforced epoxy adhesive, the carbon fiber is T300 fiber with a volume fraction of 15% and a length of 3 mm, and a coating thickness of 170 μm; the top layer adhesive is 502 isocyanate adhesive with a modulus of 2.8 GPa and a coating thickness of 60 μm.

[0105] (3) The ceramic matrix composite tensile specimens treated in step (2) were cured in three stages: first stage: 70℃, surface pressure of 0.5MPa, cured for 1.8h; second stage: stepped temperature increase to 135℃, heating rate of 2℃ / min, surface pressure of 1MPa, cured for 3h; third stage: natural cooling to 50℃, surface pressure of 1MPa, cured for 30min.

[0106] Five sets of tensile specimens obtained using the gradient curing bonding method of the ceramic matrix composite tensile specimen reinforcement sheet of Comparative Example 4 were subjected to tensile tests. Three sets of tests were invalid tests due to adhesive layer debonding, accounting for 60% of the tests.

Claims

1. A gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens, characterized in that, Specifically, the following steps are included: (1) The surface of the ceramic matrix composite tensile specimen is pretreated to form an array of staggered grooves in the bonding area of ​​the specimen, and the surface is modified with silane coupling agent. After drying, the specimen is degreased, then dry and wet polished, cleaned, dried and stored. (2) The bonding area of ​​the ceramic matrix composite tensile specimen treated in step (1) is coated with adhesive layers in sequence to form a sandwich adhesive layer structure consisting of a bottom flexible epoxy adhesive, a middle carbon fiber reinforced epoxy adhesive and a top high temperature cyanate ester adhesive. (3) The ceramic matrix composite tensile specimens treated in step (2) are cured in three stages. In the first stage, the specimens are cured under heat and pressure at 60℃-65℃. In the second stage, the specimens are cured under heat and pressure after being heated to 120℃-125℃ in a stepwise manner. In the third stage, the specimens are cured under heat and pressure after being cooled to 50℃ naturally.

2. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, In step (1), the ceramic matrix composite material is a SiCf / SiC ceramic matrix composite material; The silane coupling agent is a KH550, KH792 or KH602 silane coupling agent containing nano-SiO2 particles.

3. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 2, characterized in that, The content of nano-SiO2 particles is 30 wt.%, and the particle size is 20 nm-50 nm.

4. The gradient curing and bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, Step (1) Use laser microtexturing technology to process an interlaced groove array in the bonding area of ​​the sample. The groove width of the interlaced groove array is 50μm-100μm, the depth is 200μm-300μm, and the spacing is 1.5 times to 2 times the groove width.

5. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, Step (1) Degreasing involves blowing away dust and dirt, then wiping clean with degreased cotton soaked in detergent; dry sanding involves sanding with gauze along the fiber direction in a straight line; wet sanding involves sanding with wet sandpaper under running water; cleaning involves rinsing with a volatile polar solvent and then wiping; drying involves drying in an oven and then naturally cooling. Storage involves wrapping the product in neutral packaging paper for moisture and dust protection.

6. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, The bottom flexible epoxy adhesive is 70wt.% E-51 epoxy resin + 30wt% polysulfide rubber, with a modulus ≤1GPa; The carbon fiber in the intermediate carbon fiber reinforced epoxy resin is T300 fiber, with a volume fraction of 15% and a length of 3mm; The modulus of the cyanate ester adhesive in the surface layer is ≥3 GPa.

7. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, The thickness of the flexible epoxy adhesive coating on the bottom layer is 100±10μm; The thickness of the intermediate layer coated with carbon fiber reinforced epoxy adhesive is 150±10μm; The thickness of the surface coating with high-temperature cyanate ester adhesive is 50±5μm.

8. The gradient curing bonding method for reinforcing sheets of ceramic matrix composite tensile specimens as described in claim 1, characterized in that, The first stage of curing involves applying a pressure of 0.5 MPa to the surface and curing for 1-1.5 hours. The second stage of curing involves a step-by-step heating rate of 2℃ / min, a surface pressure of 1MPa, and a curing time of 2h-2.5h. The third stage involves applying a pressure of 1 MPa to the surface for curing, with a curing time of 30 minutes.

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