Modified bamboo enhanced laminated veneer lumber wind power blade web and preparation method thereof

Abstract

The invention discloses a modified bamboo enhanced laminated veneer lumber wind power blade web and a preparation method thereof, and belongs to the technical field of wind power composite materials. The preparation method comprises the steps that 4-6-year-old moso bamboos are made into radial bamboo splits with the specific size, and the radial bamboo splits are woven into a bamboo curtain; preparing a composite resin impregnation liquid containing epoxy resin, phenolic resin, a silane coupling agent KH-560 and nano aluminum oxide; the bamboo curtain is subjected to vacuum pressurization dipping treatment; pre-curing is carried out after glue draining; laying a plurality of layers of pre-cured bamboo curtains according to the orthogonal direction of 0 degree / 90 degrees, and coating resin adhesives among the layers; and finally, carrying out hot-pressing curing, curing and machining to obtain a web plate product. According to the method, the anisotropy, the size stability and the interface bonding performance of the bamboo wood are effectively improved through resin impregnation modification and orthogonal layering design. The manufactured web has high specific strength, high rigidity, good anti-fatigue performance and low density, the comprehensive performance meets the use requirements of wind power blades, and meanwhile the cost is low and environment friendliness is achieved.

Description

Technical Field

[0001] This invention belongs to the field of wind power composite materials technology, specifically relating to a modified bamboo-reinforced veneer laminated laminated material wind turbine blade web and its preparation method. Background Technology

[0002] As the main load-bearing structure of wind turbine blades, the web of the blade needs to possess extremely high strength, stiffness, and fatigue resistance. While traditional fiberglass webs offer good performance, they suffer from high cost and difficulty in recycling. Bamboo, as a natural high-strength composite material, boasts a longitudinal tensile strength exceeding 300 MPa and a specific strength even surpassing that of ordinary steel, making it an ideal alternative for wind power materials.

[0003] However, using bamboo directly in wind turbine webs faces the following problems: bamboo exhibits significant anisotropy and poor lateral properties; bamboo contains a large number of hydrophilic hydroxyl groups, which easily absorb moisture and lead to dimensional instability; the interfacial bonding between bamboo and resin is poor; and the durability and fatigue resistance of natural bamboo are insufficient to meet the 20-year service life requirements of wind turbine blades.

[0004] CN111531661B discloses a bamboo-wood plywood with a composite structure of bamboo strip layers and wood veneer layers, but it is mainly designed for building formwork applications, and its performance indicators cannot meet the extreme requirements of wind turbine blade webs. There is a lack of bamboo modification treatment solutions specifically for wind turbine blade web applications in the existing technology. Summary of the Invention

[0005] Technical problem to be solved: To provide a modified bamboo-reinforced veneer laminated lumber (VFL) wind turbine blade web and its preparation method, which can give full play to the high strength characteristics of bamboo, and at the same time solve the problems of anisotropy, dimensional stability and interfacial bonding of bamboo through special resin impregnation modification treatment, so as to meet the performance requirements of wind turbine blade web.

[0006] Technical solution: A method for preparing the web of a modified bamboo-reinforced veneer laminated timber wind turbine blade, comprising the following steps: (1) Bamboo pretreatment: Select 4-6 year old moso bamboo and make radial bamboo strips with a width of 5-15 mm and a thickness of 1-3 mm, retaining the bamboo green and bamboo yellow; (2) Weaving bamboo curtain: Weave the radial bamboo strips into a bamboo curtain with high temperature resistant synthetic fiber thread, the thickness of the bamboo curtain being 2-4 mm; (3) Resin impregnation solution preparation: Prepare an epoxy-phenolic composite resin impregnation solution, wherein epoxy resin E-51 accounts for 60-70%, phenolic resin accounts for 30-40%, and 1-3% of the total resin content of silane coupling agent KH-560 and 0.5-1.5% of nano alumina particles are added, with the solid content controlled at 40-50%; (4) Vacuum pressure impregnation: Place the bamboo curtain into the impregnation tank, first evacuate to -0.095 to -0.098 MPa, and maintain for 30-60 minutes; then inject the resin impregnation liquid; release the vacuum, apply a pressure of 1.0-2.0 MPa, and maintain the pressure for 120-180 minutes; (5) Adhesive application and pre-curing: Take out the impregnated bamboo curtain, drain the excess resin from the surface, and then pre-cur at 80-90℃ for 30-60 minutes; (6) Assembly and molding: Lay the pre-cured bamboo curtain in a 0° / 90° orthogonal direction, with 20-40 layers, and coat each layer with epoxy-phenolic composite resin, with an adhesive application amount of 150-250 g / m²; (7) Hot pressing and curing: Hot press and mold at a hot pressing temperature of 130-150℃ and a pressure of 2-4 MPa, with a hot pressing time calculated as 1.5-2.0 minutes / mm; (8) Post-processing: After hot pressing, cure at 23±2℃ and 50±5%RH for 14-28 days, and then CNC machine into web profile.

[0007] In step (1), the width of the bamboo strip is 8-12mm and the thickness is 1.5-2.5mm.

[0008] In step (2), the high-temperature resistant synthetic fiber thread is an aramid fiber thread.

[0009] In step (3), the amount of silane coupling agent KH-560 added is 2%, and the amount of nano alumina added is 1%.

[0010] In step (4), the vacuum degree is -0.097 to -0.098 MPa and is maintained for 45-60 minutes; the pressure is 1.5-2.0 MPa and is maintained for 150-180 minutes.

[0011] In step (5), the pre-curing temperature is 85-90℃ and the time is 30-45 minutes.

[0012] In step (6), the number of layers is 25-35, and the amount of adhesive applied is 180-220 g / m².

[0013] In step (7), the hot pressing temperature is 140-150℃ and the pressure is 3-4MPa.

[0014] In step (8), the maintenance period is 21-28 days.

[0015] The wind turbine blade web prepared by the above method is composed of 20-40 layers of resin-impregnated bamboo mats laid in orthogonal directions at 0° / 90°, with epoxy-phenolic composite resin coated between each layer of bamboo mats; the bamboo mats are woven from radial bamboo strips with a width of 5-15mm and a thickness of 1-3mm, retaining the green and yellow parts of the bamboo; the resin impregnation liquid is an epoxy-phenolic composite resin, wherein epoxy resin E-51 accounts for 60-70%, phenolic resin accounts for 30-40%, and contains 1-3% of the total resin amount of silane coupling agent KH-560 and 0.5-1.5% of nano-alumina particles.

[0016] Beneficial Effects: This invention fully utilizes the natural high strength of bamboo, exceeding the specific strength of traditional fiberglass materials. Through epoxy-phenolic composite resin impregnation modification, the dimensional stability and durability of bamboo are significantly improved. Orthogonal layup design effectively improves the anisotropy of bamboo, enhancing its transverse properties. The addition of nano-alumina further enhances the stiffness and wear resistance of the resin matrix. Compared to traditional fiberglass webs, it reduces weight and lowers costs. As a renewable resource, bamboo aligns with the sustainable development concept of the wind power industry. The modified bamboo-reinforced laminated veneer lumber prepared by this invention fully meets the performance requirements of wind turbine blade webs and has broad application prospects. Detailed Implementation

[0017] Before presenting the performance data of the embodiments, the test standards and methods for the key performance parameters involved in this application are uniformly explained. All tests are conducted in a standard environment with a temperature of 23±2℃ and a relative humidity of 50±5%.

[0018] Density (g / cm³): Measured according to the method specified in standard GB / T 17657-2013.

[0019] Longitudinal / transverse bending strength (MPa) and modulus of elasticity (GPa): Tested using the three-point bending method according to standard ASTM D790-17. Longitudinal refers to the length direction of the bamboo strip, and transverse refers to the direction perpendicular to the length of the bamboo strip.

[0020] Interlaminar shear strength (MPa): Tested using the short beam shear method according to standard ASTM D2344 / D2344M-16.

[0021] 24h water absorption rate (%): Following the method in standard GB / T 17657-2013, the sample was completely immersed in distilled water for 24 hours, and the percentage increase in its mass was measured.

[0022] Fatigue performance: In accordance with the standard ASTM D3479 / D3479M-19, a tensile-tensile fatigue test was conducted (stress ratio R=0.1, frequency 5Hz). The stress level was 50% of the static bending strength. After 10^6 cycles, the residual strength was measured and the strength retention rate was calculated.

[0023] Example 1

[0024] (1) Bamboo pretreatment: Select 5-year-old moso bamboo, cut it and split it radially to make radial bamboo strips with a width of 10mm and a thickness of 2mm, retaining the green and yellow bamboo.

[0025] (2) Weaving bamboo curtains: The above-mentioned radial bamboo strips are woven into bamboo curtains using aramid fiber thread, and the thickness of the bamboo curtains is controlled at 3mm.

[0026] (3) Preparation of resin impregnation solution: Prepare epoxy-phenolic composite resin impregnation solution. By mass, epoxy resin E-51 accounts for 65%, phenolic resin accounts for 35%, and 2% of the total resin mass of silane coupling agent KH-560 and 1% of nano-alumina particles with an average particle size of 50nm are added. The solid content is adjusted to 45% with solvent.

[0027] (4) Vacuum pressure impregnation: Place the bamboo curtain into the impregnation tank, first evacuate to -0.097MPa and maintain for 45 minutes; inject the above resin impregnation liquid while maintaining the vacuum; release the vacuum, apply a pressure of 1.5MPa and maintain the pressure for 150 minutes.

[0028] (5) Drip resin and pre-curing: Take out the impregnated bamboo mat, drip off the excess resin on the surface, and then pre-cur it in an oven at 85°C for 45 minutes.

[0029] (6) Assembly and molding: The pre-cured bamboo curtain is laid out in 0° / 90° orthogonal directions, with 30 layers. The epoxy-phenolic composite resin (solid content 45%) is applied between each layer, with an application amount of 200g / m².

[0030] (7) Hot pressing and curing: The assembled slab is placed in a hot press and hot-pressed for 60 minutes at a temperature of 140℃ and a pressure of 3MPa using a segmented heating method (calculated at 2.0 minutes / mm based on a total thickness of 30mm).

[0031] (8) Post-processing: After hot pressing, the blade is cured in a standard environment of 23±2℃ and 50±5%RH for 21 days, and then processed by CNC machining center into the required profile of the wind turbine blade web.

[0032] Example 2

[0033] (1) Bamboo pretreatment: Select 4-year-old moso bamboo and make radial bamboo strips with a width of 8mm and a thickness of 1.5mm, retaining the bamboo green and bamboo yellow.

[0034] (2) Weaving bamboo curtains: Weaving bamboo curtains with a thickness of 2.5mm using aramid fiber yarn.

[0035] (3) Preparation of resin impregnation solution: 60% epoxy resin E-51, 40% phenolic resin, 3% KH-560 and 1.5% nano alumina (particle size 50nm) of total resin mass are added, and the solid content is adjusted to 48%.

[0036] (4) Vacuum pressure impregnation: vacuum degree -0.098MPa, maintain for 60 minutes; pressure 2.0MPa, maintain pressure for 180 minutes.

[0037] (5) Applying adhesive and pre-curing: Pre-curing at 90℃ for 30 minutes.

[0038] (6) Assembly and molding: 25 layers are laid in the orthogonal direction of 0° / 90°, and the amount of adhesive applied is 180g / m².

[0039] (7) Hot pressing curing: hot pressing temperature 145℃, pressure 3.5MPa, hot pressing time 50 minutes (calculated based on a total thickness of 25mm).

[0040] (8) Post-processing: Cured for 28 days under standard conditions, and then CNC machining is performed.

[0041] Example 3

[0042] (1) Bamboo pretreatment: Select 6-year-old moso bamboo and make radial bamboo strips with a width of 12mm and a thickness of 2.5mm, retaining the bamboo green and bamboo yellow.

[0043] (2) Weaving bamboo curtains: Weaving bamboo curtains with a thickness of 3.5mm using aramid fiber yarn.

[0044] (3) Preparation of resin impregnation solution: 70% epoxy resin E-51, 30% phenolic resin, 1.5% KH-560 and 0.8% nano alumina (particle size 50nm) of total resin mass are added, and the solid content is 42%.

[0045] (4) Vacuum pressure impregnation: vacuum degree -0.096MPa, maintain for 40 minutes; pressure 1.2MPa, maintain pressure for 130 minutes.

[0046] (5) Applying adhesive and pre-curing: Pre-curing at 82℃ for 50 minutes.

[0047] (6) Assembly and molding: 35 layers are laid in the orthogonal direction of 0° / 90°, and the amount of adhesive applied is 220g / m².

[0048] (7) Hot pressing curing: hot pressing temperature 135℃, pressure 2.5MPa, hot pressing time about 70 minutes (calculated based on a total thickness of 35mm).

[0049] (8) Post-processing: Cured for 14 days under standard conditions, and then CNC machining is performed.

[0050] Comparative Example 1 (Traditional Fiberglass Web)

[0051] Using conventional E-glass fiber cloth and epoxy resin system, a web plate sample with dimensions comparable to that of Example 1 was made by a combination of hand lay-up and vacuum infusion process, with a glass fiber volume content of approximately 50%.

[0052] Comparative Example 2 (Unmodified bamboo laminated timber)

[0053] Without performing the resin impregnation modification treatment in steps (3) and (4), the bamboo curtain woven in step (2) (same as in Example 1) is directly assembled into a blank in step (6) (coated with the same epoxy-phenolic resin as an adhesive), and then hot-pressed and cured in steps (7) and (8).

[0054] Performance test results:

[0055] The samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in the table below.

[0056] Table 1 Comparison of Material Performance Test Results

[0057]

[0058] Results analysis:

[0059] As shown in Table 1, the modified bamboo-reinforced laminated veneer lumber prepared in Examples 1-3 of this invention exhibits significantly better longitudinal bending strength, elastic modulus, and interlaminar shear strength than conventional fiberglass (Comparative Example 1), despite having a much lower density. This demonstrates higher specific strength and specific stiffness. Although the transverse strength is still lower than that of fiberglass due to the inherent anisotropy of the material, its transverse performance has been greatly improved through the orthogonal layup design and resin impregnation modification of this invention (compared to the extremely low transverse strength of unmodified bamboo in Comparative Example 2). The longitudinal-to-transverse strength ratio is controlled within a reasonable range of 3.0-3.2, meeting the load-bearing requirements of the web structure. Furthermore, the material of this invention exhibits excellent fatigue resistance, superior to conventional fiberglass. The key dimensional stability index (24-hour water absorption rate) shows an order-of-magnitude improvement over unmodified bamboo (Comparative Example 2) through deep resin impregnation modification of the bamboo body, proving the effectiveness of the method of this invention in solving the problem of moisture absorption and expansion of bamboo.

Claims

1. A method for manufacturing a modified bamboo reinforced laminated veneer lumber wind turbine blade web, characterized in that, The method comprises the following steps: (1) Bamboo material pretreatment: 4-6 year old bamboo is selected to make radial bamboo splints with a width of 5-15 mm and a thickness of 1-3 mm, and the bamboo green and yellow are reserved; (2) weaving bamboo curtain: the radial bamboo splints are woven into a bamboo curtain with a thickness of 2-4 mm by using high-temperature-resistant synthetic fiber threads; (3) resin impregnation liquid preparation: an epoxy-phenolic composite resin impregnation liquid is prepared, wherein epoxy resin E-51 accounts for 60-70%, phenolic resin accounts for 30-40%, and 1-3% of the total amount of the resin of silane coupling agent KH-560 and 0.5-1.5% of nano-aluminum oxide particles are added, and the solid content is controlled at 40-50%; (4) vacuum pressure impregnation: the bamboo curtain is placed in an impregnation tank, vacuum is first extracted to-0.095 to-0.098 MPa and maintained for 30-60 minutes; then the resin impregnation liquid is injected; the vacuum is released, and a pressure of 1.0-2.0 MPa is applied, and the pressure is maintained for 120-180 minutes; (5) resin draining and pre-curing: the impregnated bamboo curtain is taken out, the excess resin on the surface is drained, and then pre-curing is carried out at 80-90℃ for 30-60 minutes; (6) assembly forming: the pre-cured bamboo curtain is laid in the 0° / 90° orthogonal direction, the number of layers is 20-40, and epoxy-phenolic composite resin is coated between each layer, and the glue coating amount is 150-250 g / m²; (7) hot pressing and curing: hot pressing is carried out at a hot pressing temperature of 130-150℃ and a pressure of 2-4 MPa, and the hot pressing time is calculated according to 1.5-2.0 minutes / mm; (8) post-treatment: after hot pressing is completed, curing is carried out at 23±2℃ and 50±5% RH for 14-28 days, and then numerical control processing is carried out to form a web profile.

2. The method of claim 1, wherein, In step (1), the width of the bamboo splint is 8-12 mm, and the thickness is 1.5-2.5 mm.

3. The method of claim 1, wherein, In step (2), the high-temperature-resistant synthetic fiber thread is aramid fiber thread.

4. The method of claim 1, wherein, In step (3), the addition amount of silane coupling agent KH-560 is 2%, and the addition amount of nano-aluminum oxide is 1%.

5. The method of claim 1, wherein, In step (4), the vacuum degree is-0.097 to-0.098 MPa, and the pressure is maintained for 45-60 minutes; the pressure is 1.5-2.0 MPa, and the pressure is maintained for 150-180 minutes.

6. The method of claim 1, wherein, In step (5), the pre-curing temperature is 85-90℃, and the time is 30-45 minutes.

7. The method of claim 1, wherein, In step (6), the number of layers is 25-35, and the glue coating amount is 180-220 g / m².

8. The method of claim 1, wherein, In step (7), the hot pressing temperature is 140-150℃, and the pressure is 3-4 MPa.

9. The method of claim 1, wherein, In step (8), the curing time is 21-28 days.

10. A wind turbine blade web made by the method of any one of claims 1-9, characterized in that, The bamboo curtain is made of 20-40 layers of bamboo curtain impregnated with resin, and is laid in 0° / 90° orthogonal direction, and epoxy-phenolic composite resin is coated between each layer of bamboo curtain; the bamboo curtain is made of radial bamboo splints, the width of the bamboo splints is 5-15 mm, the thickness is 1-3 mm, and the bamboo green and bamboo yellow are reserved; the resin impregnation liquid is epoxy-phenolic composite resin, wherein epoxy resin E-51 accounts for 60-70%, phenolic resin accounts for 30-40%, and the total amount of resin contains 1-3% silane coupling agent KH-560 and 0.5-1.5% nano-aluminum oxide particles.

Images