Carbon fiber boarding hanging ladder and forming method thereof

Abstract

The invention provides a carbon fiber boarding hanging ladder which comprises supporting columns, pedals, hooks and ladder foot pads, the supporting columns are two symmetrically-arranged stand columns, the pedals are transversely connected between the two supporting columns to form steps, the hooks are arranged at the top ends of the supporting columns and used for hanging and fixing, and the ladder foot pads are arranged at the bottom ends of the supporting columns and used for supporting. The supporting columns and the pedals are made of carbon fiber prepreg through bag pressing forming, the carbon fiber prepreg comprises carbon fiber one-way prepreg and twill carbon fiber prepreg, and the laying structures of the supporting columns and the pedals adopt a radial and / or annular laying mode. The carbon fibers are adopted to replace traditional aluminum alloy materials, the radial and / or annular multi-direction laying layer structure design is adopted, the weight is reduced, meanwhile, the bending resistance and the pressure resistance are improved, light weight is achieved, and meanwhile the bearing capacity of a product is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle accessories, and in particular to a carbon fiber vehicle ladder and a molding method thereof. Background Art

[0002] As a commonly used auxiliary boarding equipment on vehicles, the design and manufacturing of boarding ladders have been continuously developing. At present, the boarding ladders on the market are mainly made of metal materials, among which aluminum alloy is the most common. Aluminum alloy boarding ladders are usually composed of pillars, pedals and hooks, and these components are connected and fixed by rivets. Aluminum alloy materials have certain strength and processing properties, but their density is 2.7g / cm 3 , which is relatively heavy. In addition, aluminum alloy loading ladders are prone to corrosion during use and need to be oxidized to enhance their corrosion resistance, which increases the manufacturing process and cost of the product.

[0003] The existing technology has the following problems: 1. The aluminum alloy vehicle ladder is heavy and cannot meet the use requirements of special vehicles with strict weight restrictions; 2. In a highly corrosive use environment, the service life of the aluminum alloy vehicle ladder is still limited even after surface treatment; 3. The traditional riveted structure may affect the overall performance of the product.

[0004] Therefore, there is an urgent need to develop a vehicle loading ladder with lighter weight, better corrosion resistance and better overall performance to meet the needs of special usage scenarios. Summary of the invention

[0005] The technical problem to be solved by the present invention is to solve the problems that the existing vehicle hanging ladders are heavy and have poor corrosion resistance, and the strength and service life of composite material vehicle hanging ladders cannot meet actual needs, and to provide a carbon fiber vehicle hanging ladder with light weight, good corrosion resistance, high strength and long service life and a manufacturing method thereof.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a carbon fiber boarding ladder, including pillars, pedals, hooks and ladder foot pads, the pillars are two symmetrically arranged uprights, a plurality of pedals are horizontally connected between the two pillars to form steps, the hooks are arranged at the top ends of the pillars for hanging and fixing, the ladder foot pads are arranged at the bottom ends of the pillars for supporting, the pillars and the pedals are made of carbon fiber prepreg by bag pressing, the carbon fiber prepreg includes carbon fiber unidirectional prepreg and twill carbon fiber prepreg, and the layup structure of the pillars and the pedals adopts radial and / or circumferential layup methods.

[0007] Preferably, the ply structure of the pillar and pedal is from outside to inside: 1 layer of 200g 3K carbon fiber prepreg, 3 layers of radial 150g unidirectional carbon fiber prepreg, 1 layer of circumferential 150g unidirectional carbon fiber prepreg. After this structure is repeated three times, a layer of 200g 3K carbon fiber prepreg is laid on the outermost layer.

[0008] Preferably, the resin content of the prepreg is 40% ± 3%, the volatile content is not more than 0.5%, and the weight of the film is 150g / m 2 ±10g / m 2 The glue flow rate is 15%-25%.

[0009] Preferably, hooks are arranged on both sides of the pillar, and multiple connecting bolts are arranged on each side, and the tightening torque is 25-28N·m; the ladder foot pad is connected to the main body through a screw assembly, the screw spacing is 200±5mm, and the tightening torque is 15-18N·m.

[0010] A method for manufacturing a carbon fiber vehicle ladder comprises the following steps:

[0011] The mold making and prepreg laying are carried out in an environment with a temperature of 18-26°C and a relative humidity of 25%-65%;

[0012] Apply mold cleaning agent and mold release agent to the mold surface;

[0013] Carry out vacuum bag wrapping, vacuum compaction, and the vacuum degree should not be less than -0.08MPa;

[0014] The curing is carried out by adopting a staged temperature rising curing process.

[0015] Preferably, the staged temperature rising curing process comprises:

[0016] In the first stage, the temperature was raised from room temperature to 90°C ± 5°C at a rate of 2-3°C / min and kept at this temperature for 50-60 minutes;

[0017] In the second stage, the temperature was raised to 125°C ± 5°C at a rate of 2-3°C / min and kept at that temperature for 90 min;

[0018] In the third stage, the temperature is cooled to below 60°C at a cooling rate of no more than 3°C / min.

[0019] Preferably, during the prepreg laying process, the fiber prepregs in the same layer are spliced ​​in a 45° overlap manner, the overlap width is 25±2 mm, and the interface misalignment distance in different layers is not less than 50 mm.

[0020] Preferably, the support and the hook are bonded by carbon fiber cloth paste, and the surface density of the carbon fiber cloth is 200g / m 2 The width of the pasting area is not less than 30mm and the thickness is 1.0-1.5mm.

[0021] The beneficial effects of the present invention include the following:

[0022] 1. By using carbon fiber to replace traditional aluminum alloy materials and adopting a radial and / or circumferential multi-directional ply structure design, its weight is reduced while its bending and compression resistance are improved, achieving lightweight while ensuring the product's load-bearing capacity.

[0023] 2. By utilizing the characteristics of carbon fiber materials and special manufacturing processes, including strictly controlled environmental conditions and segmented temperature rise curing processes, the product has excellent corrosion resistance and environmental adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural schematic diagram of a carbon fiber vehicle ladder in Example 1;

[0025] Figure 2 is a schematic diagram of the structure of the pedal in Example 1;

[0026] Figure 3 This is a schematic diagram of the structure of the hook in Example 1;

[0027] Figure 4 This is a schematic diagram of the structure of the ladder foot rubber pad in Example 1;

[0028] Figure numerals: 1. support; 2. pedal; 3. hook; 4. ladder foot rubber pad. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and examples, but these specific implementation schemes do not limit the protection scope of the present invention in any way.

[0030] Example 1

[0031] like Figure 1-4 As shown, the present invention discloses a carbon fiber vehicle boarding ladder and a manufacturing method thereof, including pillars 1, pedals 2, hooks 3 and ladder foot rubber pads 4, the pillars 1 are two symmetrically arranged uprights, a plurality of pedals 2 are horizontally connected between the two pillars 1 to form steps, the hooks 3 are arranged at the top of the pillars 1 for hanging and fixing, and the rubber ladder foot pads 4 are arranged at the bottom of the pillars for support. The vehicle boarding ladder of the present invention is mainly used in vehicles with strict weight requirements, such as special vehicles and other scenarios. Specifically, the pillars 1 are made of carbon fiber with a thickness of 2.6mm, and are used to bear the main load of the vehicle boarding ladder; the pedals 2 are made of carbon fiber with a thickness of 2.5mm, and a plurality of anti-slip bosses are arranged on the upper surface of the pedals 2 to enhance safety during use; the hooks 3 are made of stainless steel plates with a thickness of 4mm, and are used for fixed connection with the vehicle; the ladder foot rubber pads 4 are made of chloroprene rubber with a thickness of 28mm, and provide stable support with the ground.

[0032] The pillar 1 and the pedal 2 are both made of carbon fiber prepreg through a bag compression molding process. Specifically, the prepregs are T300-12K carbon fiber unidirectional prepreg and T300-3K twill carbon fiber prepreg. Among them, the tensile strength of T300-12K carbon fiber unidirectional prepreg is 3530MPa, the tensile modulus is 230GPa, and the elongation at break is 1.5%; the tensile strength of T300-3K twill carbon fiber prepreg is 3400MPa, the tensile modulus is 220GPa, and the elongation at break is 1.4%. The resin content is controlled at 40% ± 3%, the volatile content is not more than 0.5%, and the film weight is 150g / m 2 ±10g / m 2 The flow rate of prepreg is 15%-25%.

[0033] The ply structure of the pillar 1 and pedal 2 has been optimized and designed, using the radial + circumferential ply method of [0° / 90° / ±45°]. From outside to inside, they are: 1 layer of 200g 3K carbon fiber prepreg (0° direction), 3 layers of radial 150g unidirectional carbon fiber prepreg (90° direction), 1 layer of circumferential 150g unidirectional carbon fiber prepreg (±45° direction). After this structure is repeated three times, the outermost layer is laid with another layer of 200g 3K carbon fiber prepreg (0° direction). The 0° direction is parallel to the axial direction of the component, the 90° direction is perpendicular to the axial direction of the component, and the ±45° direction provides torsion resistance. The layers are bonded with epoxy resin adhesive, and the thickness of the adhesive layer is controlled between 0.1-0.2mm. This multi-directional ply design can ensure that the component has sufficient strength and stiffness in all directions.

[0034] During the prepreg laying process, the fiber prepregs of the same layer are spliced ​​at 45° overlap, with an overlap width of 25±2mm, and the fiber interface must not be located at the turning point of the product. The interfaces in different layers must be staggered, with a staggered distance of not less than 50mm. This design can effectively avoid stress concentration and improve the overall performance of the structure.

[0035] The pedal 2 is connected to the support 1 through a pre-buried aluminum alloy sleeve. Two connection points are arranged at both ends of each pedal 2 and are connected by M8 high-strength bolts.

[0036] The pillar 1 and the hook 3 are bonded by carbon fiber cloth pasting to form the main body of the boarding ladder. Specifically, 200g / m2 carbon fiber cloth is used in combination with epoxy resin for pasting, and the width of the pasting area is not less than 30mm and the thickness is 1.0-1.5mm. The main body of the boarding ladder is then connected and fixed to the ladder foot rubber pad 4 by an M8 stainless steel screw assembly. The screw spacing is 200±5mm, and the tightening torque is controlled at 15-18N·m. The hook 3 is set on both sides of the pillar 1, and multiple M10 high-strength bolts are set on each side of the hook 3, with a tightening torque of 25-28N·m.

[0037] The manufacturing process specifically includes the following steps: First, mold making and prepreg layering are carried out in a constant temperature and humidity environment. The ambient temperature is strictly controlled between 18-26°C, the relative humidity is 25%-65%, and the content of dust particles larger than 10μm is required to be no more than 10 / L. Mold cleaning agent (CA-130) and mold release agent (1492) are applied to the mold surface, the coating uniformity is not less than 95%, and the standing time is not less than 30 minutes. More specifically, the coating of mold cleaning agent (CA-130) and mold release agent (1492) is carried out by special spraying equipment, the spraying pressure is 0.4-0.5MPa, the nozzle is 200-250mm away from the mold surface, the spraying speed is 200mm / s, and two-way cross spraying is carried out.

[0038] After laying, vacuum bag wrapping is carried out, using nylon vacuum bag material and heat-resistant sealing strips for sealing. Vacuum compaction, the vacuum degree is required to be no less than -0.08MPa, and the time is 5-15min. Then enter the curing process, and the curing process adopts a segmented heating method: in the first stage, the temperature rises from room temperature to 90℃±5℃ at a heating rate of 2-3℃ / min, and the temperature is kept for 50-60min to allow the resin to flow fully; in the second stage, the temperature rises to 125℃±5℃ at a heating rate of 2-3℃ / min, and the temperature is kept for 90min to ensure that the resin is fully cross-linked; in the third stage, the pressure can be relieved after cooling to below 60℃ at a cooling rate of ≤3℃ / min. The vacuum degree is maintained above -0.08MPa throughout the curing process, and the curing pressure is controlled at 0.3-0.4MPa.

[0039] The main dimensional parameters of the final boarding ladder are: the height of pillar 1 is 2000mm±5mm, the wall thickness of pillar 1 is 2.6mm±0.2mm; the width of pedal 2 is 400mm±2mm, the thickness of pedal 2 is 2.5mm±0.2mm; the distance between adjacent pedals 2 is 300mm±±2mm; the height of anti-slip boss is 2mm±0.2mm; hook 3 is made of 4mm thick stainless steel plate, and the width of the load-bearing part of hook 3 is 60mm±1mm; the thickness of ladder foot rubber pad 4 is 28mm±1mm, and the bottom contact area is not less than 100cm 2 .

[0040] The working principle of the present invention: the boarding ladder is hung at the designated position of the vehicle through the hook 3, and the rubber pad 4 of the ladder foot is in contact with the ground to provide support. The anti-slip boss on the pedal 2 increases the friction to ensure the safety of users boarding the vehicle. After mechanical performance testing, under normal use conditions, the bending strength of the pillar 1 reaches 580MPa, and the compressive strength reaches 420MPa; the bending strength of the pedal 2 reaches 460MPa, and the compressive strength reaches 380MPa. When subjected to a vertical downward static load of 1.8kN, the maximum deformation of the pillar 1 does not exceed 2mm, the maximum deflection of the center of the pedal 2 does not exceed 1.5mm, and there is no permanent deformation after unloading, meeting the safety requirements for use. The shear strength at the connection between the hook 3 and the vehicle is greater than 200MPa to ensure the reliability of the connection.

[0041] Compared with the prior art, the present invention has the following significant advantages:

[0042] Carbon fiber is used to replace traditional aluminum alloy materials, and the product weight is reduced from the original 12.6kg to 8.4kg, a weight reduction of about 33.3%, and the density is reduced from 2.7g / cm 3 Reduced to 1.8g / cm 3 In actual use, an adult can easily carry and install it with one hand;

[0043] Carbon fiber itself has excellent corrosion resistance and is inert to chemical media such as acids, alkalis, and salts, and does not require additional surface treatment. After 1000 hours of salt spray test (5% NaCl solution, 35°C), there is no trace of corrosion on the surface of the product, and the mechanical property retention rate reaches more than 98%;

[0044] Through special layer design and curing process, the product has stable performance in the temperature range of -40℃ to 70℃. In low temperature environment, the impact strength of the product does not decrease by more than 5%; in high temperature environment, the stiffness of the product does not decrease by more than 8%. In actual use, after 3000 up and down cycle load tests (load 1.5kN), the product has no damage or performance degradation;

[0045] The bag-pressing molding process and multi-layer composite structure design are adopted. After 10,000 reciprocating bends, the joints of the product have no delamination or debonding, and the fatigue life is more than 50% higher than that of traditional aluminum alloy products. In actual use, after 2 years of field environment exposure test, the product appearance and performance have not shown obvious deterioration.

[0046] The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of protection of the present invention. Any innovative improvement or replacement based on the present invention shall fall within the scope of the claims of the present invention. At the same time, the various parameters, materials, and processes mentioned in the above embodiments are not exclusive. Without departing from the technical essence of the present invention, a person of ordinary skill in the art may make various alternatives, and these alternatives shall also be deemed to fall within the scope of protection of the present invention.

Claims

1. A carbon fiber boarding ladder, comprising pillars, pedals, hooks and ladder foot pads, wherein the pillars are two symmetrically arranged pillars, a plurality of pedals are transversely connected between the two pillars to form steps, the hooks are arranged at the top of the pillars for hanging and fixing, and the ladder foot pads are arranged at the bottom of the pillars for supporting, characterized in that: The pillar and the pedal are made of carbon fiber prepreg by bag compression molding. The carbon fiber prepreg includes carbon fiber unidirectional prepreg and twill carbon fiber prepreg. The layup structure of the pillar and the pedal adopts radial and / or circumferential layup method.

2. The carbon fiber vehicle ladder according to claim 1, characterized in that: The ply structure of the pillar and pedal from outside to inside is: 1 layer of 200g 3K carbon fiber prepreg, 3 layers of radial 150g unidirectional carbon fiber prepreg, 1 layer of circumferential 150g unidirectional carbon fiber prepreg. After this structure is repeated three times, a layer of 200g 3K carbon fiber prepreg is laid on the outermost layer.

3. The carbon fiber vehicle ladder according to claim 1, characterized in that: The resin content of the prepreg is 40%±3%, the volatile content is not more than 0.5%, the weight of the adhesive film is 150g / m2±10g / m2, and the adhesive flow rate is 15%-25%.

4. The carbon fiber vehicle ladder according to claim 1, characterized in that: The hooks are arranged on both sides of the pillars, and a plurality of connecting bolts are arranged on each side, and the tightening torque is 25-28N·m; the ladder foot pad is connected to the main body through a screw assembly, the screw spacing is 200±5mm, and the tightening torque is 15-18N·m.

5. A method for manufacturing the carbon fiber vehicle ladder according to any one of claims 1 to 4, characterized in that: The following steps are involved: The mold making and prepreg laying are carried out in an environment with a temperature of 18-26°C and a relative humidity of 25%-65%; Apply mold cleaning agent and mold release agent to the mold surface; Carry out vacuum bag wrapping, vacuum compaction, and the vacuum degree should not be less than -0.08MPa; The curing is carried out by adopting a staged temperature rising curing process.

6. The method according to claim 5, characterized in that: The staged temperature rise curing process comprises: In the first stage, the temperature was raised from room temperature to 90°C ± 5°C at a rate of 2-3°C / min and kept at this temperature for 50-60 minutes; In the second stage, the temperature was raised to 125°C ± 5°C at a rate of 2-3°C / min and kept at that temperature for 90 min; In the third stage, the temperature is cooled to below 60°C at a cooling rate of no more than 3°C / min.

7. The manufacturing method according to claim 5, characterized in that: During the prepreg laying process, the fiber prepregs in the same layer are spliced ​​in a 45° overlap manner, the overlap width is 25±2mm, and the interface misalignment distance in different layers is not less than 50mm.

8. The manufacturing method according to claim 5, characterized in that: The support and the hook are bonded by pasting carbon fiber cloth, the surface density of the carbon fiber cloth is 200g / m2, the width of the pasted area is not less than 30mm, and the thickness is 1.0-1.5mm.

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