Carbon-glass mixed variable-thickness equal-stress composite material plate spring and mounting and preparation method thereof
By introducing stress designs such as carbon fiber and variable thickness into the fiberglass fiber leaf spring, the problems of short life and insufficient load-bearing capacity of the existing fiberglass fiber leaf spring are solved, and higher material utilization and lower weight are achieved, and fatigue resistance and load-bearing capacity are improved.
Patent Information
- Application Number
- CN202510759059.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-09
- Publication Date
- 2025-08-29
AI Technical Summary
Existing fiberglass leaf springs have short lifespans, insufficient load-bearing capacity, and low material utilization, making it difficult to meet commercial needs.
The leaf spring design of carbon glass mixed-variable thickness is adopted. By introducing carbon fiber laying into the glass fiber composite material and adopting an equal stress change thickness configuration, combined with the mixed length clamping laying layer, a leaf spring structure with reduced thickness and uniform stress is formed.
It significantly improves the load-bearing and fatigue resistance of the leaf spring, reduces weight, extends service life, and improves material utilization.
Smart Images
Figure CN120557308A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of composite leaf springs and relates to a carbon-glass hybrid variable thickness and equal stress composite leaf spring and a method for installing and preparing the same. Background Art
[0002] Leaf springs are key components in automotive suspension systems, acting as elastic elements in the vibration system. With energy shortages and environmental pollution becoming increasingly prominent, lightweighting has become a major trend in automotive development, serving as a key measure for energy conservation and emission reduction, as well as a key driver for the promotion of new energy vehicles. Using composite materials instead of traditional steel to produce leaf springs can significantly reduce the weight of leaf spring components without compromising load-bearing capacity. Furthermore, reducing the dynamic load of unsprung masses improves the vehicle's handling stability, power, economy, and safety.
[0003] Currently used composite leaf springs are primarily made of glass fiber reinforced composite leaf springs of uniform thickness. Qian Chen et al.'s paper, "Fatigue reliability design of composite leaf springs based on plyscheme optimization," notes that existing glass fiber leaf springs experience significant damage after 80,000 fatigue cycles. The paper proposes a fatigue-resistant glass fiber leaf spring that can withstand 540,000 fatigue cycles, but its load capacity is only 18.5 kN, which is insufficient to meet actual commercial load requirements. Consequently, the service life of existing glass fiber leaf springs is poor. Furthermore, existing glass fiber leaf springs of uniform thickness have low material utilization, suggesting potential for further weight reduction.
[0004] In order to solve the above problems, a carbon-glass hybrid variable thickness equal stress composite leaf spring and a preparation method thereof are proposed. Summary of the Invention
[0005] The present invention provides a carbon-glass hybrid variable thickness equal stress composite leaf spring and a preparation method thereof. By introducing carbon fiber layers and an equal stress variable thickness configuration into the glass fiber composite, the load-bearing performance and fatigue resistance of the leaf spring are significantly improved, and the weight of the leaf spring is further reduced.
[0006] The technical solution of the present invention:
[0007] A carbon-glass hybrid variable thickness constant stress composite leaf spring has a thickness trend along its length direction from the maximum thickness in the middle to the end decreasing gradually. The maximum stress level at each section along the length direction is the same, forming an equal stress configuration.
[0008] The carbon-glass hybrid variable thickness equal stress composite material leaf spring includes multiple layers of plies of different lengths, which are arranged from top to bottom in sequence: an upper surface glass fiber long ply, a carbon fiber ply, a middle glass fiber long ply, a mixed-length sandwich ply, and a lower surface glass fiber long ply; wherein the mixed-length sandwich ply includes a short ply and a long ply; by adjusting the length and number of each ply, the thickness of the carbon-glass hybrid variable thickness equal stress composite material leaf spring is achieved by showing a quadratic curve decreasing change from the middle to the two ends, and by adjusting the number and length ratio of the long ply and the short ply, the curvature of the equal stress configuration is adapted.
[0009] The mixed-length sandwich plies include short plies and long plies, both of which have the same width and thickness. The length of the short ply is less than the length of the leaf spring, and the length of the long ply is equal to the length of the carbon-glass hybrid variable thickness equal stress composite material leaf spring. The length and number of the two satisfy that the lower surface contour of the intermediate product of the carbon-glass hybrid variable thickness equal stress composite material leaf spring formed after stacking is an equal stress configuration quadratic surface.
[0010] Each layer of mixed-length sandwich plies includes four short plies and two long plies, which are stacked in an alternating manner to form an alternating unit. The number of alternating units is 50-100 groups. The short plies are glass fiber plies with a length of 200-1560mm, and the long plies are glass fiber plies with a length the same as that of the automobile leaf spring.
[0011] Glass fiber plies are used for the upper surface glass fiber long ply, the middle glass fiber long ply, the mixed length sandwich ply and the lower surface glass fiber long ply. Carbon fiber plies are used between the upper surface glass fiber long ply and the middle glass fiber long ply arranged from top to bottom close to the surface tensile layer to reduce the stress level of the glass fiber ply.
[0012] All carbon fiber plies are long plies, located below the upper surface glass fiber long plies. More than 8 layers of middle glass fiber long plies are laid between the carbon fiber plies and the mixed length sandwich plies to reduce the risk of delamination damage.
[0013] The installation method of a carbon-glass hybrid variable thickness equal stress composite leaf spring is as follows:
[0014] The carbon-glass hybrid variable thickness equal stress composite material leaf spring is obtained by assembling, pressing, mold closing and high temperature and high pressure shaping in the order of upper surface glass fiber long ply, carbon fiber ply, middle glass fiber long ply, mixed length sandwich ply, carbon fiber ply and lower surface glass fiber long ply. The specific number of each ply should be determined according to the actual design.
[0015] The loading box is located in the middle of the carbon-glass hybrid variable thickness equal stress composite material leaf spring, with a rubber pad between the two. The loading box is connected to the rear axle of the car; the end of the carbon-glass hybrid variable thickness equal stress composite material leaf spring is punched with a hole for connecting to the coil ear, which contains a bearing inside and is connected to the car body through the bearing hole.
[0016] A method for preparing a carbon-glass hybrid variable thickness and equal stress composite leaf spring, comprising the following steps:
[0017] (1) Cutting carbon fiber prepreg and glass fiber prepreg according to the designed size to obtain prepreg tape;
[0018] (2) The prepreg tapes are divided into three groups for laying, namely:
[0019] Upper surface glass fiber long ply, middle glass fiber long ply, lower surface glass fiber long ply: each ply is composed of 8 layers of 1880mm long glass fiber prepreg tapes;
[0020] Carbon fiber layup: Each layup consists of 8 layers of 1880mm long carbon fiber prepreg tapes;
[0021] Mixed-length sandwich layup: Four short glass fiber prepreg tapes and two long glass fiber prepreg tapes are positioned in a "two short layers - long layers - two short layers - long layers" layup configuration.
[0022] After the above-mentioned groups of layers are laid, they are vacuum bagged and pressed at room temperature to form a prefabricated super layer.
[0023] (3) placing the prefabricated super layer into a forming mold in the order of upper surface glass fiber long layer, carbon fiber layer, middle glass fiber long layer, mixed length sandwich layer, carbon fiber layer and lower surface glass fiber long layer, and forming the preform by vacuum bag pressing at room temperature;
[0024] (4) The molding mold is closed and placed in a hot press to form the spring at a pressure of 8-10 MPa and a temperature of 110-130°C. After the molding is completed, the spring is cooled and demolded to obtain a finished product of a carbon-glass hybrid variable thickness and equal stress composite material leaf spring.
[0025] (5) The loading box is located in the middle of the leaf spring, with a rubber pad between the two. The loading box is connected to the rear axle of the car. The end of the leaf spring body is punched with holes and connected to the coil ear with bolts. The coil ear contains a bearing inside and is connected to the car body through the bearing hole.
[0026] Compared with the prior art, the present invention has the following beneficial effects:
[0027] The present invention provides a carbon-glass hybrid variable thickness constant stress composite leaf spring and a preparation method thereof. The constant stress design is adopted, so the leaf spring has a higher material utilization rate and a lower weight than traditional products.
[0028] The carbon fiber layup reduces the stress level of the glass fiber layup. At the same time, the sandwich layup method is adopted to achieve variable thickness of the leaf spring body, realize equal stress configuration, improve material utilization, reduce the interlayer shear force level and local stress concentration, and improve the leaf spring's resistance to delamination damage, with higher load-bearing performance and service life. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 A schematic structural diagram of a first embodiment of a carbon-glass hybrid variable thickness constant stress composite leaf spring and a method for preparing the same provided by the present invention;
[0030] Figure 2 for Figure 1 Schematic diagram of super layer layup within the mixed-length sandwich ply area shown.
[0031] In the figure: 1 upper surface glass fiber long ply; 2 carbon fiber ply; 3 middle glass fiber long ply; 4 mixed length sandwich ply; 5 lower surface glass fiber long ply; 6 loading box upper ply; 7 loading box upper rubber pad; 8 loading box lower rubber pad; 9 loading box lower ply; 10 loading box pin; 11 rear roll ear; 12 rear roll ear bottom plate; 13 bearing; 14 front roll ear; 15 front roll ear bottom plate. DETAILED DESCRIPTION
[0032] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.
[0033] Example 1
[0034] Carbon glass hybrid variable thickness stress composite leaf spring structure such as Figure 1 shown.
[0035] The leaf spring body is comprised of a long glass fiber laminate 1 on the upper surface, a carbon fiber laminate 2, a middle glass fiber laminate 3, a mixed-length sandwich laminate 4, and a long glass fiber laminate 5 on the lower surface. The middle sections of the leaf spring's upper and lower surfaces, where they contact the upper and lower rubber pads 7 and 8 of the loading box, are straight. The ends of the leaf spring's upper and lower surfaces, where they contact the rear ear 11, rear ear base 12, front ear 14, and front ear base 15, are straight. The remaining sections are curved.
[0036] There is an intermediate glass fiber long ply 3 with a thickness of 2 mm and the same length as the leaf spring between the mixed-length sandwich ply 4 and the carbon fiber ply 2 to improve the anti-delamination failure performance.
[0037] The position and thickness of the carbon fiber layer 2 can be adjusted and increased or decreased according to the stiffness requirements of the finished product.
[0038] The loading box is located in the middle of the leaf spring without curvature. Its upper rubber pad 7 and lower rubber pad 8 protect the leaf spring from extrusion failure and friction damage. The loading box and the leaf spring are fixed by the tightening force generated by the bolts when the leaf spring is connected to the rear axle of the vehicle.
[0039] The leaf spring body has through-holes at its ends that correspond to holes in the rear ear 11, rear ear base plate 12, front ear 14, and front ear base plate 15. The leaf spring body is connected to the aforementioned structure via bolts and nuts. The leaf spring assembly is connected to the vehicle body via bearings 13 and to the axle via the upper and lower clamping plates 6 and 9 of the loading box.
[0040] The loading box pin 10 limits the relative movement between the loading box upper rubber pad 7 and the loading box upper clamping plate 6.
[0041] The detailed preparation method of the carbon-glass hybrid variable thickness constant stress composite leaf spring in this embodiment includes the following steps:
[0042] (1) The carbon fiber prepreg and glass fiber prepreg were cut according to the designed dimensions to obtain prepreg tapes, including 6 carbon fiber prepreg tapes, 102 glass fiber long-ply prepreg tapes, and 144 glass fiber short-ply prepreg tapes. The thickness of the carbon fiber prepreg tapes was 0.25 mm, and the thickness of the glass fiber prepreg tapes was 0.25 mm. The dimensions of the carbon fiber prepreg tapes and the glass fiber long-ply prepreg tapes were 1880 mm*80 mm. To ensure the isostress configuration of the leaf spring, the thickness of the leaf spring should have a quadratic relationship with the distance along the length of the leaf spring, and decrease from the middle to the ends. The specific implementation scheme is to use a step size of 1mm, and draw the intersection of a curve with the same side curvature as the upper surface of the leaf spring and the side curve of the lower surface of the leaf spring with isostress configuration along the thickness direction. The distance between the two intersection points along the curve with the same side curvature of the upper surface of the leaf spring is the length of the glass fiber short-ply prepreg tape at that location. By laying the glass fiber short-ply prepreg tape in the corresponding position, the lower surface contour of the intermediate product of the carbon-glass hybrid variable thickness isostress composite leaf spring formed after stacking can be a quadratic surface with isostress configuration. In this embodiment, the width of the glass fiber short-ply prepreg tape is 80mm, the length range is 200mm-1560mm, and the length step range is 20mm-50mm. As the length decreases, the step size gradually increases. The fiber direction of the prepreg tape is 0°.
[0043] (2) The prepreg tapes are laid in groups, including long layers on the upper and lower surfaces of the leaf spring, carbon fiber layers, and mixed-length sandwich layers. The long layers on the upper surface of the leaf spring, the long layers on the lower surface of the leaf spring, and the carbon fiber layers are each a group of super layers. Figure 2As shown, each set of mixed-length sandwich plies consists of four short plies and two long plies of the same length as the leaf spring, in the order of "two short plies - long ply - two short plies - long ply." Vacuum bagging at room temperature for 30 minutes yielded 42 prefabricated superlayers, including one set of upper surface long glass fiber plies, two sets of lower surface long glass fiber plies, one set of middle long glass fiber plies, one set of carbon fiber plies, and 37 sets of mixed-length sandwich plies, including 37 combinations of plies of varying lengths.
[0044] (3) The prefabricated super layer is placed in a forming mold, and 14 groups of prefabricated super layers are laid each time, and vacuum bag pressing is performed at room temperature for 30 minutes. The first time, one group of upper surface glass fiber long plies, one group of carbon fiber plies, one group of middle glass fiber long plies, and 11 groups of mixed length sandwich plies are laid, and the order is upper surface glass fiber long plies, carbon fiber plies, middle glass fiber long plies, and mixed length sandwich plies. The laying order of the mixed length sandwich plies is from long to short according to the length of the sandwich short plies. The second time, 14 layers of mixed length sandwich plies are laid, and the laying order is from long to short according to the length of the sandwich short plies. The third time, 12 layers of mixed length sandwich plies and 2 layers of lower surface glass fiber long plies are laid, and the laying order is mixed length sandwich plies, lower surface glass fiber long plies. The laying order of the mixed length sandwich plies is from long to short according to the length of the sandwich short plies. After 42 sets of prefabricated super layers were laid and vacuum bag pressed at room temperature for 30 minutes, the prefabricated body was obtained.
[0045] (4) Close the mold, place it in a hot press, pressurize it to 3 MPa, and slowly heat it to 80°C. After the internal temperature of the mold reaches 80°C, pressurize it to 10 MPa and keep it warm. During this period, adjust the mold gap to the designed range to ensure the geometric parameters of the finished leaf spring and discharge excess resin. When the mold gap is less than 1 mm, maintain the pressure of 10 MPa and increase the temperature to 120 degrees Celsius, the resin curing temperature, until the resin is completely cured. After 90 minutes of molding, cool the mold to below 35°C at room temperature and demold it to obtain the leaf spring blank.
[0046] (5) After the resin overflowing from the edge of the leaf spring blank is polished away by machining, the main body of the carbon-glass hybrid variable thickness equal stress composite leaf spring is obtained. The thickness of the carbon-glass hybrid variable thickness equal stress composite leaf spring is 62.25mm in the middle and 25.25mm at both ends, the radius of curvature is 5000mm, and the arc height is 113mm. After the mounting holes are machined at the ends, the loading box upper clamping plate 6, loading box upper rubber pad 7, loading box lower rubber pad 8, loading box lower clamping plate 9, loading box pin 10 are installed on the flat part in the center of the leaf spring in conjunction with the leaf spring surface. The rear ear 11, rear ear bottom plate 12, bearing 13, front ear 14, front ear bottom plate 15 and other accessories are installed at the ends to obtain the leaf spring assembly. The materials of the loading box upper splint 6, the loading box lower splint 9, the loading box pin 10, the rear rolled ear 11, the rear rolled ear bottom plate 12, the bearing 13, the front rolled ear 14, and the front rolled ear bottom plate 15 are steel, and the loading box upper rubber pad 7 and the loading box lower rubber pad 8 are rubber.
[0047] The carbon-glass hybrid variable-thickness, isostress-resistant composite leaf spring manufactured using this method exhibits excellent surface quality and is free of noticeable defects. The leaf spring weighs 22 kg, less than existing conventional products. After testing under a three-point bending load of 70 kN, twice the full load, and 480,000 fatigue cycles, the leaf spring showed no noticeable defects, demonstrating higher material utilization, increased load-bearing performance, and improved service life.
[0048] The above are embodiments of the present invention and are not intended to limit the scope of the present invention. Any equivalent structure or equivalent form and all variations produced by modifications or alterations made by professionals in this field to the present invention are included in the scope of the present invention.
Claims
1. A carbon-glass hybrid variable thickness equal stress composite leaf spring, characterized in that: The thickness of the carbon-glass hybrid variable thickness equal stress composite leaf spring along the length direction changes from the maximum thickness in the middle to the end, and the maximum stress level of each section along the length direction is the same, forming an equal stress configuration.
2. The carbon-glass hybrid variable thickness constant stress composite leaf spring according to claim 1, characterized in that: The carbon-glass hybrid variable thickness equal stress composite material leaf spring includes multiple layers of plies of different lengths, which are arranged from top to bottom in sequence: an upper surface glass fiber long ply, a carbon fiber ply, a middle glass fiber long ply, a mixed-length sandwich ply, and a lower surface glass fiber long ply; wherein the mixed-length sandwich ply includes a short ply and a long ply; by adjusting the length and number of each ply, the thickness of the carbon-glass hybrid variable thickness equal stress composite material leaf spring is achieved by showing a quadratic curve decreasing change from the middle to the two ends, and by adjusting the number and length ratio of the long ply and the short ply, the curvature of the equal stress configuration is adapted.
3. The carbon-glass hybrid variable thickness constant stress composite leaf spring according to claim 2, characterized in that: The mixed-length sandwich ply includes a short ply and a long ply, both of which have the same width and thickness. The length of the short ply is less than the length of the leaf spring, and the length of the long ply is equal to the length of the carbon-glass hybrid variable thickness equal stress composite material leaf spring. The length and quantity of the two plies satisfy that the lower surface contour of the intermediate product of the carbon-glass hybrid variable thickness equal stress composite material leaf spring formed after stacking is an equal stress configuration quadratic surface.
4. The carbon-glass hybrid variable thickness constant stress composite leaf spring according to claim 3, characterized in that: Each layer of mixed-length sandwich plies includes four short plies and two long plies, which are stacked in an alternating manner to form an alternating unit. The number of alternating units is 50-100 groups. The short plies are glass fiber plies with a length of 200-1560mm, and the long plies are glass fiber plies with a length the same as that of the automobile leaf spring.
5. The carbon-glass hybrid variable thickness constant stress composite leaf spring according to claim 2, characterized in that: Glass fiber plies are used for the upper surface glass fiber long ply, the middle glass fiber long ply, the mixed length sandwich ply and the lower surface glass fiber long ply. Carbon fiber plies are used between the upper surface glass fiber long ply and the middle glass fiber long ply arranged from top to bottom close to the surface tensile layer to reduce the stress level of the glass fiber ply.
6. The carbon-glass hybrid variable thickness constant stress composite leaf spring according to claim 2, characterized in that: The carbon fiber plies are all long plies, which are located below the upper surface glass fiber long plies. More than 8 layers of middle glass fiber long plies are laid between the carbon fiber plies and the mixed length sandwich plies to reduce the risk of delamination damage.
7. A method for installing the carbon-glass hybrid variable thickness constant stress composite leaf spring according to any one of claims 1 to 6, characterized in that: Here are the steps: The carbon-glass hybrid variable thickness equal stress composite leaf spring is obtained by assembling, pressing, closing the mold and finalizing the shape under high temperature and high pressure in the order of upper surface glass fiber long layer, carbon fiber layer, middle glass fiber long layer, mixed length sandwich layer, carbon fiber layer and lower surface glass fiber long layer. The specific number of each layer should be determined according to the actual design. The loading box is located in the middle of the carbon-glass hybrid variable thickness equal stress composite material leaf spring, with a rubber pad between the two. The loading box is connected to the rear axle of the car; the end of the carbon-glass hybrid variable thickness equal stress composite material leaf spring is punched with a hole for connecting to the coil ear, which contains a bearing inside and is connected to the car body through the bearing hole.
8. A method for preparing a carbon-glass hybrid variable thickness constant stress composite leaf spring according to any one of claims 1 to 6, characterized in that: Here are the steps: (1) Cutting carbon fiber prepreg and glass fiber prepreg according to the designed size to obtain prepreg tape; (2) The prepreg tapes are divided into three groups for laying, namely: Upper surface glass fiber long ply, middle glass fiber long ply, lower surface glass fiber long ply: each ply is composed of 8 layers of 1880mm long glass fiber prepreg tapes; Carbon fiber layup: Each layup consists of 8 layers of 1880mm long carbon fiber prepreg tapes; Mixed-length sandwich layup: Four short glass fiber prepreg tapes and two long glass fiber prepreg tapes are positioned in a "two short layers - long layer - two short layers - long layer" layup configuration. After the above-mentioned groups of layers are laid, they are vacuum bagged and pressed at room temperature to form a prefabricated super layer; (3) placing the prefabricated super layer into a forming mold in the order of upper surface glass fiber long layer, carbon fiber layer, middle glass fiber long layer, mixed length sandwich layer, carbon fiber layer and lower surface glass fiber long layer, and forming the preform by vacuum bag pressing at room temperature; (4) The forming mold is closed and placed in a hot press to form the spring at a pressure of 8-10 MPa and a temperature of 110-130°C. After the forming is completed, the spring is cooled and demolded to obtain a finished carbon-glass hybrid variable thickness and equal stress composite material leaf spring; (5) The loading box is located in the middle of the carbon-glass hybrid variable thickness equal stress composite material leaf spring, with a rubber pad between the two. The loading box is connected to the rear axle of the car. The end of the carbon-glass hybrid variable thickness equal stress composite material leaf spring is punched with a hole for connection with the coil ear. The coil ear contains a bearing inside and is connected to the car body through the bearing hole.