Defects in Flatness of Metal Plates and Performance Differences Between Aluminum Panels and Aluminum Composite Panels
2026-01-09
Defects in Flatness of Metal Plates and Performance Differences Between Aluminum Panels and Aluminum Composite Panels
The unevenness of metal plates is mainly manifested in obvious wave - like deformation on the surface, accompanied by local bulges, depressions, warping and even distortion in some cases.
The difference in flatness between aluminum panels and aluminum composite panels stems from the disparities in their material structures, production processes and mechanical properties. Meanwhile, various factors in engineering applications also exert a significant impact on their flatness performance.
Impact of Material Structure
Aluminum panels adopt a single homogeneous structure, which are rolled from pure aluminum or aluminum alloy. The internal atomic arrangement of aluminum panels is stable, but they lack a stress - balancing mechanism. Once stress concentration occurs, deformation is prone to happen.
Aluminum composite panels feature a sandwich structure of "face sheet - core material - face sheet", with two layers of aluminum sheets symmetrically distributed. The core material in the middle not only plays a supporting role but also buffers stress, forming a natural stress - balancing system. It can effectively offset the deformation force from the outside world, thus better maintaining the surface flatness.
Impact of Production Process
Aluminum panels are produced through a rolling process. During the rolling of thin aluminum panels, if the rolling force is uneven or there are differences in cooling speed, internal residual stress is highly likely to occur, ultimately leading to subsequent warping deformation. Although thick aluminum panels have higher rigidity, they are relatively heavy, and deflection deformation may occur due to their own weight after installation.
The production of aluminum composite panels requires a high - temperature pressing process. Part of the internal stress is released during the lamination process. In addition, the symmetrical production process greatly reduces the risk of deformation on one side of the panel, so the overall flatness is more stable.
Impact of Thermal Stability
Aluminum panels have a relatively high coefficient of thermal expansion. When the temperature changes, thin aluminum panels are prone to wave - like deformation. The deformation range of thick aluminum panels is relatively small, but local temperature differences may still cause unevenness on the panel surface.
There is a difference in the coefficient of thermal expansion between the core material and the face sheet of aluminum composite panels. When the temperature changes, the two form a "constraint effect", which restricts the excessive expansion or contraction of the face sheet. At the same time, the elastic deformation of the core material can buffer the temperature stress and achieve dynamic balance. Therefore, aluminum composite panels show more stable flatness performance in environments with temperature fluctuations.
Impact of Mechanical Properties
Thin aluminum panels have poor rigidity and are prone to permanent deformation when subjected to external forces. Thick aluminum panels have higher bending strength, but they are relatively heavy. If the supporting points are unevenly distributed during installation, deformation will still occur.
Aluminum composite panels, on the other hand, have both the characteristics of light weight and high strength. Under the condition of the same thickness, their weight is only 1/3 to 1/2 of that of aluminum panels, while their bending strength can be increased by 2 - 3 times. They are not easy to deform when subjected to external forces, and have lower requirements for installation supporting points, so the flatness after installation is more durable.
In addition to the inherent properties of the materials, the following engineering factors also significantly affect the flatness of the plates:
Selection of Material and Thickness
For aluminum panels, 3 - series or 5 - series aluminum alloy materials should be preferred, and pure aluminum with low strength and easy deformation should be avoided. The thickness of the plates should be determined in strict accordance with the specification requirements and load standards. For example, the thickness of large - sized exterior wall aluminum panels should not be less than 3.0mm to ensure sufficient rigidity.
For aluminum composite panels used in building exterior walls, the thickness of the face sheet and back sheet of aluminum alloy should reach 0.5mm, and the thickness tolerance must comply with the relevant national standards.
Design of Facade Division
Excessively large facade division sizes (such as the application of ultra - wide plates) will aggravate the flatness problem of aluminum panels, while aluminum composite panels or aluminum honeycomb panels are more suitable for curtain wall projects with large - sized division.
If large - sized division design has to be adopted, it is necessary to fully consider the displacement space required for the release of temperature stress, scientifically set the width of plate joints, and reserve sufficient deformation allowance.
Design of Stiffeners and Flanges
Reasonable arrangement of stiffeners is the key to improving the rigidity of the plates. Stiffeners should be arranged along the long side of the plates. If necessary, the number of stiffeners can be increased or steel stiffeners can be used, and the design scheme without stiffeners should be eliminated. In addition, stiffeners and plate flanges should be firmly connected to form an integral stress - bearing structure and improve the overall rigidity.
Insufficient flange height will directly weaken the edge strength of the plates. It is recommended to appropriately increase the flange height and match it with a large - rigidity frame to construct a prestressed structure, further enhancing the surface flatness.
The minimum size of the plate flange should be controlled at 25mm or more, and for large - division panels, the minimum size of the flange is recommended to be no less than 30mm.
Flatness of Keel System
The flatness of the keel system itself directly determines the final installation effect of the aluminum plates. If the keel is installed unevenly, local bulges and depressions will inevitably occur after the aluminum plates are installed. Therefore, the installation accuracy of the keel must be ensured during construction.
During the keel installation process, precision measuring instruments should be used for leveling operations to control the installation deviation within the range allowed by the specifications. The wrong construction concept of "adjusting the keel with plates" is strictly prohibited.
In summary, due to the advantages of its composite structure, aluminum composite panels are generally superior to aluminum panels in terms of flatness, stability and construction friendliness, and are especially suitable for large - area decoration projects such as building curtain walls. For aluminum panels, their shortcomings in flatness can be compensated by optimizing material selection, increasing plate thickness, improving stiffener design and other methods. In actual engineering material selection, comprehensive consideration should be given according to the specific requirements of the project.
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