Stress analysis of aluminum-plastic composite panel folding edges in metal curtain walls

Views:81 Author:Site Editor Publish Time:2026-09-14 16:47:09 Orgin:Site

share

1、Preface

Metal curtain wall is another new type of curtain wall structure developed after glass curtain wall. Metal curtain wall is often used together with glass curtain wall in the same building. Usually, glass curtain walls are used for the transparent parts of buildings, while metal curtain walls are used for the opaque parts. Due to the excellent processing performance, diverse colors, and good safety of metal panels (such as aluminum-plastic composite panels, aluminum veneers, honeycomb aluminum panels, sandwich insulation aluminum panels, etc.), they can fully adapt to various complex design shapes, and can freely add concave and convex lines, as well as process various types of curved lines. Therefore, metal curtain walls, as a highly impactful architectural form, provide architects with huge room for expression and are highly favored. Large scale metal plate surfaces are widely used in engineering, and reasonable stress calculations are required to ensure the flatness of the metal plate surfaces. There is relatively little research on the stress distribution at the folded edge of aluminum-plastic composite panels in metal curtain walls in China. This article uses finite element method to analyze the stress distribution around the folded edge of aluminum-plastic composite panels, and provides reasonable suggestions for the stress analysis of metal curtain walls.

2、Aluminum plastic composite panel folding form

2.1Aluminum-plastic composite panel

Aluminum plastic composite panel is made by rolling and heat sealing a 3mm~4mm thick layer of polyethylene (PE or polyvinyl chloride PVC) sandwiched between two layers of 0.5mm pure aluminum panels. The fluorocarbon paint on the surface of the external composite aluminum plate is also completed by rolling, pressing, and heat sealing in one go. The thickness of the coating is generally around 20um. The advantages of the composite aluminum plate are light weight, smooth surface, good flatness, no color difference in the same direction, and excellent on-site processability. It provides conditions for handling external wall size changes caused by on-site construction errors, reducing workshop processing cycles, and shortening installation periods.

2.2Aluminum plastic composite panel folding

Aluminum plastic composite panels can generally be slotted with V-shaped grooves, U-shaped grooves, etc. Several typical slotting methods are shown in Figure 1. When cutting aluminum-plastic composite panels, the size of the folded edges should be considered, usually adding about 25mm on each side. The cut composite panel needs to be grooved on all four sides, that is, cutting off a certain width of the inner aluminum plate and plastic layer. The groove depth must be strictly controlled to retain at least 0.3mm thick plastic core material behind the front aluminum plate to ensure that the aluminum-plastic composite panel has sufficient toughness and prevent the aluminum skin at the folded edge from breaking. Then, the folded edge is formed into a 90 ° angle. In this way, the self weight of the panel and the positive and negative wind load pressure that the curtain wall will be subjected to at any time are borne by the four 0.5mm aluminum plates. Therefore, the slotted and folded edge is the weakest link of the aluminum-plastic composite panel panel and the first part to be damaged under wind load.

2.3Aluminum plastic composite panel folding reinforcement

Aluminum plastic composite panels generally increase their stiffness by folding around the edges, and can also prevent the core material of the aluminum-plastic composite panel from being exposed to the atmosphere. The folded edges of aluminum-plastic composite panels can be reinforced with frames as needed. Aluminum corner brackets should not be used as frames for aluminum-plastic composite panel curtain wall panels, and aluminum profiles should be used as reinforced frames. Strengthening the frame can be achieved by using metal square tubes, groove shapes, and corner shapes, which should be reliably connected to the panel and have anti-corrosion measures. The connection between the frame and the folded edge of the aluminum-plastic composite panel can use aluminum rivets, and the connection should meet the requirements of force transmission and be reliably connected.

In practical engineering, the treatment of the folded edge of aluminum-plastic composite panels can be divided into the following two forms: ① reinforced frames can be set as needed; ② No reinforced border has been set. The form of no reinforced frame at the folded edge of aluminum-plastic composite panel is the most unfavorable for stress. The processing form of the folded edge of the aluminum-plastic composite panel in this article is that no reinforced frame is set.

3、Study on the stress of aluminum-plastic composite panel

3.1Basic bearing characteristics

The metal plate in the metal curtain wall needs to withstand various loads, including self weight, wind load, rain and snow load, earthquake load, construction load, temperature change, support displacement, and live load. And its forms of action can be divided into two categories: actions perpendicular to the surface of the metal plate and actions parallel to the surface of the metal plate. The action perpendicular to the surface of the plate causes the metal plate to bend, collectively known as out of plane action or out of plane load; The action parallel to the surface of the plate will cause shear failure of the metal plate, collectively known as in-plane action or in-plane shear force. In general, wind load plays a controlling role in building curtain walls. The curtain wall panel itself must have sufficient load-bearing capacity to avoid breakage or detachment under wind loads. This article mainly considers wind loads perpendicular to the surface of the plate.

3.2 Calculation Formula

3.2.1Fixed form of aluminum-plastic composite panel

The mechanical properties of aluminum-plastic composite panels mainly come from the two-layer aluminum plates, and the thickness of the aluminum plates has a significant impact on their mechanical properties. The plastic composite panel adopts 4mm, with a panel thickness of 0.5mm. The aluminum-plastic composite panel is folded around the edges and fixed with aluminum corner codes. There are two options: with and without reinforced frames. After the aluminum-plastic composite panel is fixed, the periphery of the panel can rotate, so it can be considered as a simply supported edge when calculating.

3.2.2Stress Calculation

The standard value of maximum bending stress under wind load perpendicular to the aluminum-plastic composite panel can be calculated using finite element method considering geometric nonlinearity. It can also be calculated separately according to the following formulas:

In the formula:

θ-parameter;

σwk--standard value of maximum bending stress in the plate generated by wind load (N/mm2);

wk--standard value of wind load (N/mm2);

I--Calculation edge length of aluminum-plastic composite panel grid (mm);

E--Elastic modulus of aluminum-plastic composite panel (N/mm2);

m-Bending moment coefficient of aluminum-plastic composite panel;

t-Thickness of aluminum-plastic composite panel (mm);

η--Reduction coefficient.

3.2.3Deflection Calculation

In the formula:

df--Maximum deflection under wind load standard value (mm);

wk--Wind load standard value (N/mm2);

I--Calculation edge length of aluminum-plastic composite panel grid (mm);

μ--Deflection coefficient;

D--Stiffness of aluminum-plastic composite panel (N · mm);

η--reduction factor

3.2.4Load calculation

The load acting on the aluminum-plastic composite panel can be transmitted to the edge ribs in a triangular or trapezoidal distribution. When calculating the edge ribs, it can be converted into an equivalent uniformly distributed load according to the principle of equal bending moment (see Figure 2)

4、Finite element analysis of aluminum-plastic composite panel

4.1Model size

The standard plate adopts 1000mmx1600mm, and the uniformly distributed load on the surface of the plate is 1.0x10-3N/mm2 (see Figure 3).

4.2Model Overview

This article takes the design of an aluminum-plastic composite panel in a certain project in Taiyuan as an example, and uses the internationally renowned finite element analysis software - ANSYS to establish a model. During the simulation of the aluminum-plastic composite panel, some simplifications were adopted, such as subtracting the aluminum corner code and fixing the position around a certain length of the folded edge. The aluminum-plastic composite panel was modeled using Shell elements (see Table 1), and regular distributed elements were generated through Mapping over a large area of the panel surface. The panel at the folded edge was an aluminum plate with a thickness of 0.5mm and a folded edge radius of R (see Figure 4).

4.3Finite element analysis without reinforced borders

When the folding radius R=1.5mm, the standard plate adopts 1000mmx1600mm, and the uniformly distributed load on the surface of the plate is taken as 1.0x10-3N/mm2 (see Figure 5).

Theoretical calculation results: The maximum bending stress standard value of the aluminum-plastic composite panel surface is 32.61N/mm2, and the maximum deflection value is 36.54mm. The finite element analysis results show that the maximum deflection value is 61.227mm (see Figure 6), the maximum bending stress standard value of the aluminum-plastic composite panel surface is 24.607N/mm2 (see Figure 7), and the maximum bending stress standard value of the aluminum-plastic composite panel surface at the folded edge is 437.973N/mm2 (see Figure 8). The calculation results show that the maximum bending stress standard value of the overall aluminum-plastic composite panel appears at the folded edge, that is, the midpoint of the long side near the fixed position of the aluminum corner code. The maximum bending stress standard value in the panel surface appears near the center of the panel, and the maximum deflection value appears near the center of the panel.

When the folding radius R is 2.0mm, the standard plate (see Figure 9) adopts 1000mmx1600mm, and the uniformly distributed load on the surface of the plate is taken as 1.0x10-3N/mm2

Theoretical calculation results: The standard value of the maximum flexural stress of the aluminum-plastic composite panel surface is 32.61N/mm2, and the maximum deflection is 36.54mm

The finite element analysis results show that the maximum deflection is 60.85mm (see Figure 10), the standard value of the maximum bending stress on the aluminum-plastic composite panel surface is 24.506N/mm2 (see Figure 11), and the standard value of the maximum bending stress on the folded edge of the aluminum-plastic composite panel surface is 452.784N/mm2 (see Figure 12)

The calculation results show that the maximum bending stress standard value of the overall aluminum-plastic composite panel appears at the folded edge, that is, the midpoint of the long side near the fixed position of the aluminum corner code. The maximum bending stress standard value in the panel surface appears near the center of the panel, and the maximum deflection value appears near the center of the panel.

When the folding radius R is 2.5mm, the standard plate (see Figure 13) adopts 1000mmx1600mm, and the uniformly distributed load on the surface of the plate is taken as 1.0x10-3N/mm2

Theoretical calculation results: The maximum bending stress standard value of aluminum-plastic composite panel surface is 32.61N/mm2, and the maximum deflection value is 36.54mm

The finite element analysis results show that the maximum deflection is 60.441mm (see Figure 14), the standard value of the maximum bending stress on the aluminum-plastic composite panel surface is 24.396N/mm2 (see Figure 15), and the standard value of the maximum bending stress on the folded edge of the aluminum-plastic composite panel surface is 469.242N/mm2 (see Figure 16)

The calculation results show that the maximum bending stress standard value of the overall aluminum-plastic composite panel appears at the folded edge, that is, the midpoint of the long side near the fixed position of the aluminum corner code. The maximum bending stress standard value in the panel surface appears near the center of the panel, and the maximum deflection value appears near the center of the panel.

5Conclusion

5.1Comparison of theoretical calculations and finite element analysis results. The results obtained through two methods show that the difference between the maximum bending stress standard value of the aluminum-plastic composite panel surface and the maximum deflection standard value is about 25% and 68%, respectively. The large difference is related to the fixed quantity and position of the aluminum corner brackets.

5.2The comparison of the folding radius in section 5.2 can be obtained through three finite element methods, and the results show that the maximum deflection and the standard value of the maximum bending stress on the aluminum-plastic composite panel surface change very little; The standard value of the maximum bending stress at the edge of aluminum-plastic composite panels increases with the increase of the edge radius R, with a difference of about 3.5%.

The above analysis of the stress at the folded edge of aluminum-plastic composite panels in metal curtain walls provides a reference for the design of metal curtain walls.