Study on the punching characteristics of corrugated board liners

[Abstract] This paper briefly describes the structure of common corrugated board liners and analyzes and compares the cushioning characteristics of several typical liners. Studying the cushioning properties of corrugated board and promoting the use of corrugated board liners are conducive to environmental protection, recycling, and cost reduction.
Key words Corrugated cardboard cushion structure Buffering characteristics 1 Structure of commonly used corrugated cardboard liners Packages are often affected by external shocks, vibrations, and pressure during the process of handling, transportation, storage, and other circulation. In order to effectively protect the goods from damage, the products need to be buffered and shockproofed. In the transport packaging, replacing the foam with a pad of paper as a cushioning material is not only beneficial to environmental protection but also recycling and reducing costs. Corrugated board liner not only can block the product in the container, but also absorbs energy when the product is subjected to external impact, prolongs the action time of the inner product to withstand the impact pulse, and has good cushioning performance.
For different product types and shape features, reasonable buffer materials and structural forms should be selected to ensure optimal buffering effect. Common corrugated board liners are of the elastic type, folded type, snap-type and angular type.
2 The cushioning performance of corrugated board liners provides reasonable cushioning and shockproof packaging for the product, which is the key to ensure that the product is not damaged during the circulation process; selecting buffer materials and determining the structure and size of the cushion are the main contents of the buffer packaging design. . Static compression test, impact test and vibration characteristic test are performed on the buffer material, and the mechanical properties of different liner structures are tested and analyzed to provide a theoretical basis for the design of the cushion liner. For example, under the effect of compressive load, the compression amount of the corrugated board liner is measured, the load-deformation curve is given, the bearing capacity and the elastic constant of the liner are determined, and under the impact load, the dynamic performance of the liner is tested and the acceleration is plotted. - Static stress curve.
The purpose of the impact test is to understand the cushioning properties of the liner, to determine the impact load on the interior product, and the associated peak accelerations, speed changes, and impact time. The impact characteristics of typical corrugated board liners were tested on an MTS impact tester, the transfer characteristics of the liners at non-drop heights were analyzed, and the thickness and load bearing area of ​​the liners used were determined.
Corrugated board cushioning effect can be described by peak acceleration (G), speed change (Δυ) and impact time (T):
Δυ=∫ioGdt
The smaller the speed change Δυ is, the better the buffering effect of the corrugated cardboard is. When the speed change Δυ is constant, the longer the impact action time T is, the smaller the peak acceleration G is.
The test impact acceleration is 150G, and the corrugated cardboard sample is BC type. If the horizontal rebound structure cushion liner is adopted, the maximum peak acceleration measured is 58G and the impact action time is 7.8ms; when it is in the middle of this kind of transverse collapsible liner With a buffer window, the maximum peak acceleration measured is only half that of the original structure, the impact action time is 2 times that of the original structure, and the deformation of the spacer is more than 3 times that of the original structure, indicating that this kind of lateral bomb with a buffer window The folded structure has a high recovery energy.
If a cushioning material with a parallel spring-folded structure is used, although it has a good cushioning property, at a small natural frequency, resonance phenomenon is easily generated, so that unstressed corrugated cardboard is damaged when it is impacted twice. Therefore, this pad is commonly used as a force pad to protect the inner product from horizontal impact.
It can be seen from the test results that cushioning structures (e) and (f) have lower cushioning performance than cushion structures (b) and (c).
3 Cushioning performance comparison The packaging simulant is buffered and packaged. The outer packaging container and the cushioning liner are made of double-sided C-type single corrugated cardboard. The basis weight of the paper and corrugated medium is 205g/m2 and 127g/m2, respectively. Bonded with a water-resistant adhesive, the corrugated board has a burst resistance of 1379 kPa. According to the requirements of the test sample temperature and humidity preconditioning, record the test site temperature and humidity. On the drop test machine, a free plane drop test was performed on the package simulant from a height of 610 mm, and three replicates of each package size, weight and pad combination were performed. During the test, the acceleration-time recorded by the piezoresistive accelerometer placed at the center of gravity of the package simulant is converted into a digital quantity, stored and recorded on a disk, and processed by a computer to obtain a smooth impact acceleration-time curve. The relationship between the acceleration peak and the static stress is derived from this, and a packing simulant with a size of 179 mm×179 mm×179 mm is taken as an example to illustrate the buffering performance when using different cushion structures.
The elastic liner is formed by breaking the paper surface on the corrugated cardboard and folding it back. The static stress is the weight of the packaged product divided by the actual contact area between the product and the liner. During the test, when the structural liners (each with a size of 179 mm×180 mm) were measured, the packaged products were subjected to impact acceleration and time. From the curves, it can be seen that as the thickness of the liner increases, the peak acceleration of the trough decreases, and the static stress increases, which means that the number of flexion of the elastic liner increases, and the buffering effect also increases.
Folding liners consist of a cardboard panel surface and a column unit with a non-loaded space. The static stress is the weight of the packaged product divided by the total top surface area of ​​the folding liner. During the test, the impact acceleration and time of the packaging product were measured when the structural liner (size 170 mm×179 mm×35 mm) was used. The curves show that the load carrying capacity (buffering performance) of the folding pad with the same size and different structure depends on the number and position of the pad cylinders. In general, the stiffness of the liner plane increases as the size decreases. Therefore, with the same liner structure, a smaller liner size can accommodate higher static stress loads.
The choice of gasket structure type should be based on the product's brittleness. Under normal circumstances, in order to give full play to the cushioning ability of the cushion, the elastic cushion should be selected for the low load (the product is lighter); the folding cushion should be selected for the high load (heavy product).