Static Strength of Particleboard and Fiberboard

Static Strength of Particleboard and Fiberboard

Static bending strength is a necessary test item for particleboard and fiberboard. The static bending strength of particleboard and fiberboard refers to the ability of the board to resist damage under static bending load. The determination of static bending strength was carried out on a wood universal testing machine. The calculation formulas are as follows:

In the formula, _ – the static bending strength (MPa) of the specimens;

Failure load (N) of P-specimens;

The distance between supports (mm) during L-test;

B-width of specimen (mm);

H-thickness of specimen (mm).

Schematic diagram of static strength test

1. Specimens 2. Bearings

In most cases, particleboard and fiberboard will bear static load. Whether they are used as horizontal parts or vertical parts, as long as they bear load, they will produce bending stress. Therefore, particleboard and fiberboard must have sufficient bending resistance. It can be seen that the static bending strength is an important mechanical property index.

The static bending strength of particleboard and fiberboard is not only related to density, raw material form and sizing amount, but also to moisture content, structure and pressure mode of the board. The greater the density of particleboard and fiberboard, the closer the contact between the raw materials in the board, the stronger the resistance to damage, and the higher the static bending strength. Within a certain limit, the static bending strength of the sheet increases with the increase of the length of the raw material and decreases with the increase of the width of the raw material. For particleboard, the fibers of high-quality particleboard are relatively complete, the thickness is the same, there is good contact surface between particles, and there is strong bonding force between particles after hot pressing. Under the same conditions, the static bending strength of board made of high-quality particleboard is higher than that of board made of low-quality particleboard. The static bending strength of particleboard and fiberboard will increase with the increase of sizing amount and the increase of bonding point between raw materials in board.

Relation between Plate Density and Static Bending Strength

(a) Particleboard (b) MDF

1. High-quality particleboard 2. Low-quality Particleboard

The moisture content of the board also affects the static strength. For example, when the moisture content of the soft fiberboard increases by 1%, the static strength decreases by 4% – 10%.

The structure of particleboard and fiberboard also has a great influence on the strength of the board. The three-layer structure or gradient structure board has a surface layer with a large amount of glue and a dense structure. Under the action of static bending load, the surface layer of the material is exactly the maximum bending stress zone, so the strength of the three-layer structure board and gradient structure board is higher than that of the single-layer board. After veneer decoration of particleboard and fiberboard, its static bending strength will be improved, and its strength increment range is related to veneer material and adhesive quality.

Pressure also affects the strength of particleboard and fiberboard. For example, the static bending strength of flattened particleboard is much higher than that of extruded particleboard. In addition, the static bending strength of particleboard and fiberboard is also related to the thickness of the board. The thicker the board, the lower the static bending strength of the board.

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