Paperboard Middle Ply Furnish Compression Mechanics under Static Bench Conditions
Middle ply CTMP bulk provides structural moment of inertia, while short-span compression bench testing quantifies network collapse risks under load.
Microfibril Compression Failure
Structural Integrity
Cell wall deformation under axial loading defines this physical degradation of wood fibres. Microfibril compression failure occurs when the crystalline cellulose regions within the secondary wall layer undergo plastic buckling. Such damage disrupts the load-bearing capacity of individual fibres by creating localized creases or kinks in the cell wall structure.
These micro-discontinuities propagate across the cross-section of the wood material, eventually reducing the overall stiffness and tensile strength of the sheet.
Deformation Mechanics
Mechanical forces exceed the elastic limit of the tracheids during harvesting or heavy industrial processing. A timber block sustains these stresses during intense wind events or high-pressure rollers within a paper mill. When the microfibrils shift, the internal bonding of the lignin-hemicellulose matrix breaks down to prevent complete collapse.
This shift alters the microscopic topography of the fibre surface, which inhibits consistent bonding during the sheet forming process. Subsequent drying cycles then lock these defects into place, creating brittle points that rupture under tension.
Material Consequences
Paper stock quality suffers whenever internal fibre damage remains undetected before final calendering. Printers face increased web breakage during high-speed production cycles because the damaged fibres fail to transfer stress uniformly across the paper surface. Reduced structural homogeneity also leads to inconsistent ink penetration and uneven surface smoothness in the finished product.
These microscopic defects impose a hard limit on the tensile strength potential of the paper batch.