Deformation Analysis
Optical measurement of paper distortion under load captures the distribution of displacement across a test specimen during tensile testing. Using digital image correlation, strain field mapping tracks the movement of a speckle pattern applied to the surface of the paper. This technique allows researchers to see how local variations in basis weight and fiber density affect the deformation of the sheet under stress.
Strain Concentration
Sheet failure begins at microscopic weak points where localized stress exceeds the average strength of the paper. Through strain field mapping, these areas of high strain are detected long before visible tearing occurs on the test specimen. This information is invaluable for optimizing fiber blends and refining processes to reduce the risk of web breaks during high-speed printing runs.
Fracture Prediction
Analyzing the progression of local strains allows for the prediction of the exact path a tear will take through the paper. In packaging materials, such as multi-ply board or corrugated liners, strain field mapping shows how different layers share the mechanical load when the box is stacked or compressed. By identifying which layers yield first, paper chemists can adjust wet-strength resins and sizing agents to create more durable board combinations.
The resulting data helps mills design lighter packaging that still meets the rigorous durability demands of the global distribution chain.
