This study addresses the question of how the difference in mechanical properties of the individual layers in a multi-ply commercial paperboard affects the outcome of the tray-forming operation. Two commercially produced paperboards with nearly identical mechanical properties when conventionally tensile tested were considered. These boards are produced on different machines with the same target grammage and density. Despite the similar mechanical properties, their performance in a given tray-forming operation was drastically different, with one of the boards showing an unacceptable failure rate. To investigate the difference seen during converting operations, a detailed multi-ply finite element model was built to simulate the converting operation. The present model considers a critical area of the paperboard known to exhibit failures. To derive the constitutive relations for each ply in the sub-model, both boards were split to single out individual plies which were then tensile tested. Including the properties of individual plies revealed large differences between the boards when it comes to the distribution of the properties in the thickness direction. In particular, the top plies differed to a large extent. This is attributed to the difference in refining energies for the plies. The results from the three-ply sub-model demonstrated the importance of including the multi-ply structure in the analysis. Weakening of the top ply facing the punch by using lower refining energy considerably increased the risk of failure of the entire board. These results suggest that there is room for optimizing the board performance by adjusting the refining energy at the ply level.

Graphical abstract

中文翻译：

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层板性能在纸板加工操作中的影响：一种提高成型性的方法

本研究解决了多层商业纸板中各个层的机械性能差异如何影响托盘成型操作结果的问题。考虑了在常规拉伸测试时具有几乎相同机械性能的两种商业生产的纸板。这些板是在具有相同目标克重和密度的不同机器上生产的。尽管机械性能相似，但它们在给定托盘成型操作中的性能却截然不同，其中一块板显示出不可接受的故障率。为了研究在转换操作过程中看到的差异，建立了一个详细的多层有限元模型来模拟转换操作。本模型考虑了已知会出现故障的纸板的关键区域。为了推导出子模型中每一层的本构关系，将两块板分开以挑选出单独的层，然后对其进行拉伸测试。当涉及到厚度方向的特性分布时，包括单个层的特性显示了板之间的巨大差异。特别是，顶层在很大程度上不同。这归因于层的精炼能量的差异。三层子模型的结果证明了在分析中包含多层结构的重要性。通过使用较低的精炼能量来削弱面向冲头的顶层，大大增加了整个板的故障风险。这些结果表明，通过调整层级的精炼能量来优化纸板性能存在空间。

图形概要