Investigating the compression properties of randomly ordered fiber networks experimentally is difficult which has resulted in ongoing disputes as to the mechanisms controlling the compression strength in such materials. In this work, we investigated compression properties of randomly oriented fiber networks with a special emphasis on cellulose products such as paperboard. We numerically reconstructed the conditions of the short span compression test widely used to quantify the compression strength of paperboard. We found that the phenomenological failure mode of such networks is elasto-plastic buckling. The x-shaped failure mode observed in physical experiments appears when test specimen restraints are included in the model. The most significant improvements to sheet strength can be obtained by improving the elastic properties while the strain to failure is increased most by an improvement of the plastic yield and hardening properties of individual fibers. Bond breaks were confirmed to have a smaller influence on the overall response. Fiber level microscopic buckling was investigated in depth, providing quantitative estimates of the fraction of mass likely to buckle at the microscopic level. The analysis indicated that only a low to moderate number of load carrying fibers can be expected to buckle. The inherent strength reserve in non-ordered fiber networks was investigated by introducing hinge mechanisms throughout the network, and the effect was shown to be small for a small to moderate number of hinges.

通过实验研究随机排列的纤维网络的压缩特性是困难的，这导致了控制这种材料的压缩强度的机制方面的争议。在这项工作中，我们研究了随机取向的纤维网络的压缩特性，特别强调了纤维素产品（如纸板）。我们用数值方法重建了广泛用于量化纸板抗压强度的短跨度压缩试验的条件。我们发现这种网络的现象学失败模式是弹塑性屈曲。当模型中包含试样约束时，就会出现物理实验中观察到的X形破坏模式。片材强度的最显着改善可通过改善弹性性能而获得，而断裂应变可通过改善单纤维的塑性屈服性和硬化性而最大地增加。确认键断裂对整体响应的影响较小。深入研究了纤维水平的微观屈曲，提供了可能在微观水平屈曲的质量分数的定量估计。分析表明，只有少量到中等数量的负载纤维会发生弯曲。通过在整个网络中引入铰链机制，研究了无序光纤网络中固有的强度储备，结果表明，对于中小数量的铰链，其影响很小。