The present article discusses the fracture behavior of medium-density fiberboard (MDF) and particleboard (PB), under mixed mode loading conditions. With wide applications in construction, marine and furniture industry, MDF and PB are two well-known, wood-based composites that are made of wood particles and fibers, adhered together using a standard polymer glue. Our examination of the elastic properties of these wooden samples in transverse and longitudinal directions via the digital image correlation (DIC) technique sheds light on the elastic isotropy of the employed MDF and PB sheets. Moreover, with the introduction of an improved three-point bend configuration for in-plane wood fracture tests, the brittle behavior of engineered wood is evidenced, which validates the utilization of the linear elastic fracture mechanic (LEFM) concepts herein. Therefore, within the framework of LEFM, we apply the maximum tangential strain (MTSN) criterion to predict the fracture initiation angles and fracture toughness for wooden specimens. Finally, in a comprehensive Weibull statistical analysis over the MDF and PB fracture test data, it is shown that, the mode II test results can be well-estimated based on the value of $K_{\mathit{If}}$, using the MTSN criterion. This is especially beneficial when the probability of mode II fracture is sought after, given the mode I statistical parameters.

本文讨论了中密度纤维板 (MDF) 和刨花板 (PB) 在混合模式加载条件下的断裂行为。随着在建筑、船舶和家具行业的广泛应用，MDF 和 PB 是两种众所周知的木质复合材料，它们由木颗粒和纤维制成，使用标准聚合物胶粘在一起。我们通过数字图像相关 (DIC) 技术对这些木制样品在横向和纵向上的弹性特性进行了检查，揭示了所采用的 MDF 和 PB 板的弹性各向同性。此外，随着用于平面木材断裂测试的改进的三点弯曲配置的引入，工程木材的脆性行为得到了证明，这验证了本文中线性弹性断裂力学 (LEFM) 概念的利用。因此，在 LEFM 的框架内，我们应用最大切向应变 (MTSN) 准则来预测木制试样的断裂起始角和断裂韧性。最后，在对 MDF 和 PB 断裂试验数据的综合威布尔统计分析中，表明，模式 II 试验结果可以基于${钾}_{\mathit{如果}}$，使用 MTSN 标准。考虑到模式 I 的统计参数，这在寻求模式 II 断裂的概率时尤其有益。