Understanding shear in anisotropic materials for enhances sample attachment strategy

平面双轴测试可以探索大范围的载荷，这里理解为力或位移，同时在两个正交方向上施加到一个近似方形的膜样样品上。只要机器的轴线与材料的首选方向（例如纤维方向或重复几何特征）对齐或正交，就可以直接理解加载条件。然而，优选方向的精确知识可能难以建立，并且不对准可能导致不受控制的剪切变形和样品中发展的力。当怀疑这一点时，应该使用无摩擦的挂钩和滑轮系统而不是用户友好和高效的刚性耙子来连接样品，以确保加载不包括剪切力。研究的问题是：能否制定实用的指导方针，让用户确切地知道什么时候应该使用钩子

Planar biaxial testing makes it possible to explore a wide range of loads, understood here as forces or displacements, applied at once in two orthogonal directions to an approximately square membrane-like sample. Understanding of the loading conditions is straightforward as long as the axes of the machine are aligned with, or orthogonal to, the preferred directions of the materials (e.g. fiber orientation, or repeating geometrical features). However, precise knowledge of the preferred directions can be difficult to establish, and misalignment may result in uncontrolled for shear deformation and forces that develop in the sample. When this is suspected, the sample should be attached using a friction-free system of hooks and pulleys instead of user-friendly and efficient rigid rakes, to make sure that loading does not include shear forces. The research question is: can practical guidelines be produced for the users to know exactly when they should employ hooks