Our research aims to develop a shear forming envelope for the preforming of textiles, a critical step in the manufacture of fibre-reinforced composite materials. This paper demonstrates the progress towards this aim by conducting picture frame tests to empirically determine the locking angle of non-crimp fabrics with different fibre orientations. While conventional shear tests typically utilise woven textile samples with orthogonal fibre directions of 0°/90°, the investigation of non-crimp fabrics, especially with non-standard fibre orientations, is less common. As a result, there is little knowledge about the shear deformation behaviour of these fabric types, despite their relevance to the aerospace industry. In this study, the shear locking angles of various carbon fibre non-crimp fabrics are investigated, gradually reducing the relative fibre angles of the textile materials from ±45° to ±22.5°. Previously, it was observed that unidirectional 0° reinforcement layers induce draping defects when forming multiaxial non-crimp fabric stacks into curved aerospace stiffeners. Their substitution by reinforcements with smaller cross-ply angles such as ±30° resulted in better formability and reduced defects. It is however unclear, how the shear locking angle decreases with more acute cross-ply angles. Here, we report for the first time a correlation between the fibre orientation of the non-crimp fabric and its shear locking angle. The resulting shear forming envelope provides composite design and manufacturing guidance for an enhanced utilisation of the advantageous but anisotropic properties of carbon fibre textiles.

我们的研究旨在开发用于纺织品预成型的剪切成型外壳，这是制造纤维增强复合材料的关键步骤。本文通过进行相框测试以凭经验确定具有不同纤维取向的非卷曲织物的锁定角度，证明了实现这一目标的进展。虽然传统的剪切测试通常使用正交纤维方向为 0°/90° 的机织纺织品样品，但对非卷曲织物的研究，尤其是非标准纤维方向的研究较少见。因此，尽管它们与航空航天工业相关，但对这些织物类型的剪切变形行为知之甚少。在这项研究中，研究了各种碳纤维无卷曲织物的剪切锁定角，纺织材料的相对纤维角度从±45°逐渐减小到±22.5°。以前，观察到单向 0° 增强层在将多轴非卷曲织物堆叠形成弯曲的航空航天加强筋时会引起悬垂缺陷。它们被具有较小交叉层角（例如±30°）的增强材料所取代，导致更好的成型性和减少的缺陷。然而，尚不清楚剪切锁定角如何随着更锐的交叉层角度而减小。在这里，我们首次报告了非卷曲织物的纤维取向与其剪切锁定角之间的相关性。由此产生的剪切成型外壳为增强利用碳纤维纺织品的有利但各向异性的特性提供了复合材料设计和制造指导。