Single-lap shear (SLS) joints are straightforward to manufacture. This makes them especially attractive for testing polymer composite welded joints. Owing to local heating, which is characteristic of composite welding processes, the production of more geometrically intricate joints (such as double-lap or scarfed joints) or bigger joints (such as end-notched flexure or double cantilever beam) typically entails significant complexity in the design of the welding process. Testing of SLS joints is also uncomplicated and, even though, owing to mixed-mode loading and uneven stress distribution, it does not provide design values, it is widely acknowledged as a valuable tool for comparison. Even so, comparing different aspects of composite welded joints through their corresponding SLS strength values alone can be deceptive. This paper shows that comparison of different welding processes, adherend materials, process parameters or different types of joining techniques through SLS testing is only meaningful when strength values are combined with knowledge on other aspects of the joints such as joint mesostructure, failure modes and joint mechanics.

This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.

单搭接剪切 (SLS) 接头易于制造。这使得它们对于测试聚合物复合材料焊接接头特别有吸引力。由于局部加热是复合焊接工艺的特点，因此几何形状更复杂的接头（例如双搭接或斜接接头）或更大的接头（例如端部缺口弯曲或双悬臂梁）的生产通常需要显着的复杂性焊接工艺的设计。SLS 接头的测试也不复杂，尽管由于混合模式加载和不均匀的应力分布，它不提供设计值，但它被广泛认为是一种有价值的比较工具。即便如此，仅通过其相应的 SLS 强度值来比较复合材料焊接接头的不同方面可能具有欺骗性。

这篇文章是讨论会问题“发明新的坚韧材料的破解方法：断裂比摩擦更奇怪”的一部分。