An improved semi-circular bend (SCB) specimen is introduced to obtain the mixed mode fracture envelope of a ductile adhesive with a considerable fracture process zone ahead of the crack tip. This specimen has been used for brittle adhesives fracture energy measurement. The proposed test procedure is very simple to implement and does not require any special loading fixture. The specimen is able to cover the whole mixed-mode ratios from pure mode I to pure mode II. Experiments are carried out on the manufactured specimens and the fracture loads are used in an inverse approach to obtain the fracture energy of the adhesive joints. The cohesive zone modelling (CZM) technique is employed as the data reduction method. Proper geometrical parameters for SCB joints are chosen through a wide-range of numerical simulations based on a linear elastic formulation. It is shown that the crack growth does not affect the mixed-mode ratio for the proposed adhesive joint. Another advantage of this specimen compared to the existing beam-based approaches (such as end-notched flexure (ENF), mixed-mode bend (MMB), etc.) is its lower risk of plastic deformation in the adherends. The mixed mode fracture envelope in the tested adhesive is obtained and the results of fracture energy under pure mode I loading are validated with the results of double cantilever beam (DCB) tests successfully.

引入一种改进的半圆弯曲（SCB）标本，以得到韧性胶粘剂的混合模式断裂包络，其在裂纹尖端之前具有相当大的断裂加工区。该样品已用于脆性胶粘剂断裂能的测量。所提出的测试程序实施起来非常简单，不需要任何特殊的加载装置。样品能够覆盖从纯模式I到纯模式II的整个混合模式比率。对制造的样品进行实验，然后以相反的方式使用断裂载荷来获得粘合接头的断裂能。内聚区建模（CZM）技术被用作数据约简方法。通过基于线性弹性公式的大量数值模拟，为SCB接头选择合适的几何参数。结果表明，裂纹扩展不影响所提出的粘合剂接头的混合模比。与现有的基于梁的方法（例如，带缺口的弯曲（ENF），混合模式弯曲（MMB）等）相比，该样品的另一个优点是其在被粘物中发生塑性变形的风险较低。获得了测试粘合剂中的混合模式断裂包络线，并通过双悬臂梁（DCB）测试的结果成功验证了纯模式I载荷下的断裂能结果。与现有的基于梁的方法（例如，带缺口的弯曲（ENF），混合模式弯曲（MMB）等）相比，该样品的另一个优点是其在被粘物中发生塑性变形的风险较低。获得了测试粘合剂中的混合模式断裂包络线，并成功地通过双悬臂梁（DCB）测试的结果验证了纯模式I载荷下的断裂能结果。与现有的基于梁的方法（例如，带缺口的弯曲（ENF），混合模式弯曲（MMB）等）相比，该样品的另一个优点是其在被粘物中发生塑性变形的风险较低。获得了测试粘合剂中的混合模式断裂包络线，并通过双悬臂梁（DCB）测试的结果成功验证了纯模式I载荷下的断裂能结果。