Nunes Tomas, Ribas Maria J P, Akhavan-Safar Alireza, Carbas Ricardo J C, Marques Eduardo A S, Wenig Sabine, da Silva Lucas F M
Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
Polymers (Basel). 2024 Aug 22;16(16):2383. doi: 10.3390/polym16162383.
This study focuses on the prediction of the fracture mechanics behaviour of a highly flexible adhesive (with a tensile elongation of 90%), since this type of adhesive is becoming widely used in automotive structures due to their high elongation at break and damping capacity. Despite their extensive applications, the understanding of their fracture mechanics behaviour under varying loading rates and temperatures remains limited in the literature. In addition, current prediction models are also unable to accurately predict their behaviour due to the complex failure mechanism that such bonded joints have. This study aims to determine whether a simple triangular cohesive zone model (CZM), which predefines the crack path, can reproduce the load-displacement curves of adhesives under various temperatures and strain rates. To achieve this, a calibrated CZM is used, adapting the model for reference joints and then validating it with independent test results conducted in a wide range of loading and environmental conditions. The tests were performed at speeds between 0.2 and 6000 mm/min and at three different temperatures ranging from -30 °C to 60 °C. Mode I fracture toughness was measured using the DCB (double cantilever beam) specimens. Using a simple triangular CZM may not be optimal for predicting the mechanical response of highly flexible adhesives with complex failure mechanisms and multiple crack paths. However, by correctly adjusting the cohesive zone properties for a limited set of reference conditions, it is possible to accurately predict the mechanical response of these joints across various test speeds and temperatures, significantly reducing costs and effort.
本研究聚焦于一种高柔韧性胶粘剂（拉伸伸长率为90%）的断裂力学行为预测，因为这类胶粘剂因其高断裂伸长率和阻尼能力而在汽车结构中得到广泛应用。尽管它们应用广泛，但在文献中，对于其在不同加载速率和温度下的断裂力学行为的理解仍然有限。此外，由于这种粘结接头具有复杂的失效机制，当前的预测模型也无法准确预测其行为。本研究旨在确定一个预先定义裂纹路径的简单三角形内聚区模型（CZM）是否能够再现胶粘剂在不同温度和应变率下的载荷 - 位移曲线。为实现这一目标，使用了一个经过校准的CZM，针对参考接头对模型进行调整，然后用在广泛的加载和环境条件下进行的独立测试结果对其进行验证。测试在0.2至6000毫米/分钟的速度范围内以及 - 30°C至60°C的三个不同温度下进行。采用DCB（双悬臂梁）试样测量I型断裂韧性。对于预测具有复杂失效机制和多条裂纹路径的高柔韧性胶粘剂的力学响应，使用简单的三角形CZM可能并非最佳选择。然而，通过针对有限的一组参考条件正确调整内聚区特性，就有可能准确预测这些接头在各种测试速度和温度下的力学响应，从而显著降低成本和工作量。
