This paper investigates the processing-induced residual strains developed in the adhesive layer of a single lap joint consisting of glass-fiber reinforced polymer (GFRP) adherends bonded with a thermoplastic adhesive, Acrylonitrile Butadiene Styrene (ABS). High-resolution optical fiber sensors were embedded inside the adhesive for in-situ monitoring of strains and temperature during the processing and cooling cycle. The experimental fiber-optic strains are the total strains experienced by the fiber and do not represent the strains in the adhesive because of interfacial effects between the fiber and the adhesive. Hence, a detailed finite element analysis (FEA) model was developed that included the optical fiber within the bondline. The experimentally measured optical fiber strains were first used to calibrate the FE models at each cooling rate. These FE models were then used to predict residual strains and stresses in the bulk adhesive.

The FE models showed that the strains calculated along the optical fiber provided a close approximation to the actual strains experienced by the ABS adhesive around it at the center of the overlap region. The experimental technique, with appropriate post-processing, can be used to get a reliable first-hand approximation of the residual strains induced in the bulk adhesive during curing/processing. A critical conclusion from the FE investigation is that, for all cooling rate cases, the von-Mises residual stresses generated inside the bulk ABS adhesive ranged between 65 and 80% of its tensile strength, which showcases the importance of processing-induced residual stresses and their effects on safety-critical components like bonded joints. The hybrid FE-experimental approach used in this work can be extended to other joint geometries and material configurations.

本文研究了由玻璃纤维增​​强聚合物 (GFRP) 被粘物与热塑性粘合剂丙烯腈丁二烯苯乙烯 (ABS) 粘合而成的单搭接接头的粘合剂层中产生的加工引起的残余应变。高分辨率光纤传感器嵌入在粘合剂内部，用于在加工和冷却循环期间现场监测应变和温度。由于光纤和粘合剂之间的界面效应，实验光纤应变是光纤经历的总应变，并不代表粘合剂中的应变。因此，开发了详细的有限元分析 (FEA) 模型，其中包括胶层内的光纤。实验测量的光纤应变首先用于校准每个冷却速率下的有限元模型。

有限元模型表明，沿光纤计算的应变与重叠区域中心周围 ABS 粘合剂所经历的实际应变非常接近。通过适当的后处理，该实验技术可用于获得固化/加工过程中大量粘合剂中引起的残余应变的可靠的第一手近似值。有限元研究的一个关键结论是，对于所有冷却速率情况，本体 ABS 粘合剂内部产生的 von-Mises 残余应力介于其拉伸强度的 65% 到 80% 之间，这表明加工引起的残余应力和它们对安全关键部件（如粘合接头）的影响。