This study analyzed variations of tensile strength and the failure mode of composite bonded scarf joint in various thermal environments. A total of 70 scarf bonded joints were manufactured using secondary bonding and co-bonding methods, in which a number of 10 scarf joints were additionally attached to an external ply over the joint area to examine its effect. Six different environmental temperatures ranged from 25°C to 150°C were chosen and tested. A pure laminate having the same stacking sequence as the parent laminate was prepared and tested at the six temperatures for references. Experimental results revealed that tensile strengths of the secondary bonded (SB) and co-bonded (CB) joints at 75°C reduced by 9.3% and 10.5% in comparison with strengths of the corresponding joints at 25°C, respectively. Particularly, at 125°C, which is higher than the resin glass transition temperature, significant reductions of 57.1% and 53.6% in strength were found for SB and CB joints, respectively. In terms of the manufacturing methods, the strengths of the SB joints were higher than those of the CB at 25°C, 50°C, and 75°C by 6.5%, 7.6%, and 8.0%, respectively. However, at high temperatures (100°C, 125°C, and 150°C) these differences were negligible. Strengths of SB joints attached external ply increased by 5.9% and 37.5% compared to those of SB joints without the external ply at 25°C and 100°C, respectively.

中文翻译：

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各种热环境条件下复合材料粘结环缝接头的抗拉强度

本研究分析了不同热环境下复合材料胶接接头的抗拉强度变化和失效模式。总共使用二次粘合和共粘合方法制造了 70 个围巾粘合接头，其中将 10 个围巾接头额外连接到接头区域的外层上以检查其效果。选择并测试了 25°C 至 150°C 范围内的六种不同环境温度。制备与母层压板具有相同堆叠顺序的纯层压板，并在六个温度下进行测试以供参考。实验结果表明，与相应接头在 25°C 时的强度相比，二次粘合 (SB) 和共粘合 (CB) 接头在 75°C 时的拉伸强度分别降低了 9.3% 和 10.5%。特别是在 125°C 时，高于树脂玻璃化转变温度，发现 SB 和 CB 接头的强度分别显着降低了 57.1% 和 53.6%。在制造方法方面，SB接头在25°C、50°C和75°C下的强度分别比CB高6.5%、7.6%和8.0%。然而，在高温（100°C、125°C 和 150°C）下，这些差异可以忽略不计。在 25°C 和 100°C 下，与没有外部层的 SB 接头相比，连接外部层的 SB 接头的强度分别增加了 5.9% 和 37.5%。分别为 6% 和 8.0%。然而，在高温（100°C、125°C 和 150°C）下，这些差异可以忽略不计。在 25°C 和 100°C 下，与没有外部层的 SB 接头相比，连接外部层的 SB 接头的强度分别增加了 5.9% 和 37.5%。分别为 6% 和 8.0%。然而，在高温（100°C、125°C 和 150°C）下，这些差异可以忽略不计。在 25°C 和 100°C 下，与没有外部层的 SB 接头相比，连接外部层的 SB 接头的强度分别增加了 5.9% 和 37.5%。