近年来新出现了一种不同于脆断和通常断裂的复合绝缘子异常断裂现象，笔者将其命名为复合绝缘子酥朽断裂。由2篇论文组成的系列论文旨在将复合绝缘子酥朽断裂作为一类单独的复合绝缘子机械断裂形式进行研究。该文作为系列论文的第1篇，从现场实际的酥朽断裂事故绝缘子的试验分析出发，解释了酥朽断裂命名方式中“酥”和“朽”的具体含义，归纳并提炼出复合绝缘子芯棒中环氧树脂基体的劣化、降解是酥朽断裂的主要特征，并指出酥朽断裂的初始劣化点位于硅橡胶护套与玻璃钢芯棒的界面处；酥朽断裂的产生机理为：放电、电流电蚀环氧树脂基体；受潮条件下放电产生酸性介质；酸性介质、机械应力“切割”玻璃纤维，且芯棒劣化的方向是从外向内。酥朽断裂的明确定义为：在受潮、放电、电流、酸性介质、机械应力共同作用下的复合绝缘子异常断裂现象。芯棒中环氧树脂基体的降解、劣化与否，是区别酥朽断裂与脆性断裂、通常断裂最直接的判据。“,”In recent years, a new kind of fracture phenomena of composite insulator happened in high voltage transmission lines, which was totally different from brittle fracture and normally mechanical fracture of composite insulator. The author named this new kind fracture the Decay-Like fracture of composite insulator. This two-part article aims to study the Decay-Like fracture of composite insulator as an individual failure type. In the first paper, detailed experimental analyses were conducted. According to the experimental analysis of an actual Decay-like fracture composite insulator, the reason why the Decay-like fracture was given was explained in detail. The main feature of Decay-like fracture is the degradation and deterioration of the epoxy resin matrix in FRP core, the initial deterioration point of FPR core is in the interface between silicone rubber housing and FRP core. The deterioration direction of Decay-like fracture core is from outside to inside. The definition of Decay-like fracture of composite insulator is following: The composite insulator Decay-like fracture is a kind of abnormal fracture mode of composite insulator which occurs under the combination action of damp, discharge, current, acidic medium and mechanical stress. Among these influencing factors, the discharge and current cause the degradation and deterioration of the epoxy resin matrix, the acidic medium and mechanical stress cause the stress corrosion cracking of the glass fiber, the acidic medium is generated by the discharge in the damp environment. Whether epoxy resin matrix degradation, deterioration or not is the criterion for distinguishing the difference between the Decay-like fracture, brittle fracture and normal fracture.