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Brittleness cracking and mechanism of composite insulator

The brittle fracture and mechanism of mechanical strength of composite insulator core expired, now there are two concepts: a thought that aging of the mechanical strength of the composite insulator will follow the insulator decreased, eventually resulting in loss of core mechanical strength; and the more recent research suggests another concept, i.e. if the load is not the insulator to the ultimate strength of the glass fiber fracture, its mechanical strength does not reduce, in other words there is no doubt creep. The two completely hostile ideas in the world today are not certain, nevertheless, the study of brittle cracking mechanism provides a new perspective.
The brittle fracture is a special way of composite insulator core cracking, usually that is when the insulator due to lower load (load tolerance is only 10%~15%), the onset of cracking mandrel.
Usually, the effect of cracking FRP mandrel so some elements:
(1) the type and strength of mechanical stresses such as tension, applied alone or in combination with the twists or strains applied to the insulator together or sequentially.
(2) the state of stress static, dynamic and impact.
(3) the effect of environmental factors with erosion effect data aging differentiation. Arc damage. The appearance of cracking and brittle cracking of FRP mandrel attack with such characteristics:
(1) with rod shaft into 90 degree straight, and cracking appearance is very lubrication.
(2) perhaps along the mandrel occurred many cracks, the formation of many independent section. In most cases, these sections are split along axes.
(3) tension and tortuous stress will occur along the axial split surface......
(4) some stepped lubrication cracking surfaces (tension and compression stress will occur when each other is straight).
(5) lubrication section is the cause of cracking of glass fiber and resin adhesive on the same plane. Only a small number of glass fibers are pulled out of the resin at the moment.
Usually the mandrel cracking has so few characteristics:
(1) cracking appearance and rod axis direction of 45 degrees
(2) the local cracking surface is also formed with the rod shaft into 45 degrees.
(3) the cracking surface at the top of the large crack axis is also at a level of 45 degrees with the rod axis.
(4) crack appearance has burr (white amorphous particle), which is caused by cracking of glass fiber and epoxy resin in the same plane. Cracking along with sound.
Brittle cracking also with lower tension load, the appearance of small crack expanding mandrel. The acid solution caused mandrel brittle cracking is not conclusive now all experts agree that this conclusion still needs further research. However, in the practice of outdoor operating environment, composite insulators will inevitably face the question of corrosion. In a variety of environments around the world, every kind of acid is presented in different ways, the electrical discharge micro interface gap discharge insulator or the internal insulator surface in wet air can occur and then the occurrence of severe corrosion of nitric acid. 
Now, the umbrella skirt of the composite insulator is made of polymer materials, because the device is damaged or umbrella skirt aging, may cause the mandrel is exposed, the possibility is affected by acid corrosion.
The weakest region is the bonding part between the umbrella skirt and accessories, because some of the data is not the same, the effect of thermal expansion is not the same, but also request to ensure the sealing adhesive, avoid wet especially acid intrusion, so the data request is very high. Glass fiber stress corrosion resistance with certain types of outstanding, the mandrel can optimize together tension load and acid etching experiments.