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测定玻璃钢的断裂韧度,首先遇到的问题就是如何在试件上预制一个足够尖锐的裂缝。金属材料是先用电火花切制出一条较宽的裂缝,然后再在疲劳机上引发出宽度在0.08mm以下的尖锐裂缝,才不影响断裂韧度的试验值。有人研究了玻璃钢的裂缝根部半径对断裂韧度的影响,结果表明,玻璃钢对裂缝根部半径是不敏感的,就是说,玻璃钢允许有较大的裂缝根部半径而不影响断裂韧度的试验值。据报道国外有人用6密耳厚的金刚石锯为玻璃钢切制裂缝,无需再到疲劳机上预制更尖锐的裂缝。也有人用超声技术为玻璃钢切制裂缝。
The first problem encountered when determining the fracture toughness of FRP is how to preform a sufficiently sharp crack in the test piece. Metal material is to use electric spark to cut a wide crack, and then lead to the fatigue in the machine width of 0.08mm below the sharp cracks, fracture toughness will not affect the test value. The effect of FRP crack root radius on fracture toughness has been studied. The results show that FRP is not sensitive to fracture root radius, that is, FRP allows larger fracture root radius without affecting fracture toughness. It is reported that someone abroad with 6-mils thick diamond saw for the FRP cut cracks, no longer need to be more severe machine fatigue prefabricated cracks. Some people use ultrasonic technology for FRP cut cracks.