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在各种载荷条件下测量了用于固体火箭发动机壳体的 S-901玻璃纤维/环氧树脂复合材料的粘弹蠕变特性。试样从纤维缠绕发动机壳体的前封头,纤维缠绕角为±20°和±70°的区域内切取。在不同的拉伸应力和四点梁弯曲应力水平的条件下对试样进行测试。通过几次蠕变——恢复周期来确定材料的蠕变特性。为了测定材料在较低的应力水平下的滞后现象也用四点梁弯曲试验进行了等位移速率试验。发现材料的特性在许多方面类似于从前在等同条件下试验的气压釜固化的平板试样的特性。蠕变特性随时间的变化服从如下幂定律:D=D_0+D_1f~n式中:D 为蠕变柔量(磅/英寸~2~(-1))D_0为初始弹性蠕变柔量。D_1和 n 确定了材料的粘弹响应特性。在线性粘弹性范围,n=0.19。这与环氧树脂本身得出的数据完全一致。在较高应力水平下,由于复合材料内部产生的微裂纹而使 n 值增加。在第一次和第二次加载循环之间,蠕变——恢复特性出现最大差值,而在随后的加载条件下 n 值稍许降低。
The viscoelastic creep properties of S-901 glass fiber / epoxy composites for solid rocket motor housings were measured under various load conditions. Samples were taken from the front head of a fiber wound engine housing with a fiber wrap angle of ± 20 ° and ± 70 °. The specimens were tested under different tensile stress and four-point beam bending stress levels. Several creep-recovery cycles are used to determine the creep properties of the material. In order to determine the hysteresis of the material at a lower stress level, a four-point beam bending test was also carried out at an equal displacement rate. The properties of the material were found to be similar in many ways to those of autoclave cured flat specimens that were previously tested under equivalent conditions. The variation of creep characteristics with time obeys the following power law: D = D_0 + D_1f ~ n Where: D is the creep compliance (pounds per square inch) D_0 is the initial elastic creep compliance. D_1 and n determine the viscoelastic response of the material. In the linear viscoelastic range, n = 0.19. This is exactly the same data as the epoxy itself. At higher stress levels, n increases due to microcracks generated inside the composite. Between the first and second loading cycles, the maximum difference in creep-recovery characteristics occurs, with a slight decrease in n under the subsequent loading conditions.