Solodov I, Pfleiderer K, Gerhard H, Busse G
Institute for Polymer Testing and Polymer Science (IKP)-Nondestructive Testing, Stuttgart University, Pfaffenwaldring 32, Stuttgart D-70569, Germany.
Ultrasonics. 2004 Apr;42(1-9):1011-5. doi: 10.1016/j.ultras.2003.12.020.
The paper reports on experimental study of elastic nonlinearity of polymers and glass fibre-reinforced (GFR-) composites in a wide range of tensile stress applied (up to a fracture limit). Focused slanted transmission mode (FSTM) of air-coupled ultrasound is adapted for remote generation and detection of flexural waves in the samples of plastics. Local noncontact measurements of flexural wave velocity as a function of static strain are used to calculate the second-order nonlinearity parameters beta2 and study their behaviour through a loading cycle. Molecular untangling and crazing phenomena are identified, respectively, with maxima of positive and negative beta2 in thermoplastics. In composites, mechanics of fibre-matrix interaction is considered for brittle and plastic fractures. Hysteresis in velocity variation during loading-unloading cycle is used as an indicator of residual defect accumulation.
本文报道了在很宽的拉伸应力范围（直至断裂极限）内对聚合物和玻璃纤维增强（GFR-）复合材料的弹性非线性进行的实验研究。空气耦合超声的聚焦倾斜传输模式（FSTM）适用于在塑料样品中远程产生和检测弯曲波。利用弯曲波速度作为静态应变函数的局部非接触测量来计算二阶非线性参数β2，并通过加载循环研究其行为。在热塑性塑料中，分别通过正β2和负β2的最大值识别分子解缠和 crazing 现象。在复合材料中，考虑了纤维-基体相互作用机制对脆性和塑性断裂的影响。加载-卸载循环中速度变化的滞后现象被用作残余缺陷积累的指标。
