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首页> 外文会议>Annual Symposium on Quantitative Nondestructive Evaluation; 19980719-24; Snowbird,UT(US) >LAMB WAVE STIFFNESS CHARACTERIZATION OF COMPOSITES UNDERGOING THERMAL-MECHANICAL AGING
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LAMB WAVE STIFFNESS CHARACTERIZATION OF COMPOSITES UNDERGOING THERMAL-MECHANICAL AGING

机译：热-机械老化复合材料的兰姆波刚度表征

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The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated by Griffis, et al. and Chen, et al.. Schubbe and Mall and Castelli, et al. have experimentally investigated both in-phase (maximum temperature at maximum load) and out-of-phase (maximum temperature at minimum load) thermal-mechanical cycling on composites. Both authors found that the damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve.
机译：在航空系统中引入新的，先进的复合材料需要彻底了解热负荷和机械负荷相结合对这些材料的长期影响。 Griffis等人研究了研究强热加热与机械载荷相结合的影响的分析方法。 Schubbe和Mall和Castelli等。已通过实验研究了复合材料的同相（最大负载下的最高温度）和异相（最小负载下的最高温度）热机械循环。两位作者都发现，损伤机理和疲劳寿命取决于测试参数以及应力水平。 Castelli等。可以确定异相循环的基体主导失效模式和同相循环的纤维主导损伤模式。近年来，已经开发了可以测量复合材料的机械刚度的超声方法。为了帮助评估老化的影响，正在使用经过适当设计的兰姆波测量系统来获取经受热机械载荷的复合材料层压板的弯曲和平面外刚度系数。该系统通过激发非对称Lamb波并根据已知的换能器间隔和测得的飞行时间计算每个频率下的速度来工作。在各种距离处接收到的波形中的同一峰值用于测量信号之间的时间差。速度测量值准确且可重复，误差在1％以内，导致重建的刚度值可重复在4％以内。在给定材料密度和板厚的情况下，可通过重建色散曲线来计算弯曲刚度和面外剪切刚度。

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