基于压电主动传感技术的高温后PVA-ECC梁冲击损伤监测研究

研究了低速冲击荷载作用下具有高温损伤的聚乙烯醇纤维增强水泥基复合材料（PVA-ECC）梁的损伤特征，对比分析不同温度损伤与室温下的PVA-ECC梁，在同一跌落高度和落锤质量上进行了一系列的落锤低速冲击试验，模拟冲击能量对梁的影响结果。采用压电陶瓷智能骨料传感器的主动监测方法和扫频波信号，监测落锤低速冲击作用下PVA-ECC梁的裂纹产生、发展、断裂全过程与波衰减的规律。基于小波包能量法分析重复冲击试验下的PVA-ECC梁裂缝发展演化。建立了PVA-ECC梁三维有限元模型，通过有限元分析得出300 ℃高温加热后的PVA-ECC梁低速冲击裂纹开展全过程，并与实测结果进行对比。结果表明:高温损伤造成PVA-ECC梁的抗冲击性能减弱；室温下的PVA-ECC梁有一定抗冲击能力，但当温度达到PVA纤维的熔点（230 ℃）时，PVA-ECC梁中的PVA纤维消失，产生孔隙，形成素水泥砂浆梁，不具有抗冲击能力；高温损伤造成PVA-ECC丧失了高强度、韧性、耐疲劳的能力特性。

Research on Impact Damage Monitoring of PVA-ECC Beam After HighTemperature Based on Piezoelectric Active Sensing Technology

The damage characteristics of PVA-ECC beams with high temperature damage under low velocity impact load were studied. A series of low speed impact tests were carried out to simulate the impact energy on the beam by comparing the temperature damage with the PVA-ECC beam at room temperature, the same drop height and drop hammer quality. The rule of crack evolution and wave attenuation were detected by the active detection method and frequency sweep signal of piezoelectric ceramic intelligent aggregate of PVA-ECC beam under falling hammer and low velocity impact. The PVA-ECC beam crack development quantization based on the wavelet packet energy analysis repeated impact test. The three dimensional finite element of PVA-ECC beam was established. Based on the finite element analysis method, the whole process of crack development of PVA-ECC beam after 300 ℃ high temperature was obtained. The results show that the impact resistance of PVA-ECC beam is weakened by high temperature damage, and the PVA-ECC beam has a certain anti-impact ability at ambient temperature, but when the temperature is 230 ℃, it reaches the melting point of PVA fiber, the PVA fiber in PVA-ECC beam disappears, the pore is produced, and the cement mortar beam is formed. It does not have the ability of resisting impact, so high temperature damage results take the strength, toughness and fatigue resistance in PVA-ECC away.