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为从超声衰减机制角度解释碳纤维增强树脂基复合材料(Carbon Fibre Reinforced Plastics,CFRP)孔隙率P与超声衰减系数a之间呈非唯一对应关系的原因,针对厚度为2 mm的热压罐成型单向CFRP层板,建立了具有不同孔隙尺寸的CFRP模型(P=0.5%~3.5%),并采用数值计算方法得到衰减系数a值。当孔隙横向尺寸D=56mm,即归一化波数kD=2pD/l<1(超声波波长l≈560mm)时,a随P增大而缓慢线性增加;当D=93mm(kD≈1)时,a随P增大呈对数增长。仿真结果表明,超声波在含孔隙CFRP中传播时,随着归一化波数的不同,超声波衰减可能包括瑞利散射和随机散射两种机制,孔隙形貌的随机复杂性导致CFRP孔隙率与超声衰减系数之间呈现非唯一对应关系。
In order to explain the non-unique correspondence between the porosity P and the ultrasonic attenuation coefficient a of carbon fiber reinforced plastics (CFRP) from the perspective of ultrasonic attenuation mechanism, For CFRP laminates, CFRP models with different pore sizes (P = 0.5% ~ 3.5%) were established, and the value of attenuation coefficient a was obtained by numerical calculation. When the transverse dimension D = 56mm, that is, the normalized wave number kD = 2pD / l <1 (ultrasonic wave length l≈560mm), a increases slowly and linearly with the increase of P. When D = 93mm (kD≈1) a increases logarithmically as P increases. The simulation results show that when the ultrasonic wave propagates in the porous CFRP, the ultrasonic attenuation may include Rayleigh scattering and random scattering with the normalized wave numbers. The random complexity of the pore morphology leads to the decrease of the porosity and the attenuation of the CFRP Non-unique correspondence between coefficients.