基于拉曼光谱mapping技术研究低温循环对炭纤维增强聚酰亚胺复合薄膜界面微观力学的影响

Raman mapping microspectroscopy of the effects of cryogenic cycling on the interfacial micromechanics of carbon fiber-reinforced polyimide composites

碳纳米管选用(CNT)作为拉曼应力传感器,通过建立拉曼光谱mapping技术研究了经多次低温循环(-198~25℃,0~300次)的炭纤维增强聚酰亚胺复合薄膜(CF/CNT-PI)的界面微观应力变化。研究发现:聚酰亚胺薄膜(CNT-PI)即使经300次低温循环,树脂内部应力依然为~175 MPa,循环次数对树脂内部应力影响较小,表明该材料具有良好的耐低温性。进一步研究了炭纤维(CF)增强的CNT-PI薄膜的内应力变化,获得了炭纤维、界面、树脂基体区域的微观应力mapping分布,发现CF区域的受力大于基体部分,表明CF在该体系中起到了对应力最主要载体的作用,并发挥了良好的增强效果。在循环次数<250次时,微观应力变化不大;但当循环次数高达300次时,炭纤维及界面区域应力值分别提高了21%和12.9%,应力在材料内部的集中增大会降低材料的力学性能。本研究有效地定量了外界温度循环变化下复合材料的增强材料、基体及界面的微观应力分布,这为检测复合材料服役过程中的使用安全性提供了一种理论依据与评判手段。

Raman spectroscopy has unique advantages in studying the micro-mechanical behavior of interfaces.Carbon nanotubes(CNTs)acting as stress sensors were added to both polyimide films(CNT-PI)and those reinforced with carbon fibers(CF/CNT-PI).Raman mapping microspectroscopy was then used to investigate the interfacial stress distributions of the films during different cryogenic-room temperature cycles(-198-25℃,0-300 cycles).It was found that the micro stress of CNT-PI films(around 175 MPa)had no significant changes even after 300 cycles.The cryogenic cycling had very little effect on the internal stress,indicating that PI had a good low temperature resistance.For the CF/CNT-PI films,the micro stress distributions of CFs,interface,and matrix regions were successfully obtained.It was found that the CFs bear a greater stress than the matrix,showing that CFs had always been the major stress bearer,confirming the strengthening effect of CFs.When the CF/CNT-PI films were cycled fewer than 250 times,the effect of cryogenic cycling on the micro stress was insignificant.But once the number of cycles reached 300,the compressive stresses on the fiber and interface increased by 21%and 12.9%,respectively,implying a deterioration of the mechanical properties.By Raman mapping,the micro-mechanical distributions of the reinforced material,matrix and interface of the composites under cyclic temperature changes were effectively quantified.This is therefore an effective method for evaluating the safety of composite materials.