本文選題：碳纖維 + 復合材料　； 參考：《中國民航大學》2017年碩士論文

【摘要】：本文研究了兩種航空碳纖維增強樹脂基復合材料(Carbon Fiber Reinforced Polymer,簡稱CFRP)的電熱作用機理及相關的電學表征方法。通過溫度場、縱向體積電阻以及介電性能測試分析了CFRP的電熱特性,完成了電熱損傷特征參量的提取。采用傅里葉變換紅外光譜儀(FT-IR)和差示掃描量熱儀(DSC)研究了電熱作用前后CFRP中環(huán)氧樹脂基體的物理及化學變化。深入探討了電熱作用前后CFRP的靜態(tài)力學性能以及動態(tài)力學性能變化規(guī)律。利用激光共焦顯微鏡和掃描電鏡分別觀察了電熱作用前后的CFRP的表面形貌和斷口形貌,分析其失效特征并總結了電熱損傷機理。電熱特性研究結果表明,電熱作用下T300/E52和T300/970兩種復合材料的溫度場隨時間均呈現(xiàn)先迅速上升后穩(wěn)態(tài)平衡趨勢。對于T300/E52復合材料,電流密度小于0.125A·mm-2的電熱作用使其表面溫度場分布均勻,縱向體積電阻降低以及介電性能提升;大于0.125A·mm-2的電熱作用在中間區(qū)域形成較高溫度場,縱向體積電阻升高以及介電性能下降。介電頻譜測試表明,介電常數(shù)和損耗角正切值隨測試頻率增加而降低,AC電導率隨頻率增加先恒定后迅速上升。對T300/970復合材料,玻璃化轉變溫度附近的電熱作用(電流密度范圍為0.25~0.31A·mm-2)基本上使其導電性能下降,介電性能提升。損耗角正切值由于對基體、界面損傷較為敏感,且電熱作用對其影響較大,可作為特征參量。電熱作用后T300/970復合材料的FT-IR圖譜中沒有出現(xiàn)明顯的新峰,羥基峰整體上在增強,這與環(huán)氧樹脂發(fā)生后固化有關。羰基峰的略微增強表明環(huán)氧樹脂發(fā)生了氧化反應。電熱作用后復合材料的DSC曲線表明,環(huán)氧樹脂的玻璃化轉變溫度明顯上升,這也說明環(huán)氧樹脂發(fā)生后固化反應。電熱作用后T300/970復合材料的動態(tài)力學分析發(fā)現(xiàn),試樣的玻璃化轉變溫度最大上升25℃,儲能模量也有明顯提升,說明電熱作用不僅使復合材料發(fā)生后固化,還對其有物理老化效果。三點彎測試表明,低于0.125A·mm-2的電熱累積作用使T300/E52復合材料的彎曲強度和彎曲模量最大分別提升11.8%和7.32%;高于0.125A·mm-2時,彎曲強度和彎曲模量最大降低8.26%和6.52%。對于T300/970復合材料,8~9A的電熱作用對其造成微損傷,使其彎曲性能最大降低13%;9.5~10A電熱作用下,后固化和物理老化速率加快,使試樣的彎曲性能有一定回升。表面形貌觀測發(fā)現(xiàn),電熱作用使T300/970復合材料發(fā)生層間基體微開裂,這主要是由纖維和基體的熱膨脹系數(shù)不匹配,在試樣中產生的殘余熱應力導致的。斷口形貌分析表明,電熱作用使試樣斷口粗糙,分層明顯,纖維/基體界面粘結性能惡化,引起界面微開裂,并且界面損傷的出現(xiàn)要早于基體微開裂損傷。
[Abstract]:In this paper, the electrothermal mechanism of two kinds of aeronautical carbon fiber reinforced polymer (CFRP) composites and their electrical characterization methods are studied. The electrothermal properties of CFRP were analyzed by temperature field, longitudinal volume resistance and dielectric properties, and the characteristic parameters of electrothermal damage were extracted. The physical and chemical changes of epoxy resin matrix in CFRP before and after electrothermal treatment were studied by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimeter (DSC). The static and dynamic mechanical properties of CFRP before and after electrothermal action were discussed. The surface morphology and fracture morphology of CFRP before and after electrothermal action were observed by laser confocal microscope and scanning electron microscope respectively. The failure characteristics of CFRP were analyzed and the mechanism of electrothermal damage was summarized. The results of electrothermal properties show that the temperature field of T300 / E52 and T300 / 970 composites increases rapidly with time and then shows a steady equilibrium trend. For the T300 / E52 composite, the electrothermal effect of current density less than 0.125A mm-2 makes the surface temperature field uniform, the longitudinal volume resistance decreases, and the dielectric property is improved, and the electrothermal action greater than 0.125A mm-2 forms a higher temperature field in the middle region. The longitudinal volume resistance increases and the dielectric property decreases. The dielectric constant and the tangent value of loss angle decrease with the increase of the frequency, and the conductivity of AC decreases with the increase of the frequency, and then increases rapidly. For T300 / 970 composites, the electrothermal action near the glass transition temperature (current density range of 0.25 ~ 0.31A mm-2) makes the electrical conductivity decrease and the dielectric property increase. The tangent value of loss angle is sensitive to the matrix, and the electrothermal effect is great, so it can be used as the characteristic parameter. The FT-IR spectra of T300 / 970 composites after electrothermal treatment showed no obvious new peaks, but the hydroxyl peaks were strengthened as a whole, which was related to the curing of epoxy resin. The slight enhancement of the carbonyl peak indicates that the epoxy resin is oxidized. The DSC curves of the composites show that the glass transition temperature of epoxy resin increases obviously, which also indicates the curing reaction of epoxy resin. The dynamic mechanical analysis of the T300 / 970 composite after electrothermal treatment showed that the glass transition temperature of the sample increased by 25 鈩，

本文編號：2096105