【摘要】：疲勞失效是工程中常見的一種破壞形式。多數(shù)金屬材料的疲勞極限是拉伸強度的40%~50%,而碳纖維/環(huán)氧樹脂復(fù)合材料則可達90%,雖然復(fù)合材料的抗疲勞性能比金屬好,但是也避免不了疲勞問題。在分析復(fù)合材料層合板疲勞分層問題時也不能再用研究金屬材料疲勞裂紋擴展的方法。在復(fù)合材料層合板使用過程中,層間分層和界面脫粘是其中兩種常見的和起決定性作用的失效形式。由于分層常常發(fā)生在低應(yīng)力水平下的周期載荷,因此機械疲勞是引起復(fù)合材料結(jié)構(gòu)分層損傷的最重要因素。由于復(fù)合材料層合板往往具有非線性,經(jīng)典斷裂力學(xué)已經(jīng)無法滿足。同時復(fù)合材料由于其鋪層方式的多樣性,層合板厚度的影響,因此若是通過實驗方法來研究復(fù)合材料層合板疲勞分層擴展將會是一個耗時費力的事情。隨著計算機技術(shù)的發(fā)展,因此尋求有效的數(shù)值模擬技術(shù),對復(fù)合材料層合板疲勞分層進行分析具有極大的工程意義。本文將斷裂力學(xué)和損傷力學(xué)相結(jié)合,利用數(shù)值模擬技術(shù)對復(fù)合材料層合板疲勞分層進行分析,同時對復(fù)合材料層合板疲勞壽命進行預(yù)報。首先介紹了單調(diào)載荷下和疲勞周期載荷下離散內(nèi)聚力模型本構(gòu)關(guān)系。在單調(diào)載荷下,視內(nèi)聚力模型關(guān)系為雙線性關(guān)系。通過彈簧單元,建立了單調(diào)載荷下的靜態(tài)損傷演化形式。同時針對高周疲勞下,建立了指數(shù)形式的疲勞累積損傷演化模型。分析了在商業(yè)有限元軟件ABABQUS中的數(shù)值運用,利用子程序進行實現(xiàn)復(fù)合材料層合板的疲勞累積損傷模型,為后面分析復(fù)合材料層合板疲勞擴展奠定理論基礎(chǔ)。其次針對單調(diào)載荷下利用離散內(nèi)聚力模型,分析了復(fù)合材料層合板I、II和復(fù)合型斷裂分層擴展情況。得到三種形式下的復(fù)合材料層合板分層演化過程,并和VCCT技術(shù)進行比較,驗證了離散內(nèi)聚力模型的有效性。同時就內(nèi)聚力模型參數(shù)彈簧單元模量和網(wǎng)格大小對離散內(nèi)聚力模型運用影響進行分析,得到離散內(nèi)聚力模型對這兩個參數(shù)的敏感性很小的結(jié)論。然后分析在高周疲勞載荷下復(fù)合材料層合板疲勞分層擴展情況。利用疲勞離散內(nèi)聚力模型對I型、II型和復(fù)合型裂紋擴展情況。得到三種形式下載荷加載初期時裂紋擴展速率。同時分析在四種載荷大小工況下的疲勞裂紋擴展速率和能量釋放率之間的關(guān)系,并與文獻中實驗數(shù)據(jù)吻合良好。最后建立了用虛擬裂紋閉合技術(shù)來預(yù)測復(fù)合材料疲勞壽命方法,對I型和II型復(fù)合材料層合板壽命進行預(yù)測分析。
[Abstract]:Fatigue failure is a common failure form in engineering. The fatigue limit of most metal materials is 40% of the tensile strength, while the carbon fiber / epoxy composite can reach 90%. Although the fatigue resistance of the composite is better than that of the metal, the fatigue problem can not be avoided. In the analysis of fatigue delamination of composite laminates, the method of fatigue crack propagation of metal materials can no longer be used. Interlaminar delamination and interfacial debonding are two common and decisive failure forms in composite laminates. Because delamination often occurs under periodic loads at low stress levels, mechanical fatigue is the most important factor causing delamination damage of composite structures. Because composite laminates are often nonlinear, the classical fracture mechanics can not be satisfied. At the same time, due to the diversity of the laminates and the influence of the thickness of the laminates, it would be time consuming to study the fatigue delamination propagation of the composite laminates by the experimental method. With the development of computer technology, it is of great engineering significance to seek effective numerical simulation technology and to analyze the fatigue delamination of composite laminates. In this paper, the fracture mechanics and damage mechanics are combined, and the fatigue delamination of composite laminates is analyzed by numerical simulation technique, and the fatigue life of composite laminated plates is predicted at the same time. The constitutive relation of discrete cohesive force model under monotone load and fatigue cyclic load is first introduced. Under monotone load, the cohesion model is regarded as a bilinear relation. The static damage evolution form under monotone load is established by spring element. At the same time, an exponential fatigue cumulative damage evolution model is established for high cycle fatigue. The numerical application in the commercial finite element software ABABQUS is analyzed. The fatigue cumulative damage model of composite laminates is realized by subroutine, which lays a theoretical foundation for the later analysis of fatigue propagation of composite laminated plates. Secondly, based on the discrete cohesive force model under monotone load, the delamination and propagation of composite laminated plates I _ (II) and composite mode fracture are analyzed. The delamination evolution process of composite laminates in three forms is obtained, and compared with VCCT technique, the validity of the discrete cohesive force model is verified. At the same time, the influence of spring element modulus and mesh size on the application of discrete cohesive force model is analyzed, and the conclusion that the sensitivity of discrete cohesive force model to these two parameters is very small is obtained. Then the fatigue delamination propagation of composite laminates under high cycle fatigue loading is analyzed. The fatigue discrete cohesive force model is used to investigate the crack propagation in mode I, II and composite mode. The crack growth rate at the initial loading stage is obtained in three forms. At the same time, the relationship between the fatigue crack growth rate and the energy release rate under four load conditions is analyzed, and it is in good agreement with the experimental data in the literature. Finally, a virtual crack closure method is established to predict the fatigue life of composite materials, and the life of type I and II composite laminates is predicted and analyzed.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB33

【參考文獻】

相關(guān)期刊論文 前2條

1 令波;程哲;張正藝;解德;;面內(nèi)裂紋擴展問題的虛擬裂紋閉合法和離散內(nèi)聚力模型[J];固體力學(xué)學(xué)報;2011年S1期

2 程小全;鄒健;楊琨;張紀(jì)奎;;縫合復(fù)合材料層合板疲勞壽命預(yù)測[J];失效分析與預(yù)防;2008年04期

相關(guān)博士學(xué)位論文 前2條

1 廖曉玲;三維編織C/C復(fù)合材料的疲勞行為以及損傷演變研究[D];西北工業(yè)大學(xué);2006年

2 張溶;纖維增強復(fù)合材料界面疲勞脫粘的數(shù)值模擬[D];北京交通大學(xué);2009年

，

本文編號：2417301