層間剪切性能及破壞機(jī)理
(中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室， 長沙 410083)
摘 要: 以瀝青四氫呋喃溶液、 瀝青四氫呋喃溶液+20%焦炭粉（質(zhì)量分?jǐn)?shù)）和酚醛樹脂四氫呋喃溶液+60%焦炭（質(zhì)量分?jǐn)?shù)）為預(yù)浸料預(yù)浸炭纖維， 模壓制成初坯體， 然后再浸漬瀝青-炭化， 制備了3種單向纖維增強(qiáng)炭/炭（C/C）復(fù)合材料試樣。 對試樣的密度、 開孔率、 層間剪切強(qiáng)度和顯微結(jié)構(gòu)進(jìn)行了測試和觀察，探討了剪切破壞的機(jī)理。 結(jié)果表明: C/C復(fù)合材料的層間剪切強(qiáng)度隨密度的增大和孔隙度的降低而提高，高溫處理雖可使致密度得到進(jìn)一步增大， 但層間剪切強(qiáng)度則由于基體炭的軟化， 以及基體炭與纖維（或焦炭粉顆粒）界面的變化而顯著降低； 由于微裂紋和孔洞的存在， 剪切裂紋前沿應(yīng)力集中被釋放，可阻止裂紋繼續(xù)擴(kuò)展， 載荷的繼續(xù)增大導(dǎo)致新裂紋的生成并擴(kuò)展， 所以C/C復(fù)合材料的三點(diǎn)彎曲剪切破壞呈多裂紋復(fù)合剪切模式。
關(guān)鍵字: 炭/炭復(fù)合材料； 浸漬； 層間剪切性能； 顯微結(jié)構(gòu)
（State Key Laboratory for Powder Metallurgy，
Central South University， Changsha 410083， China）
Abstract:Three kinds of unidirectional fiber-reinforced C/C composites were fabricated by the liquid pitch impregnation into the mould-preforms. The fibers were firstly pre-impregnated with pitch， pitch plus 20% coke and phenolic resin plus 60% coke， and then moulded into the preforms. Their densities， open porosities， interlaminar shear strengths (ILSS) and microstructures were tested and observed， as well as the destroy mechanism was studied. The microstructures were studied with optical metallograph and SEM. The results show that the interlaminar shear strengths of C/C composites decrease with increasing densities and decreasing open porosities. After high temperature treatment， the ILSS of samples decrease due to the matrix soften and the change of the interface of matrix and carbon fibers as well as coke particles. Due to presence of the microcracks and pores， the stress focus on crack-front in the shear process can be released， and the extension of cracks is prevented. The new cracks will be brought out and extended with increasing load. So the destroy of three-point bending shear in the C/C composites is a model of multi-crack complex shear. The lower the samples density， the more evidently the microcracks and pores， the lower the ILSS， and the more complex the cracks.
Key words: C/C composites； impregnation； interlaminar shear strengths (ILSS)； microstructure
