【摘要】：為了充分利用二維編織物生產(chǎn)效率高、纖維空間彎曲扭轉(zhuǎn)程度低、纖維性能損傷少、可設(shè)計(jì)性強(qiáng)等優(yōu)點(diǎn),通過設(shè)計(jì)碳纖維和芳綸纖維混雜結(jié)構(gòu),試圖提高復(fù)合材料抗沖擊性能。本課題首次以碳纖維和芳綸纖維二維編織物混雜鋪層復(fù)合材料為研究對(duì)象,主要對(duì)碳-芳綸混雜二維編織層合復(fù)合材料的沖擊性能及沖擊后壓縮性能進(jìn)行實(shí)驗(yàn)研究,來探究混雜結(jié)構(gòu)對(duì)沖擊性能的影響。本文設(shè)計(jì)制備了層間混雜、夾芯混雜、非對(duì)稱混雜三種碳-芳綸混雜二維編織復(fù)合材料層板以及用作對(duì)比的碳纖維二維編織復(fù)合材料層板。通過落錘低速?zèng)_擊實(shí)驗(yàn)研究了混雜結(jié)構(gòu)對(duì)其沖擊載荷、沖擊吸收能量、沖擊損傷形貌等抗沖擊性能的影響,且采用超聲C掃描和B掃描成像揭示了層板內(nèi)部沖擊損傷,初步判斷材料的抗沖擊性能。發(fā)現(xiàn)碳纖維層板的峰值載荷最高,混雜結(jié)構(gòu)層板峰值載荷稍有降低,然而,混雜結(jié)構(gòu)層板的韌性指數(shù)均大于碳纖維層板;在三種混雜結(jié)構(gòu)層板中,層間混雜層板同時(shí)具有較高的峰值載荷和韌性指數(shù)。超聲C掃描和B掃描成像結(jié)果顯示,碳纖維層板損傷深度最大,沖擊背面出現(xiàn)纖維抽拔斷裂;層間混雜層板損傷深度比碳纖維層板小,但沖擊正面損傷范圍大于碳纖維層板;而夾芯混雜層板出現(xiàn)最多的分層裂紋,非對(duì)稱混雜層板出現(xiàn)內(nèi)部分層現(xiàn)象,表明層間混雜結(jié)構(gòu)能有效地平衡不均衡的層間彎曲應(yīng)力,抵抗落錘的沖擊。在此基礎(chǔ)上,進(jìn)行了面內(nèi)軸向壓縮實(shí)驗(yàn)和沖擊后壓縮實(shí)驗(yàn),在實(shí)驗(yàn)過程中首次采用數(shù)字圖像相關(guān)(DIC)方法獲取試樣面內(nèi)軸向壓縮全場應(yīng)變。將沖擊前后的壓縮性能進(jìn)行對(duì)比,分析得出剩余壓縮性能較好的復(fù)合材料,從而得出具有較優(yōu)抗沖擊性能的混雜結(jié)構(gòu)復(fù)合材料試樣。壓縮結(jié)果表明,在較高面內(nèi)軸向壓縮載荷下,載荷會(huì)偏離試樣軸向(偏心),出現(xiàn)面外位移,并同時(shí)產(chǎn)生壓縮應(yīng)變和彎曲拉伸應(yīng)變。碳纖維層板應(yīng)變分布主要是彎曲拉伸應(yīng)變,其它三種混雜結(jié)構(gòu)層板應(yīng)變分布主要是壓縮應(yīng)變,說明芳綸纖維增加了復(fù)合材料韌性,層板塑性增加,軸向壓縮載荷偏離小。對(duì)比無沖擊損傷面內(nèi)軸向壓縮和沖擊后壓縮結(jié)果,發(fā)現(xiàn)碳纖維層板壓縮強(qiáng)度和壓縮模量下降最少,對(duì)低速?zèng)_擊損傷最不敏感,表現(xiàn)出較高的沖擊損傷容限。在三種混雜結(jié)構(gòu)中,層間混雜下降最少,DIC云圖中彎曲拉伸應(yīng)變最少、壓縮載荷分配均勻,說明層間混雜能提供較好的抵抗彈性變形能力以及抗失效能力。
[Abstract]:In order to make full use of the advantages of high production efficiency of two-dimensional braided fabric, low bending and torsion degree of fiber space, less damage to fiber properties and strong designability, the hybrid structure of carbon fiber and aramid fiber was designed to improve the impact resistance of composites. For the first time, the impact properties and post-impact compression properties of carbon fiber and aramid fiber composites were studied in this paper, in which carbon fiber and aramid fiber two-dimensional braided hybrid laminated composites were used as the object of study, and the impact properties and post-impact compression properties of carbon-aramid fiber hybrid two-dimensional braided composites were studied. To explore the impact of hybrid structure on the impact properties. In this paper, three kinds of carbon-aramid hybrid two-dimensional braided composite laminates, interlaminar hybrid, sandwich hybrid, asymmetric hybrid, and carbon fiber two-dimensional braided composite laminates for comparison were designed and fabricated. The effects of hybrid structure on impact load, energy absorption and morphology of impact damage were studied by low speed impact test, and the impact damage of laminates was revealed by ultrasonic C scan and B scan imaging. The impact resistance of the material is preliminarily judged. It is found that the peak load of CFRP is the highest and the peak load of hybrid laminate is slightly reduced. However, the toughness index of CFRP is higher than that of CFRP. Among the three kinds of hybrid laminates, the interlaminar hybrid laminates have high peak load and toughness index at the same time. The results of ultrasonic C scan and B scan showed that the damage depth of carbon fiber laminates was the largest and the fiber pull-out fracture appeared on the back of the impact, and the damage depth of interlaminar hybrid laminates was smaller than that of carbon fiber laminates, but the range of impact front damage was larger than that of carbon fiber laminates. However, there are most delamination cracks in sandwich hybrid laminates and internal delamination in asymmetric hybrid laminates, which indicates that the interlaminar hybrid structures can effectively balance the uneven interlaminar bending stress and resist the impact of drop hammer. On this basis, in-plane axial compression experiments and post-impact compression experiments were carried out. In the process of the experiment, the in-plane axial compression full-field strain was obtained by digital image correlation (DIC) method for the first time. By comparing the compressive properties before and after impact, the composites with good residual compressive properties were obtained, and the hybrid composite specimens with better impact resistance were obtained. The compression results show that under higher in-plane axial compression load, the load deviates from the axial (eccentric) direction of the specimen, resulting in out-of-plane displacement, and the compression strain and the bending tensile strain are produced at the same time. The strain distribution of carbon fiber laminates is mainly flexural tensile strain, while the other three hybrid structures are mainly compressive strain, which indicates that aramid fiber increases the toughness of composites, increases the plasticity of laminates, and reduces the deviation of axial compression load. Compared with in-plane compression without impact damage and compression after impact, it is found that the compression strength and modulus of carbon fiber laminates decrease least, and they are the least sensitive to low-velocity impact damage, showing a higher impact damage tolerance. Among the three hybrid structures, the interlaminar hybrid decreases the least, the DIC cloud diagram shows that the bending tensile strain is the least, and the compression load distribution is uniform, which indicates that the interlaminar hybrid can provide better resistance to elastic deformation and failure resistance.
【學(xué)位授予單位】：天津工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB332

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