【摘要】：材料結(jié)構(gòu)遭受低能量沖擊會(huì)使結(jié)構(gòu)造成不明顯的損傷,從而使性能下降繼而對(duì)構(gòu)件的安全產(chǎn)生嚴(yán)重威脅。按照損傷的部位可分為內(nèi)部損傷及外部損傷,對(duì)復(fù)合材料層合板進(jìn)行沖擊首先受到損傷的部位是外部損傷,則對(duì)外部損傷的觀察和描述更直接更客觀,對(duì)材料的沖擊損傷性能表征也是最具有說(shuō)服力的地方,所以對(duì)沖擊區(qū)域的外部損傷研究則更具有研究意義和價(jià)值。本文采用在連續(xù)纖維增強(qiáng)層合結(jié)構(gòu)復(fù)合材料中最具代表性的玻璃纖維增強(qiáng)樹脂基復(fù)合材料和碳纖維維增強(qiáng)樹脂基復(fù)合材料,纖維鋪層采用準(zhǔn)各向同性的單向?qū)雍习逡约耙凿亴訛榉礁癫嫉亩嘞驅(qū)雍习鍨檠芯繉?duì)象。對(duì)其進(jìn)行自由落體低能量沖擊試驗(yàn),單向板采用厚度的1~5倍、多向板采用厚度的2~6倍作為沖擊能量。沖擊后采用超景深電子顯微鏡對(duì)沖擊區(qū)域進(jìn)行觀察并對(duì)損傷特征進(jìn)行描述,并對(duì)沖擊區(qū)域進(jìn)行滲漏檢測(cè)。在超景深電子顯微鏡下進(jìn)行觀察,發(fā)現(xiàn)復(fù)合材料層合板沖擊損傷區(qū)域周圍隨著沖擊能量的改變,也會(huì)出現(xiàn)不同數(shù)量不同損傷特征的裂紋,即當(dāng)沖擊能量比較小時(shí),層合板損傷區(qū)域周圍沒(méi)有裂紋出現(xiàn)或者只有細(xì)小的微裂紋;隨著沖擊能量的增大,裂紋的損傷特征更加明顯,裂紋的數(shù)量和長(zhǎng)度均有所增加。從復(fù)合層合板單位厚度沖擊能量與凹坑深度關(guān)系曲線中,可以發(fā)現(xiàn)玻璃纖維單向?qū)雍习鍥_擊能量為板厚的3倍時(shí)、玻璃纖維多向?qū)雍习鍥_擊能量為板厚的4倍時(shí)凹坑深度變化曲線出現(xiàn)了拐點(diǎn)并且在出現(xiàn)拐點(diǎn)后的試件沖擊區(qū)域的背面最表面均出現(xiàn)了“泛白”現(xiàn)象并且產(chǎn)生輕微隆起現(xiàn)象,碳纖維多向?qū)雍习鍥_擊能量為板厚的3倍時(shí)凹坑深度變化曲線出現(xiàn)了拐點(diǎn)。這些拐點(diǎn)表明在該沖擊能量作用下使試件形成了明顯的沖擊損傷,此時(shí)復(fù)合材料層壓板對(duì)沖擊的抵抗能力發(fā)生了突變。經(jīng)過(guò)滲漏實(shí)驗(yàn)發(fā)現(xiàn)玻璃纖維單向?qū)雍习逶跊_擊能量為2~3J/mm、多向?qū)雍习逶跊_擊能量為3~4J/mm時(shí)出現(xiàn)滲漏現(xiàn)象,而碳纖維多向?qū)雍习逶跊_擊能量為2~3J/mm時(shí)出現(xiàn)滲漏現(xiàn)象。實(shí)驗(yàn)數(shù)據(jù)表明,玻璃纖維多向?qū)雍习灞葐蜗驅(qū)雍习逵懈玫目箾_擊能力,玻璃纖維多向?qū)雍习灞忍祭w維多向?qū)雍习逵懈玫目箾_擊能力。本文通過(guò)對(duì)沖擊凹坑深度、單位厚度沖擊損傷面積、外觀損失等這些沖擊損傷因素進(jìn)行量化表征,從而給出復(fù)合層合板的沖擊失效判據(jù),將失效損傷判據(jù)結(jié)合實(shí)際工程經(jīng)驗(yàn)便可以對(duì)常用種類的復(fù)合材料層合板進(jìn)行沖擊損傷程度鑒定。像這種由多種損傷因素錯(cuò)綜復(fù)雜地交織在一起造成復(fù)合層合板失效的問(wèn)題,難以給出精確評(píng)價(jià)。故本文基于模糊數(shù)學(xué)的理論,建立沖擊后復(fù)合材料層合板損傷情況的綜合評(píng)價(jià)指標(biāo)體系,建立模糊綜合評(píng)價(jià)計(jì)算模型及程序,從而判定復(fù)合材料層合板的損傷程度。
[Abstract]:The damage caused by low energy shock will lead to the deterioration of the performance of the structure and the serious threat to the safety of the components. According to the location of the damage, it can be divided into internal damage and external damage. The first damage to the composite laminates is the external damage, so the observation and description of the external damage is more direct and objective. The characterization of the impact damage properties of materials is also the most persuasive, so the study of external damage in the impact area is of more significance and value. In this paper, glass fiber reinforced resin matrix composites and carbon fiber dimensional reinforced resin matrix composites, which are the most representative of continuous fiber reinforced laminated structure composites, are used in this paper. Quasi isotropic unidirectional laminated laminates and multidirectional laminated laminates with laminates as grid are used as research objects. The low energy impact test of free falling body is carried out. The unidirectional plate adopts 1: 5 times of thickness and the multidirectional plate adopts 2 times of thickness as impact energy. After impact, the impact area was observed and the damage characteristics were described by using the hyperfield electron microscope, and the leakage detection of the impact area was carried out. Under the superfield depth of field electron microscope, it is found that there are different number of cracks with different damage characteristics around the impact damage zone of composite laminates, that is, when the impact energy is small, There are no cracks or only small microcracks around the damage zone of laminated plates, and with the increase of impact energy, the damage characteristics of cracks become more obvious, the number and length of cracks increase. From the relation curve between impact energy per unit thickness and pit depth of composite laminates, it can be found that when the impact energy of glass fiber unidirectional laminates is 3 times of plate thickness, When the impact energy of glass fiber multidirectional laminates is 4 times the thickness of the plate, the curve of the depth variation of the crater appears inflection point, and the most surface of the impact area of the specimen after the inflection point appears the phenomenon of "pan-white" and the phenomenon of slight bulge. When the impact energy of carbon fiber multidirectional laminated plate is 3 times of the thickness of the plate, the inflection point appears in the curve of the depth variation of the pit. These inflection points indicate that the impact damage of the composite laminates is obviously formed under the impact energy, and the resistance of composite laminates to impact is abrupt. The leakage experiments show that glass fiber unidirectional laminates have leakage at impact energy of 2J / mm, multidirectional laminates with impact energy of 3~4J/mm, and carbon fiber multidirectional laminates with impact energy of 2~3J/mm. Experimental data show that glass fiber multidirectional laminates have better impact resistance than unidirectional laminates, and glass fiber multidirectional laminates have better impact resistance than carbon fiber multidirectional laminates. In this paper, the impact failure criterion of composite laminates is presented by quantifying the impact damage factors, such as impact pit depth, impact damage area per unit thickness, appearance loss, etc. The failure damage criterion combined with practical engineering experience can be used to identify the impact damage degree of common composite laminates. For example, it is difficult to give accurate evaluation for the failure of composite laminates caused by various damage factors intertwined intricately. Therefore, based on the theory of fuzzy mathematics, the comprehensive evaluation index system of composite laminates after impact is established, and the fuzzy comprehensive evaluation model and program are established to judge the damage degree of composite laminates.
【學(xué)位授予單位】：北京建筑大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU599

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本文編號(hào)：2219825