复合材料层合板低能量冲击损伤与失效关系研究
发布时间：2018-09-03 11:17
【摘要】：材料结构遭受低能量冲击会使结构造成不明显的损伤,从而使性能下降继而对构件的安全产生严重威胁。按照损伤的部位可分为内部损伤及外部损伤,对复合材料层合板进行冲击首先受到损伤的部位是外部损伤,则对外部损伤的观察和描述更直接更客观,对材料的冲击损伤性能表征也是最具有说服力的地方,所以对冲击区域的外部损伤研究则更具有研究意义和价值。本文采用在连续纤维增强层合结构复合材料中最具代表性的玻璃纤维增强树脂基复合材料和碳纤维维增强树脂基复合材料,纤维铺层采用准各向同性的单向层合板以及以铺层为方格布的多向层合板为研究对象。对其进行自由落体低能量冲击试验,单向板采用厚度的1~5倍、多向板采用厚度的2~6倍作为冲击能量。冲击后采用超景深电子显微镜对冲击区域进行观察并对损伤特征进行描述,并对冲击区域进行渗漏检测。在超景深电子显微镜下进行观察,发现复合材料层合板冲击损伤区域周围随着冲击能量的改变,也会出现不同数量不同损伤特征的裂纹,即当冲击能量比较小时,层合板损伤区域周围没有裂纹出现或者只有细小的微裂纹;随着冲击能量的增大,裂纹的损伤特征更加明显,裂纹的数量和长度均有所增加。从复合层合板单位厚度冲击能量与凹坑深度关系曲线中,可以发现玻璃纤维单向层合板冲击能量为板厚的3倍时、玻璃纤维多向层合板冲击能量为板厚的4倍时凹坑深度变化曲线出现了拐点并且在出现拐点后的试件冲击区域的背面最表面均出现了“泛白”现象并且产生轻微隆起现象,碳纤维多向层合板冲击能量为板厚的3倍时凹坑深度变化曲线出现了拐点。这些拐点表明在该冲击能量作用下使试件形成了明显的冲击损伤,此时复合材料层压板对冲击的抵抗能力发生了突变。经过渗漏实验发现玻璃纤维单向层合板在冲击能量为2~3J/mm、多向层合板在冲击能量为3~4J/mm时出现渗漏现象,而碳纤维多向层合板在冲击能量为2~3J/mm时出现渗漏现象。实验数据表明,玻璃纤维多向层合板比单向层合板有更好的抗冲击能力,玻璃纤维多向层合板比碳纤维多向层合板有更好的抗冲击能力。本文通过对冲击凹坑深度、单位厚度冲击损伤面积、外观损失等这些冲击损伤因素进行量化表征,从而给出复合层合板的冲击失效判据,将失效损伤判据结合实际工程经验便可以对常用种类的复合材料层合板进行冲击损伤程度鉴定。像这种由多种损伤因素错综复杂地交织在一起造成复合层合板失效的问题,难以给出精确评价。故本文基于模糊数学的理论,建立冲击后复合材料层合板损伤情况的综合评价指标体系,建立模糊综合评价计算模型及程序,从而判定复合材料层合板的损伤程度。
[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.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU599
[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.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU599
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