玻璃纤维复合材料层合板冲击后的压缩强度

对不同厚度的二维编织环氧玻璃纤维层合板进行落锤冲击试验及冲击后压缩破坏试验,以研究低速冲击对复合材料层合板剩余压缩强度(CAI)的影响。用透光描影及热揭层方法对冲击损伤形式进行描述。讨论了损伤宽度、损伤面积与冲击能量及剩余压缩强度、模量间的关系,并建立有限元模型,采用开口等效及软化夹杂等分析方法对材料的冲击后压缩强度值进行估算。     

低速冲击后三维中空夹层复合材料的压缩损伤容限

为了研究低速冲击后三维中空夹层复合材料的压缩损伤容限(剩余压缩强度),制作了满足要求的实验件并进行了剩余压缩强度对比实验.采用数码照片和外观检测等方法对压缩破坏损伤发展的过程进行了研究,分析了压缩破坏机理.结果表明,冲击损伤严重影响了三维中空夹层复合材料板的抗压能力,剩余压缩强度随冲击能量的增加而减少;三维中空夹层复合材料的压缩破坏主要由前面板控制,前面板发生局部屈曲的载荷与板的压缩破坏载荷几乎相等;表面蒙皮不仅能减少冲击损伤,而且能使板内的损伤显露在表面,容易让人发现.     

电热载荷对CFRP复合材料冲击后压缩性能研究

采用实验室电热载荷试验环境与测试平台,测试了CFRP复合材料在多种电流制度下试样的表面温度分布,并获得了CFRP复合材料电阻在不同电流强度下的变化规律,初步揭示了CFRP复合材料的电阻与电流强度之间呈线性递减的关系;对五种不同电流处理的CFRP复合材料进行了冲击后的剩余压缩强度试验(CAI)测试,试验后采用超声C扫描检测、外观检查与断口侧面宏观观察方法对损伤与失效特征进行了对比分析。研究结果表明,CFRP复合材料的剩余压缩强度随通入电流强度的大小呈先保持不变后下降的趋势,当电流超过20A时,试样表面冲击凹坑深度和冲击损伤面积增长较快,分层损伤与纤维断裂现象越来越严重。     

纤维环向缠绕复合材料气瓶冲击阻抗性能研究

新能源汽车用复合材料气瓶采用复合材料/金属混杂结构,其冲击损伤特性与采用纯复合材料结构有很大的不同,本文结合复合材料气瓶和试板模拟试验,采用冲击能量吸收率、分层损伤扩展阻力、剩余强度比衰减指数等参数作为其冲击阻抗性能的评价指标。采用不同的支撑夹具对玻纤/环氧单向板进行落球冲击试验,以模拟复合材料气瓶的不同材质内胆对纤维缠绕层冲击损伤的影响。研究发现,在一定冲击能量作用下,改变复合材料/金属混杂结构的形式能使其冲击能量吸收率发生变化,并可提高层合板的冲击损伤临界值,即提高其冲击承载能力;冲击能量吸收率越高分层损伤扩展阻力越小,且含冲击损伤层合板的剩余强度衰减越快。因此在设计复合材料气瓶时,需要考虑复合材料/金属混杂结构对分层损伤扩展阻力和冲击能量吸收率的影响。     

缝合编织复合材料低速冲击以及冲击后弯曲性能研究

两片三维四向编织厚片叠层缝合和四片三维四向编织薄片叠层缝合,固化之后得到两种厚度接近的缝合编织复合材料。对两种材料进行冲击以及冲击后弯曲实验,分析其表面和内部损伤特征、分布和机理,探讨其冲击后的剩余弯曲性能。结果表明,3.2J/mm的冲击能量下,缝合编织薄片的表面损伤面积和厚度方向上的损伤小于缝合编织厚片;冲击后弯曲实验中,两种材料受压面的树脂裂纹在厚度方向上的相邻两编织片之间几乎观察不到,受拉面的树脂裂纹沿着冲击造成的树脂裂纹继续向横向、纵向和厚度方向扩展;缝合编织薄片未经冲击与冲击后的弯曲强度和弯曲模量均大于缝合编织厚片,但其弯曲断裂变形小于缝合编织厚片。     

复合材料层合板损伤容限敏感性参数研究

本文针对碳纤维增强复合材料层合板冲击下的损伤容限参数敏感性进行分析.对复合材料层合板损伤容限的影响参数、纤维角度、铺层顺序、层合板厚度、冲击速度和冲击角度等进行冲击损伤仿真,采用蔡-吴强度准则评价层合板冲击的剩余强度,并对各参数影响的敏感性排序,确定纤维角度和铺层顺序为复合材料层合板冲击下损伤容限的敏感参数.     

复合材料层合板冲击损伤剩余强度分析

民用飞机复合材料结构设计时必须考虑复合材料层合板的冲击损伤.通过试验测量和数值模拟两种方法分析碳纤维增强复合材料层合板低速冲击损伤后的剩余压缩强度,试验采用标准试验规范进行测量,数值模拟分析采用层内渐进损伤模型和层间Cohesive模型模拟分析层合板冲击损伤以及剩余压缩强度.数值模拟与试验结果对比表明,该数值模拟分析方...     

CFRP层合板冲击后剩余强度及黏弹性能研究

通过对制备的环氧基碳纤维增强复合材料(CFRP)层合板进行低速冲击剩余压缩强度试验研究，分析了CFRP层合板的冲击后剩余性能，然后观察CFRP层合板的冲击凹坑回弹现象，分析CFRP层合板的黏弹性能，深入分析冲击过程中能量的吸收与转化。结果表明：当冲击能量越来越大时，CFRP层合板的损伤越来越严重，其剩余压缩强度越来越低；从凹坑边缘到凹坑中心处，CFRP层合板的应变能密度逐渐增大；凹坑回弹部位位于凹坑中心区域附近，呈现局部突起状，最终凹坑剖面近似于不规则“W”形。     

T300／QY8911层合复合材料低能量冲击后剩余压缩强度实验研究

本文对Ｔ３００／ＱＹ８９１１层合复合材料低能量冲击后的剩余压缩强度进行了实验研究,采用落锤（自由落体）冲击试验方法预制损伤,并利用Ａ扫描无损检测方法测定了冲击后损伤区的面积然后采用自行研制的板材压缩夹具（可防止试件在压缩过程中的整体失稳）,应用电测技术测定Ｔ３００／ＱＹ８９１１层合复合低能量冲击后剩余压缩中度,半考虑了湿热环境对其影响。     

CFRP层合板冲击后压缩失效分析数值模拟

复合材料层合板的损伤容限是复合材料结构设计的关键因素。针对碳纤维增强复合材料(CFRP)层合板低速冲击损伤和压缩破坏问题,本文基于连续损伤力学和粘结单元模型,在ABAQUS中对两种不同冲击能量下的层合板进行了低速冲击和冲击后压缩仿真分析,并对层内和层间损伤进行了研究,分析了层合板的冲击损伤与压缩失效行为,通过与试验结果进行对比,验证了该模型的有效性。研究结果表明:冲击损伤对层合板的剩余压缩强度有着重要影响,试件的破坏开始于冲击损伤区域,并逐渐扩展到层合板的边缘,压缩力快速下降,层合板最终失效。     

湿热环境对碳纤维/环氧复合材料的冲击破坏特性影响

为了研究湿热环境对碳纤维/环氧树脂(CFRP)复合材料抗冲击性能的影响,对碳纤维/环氧复合材料层合板进行70℃水浴处理,采用锥头圆柱形弹体对湿热饱和试样和干燥室温试样进行速度分别为45 m/s、68 m/s、86 m/s的冲击,采用激光测速仪测量冲击前后的速度,然后采用超声C扫描检测系统、超景深三维显微系统、扫描电镜(SEM)等方法对试样的冲击破坏进行检测。实验结果表明:随着冲击速度的增加,试样的破坏投影面积增加;在速度较低时,湿热环境对碳纤维/环氧树脂层合板的损伤孔洞面积影响更大;湿热处理之后的碳纤维/环氧树脂层合板层间性能明显降低。     

聚脲弹性体/纤维增强树脂基复合材料抗冲击性能研究

玻璃纤维增强树脂基复合材料在使用过程中极易受到外力冲击,造成复合材料结构破坏,严重威胁其安全使用寿命。研究了聚脲弹性体涂层对玻璃纤维增强乙烯基树脂复合材料抗冲击性能的影响。通过简支梁摆锤冲击试验和光学显微镜对前涂覆(FCGF)、后涂覆(BCGF)及未涂覆(NCGF)试样进行对比测试。研究结果表明,聚脲弹性体涂层的弹性形变和断裂破坏能够大幅增加冲击能耗,提高整体的冲击强度。当试样聚脲涂层厚度相同时,前涂覆(FCGF)试样聚脲弹性体冲击后并未完全断裂,主要依靠弹性形变吸收冲击能量,起缓冲减震作用;后涂覆(BCGF)试样聚脲弹性体发生断裂破坏能够消耗更多的冲击能量,其整体结构破坏最小,冲击强度更高。     

Indentation Fracture Response and Damage Resistance of Al2O3-ZrO2 Composites Strengthened by Transformation-Induced Residual Stresses

Indentation fracture behavior of three-layer Al₂O₃-ZrO₂ composites with substantial compressive residual stresses was compared with the behaviors of monolithic Al₂O₃ and Al₂O₃-ZrO₂ ceramics without intentionally introduced residual stresses. The indentation cracks were smaller in the three-layer specimens relative to the monolithic specimens in agreement with the predictions of indentation fracture mechanics theory. Indentation and strength testing were used to show that a residual compressive stress of approximately 500 MPa exists in the outer layers of the three-layer composites. The three-layer specimens showed excellent damage resistance in that the strength differential between the three-layer and monolithic indented specimens was maintained at indentation loads up to 1000 N, the maximum indentation load used in the experiments.     

Low‐velocity impacts in continuous glass fiber/polypropylene composites

The low‐velocity impact behavior of a continuous glass fiber/polypropylene composite was investigated. Optical microscopy and ultrasonic scanning were used to determine the impact‐induced damage. At low impact energy, the predominant damage mechanism observed was matrix cracking, while at high energy the damage mechanisms observed were delamination, plastic deformation, which produced a residual specimen curvature, and a small amount of fiber breakage at the edge of the indentation on the impacted face of the specimens. The impact load vs. time signals were recorded during impact and showed that the load corresponding to the onset of delamination was independent of the impact energy in the range tested. The load at which the onset of delamination occurred corresponded to the values obtained by performing a linear regression of the delaminated area, obtained by ultrasonic scanning, as a function of the impact force. Tensile and flexural tests performed on impacted specimens showed that the tensile and flexural residual strengths and the flexural modulus decreased with increasing incident impact energy, while the post‐impact residual tensile modulus remained constant. The dynamic interlaminar fracture toughness was evaluated from the critical dynamic (impact) strain energy release rate of specimens with a delamination simulated by an embedded insert. The results are compared with the interlaminar fracture toughness values obtained during subcritical steady crack growth.     

Compression after impact (CAI) strength of concrete cylinders reinforced by non‐adhesive filament wound composites

Concrete cylinders reinforced by filament wound composites were fabricated, and the compressive strength of the composite/concrete cylinders was tested after low‐energy impact. In this study, a glass fiber woven cloth wrapping method and a filament winding technique were adopted to wrap the concrete cylinder. In order to investigate the influence of composite/concrete interfacial bonding on the compression after impact (CAI) strength, aluminum foil was introduced into the composite/concrete interface; thus, the compressive behavior of the composite/concrete system with or without inserting the aluminum foil was compared. The effects of aluminum foil in the curing process were also revealed. Based upon the results of this study, the placement of aluminum foil can significantly enhance the compressive strength of the composite/concrete cylinder. The CAI strength depicts that the winding angle used in the filament winding process can significantly influence the reinforcing effects. Among the tested cylinders, the FWIC (defined in the text) [90₂/±60/90₂] cylinder shows the highest CAI strength—129.4 MPa—which is 4.5 times higher than the impacted concrete cylinder and 4.1 times higher than the pure concrete cylinder. Fracture mode was also investigated on the cylinder reinforced by the composites wound with different winding angles. The placement of aluminum foil reduces shear stress transfer across the composite/concrete interface, which affects not only the impact response but also the compressive strength.     

Enhanced interlaminar shear and impact performance of woven carbon/epoxy composites interleaved with needle punched high performance polyethylene fiber nonwoven

In this study, high-performance polyethylene (HPPE) fiber-based needle punched nonwovens were interleaved in cross-plied woven carbon fabric/epoxy composite laminates to enhance their interlaminar and impact properties. The placement of needle punched nonwoven interleaves exhibited considerable enhancement in interlaminar shear strength (ILSS), impact damage tolerance, and compression after impact (CAI) strength of laminates as evidenced by higher interlaminar strength, less absorbed energy, higher elastic energy, reduced damage degree, reduced out-of-plane deformation, higher load-bearing capacity, and higher residual compressive strength as compared to control sample. In particular, the composite laminate with placement of interleaves in alternating sequence between carbon plies resulted in 205.76% increase in ILSS and 129, 103 and 85% increase in CAI at 10, 25, and 40 J impact energy, respectively. Moreover, damaged surface area and out-of-plane deformation reduced to 38.75% and 62.5%, respectively for the same specimen impacted at 40 J energy. These results suggest that the HPPE fiber-based needle punched nonwoven interleaving can be adopted as a simple and low-cost approach compared with other interleaving techniques, to enhance the resistance to delamination, impact performance, and damage tolerance of traditional structural laminates.     

冲击位置对挖补修理层合板冲击后压缩性能的影响

使用过程中的低速冲击损伤对修理后的复合材料结构同样会造成威胁.设计并进行了复合材料挖补修理结构的低速冲击及冲击后压缩试验,测量了试验件的损伤投影面积和剩余压缩强度,分析了不同冲击位置的影响.结果表明,挖补修理层合板冲击后压缩强度比未修补板的低,挖补层合板对低速冲击位置较为敏感.冲击点离开挖补区一定距离后,挖补对层合板的低速冲击及其继后压缩性能的影响消失.     

Study on the damage behavior of carbon fiber composite after low-velocity impact under hygrothermal aging

In this article, T800 carbon fiber/epoxy resin composite was subjected to hygrothermal aging. By analyzing the mass change, surface morphology before and after aging, infrared spectra, and dynamic mechanical properties, the effect of hygrothermal aging on the composite properties was studied. The hygrothermal aging of the composite after low-velocity impact, the effects of environmental factors on the damaged area, and the post-impact compression properties of composites were studied. The results showed that the saturation moisture absorption rate of the composite after aging (71°C constant temperature) was 0.88%. Upon increasing the impact energy, an indentation appeared before the inflection point at 35 J. When the impact energy was less than 15 J, aging did not affect invisible damage. Above this, the damaged area and number of internal cracks and defects in the composite were increased. After aging, the compressive strength of composite laminates with impact damage decreased obviously. During the aging stage, the residual compressive strength of the sample was the lowest in the moisture saturated state, and hygrothermal aging had little effect on the compression failure mode after impact.