铺层结构对复合材料层合板弯曲强度及失效行为的影响

通过改变偏轴角为45°和90°的[45°/–45°],[0°/90°]正交铺层组的质量分数,设计了6种复合材料层合板铺层结构。研究了两种偏轴角正交铺层组共同存在的铺层结构对真空辅助树脂传递模塑工艺复合材料层合板弯曲强度及失效行为的影响。通过弯曲实验获得6种复合材料层合板的弯曲强度、损伤特征以及应力–应变曲线。结果表明,随偏轴角为90°的[0°/90°]铺层组质量分数的增加,复合材料层合板的弯曲强度逐渐增大;两种偏轴角正交铺层组共同存在的铺层结构可引起复合材料层合板在弯曲载荷作用下的损伤模式多元化。     

复合材料双钉胶-螺混合连接结构参数对失效载荷的影响

在试验验证仿真模型可行性的基础上,通过数值模拟的方法探究了复合材料的铺层顺序,混合连接结构的宽径比、端径比、孔径比等参数对钛合金-复合材料双钉胶-螺混合连接结构承载能力的影响。研究结果表明:在常用的铺层顺序中,铺层顺序为[45°/0°/-45°/90°]_(3s)时,混合连接结构的承载能力最好;增加宽径比,连接结构的失效载荷会逐渐上升,但是连接强度却逐渐下降;在一定范围内,适当增加端径比或孔径比可以提高连接结构的承载能力,当超过这个范围时,连接结构的承载能力会下降。     

碳纤维薄壁管溃缩变形模式和吸能机理研究分析

通过铺放和缠绕组合工艺制备[0°/90°]、[±45°₂/0°/0°/90°/0°]、[±45°]、[64°₂/0°₂/64°₂/0°₂/64°₂]四种不同铺层角度的碳纤维薄壁管试件,并在试件端部设置开槽和开孔的触发机制。对试件进行轴向准静态压缩和电镜扫描,研究不同铺层角度试件的变形压溃模式和吸能机理。结果表明,不同铺层角度试件的变形模式不同,[0°/90°]试件呈钻石模式,[±45°]试件呈塔型渐变模式,[64°₂/0°₂/64°₂/0°₂/64°₂]呈开花模式变形,[±45°₂/0°/0°/90°/0°]试件变形介于[0°/90°]和[64°₂/0°₂/64°₂/0°₂/64°₂]试件变形模式之间。其中,[±45°...     

铝合金与碳纤维复合材料自冲铆接强度影响因素研究

分别采用厚度为2. 5 mm不同轴向碳纤维复合材料板和2. 5 mm 5052铝合金板进行自冲铆接实验,分析其接头的成形质量;利用万能拉伸试验机对其进行拉伸试验,并分析接头的失效形式。结果表明,相同轴向碳纤维复合材料板,7 mm铆钉接头质量和拉伸强度均优于6 mm铆钉接头质量和拉伸强度。7 mm铆钉的连接件拉伸强度比使用6 mm铆钉的拉伸强度,在[0/90]4铺层时增加了25. 45%,[0/180]_4铺层时进增加了13. 77%,[-45/45]_4铺层时增加了21. 12%;相同铆钉高度不同轴向时,接头质量并无明显差异,但最大载荷不同。高度6 mm铆钉时连接强度,[0/90]_4铺层比[0/180]_4铺层增加了29. 34%,[-45/45]_4铺层比[0/90]4铺层增加了16. 20%;高度7 mm铆钉时连接强度,[0/90]_4铺层比[0/180]_4铺层增加了42. 63%,[-45/45]_4铺层比[0/90]_4铺层增加了12. 18%。铆接件失效形式主要是铆钉从复合材料板处拉脱。在相同轴向下失效位移大致相同。     

(±45°/90°/0°)_s准各向同性层合板的拉伸强度

根据经典层合板理论,层合板(±45°/90°/0°)s是准各向同性层合板,其拉伸刚度在板面内各个方向上都相同,而拉伸强度是随偏轴角θ改变而变化,即强度方面不具有各向同性的特点。本文首先研究(±45°/90°/0°)s这种准各向同性层合板拉伸强度在偏轴角θ从0°至45°之间的变化情况,然后通过分别改变单层板强度参数和弹性常数来研究该层合板的拉伸强度的变化情况,并分析其破坏形式。最后与NCF材料的试验结果进行了比较。     

玻纤铺层方向对玻纤/EVE复合材料性能的影响

以0°,90°,0°/90°,0°/45°/-45°/90°分别作为玻璃纤维(GF)单向铺层方式,研究了不同的铺层方式对GF/EVE(环氧乙烯基酯树脂)复合材料力学性能的影响。结果表明,0°铺层方向的复合材料在单一方向的力学性能最好,0°/45°/-45°/90°铺层方向的复合材料可以看作各向同性材料,应用范围更加广泛。     

不同铺层复合材料螺栓连接的研究

实验研究了在E/D=4(边距/孔径),W/D=5(宽度/孔径)的3种铺层[90/+45/-45/0]s,[90/0/+45/-45]s,[+45/-45/90/0]s的玻璃纤维/环氧复合材料试样在不同的扭矩和垫片尺寸(外径(Dw)/内径(D))下的静态破坏强度。实验结果表明,试样破坏强度随夹持力增大而增大,但增加趋势不断减弱,在5Nm扭矩下三种铺层的强度分别比其销钉连接增大175%,196%,141%;在销钉连接下,[90/+45/-45/0]s铺层强度比[90/0/+45/-45]s铺层高12.7%,[+45/-45/90/0]s铺层强度比[90/+45/-45/0]s铺层高10.8%;在手动拧紧下[90/+45/-45/0]s铺层强度比[90/0/+45/-45]s铺层高3.5%,而[+45/-45/90/0]s铺层强度比[90/+45/-45/0]s铺层高0.37%;垫圈的外内径比在2～3范围内,试样强度伴随外内径比的增大而增大,在3～4时,强度变化很小。     

基于ANSYS的复合材料层合板的拉伸失效模拟

基于ANSYS的APDL语言开发复合材料层合板的拉伸失效模块,实现有限元分析的参数化建模和累积失效分析.采用Solid64宴体单元建立复合材料层合板的三维模型,依据改进的三维Haisin失效准则对结构单元进行失效判断,并对失效单元进行刚度退化.当失效单元贯穿所有单层时,复合材料层合板结构彻底失效.通过对铺层方式为[0/45/-45/90]s复合材料层合板结构拉伸模拟,探讨其拉伸破坏形式,得到层合结构的最终拉伸强度,并把其拉伸强度与文献实验结果进行对比,得到的结果与实验一致.该方法简便直观,便于工程运用.     

复合材料层合板面内剪切实验方法的评价

复合材料层合板的面内剪切特性是进行复合材料结构设计必不可少的参数。本文对常见的4种面内剪切实验方法进行了简单介绍。采用5种E玻璃纤维织物/乙烯基酯树脂层合板,其铺层结构分别为[0]3s,[0/90]3s,[CSM/0/90]2s,[±45]3s和[(0/90)2/(±45)2/(0/90)2]s。对2种复合材料层合板面内剪切实验方法进行了实验研究,分别为±45°拉伸实验(ASTM D3518)和V形开口轨道剪切实验(ASTM D7078)。实验结果表明,±45°拉伸实验在测试层合板面内剪切模量方面具有较高的精度,而在测试面内剪切强度方面往往偏低,具有非常差的精度。     

含裂纹金属板复合材料胶接修补结构残余热应力分析

残余热应力会增大裂纹尖端的应力强度因子SIF,加快疲劳裂纹扩展速率,缩短修补结构的疲劳寿命。利用三维有限元方法,对含裂纹金属板复合材料胶接修补结构中的残余热应力进行了分析,利用虚拟裂纹闭合技术(VCCT)计算了修复结构裂纹尖端的SIF。并以SIF为判据,讨论了补片铺层方向、固化温度、胶层的材料参数对修复结构残余热应力的影响。结果表明,[0°/45°/-45°/90°]s的铺层方式可有效降低残余热应力引起的SIF;残余热应力引起的SIF随着固化温度的升高而线性增加;胶层的材料参数及胶层厚度对残余热应力引起的SIF影响不显著。     

碳纤维树脂基复合板料的铺层方式对低速冲击性能的影响

为研究碳纤维增强树脂基复合材料(CFRP)板铺层方式对低速冲击性能的影响,设计了一系列CFRP板的冲击试验。对CFRP板的铺层方式、冲击能量的形式进行调节和改变,获取CFRP板在各种条件下的低速冲击行为;再通过冲击实验和超声波扫描的方法研究冲击过程中CFRP板的铺层方式和冲头质量对碳纤维树脂基复合材料板冲击性能的影响。结果表明,在15 J的低能量作用下冲击CFRP板时,冲头的质量越大,该板对能量的吸收率越大,损伤面积也越大;相同能量和相同冲头质量的冲击情况下,铺层方式为[0°/45°/90°/-45°]_2的抗冲击性能最好。CFRP板的冲击载荷、能量吸收和损伤形态与冲击能量的大小以及冲头动量密切相关。     

Progressive failure analysis of carbon-fibre/epoxy composites laminates to study the effect of stitch densities under in-plane tensile loading

Through thickness reinforced stitched laminates with different stitch densities (0.11 and 0.028?mm^?2) were studied in order to analyse effects on laminate behaviour, under in-plane tensile loading based on continuum mechanics. Multi-layered stitched laminates with the stacking sequence [+45/90/?45/0₂/+45/90₂/?45/0]_s were modelled on a lamina-wise basis to analyse the macroscopic damage and local stress–strain constitutive behaviour. Interfaces between lamina and stitch yarns were assumed to be perfectly glued and were modelled by the contact capability. Discretisation procedures using the principle of virtual work were applied in addition to discretisation of the contact traction. Progressive failure analysis with Puck’s failure criteria was conducted to characterise the failure behaviour of the laminate. This analysis showed that reinforcement density is one of the key factors affecting strength, stiffness and crack propagation in composite laminates. By suppressing the damage initiation, densely stitched laminates showed 15.2% higher in-plane stiffness than moderately stitched laminates. The results obtained by the finite element technique are consistent with the experimental results.     

T700／3234层合板力学性能的研究

研究了T700／3234层合板力学性能,T700／3234层合板铺层45°／-45°／0°／90°／0°／0°／90°／0°／-45°／45°.T700／3234中温固化环氧碳纤维单向预浸料适应于热压罐成型工艺方法.测试了23℃、60℃、80℃、100％下,T700／3234层合板拉伸性能、压缩性能、弯曲性能、层间剪切强度及层合板的拉伸剪切强度,得出不同温度下层合板各项力学性能的保持率,表明：T700／3234复合材料使用温度不大于80℃.     

Stress analyses of composite tee joints at elevated temperature

Thermal–structural coupling nonlinear finite element analyses are conducted in this paper to determine three-dimensional stresses of a composite tee joint, which is formed when a right angled plate is adhesively bonded to a base plate at elevated temperature. The von-Mises stresses of the adhesive layer of the tee joint with three different laminate stacking sequences viz. unidirectional [0]₈, cross-ply [(0/90)_s]₂, and angle-ply [(+45/?45)_s]₂ laminates have been evaluated when the tee joint is subjected to an out-of-plane loading through the right angled plate in addition to an elevated temperature applied at the undersurface of the base plate. The effects of laminate stacking sequence and temperature on von-Mises stresses have been investigated in this paper. The effects of the coefficient of thermal expansion and thermal conduction of the adhesive layer on von-Mises stresses have also been studied. Conclusions about the stresses of the composite tee joint with different stacking sequence, different coefficient of thermal expansion, and different thermal conduction of the adhesive layer are drawn.     

PE-UHMW/PE-LD层合板损伤声发射信号频率特征研究

为揭示聚乙烯自增强复合材料(PE-UHMW/PE-LD)不同损伤模式的声发射信号频率特征,通过对基体、单纤维复合材料、90°单向板+45°/-45°层合板的拉伸破坏,分别诱导产生基体损伤、纤维断裂、纤维/基体界面损伤和层间损伤的AE信号,并和非损伤AE信号(环境噪声、断铅模拟)频率特征进行对比。实验结果表明,非损伤AE信号和损伤AE信号之间均具有不同的峰值频率和频率分布特征。     

Morphological,mechanical, and electromagnetic interference shielding effectiveness characteristics of glass fiber/epoxy resin/MWCNT buckypaper composites

Glass fiber/epoxy resin composites (GF/EP) using one and three multi-walled carbon nanotube buckypapers (BP) were obtained and their complex parameters, reflectivity, and electromagnetic interference (EMI) shielding effectiveness (SE) at X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz) were evaluated. The preparation of BP used polyacrylonitrile (PAN) nanofibers (PF These composites show both large storage and energy loss capacity in both bands revealing promising results related to EMI SE applications. Besides, a high attenuation of around 67% and 72% were achieved for BP based composites. The cross-section view of the buckypaper and the laminates was analyzed by scanning electron microscopy (SEM). The incorporation of the CNT film into the laminates showed no improvements in the elastic properties through dynamic mechanical analyses (DMA). Nevertheless, a decrease in the shear properties by the compression shear test (CST) and interlaminar shear strength (ILSS) has been observed. GF/EP/BP/PF composite presented a reduction of 29 and 39% in its ILSS properties compared to the base laminate (GF/EP). Also, the decrease was even more significant, revealing a steep reduction in its CST properties. On the other hand, the removal of the pan nanofiber (PF) led to better mechanical properties for GF/EP/BP/RPF composites. Results have shown ILSS values of 47.4 ± 2.2 MPa which are close to the base laminate (52.4 ± 3.1 MPa). The removal of the PF provided larger porous in the CNT network, making the impregnation by epoxy easier in the BP/RPF which resulted in improved shear properties compared to GF/EP/BP/PF samples.     

RTM制备玻璃纤维增强环氧树脂复合材料的力学性能分析

以环氧树脂为基体,短切玻璃纤维和玻璃纤维布为增强材料,通过RTM工艺制备了玻璃纤维增强环氧树脂(GF/EP)复合材料,并研究了RTM工艺制备玻璃纤维布增强环氧树脂(L-GF/EP)和短切玻璃纤维增强环氧树脂(S-GF/EP)复合材料的拉伸和弯曲性能,分析了开孔对两种复合材料拉伸性能的影响。结果表明:在拉伸过程中,开孔试样因孔边产生的应力集中,导致其拉伸强度与无孔试样相比下降了30%左右;玻纤铺层类型的不同对复合材料的力学性能具有显著影响;L-GF/EP复合材料内部结构完整,在载荷作用下,复合材料的弯曲断裂呈现一定的假塑性断裂模式,达到弯曲极限挠度值后,出现一定程度的回弹现象,其力学性能优于S-GF/EP复合材料。