阳极氧化工艺对纤维-铝合金层板力学性能的影响

通过改变铝合金表面阳极氧化工艺参数,研究了阳极氧化电压和时间对玻璃纤维-铝合金(GLARE)层板抗拉强度和层间剪切强度的影响.通过SEM观察了铝合金表面Al2O3多孔膜和层板断面形貌,分析了铝合金/树脂胶接界面对层板力学性能的影响.结果表明,阳极氧化电压为20 V时,GLARE层板抗拉强度和层间剪切强度随着阳极氧化时间延长而增大,在20 min时出现最大值,继续延长阳极氧化时间,层板强度随之下降;阳极氧化时间为20 min时,GLARE层板抗拉强度和层间剪切强度随着阳极氧化电压增大而增大,在20V时出现最大值,继续增大电压,强度随之下降.     

阳极氧化铝合金-环氧树脂动态润湿行为

对铝合金板材进行了磷酸阳极化表面处理,采用电子显微镜观察了铝合金表面形貌,采用量重法测试了铝合金/环氧树脂动态接触角,研究分析了阳极化电压与时间、浸润速度等对铝合金/环氧树脂动态润湿行为的影响。结果表明,氧化电压保持20 V不变,随着氧化时间延长,动态接触角先大幅减小然后缓慢增加;氧化时间保持20 min不变,随着氧化电压上升,动态接触角先减小后增加;阳极氧化工艺参数20 V/30min处理的铝合金板具有最小前进接触角68.63°与后退接触角10.22°,相比未处理铝合金/环氧树脂前进与后退接触角分别减小18.89和25.1°;增加铝合金浸入树脂的速度,接触角增大。     

建筑用碳纤维增强环氧树脂复合材料的制备及其性能研究

选择以T700碳纤维为增强相，将碳纤维经浓HNO₃浸渍处理0,40,80,120和160 min后掺入到环氧树脂中，制备了碳纤维增强环氧树脂复合材料。分析了浸渍时间对复合材料微观形貌、力学性能和热稳定性的影响。结果表明，经浓HNO₃浸渍的碳纤维表面粗糙度增大，沟槽数量和深度增加，碳纤维和环氧树脂的结合强度增大；随碳纤维浸渍时间的增大，复合材料的界面剪切强度、层间剪切强度、弯曲强度和弯曲模量均先增大后减小，当浸渍时间为120 min时，复合材料的界面剪切强度和层间剪切强度均达到了最大值，分别为80.2和90.3 MPa,其弯曲强度和弯曲模量也达到了最大值，分别为902.6 MPa和79.3 GPa,且应力-应变最高点增大，弯曲性能提高；在800℃下浓HNO₃浸渍处理120 min的复合材料的残炭率最大为58.2%,热稳定性最佳。     

GLARE层板挤压渐进损伤分析

对GLARE36/5层板进行挤压性能试验研究,采用超声C扫描、断口微距拍摄和扫描电子显微镜等方法观测GLARE层板挤压渐进损伤过程和最终破坏模式。结果表明:GLARE层板挤压起始损伤为铝合金塑性变形;损伤扩展阶段,0°纤维主要承受挤压正应力,铝合金塑性变形增大,铺层间分层起始并扩展;0°纤维屈曲折断后层内纤维基体损伤和分层损伤急剧扩展,层板最终发生挤压破坏。将GLARE层板挤压失效分为层内失效和层间失效,采用应变描述的Hashin准则和界面单元方法并引入金属塑性建立GLARE层板挤压渐进损伤数值模型,数值模型对层板损伤起始位置、分层产生位置、损伤演化过程、最终破坏模式及破坏载荷进行了预测,计算结果与试验结果吻合较好,说明该计算方法能够有效模拟GLARE层板挤压渐进损伤性能。      

阳极氧化电压对钛合金TC4阳极氧化TiO_2膜层表面的影响

在草酸盐、硅酸盐和磷酸盐电解液体系中,在钛合金Ti-6Al-4V(TC4)表面制备阳极氧化TiO_2膜层,研究了TiO_2膜层的表面显微结构、化学组成和生物活性。在室温用恒压阳极氧化法制备TC4表面阳极氧化TiO_2膜,以TC4为阳极,不锈钢为阴极,电解液组成为:20 g/L的Na_2C_2O_4、10 g/L的Na_2SiO_3·9H_2O、9.25 g/L的NaH_2PO_4和2 g/L的NaOH,阳极氧化电压为10-120 V,氧化时间50 min,电源频率200 Hz。用XRD、AFM、SEM及XPS等手段分别测量了膜层的物相、三维形貌、氧化膜层表面的显微结构及化学组成。结果表明:氧化电压对TiO_2膜层的物相组成基本没有影响,氧化膜层呈非晶态TiO_2。当氧化电压为30 V时,TiO_2膜层表面由孔径1.3μm左右的孔和凸起颗粒组成的粗糙结构,随着氧化电压增加表面凸起颗粒逐渐减少,粗糙度降低,当氧化电压为100 V时场致溶解的作用使TiO_2膜层表面凸起颗粒不明显,TiO_2膜层表面的粗糙度低于TC4基体,表面孔径为240 nm。TC4阳极氧化TiO_2膜层表面的微纳米结构和大量的羟基—OH,有利于提高TiO_2膜层的生物活性和骨生长特性。     

2A96铝合金表面阳极氧化及性能研究

针对铝合金表面极易氧化生成结构疏松、耐腐蚀性差的氧化膜问题,利用阳极氧化法对2A96铝合金表面进行防腐蚀处理。通过改变阳极氧化实验中的氧化电压,在2A96铝合金表面制备不同的阳极氧化膜;利用金相显微镜观察各个阳极氧化膜的表面形貌、测厚仪测量其厚度、显微硬度计测定其硬度、点滴实验获取其点滴时间、电化学工作站获取其极化曲线和交流阻抗谱,进而对阳极氧化膜的耐腐蚀性进行研究。结果表明,在所测电压范围(8～16 V)内,随着电压的升高,阳极氧化膜的厚度、硬度、点滴时间也逐渐增加,耐腐蚀性能也随之增强。2A96铝合金经过表面阳极化处理后,其性能显著提高。     

酒石酸-硫酸阳极氧化工艺参数对LY12铝合金耐蚀性的影响

酒石酸-硫酸阳极氧化(Tartaric sulfuric anodizing,TSA)作为铝合金六价铬阳极氧化的有效替代工艺之一,近些年在研究和应用方面均取得了较大的进展。为了改善TSA阳极氧化膜的耐蚀性,通过均匀设计方案及试验,对TSA阳极氧化处理工艺参数进行了详细的研究,得到了阳极氧化参数与膜层耐蚀性之间的联系,并通过试验验证了优化的处理工艺。结果表明:最佳工艺参数是电解液组成为55 g/L硫酸+88 g/L酒石酸的混合液,阳极氧化的电压、时间、温度分别为14.0 V、23 min、37.0℃和17.5 V、20 min、35.5℃。     

阳极氧化对钛合金表面HA-TiO2复合涂层的影响

对钛合金表面进行阳极氧化预处理,然后用水热电化学方法在其上沉积羟基磷灰石-二氧化钛(HA-TiO2)复合涂层,研究了阳极电压对基体表面的物相、形貌、润湿性和粗糙度的影响,以及对HA的物相、形貌及生物活性的影响。结果表明:阳极氧化电压高于110 V时在钛基体表面出现金红石型和锐钛矿型TiO2,孔径尺寸随阳极电压的增加而增大。在120 V预处理的钛合金试样表面具有好的润湿性,粗糙度Ra达到0.56μm。HA涂层沿c轴方向择优生长,并呈现分层生长,HA的结晶度随着阳极氧化电压的提高先增大后减小,在120 V取得最大值。在120 V氧化处理的试样具有较好的生物活性。     

氧气流量对LY12铝合金微弧氧化膜致密性的影响

通过调整工艺参数与氧气流量在LY12铝合金表面获得均匀、致密的微弧氧化膜层。利用SEM、XRD及电化学工作站等研究膜层的厚度、微观形貌、相组成以及耐腐蚀性能,讨论通氧微弧氧化作用机制,并分析氧气流量对膜层致密性的影响。结果表明:膜层厚度随电压、氧化时间和电解液组分浓度的增加呈规律性变化;氧气的助烧结作用能促进致密层的生长,随着氧气流量的增加,致密层厚度呈现先增加后减小的规律;KF 105g/L,KOH 85g/L,NaAlO_2 12g/L,电压110V,氧化时间15min,氧气流量为0.010L/s时得到厚度30μm的致密膜层,自腐蚀电位提高至-0.11V,腐蚀电流密度下降至2.1×10^-6A/cm^2,比铝合金基体降低2个数量级以上,表现出良好的耐腐蚀性。     

国产聚丙烯腈基高强高模碳纤维电化学氧化表面处理工艺

以国产聚丙烯腈（PAN）基M55J级碳纤维（CF）为研究对象,首先在不同电解液体系中进行循环伏安多重扫描,比较其氧化能力的差异,进行电解液的筛选。然后用最佳电解液对CF进行恒流连续氧化处理,通过Raman光谱、XPS和SEM的表征,研究了电化学氧化对高强高模CF表面结构及化学组成的影响,并通过测试CF束丝拉伸性能及其与树脂结合后的层间剪切强度对CF的力学性能进行了表征。研究结果表明,NH₄HSO₄电解质溶液对CF进行表面处理时,其刻蚀能力最强,可以有效改善其表面活性,增大其表面粗糙度和含氧官能团数量。采用0.6 mol/L的NH₄HSO₄电解液体系,在1 mAcm^-2电流密度下对CF进行阳极氧化,CF与树脂间的层间剪切强度比未处理提高了164%,同时CF的拉伸强度略有提高,模量无明显变化。     

界面结合状态对玻璃纤维-Al混杂复合层板疲劳行为的影响

通过两种 Al 合金表面处理方法及水煮老化处理,得到了不同界面结合状态的玻璃纤维-Al 混杂复合层板,进行了层板层间剪切强度和疲劳裂缝扩展试验,研究了界面结合强度对层板疲劳行为的影响。试验发现,当界面结合强度较高时,层板的疲劳裂缝扩展速率较低,伴随疲劳裂缝扩展而产生的脱层破坏区尺寸较小,脱层破坏发生在树脂层与增强纤维之间;界面结合强度较低时,层板的疲劳裂缝扩展速率较高,脱层区尺寸较大,脱层破坏发生在 Al 层和树脂层之间。     

γ射线辐照对高模量碳纤维及碳纤维/氰酸酯复合材料性能的影响

通过模拟空间γ射线辐照环境,采用⁶⁰Co-γ射线对高模量碳纤维及其增强的改性氰酸酯复合材料进行辐照,采用SEM和XRD对辐照前后的碳纤维及碳纤维/氰酸酯复合材料进行了分析和表征,研究了复合材料的质量损失率、拉伸性能及层间剪切强度随γ射线辐照剂量的变化规律。结果表明,γ射线辐照能增加碳纤维表面粗糙度;质量损失率随γ射线辐照剂量增大先增加后趋于平缓,但均小于1%;碳纤维/氰酸酯复合材料拉伸性能与层间剪切强度均随γ射线辐照剂量增大先提高后降低,在吸收剂量为5×10⁵ rad时出现最大值,拉伸强度为1 803 MPa,拉伸模量为243 GPa,层间剪切强度为72 MPa。     

Response of hygrothermally aged GLARE 4A laminates under static and cyclic loadings

An experimental investigation focusing on the hygrothermal aging-structural degradation–mechanical property relationship of GLARE 4A laminates was conducted. Water immersion conditioning at 80 °C for up to 4 months was carried out on GLARE 4A laminates. It was found that although the outer aluminum layers effectively protected the glass/epoxy composite layers from hygrothermal attack, the composite layers absorbed moisture through the edges. Consequently, significant decrease in both, the tensile strength and fatigue life of the GLARE 4A laminates, was observed although no structural defects were apparently identifiable in the microstructures of the conditioned laminates. Detailed experimental investigation was conducted to study the mechanism of mechanical property decay due to hygrothermal aging. It is proposed that the strength of the S2-glass fibers was not fully realized due to the weakening of the fiber/matrix interface and the deterioration of the sizing, which consequently led to the reduction in the tensile strength and fatigue life of the GLARE 4A laminates. The stiffness degradation characteristics of GLARE 4A laminates under cyclic loading were also investigated.     

Reinforcement effects of aluminum–lithium alloy on the mechanical properties of novel fiber metal laminate

The novel fiber metal laminates based on aluminum–lithium alloy (NFMLs) were investigated to improve the stiffness and damage tolerance. The aluminum–lithium sheets were rolled from 2 mm to 0.3 mm by cold forming, aged to T3 state and anodized in phosphoric acid. Then, NFMLs were prepared by the optimized process. The mechanical properties of NFMLs were evaluated by floating roller, interlaminar shear, tensile, bending and fatigue crack growth (FCG) tests respectively. The results indicated that the aluminum–lithium alloy was mainly strengthened by δ′ phases at T3 state. The rough micro morphology was constructed on the surface of aluminum–lithium layer by anodizing process. NFMLs and conventional Glare presented similar density and quite excellent interlaminar properties. Compared with Glare, however, NFMLs exhibited slight strength increase and obvious elastic modulus improvement regardless of the fibers plies and sampling direction. A better resistance to FCG of NFMLs was also verified.     

基于纤维束增强树脂基复合材料测试的单向层合板层间剪切性能的预估方法

纤维束增强树脂基复合材料（FBC）及其单向层合板在标准Iosipescu剪切实验中表现出非常相似的破坏特征,然而测量得到的剪切强度却有明显差异。本文使用两种碳纤维和两种环氧树脂制备了3种FBC和单向层合板,对FBC剪切强度和单向层合板层间剪切强度进行了测量与分析。应用界面单元方法分析了纤维束与基体之间的界面应力场,发现FBC剪切试件中纤维束/基体界面附近的应力状态为拉剪耦合,而单向层合板中界面处于纯剪切应力状态,这一差异导致FBC剪切实验测量的强度低于单向层合板的剪切强度。本文基于Yamada-Sun强度理论建立了FBC剪切强度与单向层合板剪切强度之间的关系模型,应用该模型预测的单向层合板剪切强度与实测强度之间达到良好的一致性,相对偏差为10%左右。根据本文提出的方法,通过制样较简单的FBC试验能够预测和评估相应单向层合板的层间剪切性能。     

纳米Al2O3-碳纤维多尺度增强聚酰胺基复合材料的制备及力学性能

采用叠层模压法制备了纳米Al₂O₃-碳纤维织物多尺度增强聚酰胺基（nano Al₂O₃-CFF/PA6）复合材料层压板。借助场发射扫描电子显微镜（FESEM）、同步热分析仪（TGA/DSC）和FTIR,研究了模压温度、压力和纳米Al₂O₃加入量等因素对nano Al₂O₃-CFF/PA6复合材料力学性能的影响。研究表明：在模压温度为230℃、模压压力为3 MPa和保压时间为15 min时,CFF/PA6层压板的弯曲强度为250.3 MPa,层间剪切强度为87.6 MPa,平行层厚方向的冲击强度为41.2 MPa,垂直层厚方向为9.6 MPa。当基体中的Al₂O₃含量达到6wt%时,nano Al₂O₃-CFF/PA6层压板的弯曲强度为387.6 MPa,层间剪切强度为35.7 MPa,平行和垂直层厚方向的冲击强度分别为80.3 MPa和25.6 MPa。     

Effects of Constituents and Lay-up Configuration on Drop-Weight Tests of Fiber-Metal Laminates

Impact responses and damage of various fiber-metal laminates were studied using a drop-weight instrument with the post-impact damage characteristics being evaluated through ultrasonic and mechanical sectioning techniques. The first severe failure induced by the low-velocity drop-weight impact occurred as delamination between the aluminum and fiber-epoxy layers at the non-impact side. It was followed by a visible shear crack in the outer aluminum layer on the non-impact face. Through-thickness shear cracks in the aluminum sheets and severe damage in the fiber laminated layers (including delamination between adjacent fiber-epoxy laminae with different fiber orientations) developed under higher energy impacts. The impact properties of fiber-metal laminates varied with different constituent materials and fiber orientations. Since it was punched through easily, the aramid-fiber reinforced fiber-metal laminates (ARALL) offered poorer impact resistance than the glass-fiber reinforced fiber-metal laminates (GLARE). Tougher and more ductile aluminum alloys improved the impact resistance. GLARE made of cross-ply prepregs provided better impact resistance than GLARE with unidirectional plies.     

Effect of damage on the interlaminar shear properties of hybrid composite laminates at cryogenic temperatures

This paper presents the experimental and numerical characterization of the interlaminar shear failure of hybrid composite laminates at cryogenic temperatures. Cryogenic short beam shear tests were performed on hybrid laminates consisting of woven glass fiber reinforced polymer (GFRP) composites and polyimide films to evaluate their interlaminar shear strength. Microscopic observations of damage accumulation and failure mechanisms were also made on failed specimens. In addition, a progressive damage analysis was conducted to predict the initiation and growth of damage in the specimens, and the interlaminar shear strength was determined from the maximum shear stress in the failure region. The damage effect on the interlaminar shear properties of hybrid laminates at cryogenic temperatures was examined based on the experimental and numerical results.     

The impact properties and damage tolerance and of bi-directionally reinforced fiber metal laminates

Fiber metal laminates are an advanced hybrid materials system being evaluated as a damage tolerance and light weight solution for future aircraft primary structures. This paper investigates the impact properties and damage tolerance of glass fiber reinforced aluminum laminates with cross-ply glass prepreg layers. A systematic low velocity impact testing program based on instrumented drop weight was conducted, and the characteristic impact energies, the damage area, and the permanent deflection of laminates are used to evaluate the impact performance and damage resistance. The post-impact residual tensile strength under various damage states ranging from the plastic dent, barely visible impact damage (BVID), clearly visible impact damage (CVID) up to the complete perforation was also measured and compared. Additionally, the post-impact fatigue behavior with different damage states was also explored. The results showed that both GLARE 4 and GLARE 5 laminates have better impact properties than those of 2024-T3 monolithic aluminum alloy. GLARE laminates had a longer service life than aluminum under fatigue loading after impact, and they did not show a sudden and catastrophic failure after the fatigue crack was initiated. The damage initiation, damage progression and failure modes under impact and fatigue loading were characterized and identified with microscopy, X-ray radiography, and by deply technique.