高强高模聚酰亚胺纤维/环氧树脂复合材料力学性能与破坏机制

以高强高模聚酰亚胺（PI）纤维为增强体,以航空级环氧树脂（EP）为基体,通过热熔法制备预浸料并采用热压罐成型技术制备了PI/EP复合材料层合板,对其力学性能和破坏形貌进行了分析。结果表明:高强高模PI纤维与EP具有良好的界面结合力,PI/EP复合材料的层间剪切强度为65.2 MPa,面内剪切强度为68.6 MPa;良好的界面结合状态能充分发挥PI纤维优异的力学性能,PI/EP复合材料的纵向拉伸强度达1 835 MPa,弯曲强度为834 MPa;PI/EP复合材料纵向拉伸破坏模式为散丝爆炸破坏,同时由于高强高模PI纤维还具有优异的韧性和较高的断裂伸长率,PI/EP复合材料从受力到失效断裂的时间较长;PI/EP复合材料纵向压缩破坏模式为45°折曲带破坏。高强高模PI/EP复合材料为航空航天先进复合材料增加了一个全新的选材方案。      

Properties of synthetic diamond and graphene nanoplatelet-filled epoxy thin film composites for electronic applications

Epoxy thin film composites filled with particulate nanofillers; synthetic diamond and graphene nanoplatelets were prepared and characterized based on tensile, thermal, and electrical properties. The influences of these two types of fillers, especially in terms of their loading, sizes and shapes, were discussed. It was found that the epoxy thin film composites incorporating synthetic diamond displayed optimum properties where the addition of synthetic diamond from 0 to 2 vol.% results in higher elastic modulus, tensile strength, elongation at break, thermal conductivity and storage modulus if compared to those of graphene nanoplatelets composites. Both thin film composites showed improvement in the glass transition temperature with increasing filler loadings. Results on the electrical conductivity of both systems showed that higher conductivity is observed in graphene nanoplatelets composites if compared to synthetic diamond composites.     

Mechanical Properties of Thermoplastic and Thermoset Composites Reinforced with 3D Biaxial Warp-knitted Fabrics

In this study, two types of thermoplastic matrices (low melting point polyethylene terephthalate (LPET) fiber and polypropylene (PP) fiber) and glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate the thermoplastic and thermoset composite materials with 3D biaxial warp-knitted fabrics. Thermoplastic and thermoset composites were fabricated using hot-press and resin transfer molding (RTM) methods. The fabricated samples were tested with tensile and three-point flexural tests. In thermoplastic composites, samples in the 90° direction and LPET matrix showed the best tensile and flexural properties with an improvement of 39 and 21% tensile modulus and strength, 16 and 8% flexural modulus and strength compared to the PP samples in the same direction. In thermoset composites, samples in the 90° direction and MWCNTs showed the best improvement of the flexural modulus and strength with 97 and 58% compared to the samples without MWCNTs. This improvement can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.     

碳纳米管-玻璃纤维织物增强环氧复合材料的结构与性能

通过物理沉积法和静电吸附法在玻璃纤维织物(GF)表面包覆多壁碳纳米管(MWCNTs),制备GF-d-CNTs和GF-a-CNTs两种多尺度增强体,采用真空灌注工艺制备MWCNTs-GF增强环氧复合材料。采用静态、动态力学法、扫描电镜、红外光谱等分析手段,对复合材料的拉伸、弯曲、层间剪切、黏弹性和微观组成结构表征。结果表明:MWCNTs包覆于GF表面形成"倒刺"结构,并通过啮合作用增强了复合材料界面的强度和树脂韧性,提高了复合材料的玻璃化温度(Tg)等;与纯GF复合材料相比,GF-d-CNTs复合材料的拉伸强度和模量分别提高14.5%和37.9%,弯曲强度和模量分别提高26.2%和36.6%,层间剪切强度提高31.5%;GF-a-CNTs复合材料的Tg提高了8.9℃。     

Investigations on the fabrication and the characterization of glass/epoxy,carbon/epoxy and hybrid composites used in the reinforcement and the repair of aeronautic structures

This paper reports the fabrication and the characterization of glass/epoxy, carbon/epoxy and hybrid laminated composites used in the reinforcement and/or the repair of aeronautic structures. These composites were manufactured by the hand lay-up process. Their physical, thermal and mechanical behaviors are discussed in terms of moisture absorption, thermal stability, tensile strength, elastic modulus, flexural strength, flexural modulus and abrasive wear resistance. The impact of hygrothermal aging on the mechanical properties of each composite group has been also investigated.The main results indicated that after water immersion, all composites showed significant moisture absorption especially for glass/epoxy composite. Thermogravimetric analysis showed that the hybrid composite presented the best thermal stability behavior while the glass/epoxy composite the bad behavior. The mechanical properties of the carbon/epoxy composites, in the bulk material, were considerably higher than those of the glass/epoxy; the hybrid structure presented intermediate mechanical properties. The same trend was also observed in terms of wear properties. Finally, a deleterious effect on the strength of all composites due to hygrothermal exposure was established. However, carbon/epoxy composites seem to be less susceptible to aging damage after 90 days at 90 °C.     

静电植绒法处理多壁碳纳米管改性玻纤织物/环氧树脂复合材料的制备及力学性能

为提高玻纤增强环氧树脂复合材料的力学性能,采用静电植绒法将多壁碳纳米管(MWCNTs)附着在玻纤织物表面,得到改性的玻纤织物。利用一种低黏度的环氧树脂和所制得的改性织物,采用真空辅助成型工艺(VARI)制备了MWCNTs改性格玻纤织物/环氧树脂复合材料层合板,表征了层合板的力学性能。对进行力学实验后的MWCNTs改性玻纤织物/环氧树脂复合材料试样断口进行了SEM和OPM观察。结果显示:与未添加MWCNTs的玻纤织物/环氧树脂复合材料层合板相比,添加了MWCNTs的层合板的拉伸强度降低了10.24%,弯曲强度降低了13.90%,压缩强度降低了17.33%,拉伸模量和弯曲模量分别提高了19.38%和16.04%,压缩模量提高了13%;MWCNTs与玻纤织物之间的结合较弱,在拉伸作用下,存在明显的脱粘和分层;将改性玻纤织物在200℃下热压处理2h后,制备的MWCNTs改性玻纤织物/环氧树脂复合材料层合板的力学性能均有所提高,热压处理后树脂与玻纤织物之间的界面结合得到改善。     

聚酰亚胺表面处理玻璃纤维/环氧树脂复合材料力学性能

采用浇铸成型工艺制备含0.5wt%、长度分别为1 mm、3 mm、5 mm的短切玻璃纤维/环氧树脂（GF/EP）复合材料,研究含活性酚羟基和不含酚羟基的两种聚酰亚胺（PI）处理GF表面对纤维束拉伸强度及GF/EP复合材料力学性能的影响,并进一步研究PI处理GF对复合材料热性能的影响。研究结果表明,经过PI处理的GF,集束性和拉伸强度得到提高。含活性酚羟基聚酰亚胺（PI1）处理的GF拉伸强度由原丝束的517 MPa提高到1 032 MPa,不含酚羟基聚酰亚胺（PI2）处理的GF提高到986 MPa。当PI1处理的GF长度为3 mm时,GF/EP复合材料的力学性能最好,拉伸强度比未处理的提高23.62%,拉伸模量提高34.03%,弯曲强度提高28.74%,断裂韧性提高13.04%;PI2处理的GF,GF/EP复合材料拉伸强度提高15.87%,拉伸模量提高23.70%,弯曲强度提高14.11%,断裂韧性提高4.05%。此外,PI处理GF对GF/EP复合材料热性能也有一定程度的提高。     

Mechanical and electrical properties of carbon fiber composites with incorporation of graphene nanoplatelets at the fiber–matrix interphase

In this study, carbon fibers (CFs) were coated with graphene nanoplatelets (GnP), using a robust and continuous coating process. CFs were directly immersed in a stable GnP suspension and the coating conditions were optimized in order to obtain a high density of homogeneously and well-dispersed GnP. GnP coated CFs/epoxy composites were manufactured by a prepreg and lay-up method, and the mechanical properties and electrical conductivity of the composites were assessed. The GnP coated CFs/epoxy composites showed 52%, 7%, and 19% of increase in comparison with non-coated CFs/epoxy composites, for 90° flexural strength, 0° flexural strength and interlaminar shear strength, respectively. Meanwhile, incorporating GnP in the CF/epoxy interphase significantly improved the electrical conductivity through the thickness direction by creating a conductive path between the fibers.     

The effect of fibre content on the mechanical properties of glass fibre mat/polypropylene composites

Glass fibre mat was prepared by the fibre mat-manufacturing machine developed in our laboratory. Glass fibre mat reinforced polypropylene (PP) composites were fabricated with the variation of glass fibre content. Tensile, flexural and high rate impact test was conducted to investigate the effect of glass fibre content on the mechanical properties of the glass fibre mat/PP composite. Deformation and fracture behaviour of the glass fibre mat/PP composites was investigated to study the relationship with the mechanical property data. The tensile and flexural modulus increased with the increment of glass fibre content. However, the tensile and flexural strengths exhibited maximum values and showed a decrease at the higher glass fibre content than this point. The impact absorption energy also exhibited a similar result with the tensile and flexural property data.     

黄麻纤维/环氧复合材料及其性能分析

本文研究了黄麻单向纤维和随机分布短纤维增强环氧树脂复合材料的制作和拉伸、压缩、弯曲、层间剪切以及冲击性能,并讨论了它的破坏机理与微观形貌。黄麻纤维本身性能优异,并且具有优于其它天然植物纤维的可纺性。黄麻纤维复合材料的优异性能具有进一步研究开发的潜力。     

Plasma surface modification of advanced organic fibres

The interlaminar shear strength, interlaminar fracture energy, flexural strength and modulus of extended-chain polyethylene/epoxy composites are improved substantially when the fibres are pretreated in an ammonia plasma to introduce amine groups on to the fibre surface. These property changes are examined in terms of the microscopic properties of the fibre/matrix interface. Fracture surface micrographs show clean interfacial tensile and shear fracture in composites made from untreated fibres, indicative of a weak interfacial bond. In contrast, fracture surfaces of composites made from ammonia plasma-treated fibres exhibit fibre fibrillation and internal shear failure as well as matrix cracking, suggesting stronger fibre/matrix bonding, in accord with the observed increase in interlaminar fracture energy and shear strength. Failure of flexural test specimens occurs exclusively in compression, and the enhanced flexural strength and modulus of composites containing plasma-treated fibres result mainly from reduced compressive fibre buckling and debonding due to stronger interfacial bonding. Fibre treatment by ammonia plasma also causes an appreciable loss in the transverse ballistic impact properties of the composite, in accord with a higher fibre/matrix interfacial bond strength.     

石墨烯/环氧树脂复合材料的制备与力学性能

通过对氧化石墨热膨胀还原并用超声分散制备了石墨烯,并对所得产物进行分析表征。用超声分散和模具浇注成型法制备了石墨烯/环氧树脂纳米复合材料。研究了石墨烯含量对石墨烯/环氧树脂复合材料力学性能和断面形貌的影响,分析了石墨烯对环氧树脂的增强机理。结果表明,随着石墨烯含量的增加,石墨烯/环氧树脂复合材料的拉伸强度及模量先增加后减小;当石墨烯的质量分数为0.1%时,复合材料的拉伸强度达到最大值60.9MPa,比纯环氧树脂提高了16.88%;当石墨烯的质量分数为0.5%时,复合材料的拉伸模量达到最大值2833.3MPa,比纯环氧树脂提高了48.29%。     

Hybrid multi-scale composites developed from glass microfiber fabrics and nano-epoxy resins containing electrospun glass nanofibers

In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) and nano-epoxy resins containing electrospun glass nanofibers (EGNFs). The hypothesis was that, through dispersing a small amount of EGNFs into epoxy resin, mechanical properties (particularly out-of-plane mechanical properties) of the resulting hybrid multi-scale composites would be significantly improved. The composites were fabricated by the technique of vacuum assisted resin transfer molding (VARTM). The interlaminar shear strength, flexural properties, impact absorption energy, and tensile properties of the composites were evaluated, and the results were compared to those acquired from GFs/epoxy composite as well as GFs/epoxy composites containing chopped glass microfibers (GMFs); additionally, the reinforcement and/or toughening mechanisms were investigated. The study revealed that the nano-epoxy resin with 0.25 wt.% of EGNFs resulted in substantial improvements on mechanical properties of the resulting hybrid multi-scale composites.     

PVDF对芳纶无纺布/环氧树脂共固化复合材料力学和阻尼性能的影响

为评价热塑性结晶聚合物聚偏二氟乙烯(PVDF)对共固化复合材料动态力学和阻尼性能的影响,首先,将PVDF负载到芳纶无纺布(ANF)上,采用共固化工艺制备了PVDF-ANF/环氧树脂(EP)结构阻尼复合材料。然后,利用动态机械分析仪测试了PVDF-ANF/EP复合材料的损耗因子、损耗模量和储能模量的温度谱;通过弯曲强度、弯曲模量和层间剪切强度的测试评价了复合材料的静态力学性能;通过单悬臂梁振动实验测试了复合材料的共振频率及自由振动衰减曲线,并计算了损耗因子;通过I型、II型层间断裂韧性实验及断面微观形貌的观察研究了复合材料的断裂韧性及增韧机制。最后,对复合材料的微观结构进行分析,探讨了其兼具力学性能和阻尼性能的结构内因。结果表明:通过在ANF表面负载PVDF,可在不引起复合材料力学性能明显下降的前提下,进一步提高PVDF-ANF/EP复合材料的阻尼性能和层间断裂韧性,复合材料的损耗因子提高了33.3%,I型和II型断裂韧性分别提高了168%和208%。     

原位聚合法制备连续玻璃纤维增强PCBT复合材料及其性能

采用环状对苯二甲酸丁二醇酯(CBT)原位聚合制备了连续玻璃纤维(GF)增强聚环状对苯二甲酸丁二醇酯(PCBT)复合材料。考察了聚合反应中催化剂用量对PCBT结晶度以及GF/PCBT复合材料力学性能的影响。当催化剂用量为0.5%(质量分数)时, PCBT的结晶度为53%, GF/PCBT的力学性能达到最佳, 拉伸强度为522 MPa, 拉伸模量为27 GPa, 弯曲强度为481 MPa, 弯曲模量为24.8 GPa, 层间剪切强度(ILSS)为43 MPa。SEM观察表明, 发现催化剂用量为0.5%时, 树脂与纤维的结合性较好。进一步研究了淬火和退火后处理对复合材料力学性能的影响。发现复合材料退火处理后具有较好的力学性能, 其中拉伸强度为545 MPa, 弯曲强度为495 MPa。     

Interlaminar reinforcement of glass fiber/epoxy composites with graphene nanoplatelets

This work investigated the ability of graphene nanoplatelets (GnPs) to improve the interlaminar mechanical properties of glass-reinforced multilayer composites. A novel method was developed for the inclusion of GnPs into the interlaminar regions of plain-weave, glass fabric fiber-reinforced/epoxy polymer composites processed with vacuum assisted resin transfer molding. Flexural tests showed a 29% improvement in flexural strength with the addition of only 0.25 wt% GnP. At the same concentration, mode-I fracture toughness testing revealed a 25% improvement. Additionally, low-velocity drop weight impact testing showed improved energy absorption capability with increasing concentration of GnPs. Ultrasonic C-scans and dye penetration inspection of the impact- and back-sides of the specimens qualitatively support these results. Finally, the impact damage area was quantified from the C-scan data. These results showed that the impact-side damage area decreased with increasing concentration of GnP, while the back-side damage area increased.     

Synergistic reinforcement effect of aramid nonwoven fabrics and PVDF on mechanical and damping properties of bismaleimide matrix composites

A new type of structural damping composite was prepared by interleaving aramid nonwoven fabrics (ANF) modified with semi-crystalline polyvinylidene fluoride (PVDF) between carbon-fibre-reinforced bismaleimide (BMI) laminae. The co-cured composite exhibited an increase of 108% and 2.72% in loss factor and flexural modulus, respectively, compared with the original carbon-fibre-reinforced BMI composite. The damping behaviour of the co-cured composites was experimentally investigated using the single cantilever beam test and dynamic mechanical analysis. Furthermore, the composite interlaminar shear strength and flexural strength and modulus were also investigated. The results indicated that the composite interleaved with ANF/PVDF possessed higher flexural modulus and loss factor than the composites interleaved with ANF or PVDF films alone as a result of synergistic reinforcement of ANF and PVDF. Finally, the reinforcement mechanism of ANF/PVDF was investigated by analyzing the composite microstructure and the dynamical mechanical properties of ANF, PVDF, and ANF/PVDF interlayers.     

单向连续碳纤维-玻璃纤维层间混杂增强环氧树脂基复合材料的力学性能

为了研究连续单向纤维的层间混杂方式对复合材料力学性能及破坏方式的影响,采用碳纤维-玻璃纤维体积比为1∶1,以拉-挤成型法制备了具有不同层间混杂结构的连续单向纤维增强环氧树脂基复合材料,并研究了不同层间混杂结构的连续单向碳纤维-玻璃纤维增强环氧树脂基复合材料的力学性能及破坏形式。结果表明：具有层间混杂结构的复合材料抗拉强度处于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料之间,复合材料的拉伸断裂方式为劈裂;具有层间混杂结构的复合材料的层间剪切强度均优于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料,复合材料的剪切断裂方式为层间断裂。     

Effect of UV and water spraying on the mechanical properties of flax fabric reinforced polymer composites used for civil engineering applications

The lack of data related to durability is one major challenge that needed to be addressed prior to the widespread acceptance of natural fibre reinforced polymer composites for engineering applications. In this work, the combined effect of ultraviolet (UV) radiation and water spraying on the mechanical properties of flax fabric reinforced epoxy composite was investigated to assess the durability performance of this composite used for civil engineering applications. Specimens fabricated by hand lay-up process were exposed in an accelerated weathering chamber for 1500 h. Tensile and three-point bending tests were performed to evaluate the mechanical properties. Scanning electron microscope (SEM) was used to analyse the microstructures of the composites. In addition, the durability performance of flax/epoxy composite was compared with synthetic (glass and carbon) and hybrid fibre reinforced composites. The test results show that the tensile strength/modulus of the weathered composites decreased 29.9% and 34.9%, respectively. The flexural strength/modulus reduced 10.0% and 10.2%, respectively. SEM study confirmed the degradation in fibre/matrix interfacial bonding after exposure. Comparisons with other composites implies that flax fabric/epoxy composite has potential to be used for civil engineering applications when taking its structural and durability performance into account. Proper treatments to enhance its durability performance will make it more comparable to synthetic fibre reinforced composites when considering as construction building materials.     

橡胶改性对硼纤维/环氧单向复合材料力学性能的影响

对环氧树脂进行液体丁腈橡胶改性, 并采用缠绕无纬布层压成型工艺制备了硼纤维/环氧单向复合材料。测试了环氧树脂液体丁腈橡胶改性前后硼纤维/环氧单向复合材料的力学性能, 研究了硼纤维/环氧单向复合材料的纵向拉伸破坏模式。结果表明, 基体中的10%液体丁腈橡胶使硼纤维/环氧单向复合材料的拉伸强度、 弯曲强度、 层间剪切强度和断裂延伸率分别提高了18.42%、 13.39%、 28.45%和43.40%, 但其拉伸和弯曲模量稍有下降。基体中含10%液体丁腈橡胶的硼纤维/环氧单向复合材料的纵向拉伸破坏模式为界面层的内聚破坏和脱黏破坏共存的混合破坏。