不同组份的复合混纤聚酯长丝开发与研究

复合混纤聚酯长丝是采用两种或两种以上不同组份的聚酯,利用它们之间的不同的收缩率差,上染性差异,开发生产异收缩和异色聚酯长丝.本文对异收缩聚酯和异色聚酯的原料选择、制取和复合混纤工艺等进行了研究,认为可以在DTY机上开发各种不同组份的混纤聚酯长丝.

生物基PA 56/PET共混纤维与混纤复合丝的制备及性能研究

以生物基聚酰胺56(PA 56)及聚对苯二甲酸乙二醇酯(PET)为原料,分别通过共混纺丝、网络混纤制备PA 56/PET共混纤维、PA 56/PET混纤复合丝,研究了不同PA 56含量的PA 56/PET共混纤维的成纤性能、力学性能及染色性能,以及不同网络压力下PA 56/PET混纤复合丝的染色效果及其织物风格。结果表明:在PET中添加PA 56共混纺丝,当PA 56质量分数为20%时,PA 56/PET共混纤维具有较好的力学性能及染色性能,纤维断裂强度4.2 cN/dtex、断裂伸长率25%、条干不匀率0.96%,采用分散染料染色后纤维织物染色均匀性达灰卡标准5.0级,且染色深度比纯PET纤维织物的深;将PET纤维与PA 56纤维按5050混纤,在网络压力0.08~0.30 MPa下混纤效果好,混纤复合丝断裂强度4.0~4.2 cN/dtex、断裂伸长率24%~25%、条干不匀率1.17%~1.44%,选择不同类型的染料染色后混纤复合丝具有同染异色、同浴异染的效果,其织物的染色均匀性在2.5~3.5级,呈现明显的异彩条纹风格。

多功能混纤复合长丝纺丝设备的研制及产品开发

针对目前求新、求异的化纤市场状况,介绍了4组分多功能混纤复合长丝纺丝设备研制的总体方案及4组分纺丝箱、纺丝组件、牵伸卷绕等关键部件的特征,拟定了典型产品的纺丝工艺条件,使多功能混纤复合长丝纺丝取得了技术性突破。

混纤异收缩复合拉伸网络丝的开发与生产

本文系统地介绍了混纤异收缩拉伸网络丝的工艺流程及工艺条件。此项生产技术对于化纤行业的品种结构优化有重要的现实意义。

预取向丝-拉伸加捻丝混纤复合的品质管控

对涤纶预取向丝(POY)-拉伸加捻丝(DT)混纤复合生产过程中常见的抱合不好、染色降等、多股/少股漏检问题进行了分析,给出了解决这些问题的经验办法,对改善混纤复合丝产品品质有一定的参考价值。

差别化纤维的发展

简述了差别化纤维的品种类型及其技术特点,指出了我国与发达国家在质量与数量上存在差距的原因,并对我国今后差别化纤维的发展提出了一些建议。

合成纤维成套设备技术改造和产品升级

介绍涤纶长丝纺丝新工艺、新技术和新设备的新型"双胞胎"纺丝组件、新型双排外环吹装置、熔体直接纺纺丝热媒加热系统和一步法生产多异混纤复合纱装置的技术和特点,并指出运用新技术和设备改造现有落后装置可实现产品升级,提高企业竞争力。

Fatigue behavior of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer sheets

In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios of 1 ： 1 and 2：1 under different stress levels from 0.6 to 0.95. The results show that fractures occur first in carbon fibers or aramid fibers for the specimens with hybrid ratio of 1： 1, namely B1A1 and B1C1, while a fracture occurs first in basalt fibers for the specimens with a hybrid ratio of 2： 1, namely B2A1 and B2C1. The fatigue lives of the hybrid FRP sheets increase with the improvement of the content of carbon fibers or aramid fibers, and the influence of the carbon fibers content improvement to fatigue life is more significant. The fatigue performance of B2A1 is relatively worse, while the fatigue performance of B1C1 and B2C1 is relatively better. Finally, a new fatigue stiffness degradation model with dual variables and double inflection points is presented, which is applicable to both hybrid and normal FRP sheets.

Mechanical properties of polyvinyl alcohol-basalt hybrid fiber engineered cementitious composites with impact of elevated temperatures

In the present study,the mechanical properties of polyvinyl alcohol(PVA)-basalt hybrid fiber reinforced engineered cementitious composites(ECC)after exposure to elevated temperatures were experimentally investigated.Five temperatures of 20,50,100,200 and 400℃ were set to evaluate the residual compressive,tensile and flexural behaviors of hybrid and mono fiber ECC.It was shown that partial replacement of PVA fibers with basalt fibers endowed ECC with improved residual compressive toughness,compared to brittle failure of mono fiber ECC heated to 400℃.The tension tests indicated that the presence of basalt fibers benefited the tensile strength up to 200℃,and delayed the sharp reduction of strength to 400℃.Under flexural load,the peak deflections corresponding to flexural strengths of hybrid fiber ECC were found to be less vulnerable ranging from 20 to 100℃.Further,the scanning electron microscopy(SEM)results uncovered that the rupture of basalt fiber at moderate temperature and its pullout mechanism at high temperature was responsible for the mechanical evolution of hybrid fiber ECC.This work develops a better understanding of elevated temperature and basalt fiber impact on the residual mechanical properties and further provides guideline for tailoring ECC for improved fire resistance.

Experimental Research on Behavior of Composite Material Projectile Penetrating Concrete Target

Projectile made of carbon fiber composite material shell and metal warhead penetrates concrete target at speeds of 336,m/s,447,m/s and 517,m/s.The angles between the perpendicu-lar of target surface and projectile axis are 0°and 30°.The thickness of concrete target is 200,mm and the compression strength is 30 MPa.The experimental results indicate that the strength of composite material structure is high.Composite projectile can go through concrete tar-get without fiber segregation and breakage.The percent fill is 18.5% in the composite material projectile.It is about twice as that of metal projectile,if the density of metal is taken as 7.8,g/cm3.Comparing with metal projectile,low-density,high-strength composite material can lessen projec-tile weight,improve charge-weight ratio of detonator and enhance destructive powder.

Flexural behavior of reinforced concrete beams with high performance fiber reinforced cementitious composites

This article presents an experimental study on the flexural performance of reinforced concrete(RC)beams with fiber reinforced cementitious composites(FRCC)and hybrid fiber reinforced cementitious composites(HFRCC)in the hinge portion.Beam specimens with moderate confinement were used in the study and tested under monotonic loading.Seven diverse types of FRCC including hybrid composites using fibers in different profiles and in different volumes are employed in this study.Companion specimens such as cylindrical specimens and prism specimens are also used to study the physical properties of composites employed.The moment?curvature,stiffness behavior,ductility,crack pattern and modified flexural damage ratio are the main factors considered in this study to observe the efficacy of the employed hybrid composites.The experimental outputs demonstrate the improved post yield behavior with less rate of stiffness degradation and better damage tolerance capacity than conventional technique.

Strengthening of Pultruded Glass FRP Section Combined with Concrete Slab Using CFRP Plates

This paper demonstrates the possibility of combining both glass and carbon FRP （Fibre Reinforced Polymer） composite materials with a low-cost construction material （i.e. concrete） in a hybrid system that brings higher performance levels to the design of lightweight, corrosion resistant, yet inexpensive beams providing acceptable structural properties. The objective of the research is to investigate the behaviour of a hybrid composite section under flexure. The hybrid section consists of a top concrete slab, Glass Fibre Reinforced Polymer （GFRP） beam section and Carbon Fibre Reinforced Polymer （CFRP） laminate on the extreme underside. This maximizes the benefits of each material, that is： high tensile strength of CFRP, compressive strength and low cost of concrete, light weight and lower cost of GFRP, and high corrosion resistance of all components. Three beam samples were manufactured and tested to failure while monitoring deflections and strains. By adding CFRP layers under the concrete-GFRP composite beam increases the bending strength and reduces the deflection. The most important factor in the proposed strengthening technique of GFRP-concrete composite beams by using CFRP is the adhesive material that bonds the CFRP to the GFRP. Any weakness in CFRP-GFRP bond may cause brittle failure of the beam. The study results indicate the benefits of using hybrid FRP-concrete beams to increase flexural load carrying capacity and beam stiffness and provide a numerical model that can be further developed to model more advanced material arrangements in the future. The outcome of this research provides information for both designers and researchers in the field of FRP composites.

Nonlinear behavior of concrete beams with hybrid FRP and stainless steel reinforcements

The full-range behavior of partially bonded, together with partially prestressed concrete beams containing fiber reinforced polymer （FRP） tendons and stainless steel reinforcing bars was simulated using a simplified theoretical model. The model assumes that a section in the beam has a trilinear moment--curvature relationship characterized by three particular points, initial cracking of concrete, yielding of non-prestressed steel, and crushing of concrete or rupturing of prestressing tendons. Predictions from the model were compared with the limited available test data, and a reasonable agreement was obtained. A detailed parametric study of the behavior of the prestressed concrete beams with hybrid FRP and stainless steel reinforcements was conducted. It can be concluded that the deformability of the beam can be enhanced by increasing the ultimate compressive strain of concrete, unhonded length of tendon, percentage of compressive reinforcement and partial prestress ratio, and decreasing the effective prestress in tendons, and increasing in ultimate compressive strain of concrete is the most efficient one. The deformability of the beam is almost directly proportional to the concrete ultimate strain provided the failure mode is concrete crushing, even though the concrete ultimate strain has less influence on the load-carrying capacity.

Collapse behavior evaluation of hybrid thin-walled member by stacking condition

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

Experimental study on slender reinforced concrete columns wrapped with CFRP

By axial compression tests on 6 reinforced concrete slender columns wrapped with carbon fiber-reinforced plastic (CFRP),with slenderness ratio(SR) from 4.5 to 17.5,the results show that when SR increases the retrofitting effect declines. In the case of same SR,the stability coefficient (SC) for the reinforced concrete(RC) columns with CFRP is much less than that without CFRP. There is 20% increase of stable bearing capacity to the former as compared with the latter when the SR in less than 17.5. The study summarized the simplified formula for SC,which provides a reference for engineering designers.

Performance of Square Lightweight Concrete Specimens Confined by CFRP and GFRP

Confinement is an effective method in order to increase concrete strength and its ductility capacity. To improve the structural properties of lightweight concrete, Fiber Reinforced Polymer （FRP） can be used to confine the concrete. Effect of Fiber Reinforced Polymer on confined lightweight concrete elements is one of the most important research fields. It is generally accepted that the strength and stiffness of confined concrete is higher than unconfined one. In this research, behavior of confined and unconfined concrete specimens under uniaxial loading has been studied. In order to decrease stress concentration corners of specimens were chamfered to a radius of 5 to 25 mm. The Carbon Fiber Reinforced Polymer （CFRP） and Glass Fiber Reinforced Polymer （GFRP） were used to confine lightweight concrete specimens. The stress-strain curve of specimens is compared.

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bars

Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars-including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.

State of the art review on the production and bond behaviour of reinforced geopolymer concrete

Geopolymer is produced through the polymerization of active aluminosilicate material with an alkaline activator,leading to the formation of a green,inorganic polymer binder.Geopolymer concrete(GPC)has become a promising low-carbon alternative to traditional Portland cement-based concrete(OPC).GPC-bonded reinforcing bars offer a promising alternative for concrete structures,boasting excellent geopolymer binder/reinforcement bonding and superior corrosion and high-temperature resistance compared to Portland cement.However,due to differences in the production process of GPC,there are distinct engineering property variations,including bonding characteristics.This literature review provides an examination of the manufacturing procedures of GPC,encompassing source materials,mix design,curing regimes,and other factors directly influencing concrete properties.Additionally,it delves into the bond mechanism,bond tests,and corresponding results that represent the bond characteristics.The main conclusions are that GPC generally has superior mechanical properties and bond performance compared to ordinary Portland cement concrete(OPC).However,proper standardization is needed for its production and performance tests to limit the contradictory results in the lab and on site.