玻璃纤维/聚丙烯复合纱拉挤型材制备及其性能研究

以玻璃纤维/聚丙烯复合纱为原料,采用拉挤成型方式制备连续纤维增强热塑性复合材料,通过组建的拉挤试验线获得了拉挤型材试样,探究了复合纱穿纱方式、模具型腔结构、模具温度和拉挤速率对制品性能的影响,并观察其截面形态。结果表明:采用收敛式型腔结构、提高模具温度、降低拉挤速率,可有效改善玻纤/树脂间结合能力,提高纤维在制品中的分布均匀性,降低制品的孔隙率,提高其力学性能。      

Step Pultrusion

The pultrusion process is an efficient technology for the production of composite material profiles. Thanks to this positive feature, several studies have been carried out, either to expand the range of products made using the pultrusion technology, or improve its already high production rate. This study presents a process derived from the traditional pultrusion technology named ??Step Pultrusion Process Technology?? (SPPT). Using the step pultrusion process, the final section of the composite profiles is obtainable by means of a progressive cross section increasing through several resin cure stations. This progressive increasing of the composite cross section means that a higher degree of cure level can be attained at the die exit point of the last die. Mechanical test results of the manufactured pultruded samples have been used to compare both the traditional and the step pultrusion processes. Finally, there is a discussion on ways to improve the new step pultrusion process even further.     

Design and manufacturing of an L-shaped thermoplastic composite beam by braid-trusion

Braid-trusion is a manufacturing process for composite materials in which a braiding machine is coupled with a pultrusion die to continuously produce beams with constant cross-section and off-axis fiber orientation. This study presents a geometrical model of the tri-axial braid which allows the design of braided preforms that achieve correct filling of the pultrusion die at the same time as it limits fiber friction on die walls. The typic design parameters are listed and used for the manufacturing of a braid-truded thermoplastic composite beam where fibers are aligned at ±69° as well as 0° with respect to the beam axis. Tensile mechanical characterization and cross-section observations are also presented.     

Iterative and transient numerical models for flow simulation of injection pultrusion

During injection pultrusion, the flow front is initially transient and approaches a quasi-steady-state in a short time. It is the steady-state flow front that determines the filling quality of the pultruded composite part. Both transient and iterative finite element/nodal volume models have been developed to predict the steady-state flow fronts during injection pultrusion processes. In the present paper, the numerical performance of the transient and iterative models is systematically investigated for various pultrusion process and material parameters, such as pull speed, injection pressure and the ratio of permeabilities in the pulling and the transverse directions. It is shown that the iterative model is numerically stable and robust. It predicts steady-state flow fronts which are in excellent agreement with those predicted by the transient model in all the cases investigated. More importantly, the iterative model is much more efficient than the transient model and the high efficiency is not affected by the modelling parameters used. It generally uses less than one tenth of the computer time required by the transient model to reach the converged solutions. Therefore, the iterative model should always be used to predict the steady-state resin flow fronts.     

新型轻木GFRP夹芯板拉挤成型工艺及其界面性能

选用无碱玻璃纤维束、短切纤维毡、不饱和树脂与泡桐木芯材,制备了轻木-玻璃纤维增强塑料(GFRP)夹芯板,对其拉挤工艺进行了研究.研究表明:设定模具加热温度(凝胶区)为160 ℃、选取的拉挤速率为10 cm/min时,可制造得到表观性能良好的泡桐木-GFRP夹芯板.通过双悬臂梁(DCB)试验,在芯材表面开槽和不开槽2种情况下,研究了泡桐木与GFRP面层之间的界面黏结性能,并与真空导入工艺制作的夹芯板的界面黏结性能进行了对比.结果表明:拉挤工艺生产的泡桐木-GFRP夹芯板的界面黏结性能已达到甚至优于真空导入工艺生产的.芯材表面开槽可以有效提高试件的界面能量释放率,且对真空导入工艺制作的试件效果更为明显.在拉挤工艺中,树脂难以有效填充齿槽形成"树脂钉",故不能明显提高界面黏结力.在对界面性能要求不严格时,拉挤工艺中芯材表面可不开槽,以减少生产工序、降低生产难度.     

Fiber Volume Fraction Influence on Fiber Compaction in Tapered Resin Injection Pultrusion Manufacturing

Liquid resin is injected into the tapered injection chamber through the injection slots to completely wetout the fiber reinforcements in a resin injection pultrusion process. As the resin penetrates through the fibers, the resin also pushes the fibers away from the wall towards the centerline causing compaction of the fiber reinforcements. The fibers are squeezed together due to compaction, making resin penetration more difficult; thus higher resin injection pressures are required to effectively penetrate through the fibers and achieve complete wetout. Fiber volume fraction in the final pultruded composite is a key to decide the mechanical and/or chemical properties of the composite. If the fiber volume fraction is too high, more fibers are squeezed together creating a fiber lean region near the wall and fiber rich region away from the wall. Also, the design of the injection chamber significantly affects the minimum injection pressure required to completely wet the fibers. A tapered injection chamber is considered such that wetout occurs at lower injection pressures due to the taper angle of the injection chamber. In this study, the effect of fiber volume fraction on the fiber reinforcement compaction and complete fiber wetout for a tapered injection chamber is investigated.     

Manufacturing and mechanical properties of soy-based composites using pultrusion

Two primary cost driving factors for the composites industry are raw materials and labor. Inexpensive alternative epoxy resin systems based on epoxidized soyate resins are developed for fiber reinforced composite applications. This research investigated on the manufacturing and mechanical characterization of fiber/epoxy composites using chemically modified soy-based epoxy resins. Co-resin systems with up to 30 wt% soyate resins were used to manufacture composites through pultrusion. Mechanical tests show that the pultruded composites with soy based co-resin systems possess comparable or improved structural performance characteristics such as flexural strength, modulus, and impact resistance. Maximum mechanical properties enhancement is demonstrated by the enhanced epoxidized allyl soyate (EAS) formulation. Further property improvement is obtained through using a two-step prepolymer process. The EAS holds great potential as partial supplement for polymer and composites applications from renewable resources.     

预浸料先进拉挤成型的固化传热过程数值模拟

对M21C碳纤维/环氧树脂复合材料预浸料在先进拉挤成型过程中的温度与固化度曲线进行了研究。使用DSC测得M21C预浸料在升温与恒温状态下的固化反应动力学方程,用于树脂固化反应的计算。基于有限元软件,结合有限差分法与体积控制法编写脚本解决热传导与树脂固化反应的计算,从而得到温度与固化度曲线,并在先进拉挤生产中测得实际的温度与固化度曲线,结果表明计算与实测曲线基本吻合,因此验证了算法的可行性。改变先进拉挤的工艺参数（加热温度区间、拉挤速度）再进行模拟计算,通过计算结果优化工艺参数,得到帽形梁先进拉挤三区间加热的理想工艺参数:模具加热温度区间为160-180-200℃;拉挤速度为1 cm/60 s。      

Simulating tape resin infiltration during thermoset pultrusion process

The thermoset tape pultrusion is a widely adopted manufacturing process to produce long, constant cross-section composite structural parts. For high volume production, low cost can be achieved by maximizing the production rate which is a function of the material and process parameters, more specifically the rate of resin infiltration and resin cure. During resin infiltration, the resin saturates the dry reinforcement either under positive pressure in the pressure chamber, or, by the action of capillary and surface forces, within the resin bath. In either case, the saturation must be completed as the tape is squeezed into the final cross-sectional form at the entrance of the heated mold where the resin will be cured to form the composite part.This paper models the resin infiltration process during pultrusion, by modifying the pre-existing simulation tool for liquid molding processes. The formulated capability can be used not only to optimize the impregnation dynamics within the pressure chamber, but can also be used to predict the required forces for the selected pulling rate. The proposed model does allow one to handle a variety of tape cross-sections, not just rectangular prisms.     

基于神经网络遗传算法的GFRP拉挤双目标优化

为研究玻璃钢(GFRP)拉挤工艺参数对复合材料性能的影响,优化最佳拉挤工艺参数,建立了拉挤工艺过程数学模型,结合基于有限元/有限差分的间接解耦法进行求解,模拟得到了拉挤过程中GFRP内部的非稳态温度场和固化度变化情况.分别采用布拉格光栅光纤温度传感器和索氏萃取法检测拉挤GFRP内部的温度与固化度,实测温度和固化度均与模拟温度和固化度吻合,验证了数值模拟程序的正确性.以数值模拟结果为样本,建立反向传播神经网络,得到拉挤工艺参数(固化温度、拉挤速度)与GFRP固化度之间的非线性相关关系,再结合遗传算法解决拉挤过程中固化炉温度和拉挤速度双目标优化问题.优化得到的拉挤工艺参数可在保证复合材料固化度达标的情况下,提高拉挤速度降低固化炉温度,优化效果显著.神经网络遗传算法优化方法能有效解决此类具有复杂非线性关系的多目标优化问题.     

Pultrusion of a flax/polypropylene yarn

The present work reports the pultrusion of a flax reinforced polypropylene commingled yarn containing discontinuous flax and polypropylene fibers. This was the first attempt to pultrude this material. Rectangular cross-sectional profiles have been successfully produced using a self-designed pultrusion line. In a series of experiments carried out with yarns of two different flax fiber contents, the pultrusion parameters were varied. In particular, the preheating and die temperatures and also the pulling speed, which are the most relevant parameters regarding the potential future pultrusion of natural fiber composite profiles at industrial scale. A complete characterization of each profile was conducted in order to examine the influence of processing parameters on the profile quality. The mechanical properties were evaluated by performing three point bending as well as Charpy impact tests.     

Hybrid filler composition optimization for tensile strength of jute fibre-reinforced polymer composite

In present research work, pultrusion process is used to develop jute fibre-reinforced polyester (GFRP) composite and experiments have been performed on an indigenously developed pultrusion experimental setup. The developed composite consists of natural jute fibre as reinforcement and unsaturated polyester resin as matrix with hybrid filler containing bagasse fibre, carbon black and calcium carbonate (CaCO₃). The effect of weight content of bagasse fibre, carbon black and calcium carbonate on tensile strength of pultruded GFRP composite is evaluated and the optimum hybrid filler composition for maximizing the tensile strength is determined. Different compositions of hybrid filler are prepared by mixing three fillers using Taguchi L₉ orthogonal array. Fifteen percent of hybrid filler of different composition by weight was mixed in the unsaturated polyester resin matrix. Taguchi L ₉ orthogonal array (OA) has been used to plan the experiments and ANOVA is used for analysing tensile strength. A regression model has also been proposed to evaluate the tensile strength of the composite within 7% error by varying the above fillers weight. A confirmation experiment was performed which gives 73.14 MPa tensile strength of pultruded jute fibre polymer composite at the optimum composition of hybrid filler.     

Die-Attached Versus Die-Detached Resin Injection Chamber for Pultrusion

Resin injection pultrusion is an efficient and highly automated continuous process for high-quality, low-cost, high-volume manufacturing of composites. The main objective of this study is to explore the “attached-die configuration” and “detached-die configuration” for improving the resin injection pultrusion process. In this work the impact of pull speed on complete wet out of the reinforced fiber is investigated for attached-die and detached-die resin injection pultrusion with various chamber length considerations. A 3-D finite volume technique was applied to simulate the liquid resin flow through the fiber reinforcement in the injection pultrusion process. This work explores the resin injection pressure needed to achieve complete wet out and the corresponding maximum pressure inside the resin injection chamber so as to improve injection chamber design to keep the pressure within the injection chamber within reasonable constraints for different pull speeds.     

RTM成型工艺对复合材料制品性能的影响

RTM(树脂传递模塑的简称)成型工艺是一种将树脂注入闭合模具中浸润增强材料的复合材料成型工艺。工艺参数对复合材料制品性能有很大的影响。本文对注射压力、注射温度、真空辅助、注胶口和排气口的位置、纤维含量和结构等工艺参数对复合材料制品性能的影响进行了概述。     

热分析在挤拉成型工艺中的应用

本文采用DSC固化实验和SPI凝胶实验的热分析方法,评价挤拉成型工艺中不同树脂反应活性、不同填料、填料用量、引发剂用量、温度对树脂固化性能的影响以及树脂混合物的固化性能。通过热分析寻找合适的工艺参数,从而获得成本较低、效率较高、性能较好的挤拉制品。      

Modeling of heat transfer and unsaturated flow in woven fiber reinforcements during direct injection-pultrusion process of thermoplastic composites

This paper provides a methodology for the modeling of heat transfer and polymer flow during direct thermoplastic injection pultrusion process. Pultrusion was initially developed with thermosets which have low viscosity. But the impregnation becomes a critical point with thermoplastics which exhibit higher viscosity. There are very few reported works on direct thermoplastic impregnation with injection within the die. In addition, the rare studies have not adequately addressed the issue of unsaturated flow in woven fiber reinforcements. The solution proposed here, models the polymer flow through dual-scale porous media. A heat transfer model is coupled to a flow model enriched with a sink term. Specific changes of variables are made so as to model the steady state solution of unsaturation along a continuous process. The sink term, added to the continuity equation, represents the absorption rate of polymer by the bundles. Data were measured on a pultrusion line and micrographs confirmed the modeling strategy with an unsaturated flow approach. The flow modeling coupled to heat transfer of the thermoplastic pultrusion process aims at determining the saturation evolution through the die so as to manufacture pultruded profiles with the lowest residual porosity.     

Pultruded fibre reinforced polyurethane composites II. Effect of processing parameters on mechanical and thermal properties

This paper presents a novel process for the fabrication of pultruded polyurethane (PU) composites. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) and thermal properties (HDT) of the fibre reinforced PU composites by pultrusion have been studied. The processing parameters investigated include pulling rate (in-line speed), die temperature, filler type and content, and post-cure time and temperature. Results show that the composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio, the mechanical properties and the thermal properties of composites, the optimum die temperature can be determined. It is found that the mechanical and thermal properties increase with filler content for various types of filler. The mechanical and thermal properties increase at a suitable post-cure temperature and time. Furthermore, the properties which decreased due to the degradation of composite materials for a long post-cure time will be discussed.     

复合材料拉挤方管型材螺栓节点承载力试验

复合材料型材是采用工业化拉挤工艺生产的截面形状一致、性能稳定的连续构件（如：方形、工字形、槽形等）,其节点连接技术是难点。重点开展了复合材料型材节点螺栓机械连接的试验研究与理论分析,研究了螺栓节点孔径、端距、壁厚等参数对复合材料型材节点极限承载力的影响规律,提出了拉挤复合材料型材螺栓孔的金属垫圈孔壁增强技术,进而拟合了拉挤型材螺栓节点连接的设计公式。研究结果表明：复合材料方管拉挤型材在螺栓连接局部挤压的破坏模式下,其极限承载力与孔径和板厚的乘积（d·t）呈线性关系,接头处的破坏形式和连接接头端距与孔径的比值相关。在挤压破坏模式下,当接头板件壁厚一定时,极限承载力的增量随着孔径的增大而减小。螺栓孔采用金属垫圈增强技术,可以大幅度提高节点承载能力（提高63%）。     

Investigation of process induced warpage for pultrusion of a rectangular hollow profile

A novel thermo-chemical–mechanical analysis of the pultrusion process is presented. A process simulation is performed for an industrially pultruded rectangular hollow profile containing both unidirectional (UD) roving and continuous filament mat (CFM) layers. The reinforcements are impregnated with a commercial polyester resin mixture (Atlac 382). The reactivity of the resin is obtained from gel tests performed by the pultruder. The cure kinetics parameters are estimated from a fitting procedure against the measured temperature. The cure hardening instantaneous linear elastic (CHILE) model is adopted for the evolution of the resin elastic modulus using the temperature-dependent elastic response provided by the resin supplier. The numerical model predictions for the warpage trend at the end of the process are found to agree well with the warpage observed in the real pultruded products. In addition, the calculated warpage magnitude is found to be in the measured range of warpage magnitude for the manufactured part.     

A finite element/nodal volume technique for flow simulation of injection pultrusion

In this paper, a finite element/nodal volume technique is developed to simulate the resin flow through the reinforcement during injection pultrusion processes. The governing equations for the pressure distribution and the conservation of resin mass during injection pultrusion are first derived. The solution algorithm and its numerical implementation are described. In particular, an algorithm is developed to advance the flow front by taking into account both the resin flow relative to the reinforcement and the movement of the pultruded part as a whole. The numerical technique developed is validated against a one-dimensional analytical solution derived. A number of numerical tests are then conducted to investigate the numerical performance and capability of the technique.