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。      

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。      

冷却方式对GF/ PP 复合纱针织物复合材料基体结晶结构的影响

采用对玻璃纤维/ 聚丙烯( GF/ PP) 复合纱针织物热压的方法制备得到GF/ PP 复合纱针织物复合材料,并通过改变降温冷却阶段的降温方式得到4 组具有不同冷却方式的GF/ PP 复合材料试样。运用X 射线衍射法对不同冷却方式得到的GF/ PP 复合纱针织物复合材料基体的结晶结构进行了研究。研究表明, 所采用的几种冷却方式对基体的结晶形态没有影响, 而基体的结晶度、微晶尺寸以及球晶的尺寸均有差异: 随着冷却速度的减慢、冷却时间的延长, 基体的结晶度、微晶尺寸及球晶尺寸均呈增大趋势。      

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.     

模压工艺对玻璃纤维增强聚丙烯复合材料层合板力学性能的影响

利用热模压工艺制备玻璃纤维增强聚丙烯（GF/PP）复合材料层合板,通过差示扫描量热（DSC）法试验分析,确定相变参数,运用ANSYS有限元分析,将复合材料热力学参数与温度的非线性关系定义到材料特性中,研究模压成型过程中温度场变化情况,为模压成型工艺制度的确立提供理论指导和依据。以压缩强度、层间剪切强度和冲击韧性作为力学性能评价指标,采用响应曲面法探讨和分析制备工艺对GF/PP复合材料层合板力学性能的影响,得到最优模压工艺制备参数,获得最高复合材料层合板力学性能,为GF/PP复合材料自动铺放奠定铺放工艺基础。试验结果表明:模压加热工艺参数对复合材料层合板力学性能的影响度（从大到小）依次为:热压温度、热压时间、热压压力。较优的模压加热工艺参数为:热压温度228℃、热压时间6 min、热压压力1.1 MPa,在此工艺条件下制备的GF/PP复合材料层合板,层间剪切强度为31.12 MPa,压缩强度为100.96 MPa,冲击韧性为2.27 kJ/cm2。      

连续玻璃纤维增强聚丙烯预浸带熔融预浸过程

采用熔融浸渍法制备连续玻璃纤维增强聚丙烯（GF/PP）热塑预浸带,研究了PP熔体浸渍连续GF束过程。采用旋转流变仪对PP进行测试分析,结果显示其流变特性符合Carreau模型。以达西定律为理论基础,结合浸渍模具结构参数、材料物性参数及相应工艺参数,推导了Carreau流体树脂浸渍连续GF束的理论模型。在不同浸渍温度与牵引速度下进行实验以验证浸渍模型的准确,实验结果与理论值相符。利用浸渍模型分析模具结构参数及工艺参数对浸渍程度的影响,结果表明,通过增加模具浸渍辊数目、增大浸渍辊半径、减小辊间距及提高浸渍温度等方法可提高浸渍程度。     

用共编纱制备热塑性复合材料

介绍了一种制备增强纤维/热塑性纤维混杂纤维束的新方法——共编法,通过改变编织工艺参数、纤维丝束大小、纤维种类、编纱和轴向纱的数量等制备了一系列GF/PP共编纱。以此共编纱,成功地制备出GF/PP复合材料板材,并研究了成型压力、成型温度以及保温时间等对复合材料的预浸及板材质量的影响;同时,对增强纤维种类、丝束大小及其含量等对复合材料中空隙含量的影响也进行了研究;采用圆形模型探讨了GF/PP共编纱中树脂对玻璃纤维的预浸过程,提出了影响预浸效果的主要因素。     

碳纤维/尼龙6预浸料的制备及盒体的热冲压成型工艺

首先利用自主设计的熔融浸渍机头制备了60 mm幅宽的连续碳纤维增强尼龙6（CF/PA6）热塑单向带,并利用快速热冲压成型技术制备了CF/PA6复合材料矩形盒体。结果显示,在CF/PA6预浸料制备过程中,纤维展纱包覆角与纤维展宽呈线性关系;预紧力增加展纱宽度的同时,牵引力会呈指数急剧上升,因此应避免大的预紧力;CF/PA6预浸料的浸渍质量随牵引速度的增加而降低;预热有利于改善高浸渍速度下的浸渍质量。在热冲压成型过程中,CF/PA6复合材料的最佳预热温度为260~280℃,模具温度为130~160℃,并应经过预压实。      

GFRP拉挤成型工艺模拟优化

为了对GFRP (玻璃纤维增强塑料) 拉挤成型非稳态温度场与固化度进行数值模拟, 依据固化动力学和非稳态导热理论, 建立了温度场和固化度动力学模型。通过 DSC试验分析确定了模型中固化度动力学参数。利用有限元与有限差分相结合的方法, 建立温度场和固化度数值模型, 应用Euler-Cauch逐步迭代法实现计算机解耦。利用有限元软件FEPG编制拉挤固化模拟程序, 详细探讨了模具温度、拉挤速度、初始温度等拉挤工艺参数对模具内温度和固化度分布的影响。数值模拟值与FBG光栅测量值比较结果吻合, 能够对拉挤工艺参数制定提供有用的信息, 以指导拉挤工艺制定。      

BMI-QC130双马树脂拉挤工艺

为了研究分析双马树脂的拉挤工艺特性和工艺参数,采用差示扫描量热法(DSC)研究了BMI-QC130双马树脂的固化反应动力学,建立了该BMI树脂的固化度预测模型,通过该预测模型得到的固化度预测值与试验值较为吻合,采用双Arrhenius方程建立了该BMI树脂的黏度预测模型,该黏度预测模型在温度低于120℃范围内具有很高的预测精度。根据所建立的固化度预测模型和黏度预测模型确定了BMI-QC130双马树脂的拉挤工艺参数为：胶槽恒温95℃,拉挤模具温度控制在200℃,出模后经过温度为280℃的烘道进行后固化。在此工艺条件下,成功地连续拉挤出碳纤维增强BMI-QC130复合材料样品。     

Non-isothermal forming of glass fiber/polypropylene commingled yarn fabric composites

The commingled glass fiber/polypropylene (GF/PP) composites were fabricated using a double-belt press and the influence of temperature and velocity on the consolidation quality and mechanical performance of the composites were investigated. The contents and distribution of the voids in the composites were changed with varying the level of the processing parameters, and the composite tensile and flexural properties were dramatically decreased when the void contents were beyond 3.6%. Reducing the viscosity of the matrix or increasing the uniformity of fibers in the commingled yarns was important to improve the consolidation quality. But the production efficiency was not improved as hoped by increasing the velocity at higher temperatures because of the weakened interfacial bonding. The crystal form and crystallinity degree had no obvious changes under different processing conditions, but the composite mechanical performance was enhanced when the degree of order in the crystal structures was decreased, which might be caused by more effective stress transferring or less initial cracks.     

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.     

Consolidation of GF/PP commingled yarn composites

Consolidation quality and corresponding mechanical properties of GF/PP thermoplastic composites manufactured from a commingled yarn system have been investigated. A small compression mould with a laboratory hot press was used to apply the different processing variables (i.e. pressure, holding time and processing temperature). The consolidation quality of finished samples was characterized mainly through (a) microscopic studies of the material's microstructure, (b) density measurements, and (c) evaluations of mechanical properties using a small transverse flexure testing facility. A model for qualitatively describing the impregnation and consolidation processes in commingled yarn based thermoplastic composites was applied to predict variations of void content during consolidation and the time, temperature and pressure required to reach full consolidation. Based on a desired, minimum level of void content (X _v =2.0%), optimum processing windows for manufacturing of GF/PP commingled yarn composites are suggested.     

Penetration impact resistance of hybrid composites based on commingled yarn fabrics

The penetration impact resistance of hybrid composites based on commingled yarn fabrics was investigated. The commingled yarn fabrics were composed of E-glass fibres (GF) and thermoplastic fibres blended together within the fibre bundles. Various thermoplastic fibres such as polypropylene (PP), polyamide (PA) and modified polyethylene terephthalate (mPET) were studied. Various resin matrices with different cure cycles were studied such as Quickcure polyester, Cycom X823 RTM epoxy, and Shell Epikote 828 epoxy resin. Depending on the crystalline melting temperature (T_m) of the thermoplastic fibres, the hybrid composites can be categorised as fibre-hybrid composites or matrix-hybrid composites. Fibre-hybrid composites refer to those in which the thermoplastic fibres remain in the fibre form after curing, for example the GF–PP and GF–PA hybrid composites. For matrix-hybrid composites, the thermoplastic fibres melt and dissolve into the thermosetting matrix during curing such as the GF-mPET hybrid composites. The results from the penetration impact showed that the total absorbed energy of the fibre-hybrid composites were significantly higher than for the plain glass composites. Plastic deformation in the thermoplastic fibres is the key factor that improves the absorbed energy of the hybrid composites. When the thermoplastic fibres dissolved into the thermosetting matrix as in matrix-hybrid composites, the total absorbed energy was similar to that of the plain glass fibre composites. This suggests that the total absorbed energy is dependent on the properties of the fibres rather than the matrix. However, the fibre-hybrid composites showed slight differences in the total absorbed energy for different matrices. The differences are thought to be related to the differences in the bonding between the thermoplastic fibres and the thermosetting matrix which have yet to be investigated.     

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.