具有金属内衬复合材料纤维缠绕容器固化过程的数值模拟

基于固化反应动力学、热传导和复合材料层合理论, 采用了有限元分析方法, 对具有金属内衬的复合材料纤维缠绕压力容器在固化工艺过程中的温度和热应力分布及其变化规律进行了数值模拟。通过一典型容器数值分析, 表明在固化工艺过程中, 中容器内部的所有应力分量具有同时达到峰值的特征, 其中应力分量的峰值出现在固化降温阶段的初期。提出了数值模拟的方法和分析结论对复合材料结构设计师和工艺师合理制订金属内衬复合材料纤维缠绕容器的工艺标准具有一定的参考价值。      

603环氧树脂体系固化动力学模型的建立与验证

采用非等温差示扫描量热法（DSC）研究了603热塑增韧环氧树脂体系的固化反应动力学。研究发现,在低升温速率测试条件下603环氧树脂体系固化反应的DSC曲线有两个重叠的放热峰,通过分离两个重叠的放热峰,研究了603环氧树脂体系固化动力学的特性。利用Kissinger方法和Kamal方程分别拟合得到603树脂体系固化反应的活化能和固化动力学参数,选择三种典型固化工艺制度下预测的树脂固化反应结果与实验数据对比,验证了所建立动力学模型的可靠性。基于不同升温速率的放热曲线,通过外推法得出该树脂占总反应比例70%的第一个反应固化温度为（177.3±2.2）℃,占总反应比例30%的第二个反应的起始温度和固化温度分别为（178.6±0.7）℃和（216.9±1.7）℃。研究结果对于多组分热固性树脂体系固化动力学的分析和复合材料成型工艺的优化具有重要的指导意义。     

CFRP拉挤过程非稳态温度场数值模拟与FBG实时检测

碳纤维增强聚合物基复合材料的拉挤成型过程是动态的,其固化度与温度变化为强耦合关系。温度场是工艺过程控制关键之一。根据固化动力学和传热学理论,建立了非稳态温度场与固化动力学数学模型。通过差示扫描量热仪（DSC）分析计算出模型中固化动力学参数。采用有限元与有限差分相结合的方法,依据ANSYS求解耦合场的间接耦合法,编制了计算程序,对拉挤工艺不同工况CFRP内部非稳态温度场进行数值模拟。采用专门设计制作的铝毛细管封装的布拉格光栅光纤(FBG),排除了非温度应变的干扰。通过试验确定了FBG温度传感特性表征及FBG温度灵敏度系数值,保障了CFRP内部温度场实时动态检测的准确度。模拟与实验结果基本吻合,为取代传统试凑性实验,优化CFRP拉挤工艺提供了科学快捷的理论依据。      

缠绕用改性BMI树脂固化反应最大概然机理函数的确定

采用动态DSC法研究了缠绕用改性树脂体系的固化反应特性.结果表明,缠绕用树脂体系的同化反应在182.7～300.4℃区间,固化温度为234.4℃.采用等转化率原则,求解了体系固化反应表观活化能;依据J.Malek的最大概然机理函数法建立了固化反应机理函数得到了固化反应动力学模型.缠绕用树脂体系固化反应按照自催化反应机理...     

聚合物基复合材料模压成型过程固化度与非稳态温度场的数值模拟

聚合物基复合材料模压成型过程固化度与温度的动态变化为强耦合关系。本文作者根据固化动力学和传热学理论,建立了非稳态温度场与固化动力学数学模型。通过DSC实验分析确定模型中固化动力学参数。利用有限单元与有限差分相结合的方法,建立了温度场和固化度数值模型。应用Euler逐步迭代法实现解耦。对聚合物基复合材料模压成型过程固化度与非稳态温度场动态变化进行计算机数值模拟,与试验测定结果吻合。为优化模压成型工艺提供理论依据。     

超声振动对快速固化环氧树脂体系固化动力学特性的影响

通过非等温差示扫描量热法,结合黏度测试和傅里叶红外光谱分析,研究了不同超声波振动条件下环氧树脂体系的固化特性。基于Flynn-Wall-Ozawa/FWO、Kissinger-Akahira-Sunose/KAS和Boswell积分型动力学模型,计算了不同超声波振动下环氧树脂体系的活化能。结合Malek最大概然函数法,得到了超声振动下树脂体系的固化反应动力学方程,并与实测固化度对比进行了验证。研究表明,超声振动振幅越大,树脂体系黏度降低越明显,较小的超声波振幅振动下树脂体系活化能增大,而振幅增大后活化能有明显的降低。固化物的红外光谱分析表明,随着超声振幅的增大,羟基吸收峰减弱,表明超声效应加速了胺基加成反应或者羟基醚化反应。超声振动条件下的树脂固化反应模型符合自催化模型形式,但超声振动并不能改变树脂体系的固化反应机制。以上研究结果对设计和优化碳纤维增强树脂复合材料超声振动辅助树脂传递模塑成型(RTM)工艺具有一定的指导意义。     

改性双马来酰亚胺树脂固化工艺动力学模型的建立

利用固化反应动力学模型对复合材料成型工艺的固化工艺进行了模拟计算.以改性双马来酰亚胺树脂体系为例,采用DSC实验方法,以Least-aquare与Malek两种方法处理实验数据,选择并确定准确的固化反应动力学模型,进一步确定固化工序中的工艺参数.     

5428双马树脂体系动态固化反应动力学研究

采用示差扫描量热法(DSC)对5428双马树脂体系的动态固化反应动力学进行了研究,以自催化反应动力学模型为基础方程建立了动态固化反应动力学方程.并模拟实际固化温度历程,采用测定不同固化阶段样品残余反应热的方法对动态固化反应动力学方程进行了验证,结果表明动态固化反应动力学方程能反映体系实际固化反应历程.     

CFRP感应加热线圈中心区域温度场

感应加热技术是实现碳纤维增强树脂复合材料(CFRP)低能耗高效固化成型的有效方法,提高CFRP感应加热温度场均匀性是保证成型质量的关键,而线圈中心区域温度场均匀性是保证材料整体温度均匀性的关键。根据电磁加热原理建立了CFRP有限元多场耦合的分析模型,通过对模拟计算和实验过程的温度场升温及分布情况的对比分析,证明了本仿真可以准确模拟CFRP感应加热温度场分布。根据图像的熵值理论将温度场均匀性通过熵值大小进行表示,实现了CFRP感应加热温度场均匀性的量化分析,并通过有限元模型计算研究了线圈直径及线圈与材料间距对线圈中心区域温度场均匀性的影响,得到了中心区域温度场均匀性与线圈直径及材料间距之间的关系曲线,为组合式线圈均匀加热CFRP提供了线圈直径及材料间距大小选择的理论依据。      

典型双马来酰亚胺树脂固化动力学模型的研究

对由二苯甲烷双马来酰亚胺与二烯丙基双酚A体系制得的典型双马来酰亚胺树脂体系的固化动力学模型进行研究,目前国内绝大多数双马来酰亚胺树脂体系都是在此基础上改性得到的。并采用DSC方法研究典型双马来酰亚胺树脂的固化过程,用恒温和动态两种方法分析其固化反应。根据自催化与n级反应方程,采用least-squares方法和Kissinger方法进行数据处理,建立该树脂体系的固化动力学模型并确定其固化动力学参数,此模型与实验结果具有良好的吻合性。同时该模型揭示了典型双马来酰亚胺树脂体系的固化反应是按不同机理分段进行的,在反应过程中由自催化模型转变为n级反应模型。此模型为合理的研究双马来酰亚胺树脂体系的工艺参数,保证产品质量以及工艺优化提供了必要的前提条件。      

Cure simulation with resistively in situ heated CFRP molds: Implementation and validation

In composite processing of parts with varying cross-sections, homogeneous cure is sought but poses a significant challenge. Electrically heated molds for resin transfer molding (RTM) processes offer the potential to locally introduce heat and, thus, achieve more homogeneous cure and enhanced part quality. However, low conductivity of CFRP poses a risk of uncontrolled exothermic reactions. To target this potential, an appropriate and efficient numerical method is presented in this study to simulate part cure governed by resistive heated CFRP molds. A numerical control algorithm for 3D finite element cure simulations is developed, which uses the reaction flux of a temperature boundary condition to calculate the arising tool temperature field. The capability of this method to predict non-uniform tool temperatures of self-heated CFRP molds with close to thermocouple accuracy during the cure process is shown by means of numerical verification and experimental validation on a self-heated CFRP plate.     

覆铜箔层压板专用低溴环氧树脂/双氰胺体系的固化反应动力学

采用程序升温DSC法研究了覆铜箔层压板专用的低溴环氧树脂／双氰胺体系的非等温固化反应动力学。分别用Kissinger方程和Ozawa—F1ynn—Wall方程推导了该固化体系的固化动力学方程，并计算了固化反应活化能。结果显示Kissinger方程能够较好地反映该体系非等温固化过程中放热峰顶温度的动力学参数，而Ozawa—F1ynn—Wall方程则可在较大固化度范围内计算该固化体系的动力学参数。本研究为环氧树脂／破纤布基覆铜箔层压板及多层印刷电路板的制作工艺提供了理论指导。     

GFRP厚板制件固化过程固化度分布

采用真空导入模塑工艺(VIMP) 制备了85 mm 厚玻璃纤维增强环氧树脂层合板, 单面刚性模具加热固化, 沿铺层厚度方向设置热电偶, 进行了实时固化温度监测, 发现固化时厚度方向存在明显的温度差异。通过DSC方法得到等温环氧树脂固化度-时间实验数据, 建立了基于自催化反应模型的等温固化反应动力学方程, 模型计算值和实验值符合良好; 提出了时间离散分步计算法, 对非等温固化条件下, 厚度方向的固化度分布进行了计算。结果表明: 固化过程中厚度方向固化度存在差异, 短时间的后固化可以消除此差异。该方法可以模拟出由温度差异导致的固化度的不均匀分布, 用于指导优化固化工艺。      

Cure kinetics and rheology characterisation and modelling of ambient temperature curing epoxy resins for resin infusion/VARTM and wet layup applications

Ambient temperature curing epoxy resins are widely used as the matrix material in fibre reinforced plastics in the marine and wind energy sectors, where they are popular due to their relatively high mechanical performance yet low processing and tooling costs. To date, the characterisation of ambient curing epoxy resins has been limited to relatively simple measures, not suitable for use in heat transfer and flow process models. A complete cure kinetics and rheology model allows the prediction of the progression of degree of cure and viscosity for any time–temperature history. The progression of degree of cure of two epoxy resin systems was measured by differential scanning calorimeter and fitted to an nth order model incorporating vitrification effects. Viscosity was measured using an oscillatory rheometer and fitted to a model from the literature. The resulting cure kinetics and rheology model enables the improvement of resin infusion and wet layup processes by providing a thorough understanding of the interlinked relationship between time, temperature, degree of cure and viscosity.     

等温DSC法研究RFI用环氧树脂固化动力学

为了预测固化反应的进程,采用STA 449C型差示扫描量热仪,用等温DSC法研究了室温下成膜、中温固化的RFI工艺用(E-44/E-21(6/4,质量比))/GA-327＝100/40(质量比)环氧树脂体系在80、90、100、110、120℃下的固化过程,通过Matlab数据拟合良好性统计法得到了n级固化模型、自催化模型及复合模型方程中的各个参数值。根据R2和离差平方和SSE确定了适合的动力学模型。研究表明:该树脂体系的固化反应具有自催化和扩散控制的特征,低温下受扩散控制的影响更大;该体系的固化反应动力学符合自催化反应动力学模型,其表观活化能E_a为56.7kJ/mol,指前因子A为1.18×107 s-1,固化反应的反应级数m、n分别为0.529和1.561。      

Material characterization of a polyester resin system for the pultrusion process

In the present work, the chemo-rheology of an industrial “orthophthalic” polyester system specifically prepared for a pultrusion process is characterized. The curing behaviour is first characterized using the differential scanning calorimetry (DSC). Isothermal and dynamic scans are performed to develop a cure kinetics model which accurately predicts the cure rate evolutions and describes the curing behaviour of the resin over a wide range of different processing conditions. The viscosity of the resin is subsequently obtained from rheological experiments using a rheometer. Based on this, a resin viscosity model as a function of temperature and degree of cure is developed and predicts the measured viscosity correctly. The evolution of the storage and loss moduli are also measured as a function of time using the rheometer which provides an information about the curing as well as the gelation. The temperature- and cure-dependent elastic modulus of the resin system is determined using a dynamic mechanical analyzer (DMA) in tension mode. A cure hardening and thermal softening model is developed and a least squares non-linear regression analysis is performed. The variation in elastic modulus with temperature and phase transition is captured for a fully cured resin sample.     

Optimization for CFRP pultrusion process based on genetic algorithm-neural network

The temperature and the degree of cure of carbon fiber reinforced polymer (CFRP) are coupled during pultrusion. In this paper, the governing equations for heat transfer and resin curing are solved by the combination of finite element method, finite different method and indirect decoupling method. The kinetic parameters needed for simulation are obtained from differential scanning calorimetry (DSC) measurement. The temperature of composites on real time during pultrusion is monitored by the fiber Bragg grating (FBG) sensor. And the final degree of cure of composites is also measured through Sorbitic extraction. It shows that the simulation procedure is effective and reliable and predicts temperature and degree of cure which are in good agreement with the experimental results. On the basis of the simulated results, the relationship between processing parameters and degree of cure is formed by artificial neural network. And genetic algorithm combines with the artificial neural network to solve the bi-objective optimization for CFRP pultrusion. It shows that there are considerable improvements in pull speeds and die temperatures after optimization by ANN and GA.