烧蚀防热复合材料用压力辅助RTM工艺

针对目前模压、缠绕等工艺成型烧蚀防热复合材料易造成层间结合差、脱粘、抗烧蚀性能差、易剥蚀等问题,提出了一种新型压力辅助RTM工艺,并对其进行了树脂充模流动模拟,制备了烧蚀防热复合材料,测试了材料的孔隙率、力学性能、烧蚀性能。结果表明:压力辅助RTM工艺具有可行性与优越性,复合材料孔隙率4.64%,层间剪切强度39.3 MPa,线烧蚀率0.017 mm/s,质量烧蚀率0.053 8 g/s。说明压力辅助RTM工艺适合成型烧蚀防热复合材料。      

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。      

复合材料带缠绕成型工艺参数耦合机制及优化

基于复合材料缠绕成型工艺过程研究,分别对成型过程中紧密接触与自粘接过程进行理论分析,提出影响复合材料缠绕制品质量的关键工艺参数:缠绕温度、缠绕压力和缠绕张力;以层间剪切强度(ILSS)为优化目标,根据响应面法Box-Behnken Design(BBD)原理设计实验,建立工艺参数耦合对剪切强度的回归模型,通过对残差、方差(ANVOA)、预测值与实际值对比等检验分析,验证回归模型的可靠性及有效性,进而获得缠绕成型最优工艺参数。结果表明:在最优工艺参数作用下,层间剪切强度达到22.9 MPa,缠绕制品结合强度最高。     

RTM快速成型环氧树脂时间-温度-转变图的构建及其碳纤维/环氧树脂复合材料评价

针对自行研制的树脂传递模塑工艺（RTM）快速成型环氧树脂,利用唯象动力学模型、DiBenedetto方程和凝胶模型研究了树脂体系的等温及非等温固化动力学,构建了时间-温度-转变（TTT）的关系图,表明树脂体系兼具较长的适用期与快速固化特性。以此设计RTM快速成型工艺,考察了树脂体系对碳纤维织物的浸润流动行为,并评价了快速成型碳纤维/环氧树脂复合材料的界面力学性能与微观形貌。结果表明,注射温度下树脂体系的浸润填充性良好,RTM快速成型碳纤维/环氧树脂复合材料的力学性能和内部成型质量较好。      

6421双马来酰亚胺树脂的反应流变性及树脂传递模塑成型工艺研究

对用于RTM工艺的6421双马来酰亚胺（BMI）树脂体系的反应流变特性进行了研究，并根据流变特性确定RTM工艺的两个主要参数：模具温度110－140摄氏度，注射压力小于0．5MPa，结果表明，按此工艺条件可顺利成型先进RTM复合材料，且复合材料的表面质量良好，孔隙率低，达到先进复合材料的性能要求，同时对RTM成型的编织复合材料的力学性能进行了初步的表征。     

真空辅助树脂灌注工艺成型泡沫夹芯结构工艺设计与控制

采用无屈曲织物(NCF)、 CYCOM^® 890 RTM树脂体系和聚甲基丙烯酰亚胺(PMI)泡沫以及真空辅助树脂灌注成型工艺(VARI)成型泡沫夹芯复合材料平板, 结合力学性能测试和微观结构分析等手段研究了成型过程中抽胶对夹芯板界面质量以及纤维体积分数的影响, 分析产生的缺陷类型及原因, 优化了工艺参数。结果表明: 抽胶有利于提高泡沫夹芯板的纤维体积分数和力学性能, 在100～120 ℃温度范围内进行30 min的抽胶, 工艺稳定, 层间剪切强度和弯曲强度显著提高。     

真空辅助树脂灌注工艺成型泡沫夹芯结构工艺设计与控制

采用无屈曲织物(NCF)、CYCOM(R) 890 RTM树脂体系和聚甲基丙烯酰亚胺(PMI)泡沫以及真空辅助树脂灌注成型工艺(VARI)成型泡沫夹芯复合材料平板,结合力学性能测试和微观结构分析等手段研究了成型过程中抽胶对夹芯板界面质量以及纤维体积分数的影响,分析产生的缺陷类型及原因,优化了工艺参数.结果表明:抽胶有利于提高泡沫夹芯板的纤维体积分数和力学性能,在100～120℃温度范围内进行30 min的抽胶,工艺稳定,层间剪切强度和弯曲强度显著提高.     

制备工艺对单向连续碳纤维增强聚醚砜复合材料层间结合强度的影响

采用溶液浸渍和热压成型制备了以聚醚酚为基体的单向连续碳纤维增强复合材料,研究了不同树脂浓度和热压工艺参数下复合材料的层间剪切强度。结果表明:成型温度高的复合材料具有较高的层间剪切强度,适当延长保温时间能够大幅度提高复合材料的性能。扫描电镜和热重分析表明树脂基体与碳纤维之间结合紧密,不同树脂含量的复合材料在热压成型过程中,界面处有不同的作用机理。     

软模辅助RTM成型舱段构件及其性能研究

某些复合材料结构件尺寸较大且内部结构复杂,难以通过传统RTM工艺一次整体成型,并且因其成型压力低而致纤维含量不高,成型构件力学性能不佳.本研究用硅橡胶来浇铸成型特定形状的软模,采用软模辅助RTM来制备舱段构件这一典型航天结构件.由于硅橡胶软模在复合材料固化成型过程中发挥了设计中的膨胀挤胶作用,复合材料的纤维体积含量和力学性能得到了显著提高,舱段整体力学性能满足了航天主承力结构件的使用要求,因此软模辅助RTM在制备具有内部复杂结构的装备结构件上具有广阔的发展前途.     

RTM成型复合材料T型接头工艺参数优化与力学性能实验研究

对树脂传递模塑(RTM)成型的复合材料T型接头进行了工艺参数优化、制备及力学性能实验研究。应用流动模拟软件,对RTM成型的复合材料T型接头进行了基体流动数值模拟,确定模具最佳注射方式和出胶口位置,并优化了影响树脂充模时间的工艺参数,显著提高了RTM接头的工艺性能。根据优化工艺参数结果,制备了RTM成型的复合材料T型接头试样,并进行了拉伸和压缩试验,分析了其破坏机制。根据拉伸和压缩试验现象和结果,发现RTM成型的复合材料T型接头拉伸破坏模式主要为富树脂三角区的树脂与纤维布界面分层,其拉伸破坏主要取决于树脂基体抗剥离分层的拉伸强度;压缩破坏模式为底板中央部位的弯曲分层与折断,其压缩破坏由接头底板中的纤维布抗拉强度决定;T型接头的压缩破坏强度高于拉伸破坏强度。     

石墨烯/钛基复合材料的界面反应控制、微观组织和压缩性能

将Ti6Al4V（TC4）粉末与少层石墨烯（GR）粉末进行三维机械旋转混合,实现了GR在TC4球形粉末表面的均匀包覆,经放电等离子烧结(SPS)得到增强相呈三维网络状分布的GR/TC4复合材料。对不同的SPS烧结温度、保温时间、升温速率和轴向压力对GR与钛基体原位界面反应程度的影响进行了研究,并对界面处不同GR/TC4比例的网状结构复合材料的物相结构、显微组织及室温压缩性能进行了系统性的研究。结果表明,烧结温度和升温速率是影响GR与基体反应程度的主要因素,压力主要影响材料致密度,低温高压快速烧结可以降低GR与基体的反应程度,但高比例的GR残留并没有带来力学性能的大幅提升。对于0.25wt%的GR添加量,GR的反应比例约为70%~80%能得到更加良好的异质界面的结合,获得综合力学性能优异的GR/TC4协同增强的钛合金基复合材料。GR在钛合金基体中的三维网络状分布能调控钛基复合材料的强度与塑性的矛盾。      

Optimization of chemical composition for TC11 titanium alloy based on artificial neural network and genetic algorithm

It is quite difficult for materials to develop the quantitative model of chemical elements and mechanical properties, because the relationship between them presents the multivariable and non-linear. In this work, the combined approach of artificial neural network (ANN) and genetic algorithm (GA) was employed to synthesize the optimum chemical composition for satisfying mechanical properties for TC11 titanium alloy based on the large amount of experimental data. The chemical elements (Al, Mo, Zr, Si, Fe, C, O, N and H) were chosen as input parameters of the ANN model, and the output parameters are mechanical properties, including ultimate tensile strength, yield strength, elongation and reduction of area. The fitness function for GA was obtained from trained ANN model. It is found that the percentage errors between experimental and predicted are all within 5%, which suggested that the ANN model has excellent generalization capability. The results strongly indicated that the proposed optimization model offers an optimal chemical composition for TC11 titanium alloy, which implies it is a novel and effective approach for optimizing materials chemical composition.     

ZA22/Al2O3f复合材料机械性能的神经网络模拟研究

采用人工神经网络的典型模型即B-P算法对ZA22/Al₂O_3f复合材料的机械性能进行分析和预测,结果表明:B-P模型不仅适用于单变量输出非线性系统的拟合与预测,同时还适用于多变量输出的非线性系统;B-P模型对研究复合材料ZA22/Al₂O_3f的机械性能有良好容错性.     

Finite Element Analysis of Mechanical Properties of 3D Four-directional Rectangular Braided Composites—Part 2: Validation of the 3D Finite Element Model

In the first part of the work, we have established a new parameterized three-dimensional (3D) finite element model (FEM) which precisely simulated the spatial configuration of the braiding yarns and considered the cross-section deformation as well as the surface contact relationship between the yarns. This paper presents a prediction of the effective elastic properties and the meso-scale mechanical response of 3D braided composites to verify the validation of the FEM. The effects of the braiding parameters on the mechanical properties are investigated in detail. By analyzing the deformation and stress nephogram of the model, a reasonable overall stress field is provided and the results well support the strength prediction. The results indicate it is convenient to predict all the elastic constants of 3D braided composites with different parameters simultaneously using the FEM. Moreover, the FEM can successfully predict the meso-scale mechanical response of 3D braided composites containing periodical structures.     

Development of an image-based numerical model for predicting the microstructure–property relationship in alumina trihydrate (ATH) filled poly(methyl methacrylate) (PMMA)

Particulate composites are found in a wide range of applications. Their heterogeneous microstructure affects their bulk behavior and structural performance, however tools for predicting this important structure-property relationship are still lacking. In this study, a numerical method that can provide predictions of the mechanical response of a particulate polymeric matrix composite as a function of volume fraction and particle mean diameter is presented. The work is derived for an alumina trihydrate filled poly(methyl methacrylate) but the methodology is generic and can be used for any particulate composite. Representative Volume elements are determined through images obtained from scanning electron microscopy. The model takes into account the possibility of failure through interface debonding as well as cracks through the matrix. The model predictions for the modulus and fracture strength of the composites are validated through independent experiments on the composite. The numerical results are also used to qualitatively explain the trends measured regarding the fracture toughness of the composites. Compared to other literature on particulate composites, our study is the first to report accurate stress–strain distributions as well as fracture predictions whilst all the necessary model parameters defining the failure criteria are all derived through independent experiments. This paves the way for a relatively simple methodology for determining structure-property relationships in composites design, enabling smarter material utilization and optimal mechanical properties.     

热塑性复合材料自动铺放工艺参数分析与优化

热塑性复合材料自动铺放原位成型（AFP）技术是高效低成本制造大型复合材料构件的关键,而自动铺放过程中工艺参数的选取及控制精度对成型构件的性能有较大影响,因此为保证原位成型后成型构件的性能,需分析自动铺放工艺参数对成型构件性能的影响并对其进行优化。本文基于热塑性复合材料自动铺放平台,以连续玻璃纤维增强聚丙烯（GF/PP）预浸纱为原料制备复合材料层合板,以层合板的力学性能为优化目标,根据响应曲面法原理设计试验,分析热气温度、热压辊压力及冷压辊压力各工艺参数及其耦合作用对层合板力学性能的影响,建立各工艺参数与层合板力学性能的二次多项式回归方程预测模型,通过预测值与实际值对比等检验分析,验证回归模型的有效性和可靠性,进而获得热塑性复合材料AFP最优工艺参数组合为热气温度为385℃、热压辊压力为0.3 MPa、冷压辊压力为1.1 MPa。     

Mechanical and tribological properties of 2-D carbon/carbon composites densified through pulse chemical vapor infiltration

This paper presents the mechanical and tribological properties of 2-D carbon/carbon composites (C/C) fabricated by the Pulse Chemical Vapor Infiltration (PCVI) process. In the PCVI process, various fabrication temperatures and different reactant pressures were adopted to investigate the influence of processing condition on physical properties, microstructure and mechanical properties. In the densification process by PCVI, holding time and pulse number are two parameters which significantly affect physical properties (such as density, porosity, and weight gain) and mechanical properties (such as interlaminar strength and wear properties). It is found that the wear properties of carbon/carbon composites can be improved obviously after the densification by 1000 pulses. Effects of initial open porosity on density of the fabricated composites are also studied. In this work, tribological performance of the specimens fabricated through the Isothermal Chemical Vapor Infiltration (ICVI) process and the PCVI process under different pulse cycles are compared. Scanning Electronic Microscopy (SEM) was used to examine the morphology of worn surface. The relationship between the tribological performance and surface morphology was studied.     

遗传算法在无钴高强韧钢设计中的应用

提出一种利用残缺实验数据建立无钴高强韧钢力学性能与钢的合金成分及热处理条件关系模型的方法,依据该方法建立了人工神经网络模型,并应用跗算法,对无钴高强韧钢进行了优化设计,实践表明所提出的方法是有效的,为研制新材料开辟了一条新途径。     

Effect of fiber arrangement on mechanical properties of short fiber reinforced composites

The present paper developed a three-dimensional (3D) “tension–shear chain” theoretical model to predict the mechanical properties of unidirectional short fiber reinforced composites, and especially to investigate the distribution effect of short fibers. The accuracy of its predictions on effective modulus, strength, failure strain and energy storage capacity of composites with different distributions of fibers are validated by simulations of finite element method (FEM). It is found that besides the volume fraction, shape, and orientation of the reinforcements, the distribution of fibers also plays a significant role in the mechanical properties of unidirectional composites. Two stiffness distribution factors and two strength distribution factors are identified to completely characterize this influence. It is also noted that stairwise staggering (including regular staggering), which is adopted by the nature, could achieve overall excellent performance. The proposed 3D tension–shear chain model may provide guidance to the design of short fiber reinforced composites.