桐油改性双环戊二烯不饱和树脂的固化研究

采用红外光谱(FT-IR)和示差扫描量热法(DSC)对桐油改性DCPD-UPR的固化特性和固化动力学进行了研究。利用Kissinger方程和Crane方程计算得到桐油改性DCPD-UPR的表观活化能94.03 kJ/mol,反应级数为0.94,指前因子为2.185×1012。利用T-β外推法确定了桐油改性DCPD-UPR的固化温度为107.28℃,后处理温度为120.65℃。较未改性的DCPD-UPR,桐油改性DCPD-UPR的固化放热曲线平缓,放热峰温度低,固化时间长,可以避免树脂固化成型时翘曲、开裂等现象的发生。     

电子束固化碳纤维缠绕复合材料性能研究

结合压力容器缠绕成型工艺,研究了电子束固化树脂体系的工艺性能、固化参数及力、热性能;在国内首次采用电子束固化技术制备了T700碳纤维复合材料压力容器并通过水压试验验证。试验结果表明:电子束固化环氧体系(EB-1)具有较好的工艺性能和力学性能,耐热性能优良,达到191. 4℃;采用电子束固化工艺制备的T700碳纤维/EB-1复合材料NOL环的拉伸强度为2020 MPa,层间剪切强度为68. 9 MPa;制备的150 mm压力容器的特性系数PV/Wc为44 km,达到了目前同类热固化复合材料的水平,固化周期仅为热固化复合材料的1/15。     

热固性碳纤维编织复合材料C形结构隔膜成型工艺

详细介绍了热固性碳纤维编织复合材料C形结构的热隔膜成型工艺。测量了CYCOM970/PWC-T300预浸料在60~120℃不同温度下的滑动摩擦系数。采用烘箱固化和热压罐固化两种方式,进行了热隔膜预成型体的固化试验。通过对试件进行三维激光扫描,得到了C形结构隔膜成型体的厚度、回弹大小分布规律以及滑移角的大小。通过对截面进行扫描,得到了成型试件的孔隙率。     

ABS材料熔融沉积成型过程中换热系数的反求

熔融沉积成型过程的换热系数是建立热边界条件的重要参数,也是温度场模拟过程的关键参数。本文推导出熔融沉积成型过程的热传导控制方程组有限差分格式。依据此方程组,考虑了熔融沉积成型过程中的内热源和相变潜热,以及热物理性能参数的变化,借助非线性迭代估算理论得到熔融沉积成型过程中表面综合换热系数的增量。在此基础上,利用MATLAB软件编写了反求换热系数程序,并进行了数值模拟,将模拟结果与实测结果进行比较,验证了计算结果的有效性。结果表明,本文所述方法是一种有效计算换热系数的方法。     

耐高温拉挤环氧树脂及其复合材料性能研究

本文研究了改性多元缩水甘油胺型耐高温环氧树脂的固化动力学,分析了该树脂体系的浇注体性能,制备了碳纤维拉挤复合材料,并通过热机械分析(DMTA)考察了树脂浇注体及其复合材料的动态热机械性能.结果表明,树脂体系的凝胶化温度与固化温度相差较小,固化反应放热集中,适合于快速拉挤成型;其复合材料具有优良的耐高温性能,玻璃化温度(Tg)达到210℃以上.     

DSC法研究聚异氰酸酯/环氧树脂胶粘剂的固化反应动力学及固化工艺

采用差示扫描量热法(DSC)研究了聚异氰酸酯/环氧树脂的固化过程,研究了不同配比对固化反应的影响、固化度与固化温度的关系,计算了固化反应表观活化能和反应级数,确定了聚异氰酸酯/环氧树脂胶粘剂的固化工艺。结果表明:胶粘剂中固化剂的含量对环氧树脂的固化反应过程有显著的影响,随着聚异氰酸酯含量的增加,固化放热量增加。当聚异氰酸酯的含量达到1.2份时,固化反应放热量达到最大值;在不同升温速率下,体系固化温度有很大差异,随着升温速率的提高,固化温度升高。通过动力学计算得到体系最佳固化温度为108℃,固化时间为6—8h,固化体系的活化能为43.31kJ/mol,反应级数为1.17。     

胶接用胶粘剂固化过程中温度预测及影响因素研究

针对单搭接接头,根据胶粘剂固化过程中的传热情况,将其温度场简化为无内热源的热传导问题,将平均换热系数看作固化温度的函数,采用集总参数法,得到胶粘剂固化过程中温度的预测公式,并用实验对公式计算结果进行了验证。运用该公式,分别讨论了固化温度、固化时间、被粘物材料属性、被粘物厚度、搭接长度、被粘物长度、胶粘剂初始温度、搭接宽度对胶粘剂固化过程中的温度影响规律。结果表明,前面5个因素对胶粘剂固化过程中的温度影响较大,后面两个因素基本无影响,当搭接长度相同,且与被粘物长度比值小于0.3时,被粘物长度也基本无影响。     

DSC法研究聚异氰酸酯／环氧树脂胶粘剂的固化反应动力学及固化工艺

采用差示扫描量热法(DSC)研究了聚异氰酸酯／环氧树脂的固化过程,研究了不同配比对固化反应的影晌,固化度与固化温度的关系,计算了固化反应表观活化能和反应级数,确定了聚异瓤酸酯／环氧树脂胶粘剂的固化工艺。结果表明:胶粘剂中固化剂的含量对环氧树脂的固化反应过程有显著的影响,随着聚异氰酸酯的增加,固化放热量增加。当聚异氰酸酯的含量达到1．2份时,固化反应放热量达到最大值;不同升温速率下,体系固化温度有很大差异,随着升温速率的提高,固化温度增加。通过动力学计算得到体系最佳固化温度为108℃,固化时间为6-8h,固化体系的活化能为43．31kJ／mol,反应级数为1．17。     

环氧树脂基预浸料热固化特征温度和固化度研究

基于固化动力学理论和有限元分析方法,建立了树脂基预浸料热固化过程中温度场研究的数学模型,数值模拟了预浸料固化过程的温度和固化度变化特征,将数值计算结果与已有文献实验结果对比,验证了计算模型和计算方法的正确性.研究了升温速率、玻璃纤维等因素对环氧树脂体系固化反应特征温度以及固化时间的影响.结果表明,升温速率增加,固化反应放热峰Tp向高温方向移动,同时固化起始温度Ti和固化终止温度Tf也相应地向高温移动,固化过程中材料内温度梯度增大,内部热应力增大.但提高升温速率可缩短固化完成所需时间.玻璃纤维的加入使树脂基预浸料各项固化反应特征温度降低,达到固化起始温度的时间延长,但对完成固化时间的影响可忽略.     

桥梁加固用环氧树脂胶粘剂体系固化动力学研究

制备了三种温度环境条件固化剂,对照组不经处理直接调配,常温组在19～24℃条件下处理7 d,低温组在4℃条件下处理7 d。将制备完成后的三种固化剂与环氧树脂按照质量比4∶10充分混合,并按照相关规定测试三组试验材料的力学性能,使用差示扫描量热法分析环氧树脂胶粘剂体系的固化动力学性能。研究结果表明:两种温度环境配制的环氧树脂胶粘剂体系的力学性能均有提高,升温速率快,放热峰向高温方向移动;经计算反应活化能为59.79 kJ/mol,反应级数为0.95;低温固化后的试验样品存在明显放热峰,常温固化后的试验样品转变为玻璃化状态。     

Non-autoclave processing of advanced composite repairs

Historically, the repair of 180°C (350°F) curing carbon fiber reinforced plastic (CFRP) laminates has required the use of an autoclave during the cure process to produce acceptable void-free laminates. A common technique for repairing 180°C (350°F) CFRP laminates without an autoclave is to use a 121°C (250°F) CFRP material or a wet lay-up. These repair laminates produce comparable RT/dry test results, although under the hot/wet condition there is a reduction in the laminate strength. Current high-pressure autoclave cure techniques work by pushing most of the entrapped air out of the laminate while compressing the remaining pockets of air into very small sizes. Using vacuum and ambient atmospheric pressure there is not enough pressure differential to squeeze out the entrapped air or compress the remaining pockets to small acceptable sizes. The double vacuum bagging technique produces a temporary degassing chamber over the repair laminate. A research program was established to develop a repair process that produces an autoclave quality laminate without the use of an autoclave. When combined with the C-staging of the repair laminate, the repair adaptation of the double vacuum bagging process is very promising.     

Analysis of heat transfer in autoclave technology

In autoclave technology, polymer based composites are manufactured under the application of pressure and heat. The heat transferred between the energy carrying fluid and the bag‐composite‐tool element activates exothermic curing reactions, leading to composite consolidation. The convective heat transfer mechanism is the most relevant aspect controlling the rate of chemical and physical transformations associated with composite curing. Moreover, the fluidodynamic regime that results from the interactions between the autoclave and the tool geometry, even if totally predictable in theory, is unattainable in practice. In this study, the heat transfer phenomena occurring during the autoclave manufacturing cycle have been analyzed. The assumption of a negligible through‐the‐thickness thermal gradient led to simplified energy balance equations. In this case, the thermal evolution of the manufacturing elements has been completely determined by two parameters: the global convective heat exchange coefficient, setting the rate of the heat transfer between the autoclave environment and the bag‐composite‐tool element, and the adiabatic temperature rise, establishing the relevance of the polymerization exotherm. A scaling analysis has been performed in order to identify the dimensionless parameters controlling the autoclave process. The developed semitheoretical methodology has been extensively tested by comparison with experimental data from an industrial autoclave.     

复合材料压力容器的树脂体系的固化动力学研究

本文采用非等温DSC方法对碳纤维增强复合材料压力容器的树脂体系进行固化动力学研究。应用Malek方法处理实验数据,得到此树脂体系机理函数服从一个二参数(m,n)的自催化模型,其中活化能通过Ozawa法得到。通过温度场模拟结果与试验值比较,验证本文建立的动力学模型的可靠性。因此,可为复合材料压力容器固化成型过程中瞬态温度场的模拟提供必要子模型。     

Experimental characterization of autoclave-cured glass-epoxy composite laminates: Cure cycle effects upon thickness,void content,and related phenomena

This article presents results from over 100 experimental autoclave curing fiber-glass-epoxy composite laminate curing runs. The primary objective was to verify shrinking horizon model predictive control—SHMPC—for thickness and void content control, using readily available secondary measurements. The secondary objective was to present and analyze the extensive experimental results obtained through this verification. Seven series of curing runs (16 per series) were performed, with cure settings governed by partial- or full-factorial orthogonal array based design of experiments. Through t-tests and two-way analysis of variance, it was found that pressure magnitude had the largest influence on laminate thickness and void content, while first hold duration/temperature, pressure application duration, and run delay influenced void content more than thickness. Thinner laminates with lesser void contents resulted from pressure application before the second temperature ramp. Prepreg age also affected thickness and void content. Photomicrographs revealed not one large void, but void clusters. Interrupted autoclave cure cycles revealed that significant laminate thickness reduction occurred during all curing cycle stages. The percentage of resin weight loss through laminate sides increased with pressure magnitude and application duration. Ten test curing runs indicated that SHMPC met difficult thickness targets while minimizing void content.     

Effect of Autoclave Bonding Pressure and Temperature on Polycarbonate Single Lap Joints with polyurethane adhesive

Adhesive joints are good replacement for bolted and welded joints. Adhesive joint performance over the life depends on joint strength. Strength of joint depends upon curing process parameters used during bonding. This study investigates the effect of cure temperature and pressure on the mechanical performance of autoclave-bonded single lap joints (SLJ). Joint load transfer capacity (LTC) data and failure mode analysis are provided. Test joints are made of two polycarbonate lexan adherends that are autoclave-bonded together using aliphatic polyether (Polyurethane) film adhesive (Huntsman PE399). Two levels of cure pressure and cure temperature are investigated, for their effect on joint load transfer capacity, failure mode, and joint stiffness after heat cycling at a low or high level of relative humidity. Experimental results showed higher cure temperature increases joint performance.     

5428/T700体系制造大厚度构件的工艺适宜性研究

对一种航空用改性双马来酰亚胺树脂/碳纤维(5428/T700)复合材料体系制造大厚度构件的工艺适宜性进行研究,通过差示扫描量热法研究了5428树脂的固化反应特性,并测量了5428/T700厚板在固化过程中的温度场。发现5428树脂固化反应放热缓慢而均匀,有利于制造大厚度构件;5428/T700厚板在固化过程中其厚度方向上的温度分布均匀,没有出现明显的温度突增现象;并通过热压罐技术制造出了质量良好的厚板试件。结果表明,5428/T700体系适合于制造大厚度复合材料构件。     

A novel application of alumina fiber mats as TBC protection for CFRP/epoxy laminates –Laboratory tests and numerical modeling

A novel method is proposed to create a TBC on the CFRP/epoxy laminate surface in a single technological process by formation of one additional layer made of a commercially available alumina fiber mat. Both materials: the CFRP/epoxy laminate made of four layers and the ceramic mat were joined during prepreg curing.The quick thermal heating tests of the TBC system were conducted for different times with a propane-butane torch. Changes of material strains due to temperature influence are determined experimentally in uniaxial tensile tests via the Digital Image Correlation (DIC) method. A numerical model corresponding to the experimental quick heating test is built in Abaqus standard finite element software to determine temperature distribution in the CFRP/epoxy laminate.The experimental and numerical investigations lead to a conclusion that the alumina fiber mat is an effective protection of the CFRP/epoxy laminate against temperature degradation and can be used in industrial practice.     

轮胎直压硫化工艺的有限元仿真

传统的蒸汽硫化机具有胶囊和蒸汽室,使用过热蒸汽加热轮胎使之硫化。蒸汽的传热效率低,能量浪费严重。由于蒸汽的放热冷凝,蒸汽室底部的温度低于蒸汽室顶部的温度,这导致轮胎的不均匀硫化。直压硫化则采用电磁加热方式,其产生的温度场均匀,局部区域温度具有可控性。其次直压硫化工艺用大小鼓瓦与轮胎直接接触传热的方式,其传热效率应该比蒸汽硫化工艺高。本文基于ABAQUS软件,编写HETVAL和UVARM子程序模拟实际硫化工艺得到255/30R22轮胎的温度场和硫化程度场,在相同硫化条件下比较两种工艺的硫化效果。结果表明直压硫化工艺的硫化效率大约提高了三分之一。     

石蜡/纳米石墨复合相变储热材料的换热与放热效率

相变储热是提高能源利用率的重要手段之一,相变储热材料的换热系数与放热效率研究对太阳能高效利用具有重要意义。通过变换铝管管径、循环风速以及空气温度,计算出复合相变储热材料的换热系数及放热效率。结果表明:铝管管径不变,循环风速小于3m/s时,空气温度对换热系数影响很小,差值在1W/(m2·℃)左右;换热系数、放热效率都随风速的增大而有所提高,放热效率最大可达95.3%;随着管径增大,换热系数逐渐减少,放热效率却逐渐增大;适合石蜡/纳米石墨复合相变储热材料的最佳条件为管径30mm、循环风速3m/s以及空气温度90℃。