玻璃纤维/环氧树脂复合材料热解特性研究

采用热重-差热分析仪研究玻璃纤维/环氧树脂复合材料在空气及氮气氛围下不同升温速率的热解特性规律。结果表明,在空气气氛下,热解分为两个阶段;氮气气氛下,热解只存在一个热分解阶段,与空气气氛相比热解初始分解温度较高,热解温度范围变窄,失重速率明显变大。在两种气氛下,玻璃纤维均不参与热解。随着升温速率的增加,热解反应各阶段的起始温度、终止温度、最大失重速率温度均向高温方向移动,热解温度范围大小都基本保持不变。氮气气氛下使用Kissinger法、FWO法和Starink法计算出玻璃纤维环氧树脂的平均表观活化能分别为106.42、123.09和119.48kJ/mol。复合材料活化能随转化率的增加而升高,表观活化能保持在一定数值范围内且数值相近,热解反应比较稳定,具有较低A值,表明其具有较强的热稳定性。     

层间增韧环氧树脂碳纤维单向带的热解特及动力学研究

利用差热-热重同步分析仪研究层间增韧环氧树脂碳纤维单向带的热稳定性,研究在不同升温速率条件下该复合材料的失重温度和失重规律。研究结果表明,随着升温速率的提高,层间增韧环氧树脂碳纤维单向带每个阶段的初始分解温度、反应最终温度及最大失重速率温度均向高温方向移动,热解温度范围逐渐扩大,质量损失明显增加。分别应用微分法和积分法对样品进行热解动力学相关参数计算,计算结果表明,层间增韧环氧树脂碳纤维单向带整体活化能较高,分子间碰撞激烈,热分解反应不易进行,其热稳定性较高。     

单向碳纤维/环氧树脂预浸料热解特性

通过热重实验研究了单向碳纤维/环氧树脂预浸料的热解性能,利用FESEM测试分析了单向碳纤维/环氧树脂预浸料的热解残留物的形貌特征,得到其热解反应过程的物质参与。研究结果表明,单向碳纤维/环氧树脂预浸料的热解反应在空气中分为三个阶段,其中第一、二阶段是环氧树脂基体的热解,第三个阶段是碳纤维的热解。不同形态的单向碳纤维/环氧树脂预浸料在不同加热速率下的热解规律：随加热速率的增加,每个阶段的初始分解温度、反应最终温度及最大失重速率温度均向高温方向移动,热解温度范围逐渐扩大,质量损失明显增加。在相同的升温速率下,块状的单向碳纤维/环氧树脂预浸料相对于其粉末材料的热解时间较长,每个阶段的热解温度较高。     

多官能团环氧树脂体系的固化反应

采用非等温差示扫描量热（DSC）对多官能团环氧树脂体系固化反应进行了研究,确定了环氧树脂所用固化剂为甲基纳迪克酸酐（MNA）。对AG-70/MNA/2-乙基-4-甲基咪唑（EMI-2,4）环氧树脂体系在不同升温速率下的固化反应进行测试,根据DSC曲线,用温度-升温速率外推法,求出环氧树脂体系的三个特征温度,温度参数能为...     

聚氨酯/环氧树脂互穿网络半硬泡沫的热稳定性

制备了聚氨酯/环氧树脂互穿网络半硬泡沫,通过热重分析(TGA)研究了其热分解,计算了各分解阶段的热分解反应动力学参数。结果表明,氮气中,互穿聚合物网络(IPN)泡沫根据环氧树脂含量不同其分解过程有2~3个失重阶段,随着环氧含量增加,第一阶段的失重率减小,第二阶段的失重率增大。IPN泡沫在第一、二两阶段总的热失重率低于纯聚氨酯泡沫及纯环氧树脂。环氧树脂含量为30%(质量分数,下同)时泡沫的热稳定性最好。预测IPN半硬泡沫在100℃氮气中失重5%时的热老化寿命可达2.4E7年,表明IPN泡沫具有很好的热稳定性。     

齿板-玻璃纤维混合夹层结构弯曲性能试验

提出了一种齿板-玻璃纤维混合面板和泡沫芯材组成的新型混合夹层结构,齿板通过齿钉与泡沫芯材相连。该结构采用真空导入成型工艺制备,通过三点弯曲试验研究该结构在不同跨度以及不同芯材密度情况下的破坏模式和弯曲性能,并与普通泡沫夹层结构进行对比分析,同时探究了齿板对该结构界面性能的影响。结果表明:在泡沫芯材密度为35kg/m~3、80kg/m~3和150kg/m~3情况下,齿板-玻璃纤维混合泡沫夹层梁弯曲承载能力与普通泡沫夹层梁相比分别提高了168%、211%和258%,其界面剪切强度依次为0.09 MPa、0.21 MPa和0.45 MPa;随着芯材密度和跨度的变化,该结构主要产生芯材剪切和芯材凹陷两种破坏形态,齿板的嵌入有效抑制界面的剪切失效。另外,利用理论公式估算了试件受弯极限承载能力,理论值与实测值吻合较好。     

分子筛4A填充海藻酸钠的热分解研究

用热重法研究了分子筛4A填充海藻酸钠在空气中的热分解过程,升温速率分别为5,10,15,20和30K/min,从室温升温到1250 K,并利用TGA曲线分析了复合材料的热降解特点。结果表明,热分解反应最剧烈的温度区间介于450～650 K之间;热分解动力学分析表明,该热分解过程为一级反应。通过模型计算确定了热降解反应的动力学参数,以最大失重速率法求得活化能为187.47 kJ/mol,频率因子lnA为38.87 s-1;采用Ozawa等失重法求得活化能为154.50 kJ/mol,频率因子lnA为34.69 s-1。     

典型碳纤维编织布的热解动力学

使用DTG-60(AH)热重-差热同步分析仪研究了升温速率对典型碳纤维编织布(T300-3000)热解特性的影响。结果表明,升温速率对典型碳纤维编织布的热解过程有显著的影响。随着升温速率的提高最大失重速率温度向高温方向移动,两峰之间的距离逐渐增大,峰面积不断增加。碳纤维编织布的热解分可为三个阶段:环氧树脂基两个分解阶段和碳纤维分解阶段。用Kissinger法和Flynn-Wall-Ozawa法进行热解动力学分析,得到了不同升温速率条件下的表观活化能和表观指前因子。用两种计算方法得到的结果基本上一致,加入环氧树脂基材的碳纤维编织布在一定质量损失范围内的热稳定性较强且可控。     

丙烯酸树脂-壳聚糖复合涂膜非等温热分解动力学机理函数推测

通过热重分析法研究了含有功能单体AAEM(乙酰乙酸基甲基丙烯酸乙酯)的丙烯酸树脂-壳聚糖交联复合涂膜的热分解反应。结果表明,该复合涂膜的热分解过程表现为两个台阶:第1台阶分解温度区间为199.4~349.0℃;第2台阶分解温度区间为323.9~450.7℃,该分解区间出现最大分解速率,而且分解速率随着升温速率的提高而提高。通过Kissinger法和Ozawa法计算复合涂膜的热分解表观活化能E分别为119.19和123.05kJ/mol。该复合涂膜热分解反应可分为3个阶段:第1阶段的转化率25%;第2阶段的转化率为25%~45%;第3阶段的转化率45%。在反应初期为化学反应机制,最可几机理函数为C5,反应级数n为5;在反应后期则变为扩散反应机制,最可几机理函数为D6;反应中期则为过渡阶段。     

840S环氧树脂体系固化反应特性

用差示扫描量热法(DSC) 在动态条件下对840S 环氧树脂体系的固化反应动力学进行了研究。根据所测量的不同升温速率的DSC 曲线, 运用温度升温速率( T-β) 图外推法得到该环氧树脂体系的固化工艺参数, 即凝胶化温度、固化温度、后处理温度, 这些温度参数为制定合理的固化工艺提供了理论基础。采用Kissinger 方程和Crane 方程计算该840S 环氧树脂体系的动力学参数, 即表观活化能E_a 、表观频率因子A 和反应级数n 。根据所计算的动力学参数, 建立了该840S 环氧树脂体系的固化动力学模型。利用所建立的固化动力学模型分别预测了等温和动态条件下840S 环氧树脂体系的固化反应特性。      

玻璃纤维/酚醛树脂复合材料热响应预报方法玻璃纤维/酚醛树脂复合材料热响应预报方法

为研究航空复合材料在火灾环境下的热响应,考虑材料热解过程,建立了复合材料热响应方程组,推导了显式有限差分格式,研究了玻璃纤维/酚醛树脂复合材料内部瞬态热响应与碳化规律。结果表明:建立的非线性热响应方程组与计算方法能够预测玻璃纤维/酚醛树脂复合材料的温度-时间历程,800 s时的受热表面温度达到了1048℃,背面温度为226℃,与实验值吻合较好;随着材料深度增加,材料达到热解温度所需的时间更长,材料密度下降速率随之降低,碳化过程变慢;热解反应区中不同深度位置的材料剩余质量分数在同一温度下略有不同,位置越深,剩余质量分数越小,碳化程度越高;随着时间推移,发生热解的材料比重增大,碳化范围逐步扩大,热解层厚度范围也逐渐扩大。      

Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.     

尼龙66及其复合材料的热分解动力学

使用热重分析仪测定尼龙66(PA66)和两种不同玻纤增强尼龙66复合材料(GF/PA)的热分解曲线,用Kissinger法和Crane法研究了PA66和GF/PA的热分解动力学。结果表明:PA66、GF/PA-1和GF/PA-2的热分解反应级数分别为0.949、0.912和0.921,表明均为一阶热分解过程;热分解活化能分别为218.65 kJ/mol、121.81 kJ/mol和132.23 kJ/mol,表明玻纤的加入显著降低了PA66的热分解活化能。在加热速率相同的条件下两种GF/PA达到最大热分解速率的温度都比PA66的低,表明玻纤虽然改善了PA66的性能,但是加快了PA66的热分解过程,说明存在着“灯芯效应”。     

High Temperature Residual Properties of Carbon Fiber Composite Sandwich Panel with Pyramidal Truss Cores

A study on the mechanical property degradation of carbon fiber composite sandwich panel with pyramidal truss cores by high temperature exposure is performed. Analytical formulae for the residual bending strength of composite sandwich panel after thermal exposure are presented for possible competing failure modes. The composite sandwich panels were fabricated from unidirectional carbon/epoxy prepreg, and were exposed to different temperatures for different time. The bending properties of the exposed specimens were measured by three-point bending tests. Then the effect of high temperature exposure on the bending properties and damage mechanism were analyzed. The results have shown that the residual bending strength of composite sandwich panels decreased with increasing exposure temperature and time, which was caused by the degradation of the matrix property and fiber-matrix interface property at high temperature. The effect of thermal exposure on failure mode of composite sandwich panel was observed as well. The measured failure loads showed good agreement with the analytical predictions. It is expected that this study can provide useful information on the design and application of carbon fiber composite sandwich panel at high temperature.     

Experimental investigation into the thermoelastic spring-in of curved sandwich panels

An investigation into the thermoelastic spring-in of curved sandwich panels has been conducted. Sandwich panels incorporating solid foam cores and biaxial glass–epoxy skins were manufactured and spring-in measured. The major contributors to spring-in were found to be the thermal expansion and Poisson’s ratio of the foam which were subsequently characterised. Also important was the development of resin rich regions on the surface of the panel. Experimental findings were implemented into a finite element (FE) model developed using 3-dimensional elements in ANSYS. The investigation was extended to panels including a core with machined slots. A refined FE model highlighted the influence of in-plane restraint reduction within the core, as well as the effect of a much thicker resin rich region caused by core segmentation. Results showed good agreement with experiment and provided a good basis for shape prediction of sandwich panels.     

浸泡腐蚀对玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料弯曲性能的影响

制备了不同纤维质量分数的玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料。通过三点弯曲试验研究了纤维质量分数对复合泡沫材料力学性能的影响。将复合泡沫材料试件置于蒸馏水和海水中浸泡,研究了浸泡腐蚀对试件弯曲性能的影响,并结合扫描电镜照片分析其原因。研究表明:纤维质量分数越高,玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料的吸湿率越大,且在蒸馏水中的吸湿率较海水中的更大。试件的弯曲强度随纤维质量分数增加而增大,当纤维质量分数为10%时达到最大,比未添加纤维的试件增强了51%,之后则随纤维质量分数增加逐渐降低。浸泡腐蚀降低了试件的弯曲性能,其中海水浸泡后的试件弯曲性能最低。玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料弯曲强度降低的直接原因是浸泡腐蚀使得部分玻璃微珠和玻璃纤维与环氧树脂基体间的界面层受到破坏。     

Composite wrist blocks for double arm type robots for handling large LCD glass panels

Recently, robot structures handling liquid crystal display (LCD) glass panels are increased in size as the size of LCD is increased. In order to handle large LCD panels, the robot structures should have high stiffness to reduce the deflection of robot end effector under the weights of LCD. The LCD manufacturing industries have a trend to employ double arm type robots rather than single arm type robots to increase productivity. Currently, two aluminum wrist blocks that have different configurations not to interfere with each other are mounted on the robot arms. The aluminum wrist block becomes one of the largest deflection sources as the size of the robot structures increases. Since the size of the wrist block can not be increased indefinitely to increase the stiffness due to the limitation of driving motor power, the best way to increase the stiffness of the wrist block is to employ carbon fiber epoxy composite material for structural material of the wrist block because the carbon fiber epoxy composite material has much higher specific stiffness and damping than aluminum. In this work, the two wrist blocks for the double arm type robot for handling large LCD glass panels were designed and manufactured using foam core sandwich structure. Finite element analysis was used along with an optimization routine to design the composite wrist blocks. Box type sandwich structures were employed to reduce shear effect arising from the low modulus of polyurethane foam core. The weight reduction of the composite wrist blocks was more than 50% compared to those of comparable aluminum wrist blocks and found that the composite wrist blocks had much improved performances compared to those of the aluminum wrist blocks from the static and dynamic tests.     

Time-Variant Simulation of Multi-Material Thermal Pultrusion

Pultrusion being the viable and economical process for producing constant cross-section composite products, many variants of it are being tried out. This paper embarks on the pultrusion with multi-materials; typically of polymer foam/glass fibre reinforced polymer (GFRP) sandwich panels. Unlike conventional composites pultrusion, this process with more than two material phases, one of them dry, poses a challenge in simulating the thermal co-curing within the die. In this paper, the formulation and development of three-dimensional, finite element/nodal control volume (FE/NCV) approach for such multi-material pultrusion is presented. The numerical features for handling the dry-wet material interfaces, material shrinkage, variations in pull speed and die heating, and foam-to-skin thickness ratio are discussed. Implementation of the FE/NCV procedure and its application in analyzing pultrusion of polymer foam/GFRP sandwich panels with multi-heater environment are presented.     

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.