填充环氧树脂界面残余应力研究 Ⅴ.界面应力集中及残余应力的影响

本文针对橡胶和玻璃珠填充环氧树脂体系,通过显微光弹法测定填充粒子的界面应力集中系数,发现橡胶填充体系的应力集中发生在粒子赤道处,而玻璃珠体系发生在粒子两极。在低拉伸时,界面残余应力对应力集中的影响较大,但在高拉伸,特别是达到材料伸长率时,界面残余应力的作用可忽略。     

填充环氧树脂界面残余应力研究——Ⅲ.界面残余应力的热行为

本文针对橡胶填充环氧树脂体系和玻璃珠填充环氧树脂体系,研究了界面残余应力的退火效应和温度变化行为。样品的残余应力与退火时间有关。温度与界面残余应力成线性反比关系。在两体系中,界面残余应力随温度升高而下降的速度不相同。     

填充环氧树脂界面残余应力研究——Ⅳ.界面残余应力形成的分子机理

本文针对橡胶改性环氧树脂体系,从微观分子运动角度对界面残余应力形成原因进行了初步探索,发现复合材料界面残余应力的生成是界面处分子运动不平衡所导致的。同时界面残余应力有效体积是一个重要参数,它和材料温度以及界面键合强弱有关。     

填充环氧树脂界面残余应力研究,Ⅰ.球面应力—光学等式

采用显微光弹法测量了橡胶填充环氧树脂(RMER)和玻璃珠填充环氧树脂(GMER)这两种复合体系中的界面残余应力,介绍了适用于这些体系的球面应力—光学等式,并观察了填料界面残余应力产生的光弹图像.     

A study of the residual microstress at the matrix interface in filled epoxy resins

Using the technique of photoelasticity, we have studied in detail the magnitude of the residual microstress at the matrix interface between epoxy resin and rubber particles or glass beads. A spheric stress-optic equation applicable to these composites was derived. The photoelastic figures induced by the interfacial residual microstresses and the factors affecting the intensity of light are discussed. The experimental results show that the residual microstresses at the matrix interface are independent of the particle size of rubbers or glass beads, but depend on the nature of fillers, which have different thermal expansion coefficients and mechanical properties. Thermal history and interfacial chemical bonding of filled epoxy resins have distinct effects on the residual interfacial microstresses and the matrix internal stresses.     

RTM制备玻璃纤维增强环氧树脂复合材料的力学性能分析

以环氧树脂为基体,短切玻璃纤维和玻璃纤维布为增强材料,通过RTM工艺制备了玻璃纤维增强环氧树脂(GF/EP)复合材料,并研究了RTM工艺制备玻璃纤维布增强环氧树脂(L-GF/EP)和短切玻璃纤维增强环氧树脂(S-GF/EP)复合材料的拉伸和弯曲性能,分析了开孔对两种复合材料拉伸性能的影响。结果表明:在拉伸过程中,开孔试样因孔边产生的应力集中,导致其拉伸强度与无孔试样相比下降了30%左右;玻纤铺层类型的不同对复合材料的力学性能具有显著影响;L-GF/EP复合材料内部结构完整,在载荷作用下,复合材料的弯曲断裂呈现一定的假塑性断裂模式,达到弯曲极限挠度值后,出现一定程度的回弹现象,其力学性能优于S-GF/EP复合材料。     

Residual stress in particulate epoxy resin by X-ray diffraction

Residual stress in particulate epoxy resin was investigated by X-ray diffraction. Microdeformation of incorporated Al and α-SiO₂ crystal, which was induced by the residual stress, could be detected as a shift of X-ray diffraction peak. The residual stress at the interface between the adherend and the particulate epoxy resin was found to decrease with the increase of volume fraction of filler. It was shown that the difference in the thermal expansion coefficients between the adherend and the particulate epoxy resin is much more effective on residual stress than the increment of Young's modulus owing to the incorporation of filler. When epoxy resin was cured on the Al plate, incorporated particles were subjected to a tensile stress; while cured on polytetrafluoroethylene sheet, particles were subjected to a compressive stress. The incorporation of some inorganic particles is considered effective to reduce the residual stress.     

Effect of patch hybridization on the tensile behavior of patch repaired glass/epoxy composite laminates using acoustic emission monitoring

This paper investigates the tensile response of damaged glass/epoxy composite laminates repaired using hybrid external patches. Hybrid external patches based on glass and Kevlar woven fabrics bonded on both faces of the damaged parent laminate were considered. Five different kinds of plain weave woven fabrics with a different ratio between glass and Kevlar fibers (100/0, 75/25, 50/50, 25/75 and 0/100) were used as the external patches. The intention of using these hybrid patches was to combine the excellent tensile stiffness of Kevlar fiber with the superior resin adhesion property of glass fiber. The virgin and damaged specimens were taken as the reference specimens for comparison of residual mechanical properties and damage mechanisms. Damage evolution and the failure progression of the repaired glass/epoxy specimens were monitored using real-time Acoustic Emission (AE) monitoring technique. The Acoustic Emission (AE) results depict different damage profiles and link them with mechanical test results to reveal the load to a change in failure mechanisms during mechanical loading concerning the influence of each hybrid patches on the performance of repaired glass/epoxy specimens. Good correlation of the acoustic emission results with the photographic images of fractured specimens was obtained. Specimens repaired with the equal volume fraction of glass and Kevlar fibers in the external patches presented the most favorable residual tensile response by effectively releasing the stress concentration in the damaged area.     

淀粉纳米晶对玻璃纤维的表面改性研究

采用自制的淀粉纳米晶(SNC)对玻璃纤维进行表面处理,增加其与环氧树脂基体的界面剪切强度(IFSS)。研究了处理方式、处理时间、SNC乙醇分散液浓度、热处理温度等工艺参数对SNC在玻璃纤维表面沉积情况的影响,以及对改性玻璃纤维与环氧树脂的界面性能的影响规律。采用扫描电子显微镜、单纤维强力仪对处理前后玻璃纤维进行表征,并采用微脱粘法测试玻璃纤维与环氧树脂的界面粘结情况。结果表明,当重力静置处理时间24 h,SNC乙醇分散液浓度为1 g/100 m L时,SNC在玻璃纤维表面均匀沉积,且能显著提高玻璃纤维与环氧树脂的IFSS,为27.29 MPa,较未处理的纤维增加29.3%。150℃热处理4 h后,X射线光电子能谱结果显示SNC与玻璃纤维形成化学键合,进一步增加纤维与环氧树脂的界面粘结,IFSS值达到32.30 MPa,较未处理的纤维增加53%,且纤维的拉伸强度得到较好的维持。     

Curing cycle modification for RTM6 to reduce hydrostatic residual tensile stress in 3D woven composites

Triaxial residual tensile stresses resulting after cooling a 3D woven composite from the curing temperature cause cracking in the resin pockets for weave architectures that have high through‐the‐thickness constraint. We show how curing cycle modifications can reduce the hydrostatic tensile stress generated by thermal mismatch during cooling of Hexcel RTM6 epoxy resin constrained in a quartz tube which simulates extreme constraint in a composite. The modified curing schedule consists of a high temperature cure to just before the glass transition, a lower temperature hold that takes the resin through the glass transition thereby freezing in the zero stress state, followed by high temperature cure to bring the resin to full conversion. We show that this process is sensitive to heating rates and can reduce the zero stress state of non‐toughened RTM6 resin to a temperature similar to a commercial rubber‐toughened resin, Cycom PR520. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43373.     

Tensile behavior of glass‐fiber‐filled polyacetal: Influence of the functional groups of polymer matrices

We investigated the tensile behavior of glass‐fiber‐filled polyacetal [i.e., polyoxymethylene (POM)], focusing on the mutual influence of the functional groups in the POM matrices and the glass binder system. The different POM matrices were compounded with three kinds of glass fibers (20 wt %) treated with different glass binders, namely, epoxy resin, thermoplastic polyurethane (TPU), and a mixture of TPU and epoxy resin. A good correlation between the tensile strength and elongation at break was observed, regardless of the difference in the glass binders. The composites based on the modified POM matrix, which had both a carboxyl end group and a hydroxyl end group, improved the tensile properties noticeably in comparison with those based on the normal POM matrix. The composites were strengthened with an increase in the concentration of the functional groups. The results of scanning electron microscopy observations indicated that the fractured surfaces of a specimen having maximum tensile strength and elongation exhibited cohesion of the modified POM on the surfaces of the glass fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

玻纤增强ABS复合材料的制备及性能

以丙烯腈-丁二烯-苯乙烯共聚物(ABS)及玻璃纤维(GF)为原料,以环氧树脂作为界面相容剂,研究了界面相容剂对玻璃纤维增强ABS复合材料力学性能及界面粘接的影响.结果表明:加入环氧树脂,玻纤增强ABS复合材料的力学性能明显提高;随着玻纤质量分数的增加,复合材料的拉伸强度、弯曲强度、冲击强度均逐渐增加;玻纤质量分数为30%时,GF/ABS/环氧树脂复合材料的拉伸强度比未改性的复合材料的拉伸强度提高了30%,弯曲强度提高了25%,冲击强度也提高了50%.     

Incorporation of epoxidized soybean oil as co‐matrix in epoxy resin toward developing plastisol/particulate toughened glass fiber composites

Epoxidized soybean oil was incorporated as a co‐matrix into an epoxy resin, and the hybrid resin system was used for preparing glass fiber‐reinforced composites. Effect of addition of poly(vinyl chloride) plastisol and selected particulate fillers (fly ash and wood flour) to epoxy/epoxidized soybean oil matrix on mechanical and water uptake properties of glass fiber‐reinforced composites were studied. Fourier transform infrared spectroscopy was used to reveal the curing state of these composites. It was observed that tensile strengths and moduli decreased with the inclusion of all additives. However, addition of poly(vinyl chloride) plastisol, fly ash, and wood flour particulate fillers showed significant increase in impact strengths compared with neat epoxy composite in a synergistic manner. Water uptake results of the composites were found to be in good agreement with ? OH peak intensities obtained from Fourier transform infrared spectroscopy. Finally, acousto‐ultrasonic nondestructive technique was successfully used to assess damage states and to relate stress wave factors with tensile strength properties of modified epoxy‐based glass fiber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40586.     

无机填料对低粘度高性能环氧树脂性能的影响

研究了空心玻璃微珠QH550、石英砂、氧化锌、白炭黑等无机填料对低粘度高活性环氧树脂体系的填充效果,通过比较树脂体系的拉伸性能、弯曲性能和冲击性等力学性能表明,用氧化锌作为填料时,树脂体系各项力学性能达到最优;研究了氧化锌的填充量对树脂体系力学性能的影响,找到了最佳填充量为树脂总质量的60%。     

风电叶片用环氧树脂和不饱和聚酯性能的对比研究

对比了环氧树脂和不饱和聚酯的各项性能,通过对树脂的黏度-时间曲线测试,结果显示不饱聚酯在整个操作时间内黏度变化不大,具有优异的工艺调控性。结合扫描电子显微镜(SEM)对两种树脂断口形貌的观察和力学性能测试来研究两种树脂的区别,结果表明,虽然不饱和聚酯的弯曲强度和抗压强度较高,但是平均2.41%的断裂伸长率远低于环氧树脂的8.71%。由玻璃化转变温度(Tg)测试分析主要是不饱和聚酯内自由体积较低,在本体受到拉伸时无法通过分子内链段的运动来降低体系内拉应力,所以本体脆性增大,最终导致了材料在变形量较大时的使用受到限制。     

填充环氧树脂界面残余应力研究 Ⅱ.影响界面残余应力的因素

本文针对橡胶改性环氧树脂体系和玻璃珠改性环氧树脂体系,研究了影响界面残余应力的因素.填料的粒径不影响界面残余应力的测量.界面键合强弱的影响在两体系中不相同.     

复合材料缠绕成型用电子束固化环氧树脂体系研究

为了研究适合于缠绕成型的低粘度可电子束固化复合材料的耐热环氧树脂基体,研究了不同组成的电子束固化树脂体系的粘度与温度的关系、耐热性与辐射剂量的关系及浇注体的力学性能。研究表明,树脂EB-4在60℃时粘度为389 mPa.s,树脂辐射固化的最佳剂量为150 kGy,而且在150 kGy辐射固化的EB-1、EB-4的玻璃化转变温度Tg分别为212.96℃、214.77℃,EB-4树脂浇注体的拉伸强度可以达到52.7 MPa,拉伸弹性模量2.79 GPa,断裂延伸率为2.18%,是1种适用于室温或低温下缠绕成型的耐热电子束固化环氧树脂基复合材料树脂体系。     

Curing behavior of dicyandiamide/epoxy resin system using different accelerators

Various amounts of dicyandiamide (Dicy), two grades of epoxy resins, i.e. Epiran 06 and Epikote 828, and three different accelerators including benzyl dimethyl amine (BDMA), 3-(4-chlorophenyl)-1,1-dimethyl urea (Monuron) and 2-methyl imidazole (Im) were used in curing of Dicy/epoxy resin system. Both of the used epoxy resins were based on diglycidyl ether of bisphenol A (DGEBA). The effects of type and concentration of accelerators on curing behavior were studied by differential scanning calorimetry (DSC) method in dynamic or non-isothermal mode. The optimum concentration of Dicy for curing of epoxy resins was obtained based on the glass transition temperature of the cured epoxy/Dicy formulations. The maximum glass transition temperature of 139 °C was obtained at the stoichiometric ratio of Dicy to epoxy of 0.65. The results showed that BDMA has a broader curing peak in DSC and starts the cure reaction earlier than the others. However, Monuron has a narrow curing reaction peak with good cure latency. The tensile properties of Dicy-cured Epiran 06 and Epikote 828 epoxy resins reinforced with chopped strand mat showed that these two epoxy resins have similar mechanical properties. For composites based on the Epiran 06 and Epikote 828 reinforced with 40 wt % glass chopped strand mat, tensile strength and modulus were 156 and 153.4 MPa and 11.6 and 12.4 GPa, respectively.     

端环氧基丁腈橡胶增韧环氧树脂的结构与性能

采用端环氧基丁腈橡胶(ETBN)对环氧树脂进行增韧,研究了增韧环氧树脂浇注体的力学性能.结果表明,随着ETBN含量的增大,冲击强度、断裂伸长率明显增加,其弯曲强度、拉伸强度及拉伸模量降低,表明ETBN对环氧树脂具有明显的增韧效果.环氧树脂浇注体拉伸断面SEM照片表明,固化反应过程中ETBN均匀地分散在环氧树脂体系中.