激光加工通过迅速升温实现材料去除,能够克服传统碳纤维增强复合材料(CFRPs)加工过程中出现的热损伤而导致的加工质量问题,成为了CFRPs精密加工的先进技术.为探究激光功率对CFRPs切割过程的影响机理,针对CFRPs激光切割过程,建立了综合考虑激光功率分布特性、材料相变烧蚀特性、材料各向异性和空气对流的三维介观耦合模型,应用COMSOL5.6进行了数值模拟.模拟结果表明,环氧树脂的烧蚀量随时间的变化呈三次函数关系,碳纤维的烧蚀量呈一次函数关系,且环氧树脂的去除速率高于碳纤维去除速率.此外,热影响区(HAZ)宽度随激光功率增大而增大,随时间变化呈三次函数关系.

Most composites require a certain amount of pressure to cure, therefore, it is crucial to comprehend the effect of pressure on the curing reaction. Nonetheless, the majority of studies on curing reaction focus on isothermal or non-isothermal DSC measurements at ambient pressure. Using a high-pressure differential calorimetry scanner (Netzsch DSC 204HP), the curing process of a bisphenol A diglycidyl ether system is studied in order to evaluate the influence of curing pressure. The results indicate a competitive relationship between the effect of heating rate and pressure on the reaction rate, with the influence of heating rate being stronger. The reaction follows the autocatalytic model, and the average activation energy E-P and pre-exponential factor A(P) decrease as the pressure increases. The obtained kinetics are used to simulate the process of forming composite laminates. When the thickness of laminates exceeds 18 mm, the maximum difference of the temperature and curing degree between ambient pressure and 2 MPa pressure is 20.65 ? and 0.161, respectively, indicating that the simulation results of thick composites are affected by whether the curing pressure is considered in kinetics.

由于热固性树脂固化过程中固化度、热膨胀和固化收缩之间强耦合,常规仪器无法测量热膨胀系数和固化收缩率.为解决这一问题,基于PVT-α法开发了热膨胀系数与固化收缩率测量装置.通过热流传感器和热电偶确定反应热和固化温度,积分反应热确定固化度;通过位移传感器确定体积变化.将体积变化与固化度变化相结合,解耦热膨胀和固化收缩体积,实现热膨胀系数与固化收缩率的测量.为验证装置可行性,测量了硅橡胶材料的热膨胀系数,误差为4.93％.对热固性树脂(环氧树脂E-51)进行了固化过程热膨胀系数和固化收缩率测量,热膨胀系数随固化度α呈线性变化:CTEcross(α)=8.265 1×10-4(1-α)+7.566 4×10-4α(1/℃),固化收缩率为1.87％.本文开发的装置可以为热固性树脂固化过程热膨胀系数和固化收缩率测量提供手段.

Fiber-reinforced phenolic composite has become an ideal material for solid rocket motor’s (SRM) nozzle, because of its excellent high temperature resistance and ablation resistance. The physical and chemical properties of reinforcing fiber would significantly affect the cure reaction of phenolic (PF) resin, which results in the obvious difference between the cure characteristics of the fiber-reinforced phenolic system and neat resin. To clarify the difference in cure reaction between fiber-reinforced phenolic system and PF resin, meanwhile, to obtain the kinetics of high silica glass fiber/phenolic (GF-HSi/PF) prepreg and carbon fiber/phenolic (CF/PF) prepreg, the dynamic experiments of PF resin, GF-HSi/PF prepreg and CF/PF prepreg are carried out by differential scanning calorimetry (DSC). Iso-conversional kinetics is proposed, and the activation energy is determined as a function of cure degree. The reaction model f(α) is obtained by introducing the kinetics compensation effect, founding that the f(α) of PF resin is influenced significantly by reinforcing fiber. The kinetics of three materials are determined by the model-fitting method, founding that the kinetic models of PF resin, GF-HSi/PF prepreg and CF/PF prepreg are a one-step autocatalytic model, two-step model from autocatalytic reaction to N-order reaction and three-step model from autocatalytic reaction to N-order reaction respectively.

复合材料扩张段是固体发动机喷管的关键部件,为抵抗高温、高压、烧蚀、高速燃气和力学载荷的综合作用,其结构为超厚壁变曲率的复杂混合复合材料结构.由于扩张段的低导热性、超厚壁特征和固化工艺的不合理,成型过程容易出现剧烈的过热峰.为减小固化变形,提高扩张段成型质量,必须抑制固化过热,提高固化均匀性.本文首先采用高压差示扫描量热仪表征2 MPa压力下高硅氧玻璃纤维/酚醛和碳纤维/酚醛预浸料的动力学.然后考虑成型过程多场耦合特点及成型模具和固化工艺的影响,构建固化过程耦合模型,分析扩张段固化过热和非均匀固化现象.最后,提出在剧烈固化前插入降温段的方法优化固化工艺,抑制固化过热.结果表明,优化工艺可以有效抑制扩张段过热现象,优化后最大过热峰由54.2℃下降为23.5℃,最大固化度差值由0.6下降为0.34,下降幅度分别为56.64％和43.33％.

为保证发动机能在恶劣的环境中运行,在绝热层的设计中,绝热层的厚度将直接影响着发动机结构的稳定性,而绝热层的烧蚀预估对于绝热层厚度的合理设计非常重要.为解决固体火箭发动机三元乙丙橡胶(EPDM)绝热层烧蚀性能工程预估问题,结合固体火箭发动机内两相流动的环境特点,以热化学烧蚀三方程模型和扩散化学动力学双控制机制为基本数学模型,以炭化层表面孔隙率为耦合参数,并综合考虑气流和粒子的侵蚀效应,建立了绝热层多因素耦合烧蚀模型的控制方程.通过对控制方程的隐式求解和对绝热层温度分布以及烧蚀线、炭化线、热解线位置的综合分析,获得了两相环境下EPDM绝热层的理论炭化烧蚀率.所得烧蚀率与实验结果对比,误差小于10％,表明给出的烧蚀预估方法可用于固体火箭发动机两相环境下EPDM绝热层烧蚀工程分析.

The case for modern solid rocket motor (SRM) is a complex compose structure with fiber reinforced resin matrix composite, insulation layer and metal connections, the case forming process is a multi-physical–chemical process which involving heat transfer, chemical reaction and structure deformation. During the cure process, temperature determines whether the case cure completely and the uniformity of temperature field is an important factor in causing residual thermal stress and shrinkage stress, so temperature field is the key to the mutual coupling effect of each physical and chemical process, and the basis to analyze the cure process of the case. During the cure process of case, fluctuation of cure temperature, cure time or heat transfer of hot air in the furnace may occur, which make the actual forming process of case deviate from the ideal cure process. In order to investigate the sensitive degree of thermal cycle, convective heat transfer coefficient and thermal properties to cure uniformity during cure process of composite case, the influence rule of the three factors on uniformity of temperature and cure degree fields were analyzed by numerical simulation. A thermal-chemical model was built for a simplified composite SRM case firstly, and the model was verified. Then, the influence degree of the three factors on cure uniformity of composite case was analyzed and quantized by the Morris global sensitivity analysis method. The results show that he sensitivity order of the uniformity of temperature field for the four parameters is: thermal diffusion coefficient > heat transfer coefficient > duration time > cure temperature. Besides, he temperature and duration time of the fourth dwell stage have less effect on the cure uniformity of composite case than that of heat transfer coefficient. Therefore, it is a challenge to design a thermal cycle that can not only guarantee the vulcanization of EPDM insulation layer, but also improve the cure uniformity.

鉴于热塑性树脂基复合材料激光原位固化技术在武器装备制造领域的巨大应用前景,为促进激光原位固化复合材料成型技术发展,本文在对激光原位固化成型技术进行国内外的研究和应用总结基础上,对激光原位固化过程所涉及的机理进行了讨论,对激光原位固化实验研究进行了总结,对固化过程中的温度场仿真进行了论述,同时对该技术在航空航天领域的发展和研究方向进行了探讨.从机理研究、固化实验和温度场模拟3个方面对热塑性树脂基复合材料激光原位固化成型技术国内外的研究和应用情况进行回顾和总结,并探讨了激光原位固化技术的最新发展趋势.

大尺寸复合材料固化过程因加热不均,出现较大的温度梯度,进而导致固化不均匀;温度梯度和固化度梯度使得壳体内出现热应变和固化收缩应变,最终形成残余应力和结构形变.为分析复合材料壳体固化过程的结构变形,本文结合壳体的实际成型过程,考虑树脂的固化放热、固化收缩和复合材料的各向异性特性,采用CHILE(α)弹性模型,对复合材料壳体固化成型过程的热传递、残余应力衍化及固化变形进行数值研究.研究结果表明,凝胶点前,复合材料仅受到热膨胀作用;凝胶点后至降温前,受到热膨胀和固化收缩的共同作用,壳体先快速收缩后膨胀;降温阶段,壳体缓慢收缩.固化完成后,壳体的固化变形约为0.08,残余应力约为106 N/m2.

为解决固体发动机复合材料壳体固化成型过程中由于加热不均和固化不均导致的脱粘分层等质量缺陷问题,综合考虑了树脂的固化反应特性、固化炉内的热空气流动特性、复合材料物性参数的时变特性、模具和辅助材料的影响及其物性参数的时变特性,建立了壳体固化成型过程的热-化学耦合数学模型,数值模拟了固化过程中壳体温度的变化历程,获得了壳体固化过程中温度的变化规律.研究结果表明,模拟结果与测量结果的误差小于1.5％,表明所建立的模型能对壳体固化过程温度场进行较为准确的预估;壳体固化过程中没有出现放热峰,表明树脂的固化反应热对壳体固化过程影响微小;壳体固化过程中,最低温出现在临近接头区域.