基于单体反应物自聚合方法的高韧性聚酰亚胺树脂结构与性能

采用单体反应物自聚合(PMR)方法,以4-苯乙炔苯酐为反应性封端剂,2,3,3',4'-联苯四甲酸二酐(α-BPDA)和4,4'-二氨基二苯醚(4,4'-ODA)为二酐和二胺单体,合成了不同相对分子质量的热固性聚酰亚胺树脂。借助差示扫描量热分析、动态力学热分析、热重分析和流变性能分析等方法,研究了相对分子质量与固化反应特性、流变特性、耐热性能、韧性性能的关系及影响机理。结果表明,随着相对分子质量增加,熔体最低黏度由10.4 Pa·s增加至1449.4 Pa·s;玻璃化转变温度由378℃下降至346℃,冲击强度由31.69 kJ/m^(2)提高到62.15 kJ/m^(2)。通过优化相对分子质量可实现对韧性性能、耐热性能与工艺性能的综合调控。

Through-Thickness Thermal Conductivity Prediction Study on Nanocomposites and Multiscale Composites

In this research, a modeling and experimental study was conducted to explore the effects of nanoparticle type (aluminum nanoparticles and carbon nanotubes), filler concentration and interactions between the nanoparticle and reinforcing fibers on through-thickness conductivity of nanoparticle/epoxy nanocomposites and nanoparticle/fiber-reinforced multiscale composites. Multiple, notable micromechanical models were evaluated to predict through-thickness thermal conductivity of both composite systems, and then compared to the experimental results. The results showed that filler volume fraction ranges and thermal conductivity differences of the constituent materials for the thermal conductivity ratio (km/kf or kf/km) used in the models can affect the resulting predictions. Certain models were found to be suitable for varying conditions on the thermal conductivity ratio. Finite element models (FEM) were developed to reveal heat transport mechanisms of the resultant nanocomposites and multiscale composites. The nanocomposite design for finite element analysis (FEA) provided close predictions and performed better than the micromechanical models. On the multiscale composite system, predictions were concluded to be dependent upon the FEM design where the interactions between nanoparticles and fibers are critical to accurately determine the through-thickness thermal conductivity.

Thermo-mechanical properties of RTM-made carbon fibre/polyimide composite attaching collar under transient heating

This study focuses on the thermo-mechanical properties of Carbon Fibre/Polyimide Composite(CFPC)attaching collars under transient heating.The CFPC attaching collars were fabricated by a high-temperature resin transfer moulding process,and their thermo-mechanical properties under the conditions of simultaneous transient heating and bending load were investigated.The results show that the attaching collar tends to fail at 118% of the limit load.The failure mode includes the fracture of the connecting screws,local extrusion damage of the hole edges,and slight ablation damage at the outer plies.And there is no observable residual deformation in the composite attaching collar.Furthermore,considering that the material properties vary with temperature,a progressive damage model based on the sequential thermo-mechanical coupling method was established to study the failure mechanism of the attaching collar.Finally,the damage factor of the CFPC was calculated to assess the safety status of the attaching collar.The results show that the primary damage modes of the composite attaching collar are intralaminar failure,which mainly occurs at the heat insulation layer and the hole edges,and these slightly affect the structural bearing capacity.A good correlation between the experiment and FEA is obtained.The test methods and analysis models proposed contribute to the safety assessment of composite structures under transient heating.