碳布/树脂复合材料TiO2过渡界面层可控构筑及摩擦学行为研究

Carbon fabric reinforced resin composites are the pivotal friction materials for transmitting torque in the wet clutch/brake system. Interface debondings between carbon fibers and resin matrix, as well as resin peeling off from the carbon fiber surface severely restrict the improvement of the friction stability and service life of the composites. As such, this project develops a new thought about constructing a transition layer which is composed of active layer, TiO2 buffer layer and TiO2 nano-pinned layer. It can give fully play to the synergies of chemical binding and mechanical interlocking between each layer. Firstly, active layer will be grafted onto carbon fibers surface based on diazonium reaction without damaging its structure. And then TiO2 film layer will be prepared on carbon fabric surface via sol-gel method. The preformed layer will be transmuted into desired TiO2 buffer and nano-pinned layer. Hence, a gradient transition will be formed between the two layers, within which the morphology and microstruction can vary gradiently. Lastly, the composites will be prepared by hot pressing. Based on the study of the variation of composition, structure and morphology for the three layers mentioned above, the mechanisms of diazotization on the surface of carbon fibers as well as the crystallization and growth mechanisms of TiO2 buffer and nano-pinned layer will be revealed. By studying the interface characteristics of every unit of transition layer, the influence of microstructure and mechanical properties for composites will be expounded, and the strengthening and toughening mechanism of TiO2 transition layer will be further revealed. The evolution of transition layer will be explored during friction process of the composites to clarify its influence on micro-wear behaviors and to reveal the friction and wear mechanism. The project will provide a theoretical basis for greatly improving the friction stability and service life of the composites under severe working conditions.

碳布/树脂基复合材料是湿式离合/制动系统中关键的传扭材料，纤维树脂间的界面脱粘，树脂剥离严重制约该类材料摩擦稳定性和使用寿命的提升。鉴于此，本项目提出在碳布表面构筑活性层/TiO2缓冲层/纳米TiO2钉扎层过渡界面的新思路，充分发挥各层之间化学结合和机械啮合的协同作用。首先基于重氮化反应无损接枝活性层，采用溶胶-凝胶法预制TiO2薄膜层，随后水热条件下，TiO2预制层可控转化为TiO2缓冲层/纳米钉扎层，层间形貌结构梯度过渡，并热压成型复合材料。研究活性层、缓冲层和钉扎层的组成、结构和形貌变化规律，揭示重氮化接枝机制和TiO2缓冲层/钉扎层晶化生长机理；研究过渡层各单元间的界面特征，阐明其对复合材料结构和力学性能的影响规律，揭示强韧化机制；研究过渡层在摩擦过程中的演变规律，阐明其对微观磨损行为的影响规律，揭示摩擦磨损机理，为提升该类材料恶劣工况下的摩擦稳定性和使用寿命奠定基础。

湿式传动/制动系统对高性能碳布增强树脂基复合材料提出了迫切需求，但由于碳布表面能低，与树脂界面结合性能差，严重影响了该复合材料的摩擦稳定性和使用寿命。针对上述问题，本项目提出在碳布表面生长 TiO2 纳米棒和 TiO2 纳米线钉扎层/TiO2 薄膜缓冲层，构筑多尺度增强体的新思路。首先基于重氮化反应在碳纤维表面无损接枝苯甲酸官能团，采用溶胶凝胶法和水热法在其表面制备 TiO2 纳米棒和 TiO2 纳米线钉扎层/TiO2 薄膜缓冲层，构筑多元多尺度增强体，并热压成树脂基复合材料。研究了碳布表面苯甲酸官能团无损接枝规律，揭示重氮化反应机制；研究了镀膜厚度和水热温度等对 TiO2 纳米棒和 TiO2 纳米线钉扎层/TiO2 薄膜缓冲层生长的影响规律，揭示其生长机理；探索 TiO2 纳米棒和 TiO2 纳米线钉扎层/TiO2 薄膜缓冲层与碳纤维及树脂间的界面增强机理，建立多尺度增强体与复合材料微观结构及力学性能之间的关系；阐明多尺度增强体在摩擦过程中的作用机制。通过改变水热温度对 TiO2 纳米棒在碳布表面的形貌进行调控，获得了最优的温度参数，当水热温度为150 ℃时所制备的复合材料的力学性能和摩擦学性能最佳。通过镀膜次数来控制 TiO2 非晶薄膜厚度，当镀膜次数为3时，水热晶化后在碳纤维表面生长了长度约为0.4 μm且形貌均一的 TiO2 纳米线层，所制备的复合材料的拉伸强度和抗弯强度分别达到210.6 MPa、104.5 MPa，各自提高了37.2 %和32.8 %，磨损率降低了39.8 %。相较于原始碳纤维增强树脂基复合材料，PDA/TiO2 过渡层/氨基化碳纤维增强树脂基复合材料的拉伸强度为310 MPa, 提升了129.63 %，磨损率为1.89×10-5 mm3/(Nm)，降低了43.8 %。上述研究工作将为该类复合材料的多尺度设计提供有益指导。