有效的增强要求填料与基体之间有良好的结合，特别是对于短纤维。 对于一种

Effective reinforcement requires a good bond between the filler and the matrix, especially for short fibers. For an ideal unidirectional composite material (that is, a continuous fiber arranged in the same direction), its modulus is much higher than that of the matrix, and its longitudinal tensile strength is independent of the fiber matrix bonding strength, while the transverse tensile strength and fracture mode The number (longitudinal or lateral bending) increases with the increase of the fiber matrix bonding strength. On the other hand, excessive fiber-matrix bonding will make brittle matrix (such as carbon and ceramic) composites more brittle, because strong fiber-matrix bonding will cause cracks to propagate linearly in a direction perpendicular to the fiber-matrix interface, while It will not propagate along the interface. For composite materials with ductile matrix (such as metals and polymers), when the brittle fiber reaches the ductile matrix, even if the fiber matrix is ​​strongly bound, the cracks in the brittle fiber will tend to passivate. Therefore, brittle matrix composites require an optimal fiber matrix bonding strength (not too strong or too weak), while tough matrix composites require a high fiber matrix bonding strength (6. 2). In particular, the fiber-based bonding strength of carbon-carbon composite materials must be optimal. If the bond strength is too high, this composite material may be extremely fragile, showing catastrophic failure and poor strength. The mechanism of filler-matrix bonding includes chemical bonding, interdiffusion, van der Waals bonding and mechanical bonding. If the density of the chemical bond between the filler and the matrix is ​​high, and there is no reaction product between the filler and the matrix, then the chemical bond can provide a relatively large bonding force. By (i) chemically treating the filler, (ii) using a suitable sizing agent (coating) on ​​the filler, and (iii) using a molecular coupling agent, the density of chemical bonds can be increased. Interdiffusion at the filler-matrix interface will also lead to bonding, but its occurrence requires a fairly clean interface. If the fibers form a three-dimensional network structure, the mechanical linkage between the fibers and the matrix makes an important contribution to the bonding. In addition, the filler should have a rough surface so as to be replaced by a small degree of mechanical interlocking. Chemical connection, interdiffusion and van der Waals connection require the filler to be in intimate contact with the substrate. In order for intimate contact to occur, the matrix or matrix precursor must be able to wet the surface of the filler when the matrix or matrix precursor penetrates into the filler preform. Wetting is determined by surface energy. By affecting the surface energy of the fiber, the fiber can be chemically treated and coated to improve wettability. The choice of treatment or coating depends on the substrate. A related method involves adding a wetting agent to the matrix or matrix precursor before penetration. Since the wettability changes with temperature, the infiltration temperature can play a role in increasing the wettability. Although wetting is controlled by thermodynamics, it is strongly affected by kinetics. Therefore, another method to enhance wetting is to use high pressure during the infiltration process.

有效的增强要求填料与基体之间有良好的结合，特别是对于短纤维。 对于一种理想的单向复合材料(即一根沿同一方向排列的连续纤维) ，其模量远高于基体，其纵向抗拉强度与纤维基体结合强度无关，而横向抗拉强度和断裂模数(纵向或横向弯曲)随纤维基体结合强度的增加而增加。 另一方面，过度的纤维-基体结合会使脆性基体(如碳和陶瓷)的复合材料变得更脆，因为强纤维-基体结合会导致裂纹沿垂直于纤维-基体界面的方向线性传播，而不会沿着界面偏转传播。 对于具有延性基体的复合材料(例如金属和聚合物) ，当脆性纤维达到延性基体时，即使纤维基体结合强烈，脆性纤维中的裂纹也会趋于钝化。 因此，脆性基体复合材料需要一个最佳的纤维基体结合强度(不太强也不太弱) ，而韧性基体复合材料需要一个高度的纤维基体结合强度(6.2)。 特别是碳-碳复合材料的纤维基结合强度必须是最佳的。 如果粘结强度过高，这种复合材料可能极其脆弱，表现出灾难性的破坏和较差的强度。 填料-基体结合的机理包括化学结合、相互扩散、范德华结合和机械结合。 如果填料与基体之间的化学键密度很高，并且填料与基体之间没有反应产物，那么化学键可以提供相对较大的键合力。 通过(i)对填料进行化学处理，(ii)在填料上使用合适的施胶剂(涂料) ，以及(iii)使用分子偶联剂，可以提高化学键的密度。 在填料-基体界面上的相互扩散也会导致结合，但其发生要求界面相当干净。 如果纤维形成三维网状结构，则纤维与基体之间的机械连锁对结合有重要贡献。 另外，填料应该有一个粗糙的表面，以便有一个小程度的机械连锁来取代。化学连接、相互扩散和范德华连接要求填料与基体亲密接触。 为了发生亲密接触，母体或母体前体必须能够在基体或母体前体渗入到填料预制体时湿润填料表面。 润湿是由表面能决定的。 通过对纤维表面能的影响，可以对纤维进行化学处理和涂层，以提高润湿性。 处理或涂层的选择取决于基质。 一种相关的方法，涉及在渗透前向基质或基质前体中添加润湿剂。 由于润湿性随温度的变化而变化，入渗温度可以起到增加润湿性的作用。 虽然润湿是由热力学控制的，但它强烈地受到动力学的影响。 因此，另一种加强润湿的方法是在渗透过程中使用高压。

Effective reinforcement requires a good bond between the filler and the matrix, especially for short fibers. For an ideal unidirectional composite (i.e. a continuous fiber arranged in the same direction), its modulus is much higher than that of the matrix, its longitudinal tensile strength is independent of the bonding strength of the fiber matrix, and its transverse tensile strength and fracture modulus (longitudinal or transverse bending) increase with the increase of the bonding strength of the fiber matrix. On the other hand, excessive fiber matrix bonding will make the composite of brittle matrix (such as carbon and ceramics) more brittle, because the strong fiber matrix bonding will cause the crack to propagate linearly along the direction perpendicular to the fiber matrix interface, rather than along the interface deflection. For composites with ductile matrix (such as metals and polymers), when the brittle fiber reaches the ductile matrix, the cracks in the brittle fiber tend to be passivated even if the fiber matrix is strongly bonded. Therefore, the brittle matrix composite needs an optimal fiber matrix bonding strength (not too strong or too weak), while the ductile matrix composite needs a high fiber matrix bonding strength (6.2). In particular, the fiber-based bond strength of carbon carbon composites must be the best. If the bond strength is too high, the composite may be extremely fragile, showing catastrophic failure and poor strength. The mechanism of packing matrix combination includes chemical combination, mutual diffusion, van der Waals combination and mechanical combination. If the chemical bond density between the filler and the matrix is very high, and there is no reaction product between the filler and the matrix, the chemical bond can provide a relatively large bond force. The density of the chemical bond can be increased by (I) chemical treatment of the filler, (II) the use of appropriate sizing agent (coating) on the filler, and (III) the use of molecular coupling agent. However, the interface is required to be clean. If the fiber forms a three-dimensional network structure, the mechanical linkage between the fiber and the matrix has an important contribution to the bonding. In addition, the packing should have a rough surface so that it can be replaced by a small degree of mechanical interlocking. Chemical bonding, mutual diffusion and van der Waals bonding require the filler to be in close contact with the substrate. In order to have intimate contact, the parent or parent precursor must be capable of wetting the surface of the filler as the parent or parent precursor penetrates into the filler preform. Wetting is determined by surface energy. Through the influence on the surface energy of the fiber, the fiber can be chemically treated and coated to improve the wettability. The choice of treatment or coating depends on the substrate. A related method relates to adding a wetting agent to a matrix or matrix precursor before permeation. Because wettability changes with temperature, infiltration temperature can increase wettability. Although wetting is controlled by thermodynamics, it is strongly affected by dynamics. Therefore, another way to enhance wetting is to use high pressure during infiltration.<br>