飞机用复合材料斜胶接修补结构的冲击损伤

高传力效率的斜面式胶接在飞机复合材料传力接头和修补中被广泛使用，但该结构的低速冲击损伤阻抗和损伤容限未在飞机结构设计中考虑。本文研究了低速冲击下的较厚的复合材料斜胶接板的力学性能及损伤失效。在胶接区域布置不同冲击点，寻找最敏感位置，在该位置进行冲击能量变化研究，通过冲击响应（冲击载荷、挠度、能量等）及冲击损伤两个方面获取其规律和失效机制。小能量和大能量冲击结果表明，胶接区域5个典型冲击位置中，中心位置冲击损伤最大，冲击敏感性最高，因此中心点为冲击损伤阻抗最小位置。中心点不同能量冲击时，冲击响应研究揭示了冲击过程中冲击载荷具有典型的4阶段行为。冲击载荷还具有双峰值力的现象。冲击后沿试样中心线切开的显微损伤图揭示了该结构有两种损伤模式，包括复合材料损伤及胶层损伤。复合材料的损伤包含90°和45°层基体的开裂和0°与90°层之间的层间损伤。胶层损伤出现在试样冲击点正下方背部的复合材料斜接尖端部位。进一步通过考虑复合材料层内、层间损伤及胶层损伤的渐进损伤模型对试验进行仿真研究，找出导致第Ⅱ阶段冲击载荷突降的主要原因为复合材料层间损伤，第Ⅳ阶段冲击载荷再一次突降是由于胶层出现了损伤。

Impact damage of composite scarf bonded repair structure for aircraft

The high efficiency load transferred scarf joints have been applied widely in composite junctions and repairs. However, the damage resistance and damage tolerance were not considered in aircraft structure design. The mechanical and fracture properties of composite scarf repair under low velocity impact were investigated. In the bonded zone, different impact locations were set to found the most sensitive location. Then at this position the variation of impact energy was studied. Low impact energy level and high energy level studies imply that the central position has the lowest impact resistance. Impact responses of impact load reveal that four typical phases exist during impact procedure. The impact load has double peak forces phenomenon. The first peak keeps constant while the second one rises with the increase of impact energy. From the failure investigating on the central section, it is found that there are two damage modes of the composites laminates and the adhesive. Composite damage contains the matrix crack on 90ånd 45° plies and the delamination between 0° and 90° plies. Adhesive damage appears at the backside of specimen opposite to the impact location. Further study of simulation reveals the whole impact behavior of the composite scarf repair. The composite damage leads to impact load dropping at PhaseⅡ, and adhesive damage causes the impact load dropping again at the beginning of phase Ⅳ.