Investigations on the influence of notched z-pins on the mechanical properties of carbon-fiber reinforced plastics

纤维增强塑料（FRP）由于其承载纤维和成型基体的微结构结构，在纤维方向上具有优异的力学性能。相比之下，由垂直于层压平面的FRP制成的结构表现出较差的机械性能，使其容易分层，例如由于层间剪切或冲击应力。通过聚合物基复合材料的厚度插入z-pin是一种很有前途的低成本方法，可以提高层间剪切强度并减少上述分层脆弱性。z形销是针状的，通常是圆棒，直径通常为0.1-1.0毫米，由高刚度和强度的材料组成，如钢、钛或碳纤维增强塑料（CFRP）。与预浸渍半成品（预浸料）相结合，z-pin技术是最常用的FRP全厚加固方法。大量研究表明，z形钉钉是提高FRP损伤容限的一种非常有效的方法。该项目的目的是通过超短激光脉冲应用表面结构，从而在引脚和层压板之间形成闭合形式，进一步提高z-引脚的有效性。在内部前期工作的基础上，确定不同表面结构对碳纤维增强塑料力学性能的影响，确定最佳表面几何形状。

Fiber reinforced plastics (FRP) offer excellent mechanical properties regarding the fiber direction due to their microstructural construction of load-bearing fibers and shaping matrix. By contrast, a structure made of FRP loaded perpendicular to the laminate plane exhibits inferior mechanical properties, making it susceptible to delamination, e.g. due to interlaminar shear or impact stresses. The insertion of z-pins through the thickness of polymer matrix composites has been found to be a promising and low-cost method to enhance the interlaminar shear strength and reduce the mentioned vulnerability to delamination. Z-pins are needle-shaped, usually round bars, with diameters of typically 0.1-1.0 mm, and consist of materials with a high stiffness and strength, such as steel, titanium or carbon fiber reinforced plastics (CFRP). In conjunction with pre-impregnated semi-finished products (prepregs), the z-pinning technique is the most commonly used method for through-thickness reinforcement of FRP. Numerous studies have shown that the z-pinning is a very effective method to increase the damage tolerance of FRP. The aim of this project is the further increase of the effectiveness of z-pins by the application of a surface structure via ultra-short laser pulses and thus the creation of a form closure between the pins and laminate. Based on internal preliminary work, the influence of different surface structures on the mechanical properties of carbon fiber reinforced plastics and an optimal surface geometry should be determined.