Behaviour of rectangular z-pins for translaminar reinforcement of fiber reinforced plastics under dynamic loading

纤维增强塑料（FRP）由于其承载纤维材料的微观结构构造和成形基体而在层压板的平面中提供非常好的机械性能。与此相反，由FRP制成的结构垂直于层压板平面加载，显示出较差的机械性能。特别是冲击或类似冲击的载荷，由于低冲击强度和相关的分层敏感性以及低损伤容限，经常导致剩余强度的降低。FRP结构通常由预浸渍的半成品（称为预浸料）制成。提高其抗冲击性、分层行为和损伤容限的唯一批准的方法是所谓的z钉扎方法，在该方法中，在固化之前在z方向上将细销引入部件中。Z销是针形的，通常是直径通常为0.1... 1.0大量研究表明，z钉扎是一种非常有效的方法，以增加冲击脆弱的结构。该项目的目标是研究在动态载荷下用矩形z销增强的纤维增强复合材料。该项目是前一个项目的逻辑延续，该项目集中于研究纤维增强塑料的非圆形z销的跨层增强。实验和数值研究表明，矩形销，由于其更大的表面积，有一个改善与周围材料的相互作用，从而更有效地提高层间性能，提高FRP结构的损伤容限。由于其相对尖锐的边缘，矩形z销被怀疑在材料中引起应力峰值，从而与用圆形销加强的结构相比降低疲劳强度。通过实验研究和有限元分析，应说明以前项目的积极结果是否可以转移到动态应力上，销的几何形状是否以及如何影响疲劳强度，以及哪种几何形状是上述问题的最佳解决方案。

Fiber reinforced plastics (FRP) offer, because of their microstructural construction of load-bearing fiber materials and the shaping matrix very good mechanical properties in the plane of the laminate. In contrast to this a structure made of FRP loaded perpendicular to the plane of the laminate shows inferior mechanical properties. Especially shock or impact like loads often lead, because of the low impact strength and the associated susceptibility to delamination as well as the low damage tolerance, to a reduction of the residual strength. FRP structures are often built up of pre-impregnated semi-finished products, known as prepregs. The only approved method to improve them in impact resistance, delamination behavior and damage tolerance is the so-called z-pinning method at which thin pins are introduced in the component in the z-direction before curing. Z-pins are needle-shaped, usually round bars with diameters of typically 0.1...1.0 mm. Numerous studies have shown that the z-pinning is a very effective method to increase impact vulnerable structures. The goal of the project is the investigation of fiber reinforced composites reinforced with rectangular z-pins under dynamic loading. This project represents the logical continuation of the previous project which concentrated on the study of non-circular z-pins for translaminar reinforcement of fiber reinforced plastics. Experimental and numerical investigations revealed that rectangular pins, because of their greater surface area, have an improved interaction with the surrounding material and thereby turn out as much more effectively to improve the interlaminar properties and increase the damage tolerance of a FRP-structure. Due to their relatively sharp edges rectangular z-pins are suspected to induce stress peaks in the material and thereby reduce the fatigue strength compared to structures reinforced with round pins. Via experimental studies and FE analysis statements should be made whether the positive results from the previous project can be transfered on dynamic stress, whether and how the geometry of the pins affect the fatigue strength and which geometry is an optimal solution in terms of the mentioned problems.