嵌锁式CFRP方形蜂窝夹芯梁低速冲击响应及失效机理

Low-velocity impact response and failure mechanism of CFRP sandwich beams with a square honeycomb core fabricated by the interlocking method

采用嵌锁组装工艺制备了碳纤维/树脂基复合材料方形蜂窝夹芯梁,实验研究了低速冲击载荷下简支和固支夹芯梁的动态响应及失效机理,获得了不同冲击速度下夹芯梁的失效模式,分析了其损伤演化过程和失效机理,探讨了冲击速度、边界条件、面板质量分布以及槽口方向等因素对夹芯梁破坏模式及承载能力的影响。研究结果表明,芯材长肋板槽口方向对夹芯梁的失效模式有较大影响,槽口向上的芯材跨中部分产生了挤压变形,而槽口向下的芯材跨中部分槽口在拉伸作用下出现了沿槽口开裂失效,继而引起面板脱粘和肋板断裂;同等质量下,较厚的上面板设计可以提高夹芯梁的抗冲击能力,冲击速度越大,夹芯梁的峰值载荷和承载能力越高;固支边界使得夹芯梁的后失效行为呈现出明显的强化效应,在夹芯梁跨中部分发生初始失效后出现了后继的固支端芯材和面板断裂失效模式。

Composite sandwich beams with a carbon fiber reinforced polymer(CFRP)square honeycomb core were designed and fabricated by using the interlocking method.The dynamic response and failure mechanism of fully-clamped and simplysupported sandwich beams subjected to low-velocity impact were investigated experimentally and the corresponding failure modes of the sandwich beams were obtained.Meanwhile,the damage evolvement process and the failure mechanism were analyzed in detail.Influences of the impact velocity,boundary conditions,the mass distributions of face sheets and the direction of the slots on the failure modes and load-carrying capacity of the sandwich beams were explored.The low-velocity impact experiments of composites specimens with two kinds of boundary conditions were carried out by using the drop-hammer impact test system.Three kinds of initial impact velocity were considered for the simply-supported and the fully-clamped sandwich beams sandwich beams,respectively.In the experiments,the time history curves of the impact load and the midspan deflection of the specimens were recorded by a load cell and a laser displacement sensor.Meanwhile,the deformation processes of the sandwich beams were captured by a high-speed camera.The experimental results show that the directions for the slots of the long ribs have significant influence on the failure modes of the sandwich beams.The sandwich core with the upward slots at the midspan has compression deformation whilst the cracking failure along the direction of the downward slots at the midspan is observed due to the tension,which results in the face-sheet debonding and rib fracture successively.It is found that for the same mass,the design of the thicker upper face sheet can enhance the impact resistance of the sandwich beams.The peak load and load-carrying capacity of the sandwich beams increase with increasing the impact velocity.The fully-clamped boundary conditions make the sandwich beams exhibit hardening post-failure behaviors obviously.After the initial failure at the midspan,the fully-clamped ends of the cores and the face-sheets of the sandwich beams experience the fracture failure.