| Composite sandwich structures with the characteristics of high stiffness and modulus to weight ratios, as well as outstanding design possibilities,damping and energy absorption, are widely used in aerospace and warship housing, high-speed train cars and building materials. However, during the sandwich structure maintenance installation,service life and other process are vulnerable to unpredictable external shape of the object impact, such as birds, hail, sand and gravel.It’s internal structure will produce invisible impact damage(such as core collapse or crush damage),which will severely reduce the strength and service life of the structure. That is the potential threat on the safe use of the structure. Therefore, it is necessary to study its impact and deformation behavior under static or dynamic loads, in order to optimize the design of the structure can provide a theoretical basis for the designers.In this paper, three- dimensional PVC foam carbon fiber / epoxy sandwich finite element model is modeled in abaqus finite element analysis software. hashin failure criteria is adopted to predict the skin initial failure mode. Zero thickness of interfacial bonding element is used to simulate the interfaces between the different inter-layers damage. Crushable foam plastic model is used to simulate plastic strain behavior of PVC foam core. The feasibility and effectiveness of the model modeling methods are verified by the results of the literature experiments. Then analyzing two contact algorithms and the mesh size of the interaction region have influence on the contact force- displacement curve, internal energy and dissipate impact energy and the size of inter-layer damage. Then analyze the core thickness, the shape of the punch. Hybrid fiber panels have an influence on dissipated energy and the size inter-layer damage. The analysis results show that:(1) Under the general contact and surface to surface contact, the surface to surface contact is more suitable for the analysis of impact response sandwich structure. The surface to surface contact gets contact force history curve is more smoothly, and less impact on the critical value and the interaction time, small experimental error.(2) The results of the interaction of mesh size in the region show that: Damage dissipated energy rely on the mesh size, larger dissipated energy increases with the mesh size increases. Relatively speaking, the smaller the influence on the contact force.PVC core thickness analysis results show that: The maximum contact force has decreased as the sandwich core thickness increases.The maximum contact force time has also been delayed.While the core material thickness increases, in the same impact energy, the impact of the contact time will increase.(3) Three kinds of punches results show that: The larger the contact surface of the head, the width of the contact force curve becomes narrower. The much shorter top gentle curve area, interaction with the shortest time occurrence. In the same initial impact energy, there is maximum contact force on the contact force curve. Short gentle curve to the top region, Shortest interactions time occurs with sandwich skin. Indenter with small contact surface, the contact force curve has long gentle to the top region. Maximum contact force is small, but the longest interaction time with the panel. Analysis impact before and after the change of velocity with time we can see the relationship. A larger contact surface with the punch interaction with the panel after with maximum residual velocity. Small contact surface of tapered punch with the minimum absolute residual velocity.(4) Hybrid fiber sandwich structure analysis results showed that: Through analysis the inter-layer damage,while increasing the ratio of the carbon fiber layer sandwich panel can improve overall impact resistance, but the greatest damage to the inter-layer. Kevlar fiber surface layer in contact with the first punch can effectively reduce the damage to the area of the inter-layer. Analysis the displacement histories of skin and core unit node of ACCCA, CACAC, CCACC three kinds mixed panel, ACCCA panel core sandwich structure has appeared displacement load drop when the impact energy are 4 J and 5.66 J.The outermost surface of the skin surface is the aramid fibers,can not reduce the extent of damage of the core material. As can be seen from CACAC and CCACC hybrid panels, carbon fibers and aramid fibers cross-plied, that could reduce the structural damage dissipated energy and beneficial to improve PVC foam sandwich panel’s impact resistance. |
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