Research On Low-velocity Impact Properties Of Stitched Foam Core Sandwich Composites

Stitched foam sandwich structure composite materials in the engineering application is late, it was put forward until the early 21 st century, it was added fibre suture in the direction of thickness on basis of traditional foam sandwich structure, not only retain the traditional foam sandwich structure characteristics of lightweight, high strength, high stiffness, good impact resistance, heat insulation and sound insulation but also overcome the defect of easy-layered which the foam sandwich structure usually has, improve the impact resistance of laminate, at the same time the enrichment resin beside the suture will form resin column make sandwich structure composite still has excellent surface properties. The stitched foam sandwich structure composite materials has a wider application prospect. Sandwich structure damage form become more complex due to the addition of the suture in stitched foam sandwich composite material, involving the interaction of shock, panels, foam core and suture resin column under the process of low-velocity impact. Researching the process of shock response, failure behavior and the mechanism of the various influence factors in the process of impact under low-velocity impact has important guiding significance for stitched foam sandwich composite material structure design, and it is the theoretical foundation of the further application for foam sandwich structure composite materials in aerospace, shipbuilding, automobile, etc. In this paper, the main research work for the stitched foam sandwich composite materials under low-velocity impact are summarized as follows:(1) The improved lock suture method was used to sewn the adequate perform, and the perform was processed to test-piece by VARTM. The 5J and 10 J energy low-velocity impact experiment of stitched and unstitched foam sandwich composites were tested by drop hammer impact instrument based on ASTM D7136 standard respectively. The results of stitched and unstitched foam sandwich composites under different energy low velocity impact were compared and analyzed, and provide the reference basis for the numerical simulation of the low velocity impact.(2) A dynamics finite element model was established for the stitched foam core sandwich composite laminate under low velocity impact in ABAQUS. The stitching resin columns were described as truss elements in the model. Hashin failure was used to predict the intralaminar damage of laminate.and crushable foam model with isotropic hardening was used to predict the evolution of foam damage. The low-velocity impact response and damage of stitched/unstitched foam core sandwich structure were simulated by this method. The numerical results well agree with the experimental results and it verified the effectiveness and accuracy of the model.(3) The influence of various factors on the low velocity impact damage of stitched foam sandwich composite was simulated. Research the effects of the impact quality, impact velocity, foam thickness, fiber panel thickness, density and suture needle diameter and other factors for low velocity impact damage of stitched foam sandwich composite material. It provides a theoretical reference for the further understanding of the low velocity impact mechanism of stitched foam sandwich composites and the design of impact resistance damage.