“…The mesh sizes are set to 0.4 mm × 0.4 mm × 0.4 mm for both the panel encryption area and the folded core, ref. 17.Figure 10.Impact finite element model.…”
Section: Numerical Simulation and Discussionmentioning
confidence: 99%
“…A 3D progressive damage model is chosen for the material model, as shown in the literature. 13 The material parameters used are shown in Table 2, ref. 14.…”
Section: Damage Model and Finite Element Modelmentioning
Foldcore sandwich structure has promising applications for load-bearing, and in this study, M-type foldcore sandwiches are prepared through a molding and pressing process with fiberglass. To be specific, the sandwich structures are investigated for dynamic response and damage mechanism under low-velocity impacts with various impact positions and energy. The results show that impact position significantly affects the damage mode of the sandwich plate, the damage mode of crush fracture and collapse failure at node position can dissipate higher energy compared with tensile fracture at base position. Moreover, the impact energy shows a certain influence only when the sandwich panel is not penetrated. Besides, numerical prediction closely matches experimental results in terms of load-displacement and energy-displacement histories. Effects of geometric configuration are explored, and the results suggest that although increasing the thickness of panel and core can effectively improve the load-bearing capacity under low energy impacts, increasing the core thickness is a more effective method in lightweight design than increasing the thickness of plane. Furthermore, the impact resistance can be enhanced by selecting the appropriate platform length and narrowing the platform angle. Notably, M-type foldcore sandwich is superior to V-type foldcore sandwich and corrugated sandwich in terms of specific energy absorption.
“…The mesh sizes are set to 0.4 mm × 0.4 mm × 0.4 mm for both the panel encryption area and the folded core, ref. 17.Figure 10.Impact finite element model.…”
Section: Numerical Simulation and Discussionmentioning
confidence: 99%
“…A 3D progressive damage model is chosen for the material model, as shown in the literature. 13 The material parameters used are shown in Table 2, ref. 14.…”
Section: Damage Model and Finite Element Modelmentioning
Foldcore sandwich structure has promising applications for load-bearing, and in this study, M-type foldcore sandwiches are prepared through a molding and pressing process with fiberglass. To be specific, the sandwich structures are investigated for dynamic response and damage mechanism under low-velocity impacts with various impact positions and energy. The results show that impact position significantly affects the damage mode of the sandwich plate, the damage mode of crush fracture and collapse failure at node position can dissipate higher energy compared with tensile fracture at base position. Moreover, the impact energy shows a certain influence only when the sandwich panel is not penetrated. Besides, numerical prediction closely matches experimental results in terms of load-displacement and energy-displacement histories. Effects of geometric configuration are explored, and the results suggest that although increasing the thickness of panel and core can effectively improve the load-bearing capacity under low energy impacts, increasing the core thickness is a more effective method in lightweight design than increasing the thickness of plane. Furthermore, the impact resistance can be enhanced by selecting the appropriate platform length and narrowing the platform angle. Notably, M-type foldcore sandwich is superior to V-type foldcore sandwich and corrugated sandwich in terms of specific energy absorption.
“…The material properties of the GFRP are shown in Table 2. 21 Glass fiber panels were prepared by vacuum bag hot compression molding method with lay-up angles of [0 /90 /90 /0 ]. The prepreg is first laid layer by layer according to the required angle, and the prepreg is wrapped with a non-porous isolation film after laying to prevent the prepreg from being contaminated with impurities and affecting the mechanical properties.…”
Section: Preparation Of Specimens and Simulated Hail Icementioning
Nowadays, more and more aircraft components are made of composite sandwich structures, and ice impacts are prone to cause internal damage to composite sandwich structures, so it is crucial to study the impact of hail on composite sandwich structures. Since hail impacts may occur several times at a single point, an experimental approach was used to investigate the dynamic response of GFRP/Nomex honeycomb sandwich panels under multiple hail impacts. The dynamic response of the structure was investigated in terms of response rate and deflection‐profile curves using 3D digital image correlation methods, and the effects of impact energy, hail size, and number of impacts on the impact resistance of the honeycomb sandwich structure were explored. The results show that the dynamic response process of sandwich panels can be categorized into the ball‐and‐crown phase, the rebound phase, and the vibration phase. Under the same impact energy, the impact of small‐sized hailstones is more threatening to honeycomb sandwich panels. As the number of impacts increases, the maximum deflection value of the back panel first increases uniformly, and when the layered damage area reaches the threshold value, fiber stripping occurs, and the increment of the maximum deflection value increases significantly.Highlights
Since hail impacts may occur several times in real situations, this study conducted multiple impact experiments for one impact site. The dynamic response and damage pattern of the GFRP/Nomex honeycomb sandwich panels under multiple hail impacts were also investigated.
The dynamic response process of GFRP/Nomex honeycomb sandwich panels was categorized into three phases: ball‐crown stage, rebound stage, and vibration stage.
With the increase of the number of impacts, fiber stripping and fiber break damage began to occur when the layered damage area of the panel reached the threshold value. The honeycomb core has three main failure modes: cell wall folds, cell wall fracture, and cell wall debonding at the TGPW interface.
Small‐diameter hails pose a more significant threat of damage to honeycomb sandwich panels at the same impact energy.
“…The molding method used the split mold, because the integral molds suffer from being bulky, heavy, and not easy to handle. [32] As shown in Figure 2, the split mold is a combination of the split upper mold and the integral lower mold. The preparation process of the core is as follows: (a) The mold surface was cleaned with acetone, then sprayed with release agent and the mold was preheated to facilitate the smooth pressing in of the prepreg; (b) The prepreg was pressed into the lower mold in turn using the upper mold, and the fastening bolts were used to apply fixing pressure; (c) The mold was placed in the insulated cabinet and cured according to the scheduled curing system; (d) The mold was demoulded at room temperature to obtain the core.…”
The proposed folding structure is inspired by origami, which has unique mechanical properties. To investigate the ballistic properties of the optimized S-shaped folded sandwich structure, micro-bead modified (HGB) epoxy resin was injected into S-shaped folded sandwich panels and high-velocity impact tests were conducted. The experimental results demonstrated that the damage pattern of the core determines the ballistic properties of the sandwich panel.And the node position's ballistic performance is superior to that of the base position. The modified resin improves the ballistic resistance of the sandwich panel and increases the weight of the sandwich structure. Moreover, the effect of the back-filled modified resin on the ballistic properties of the sandwich panel can counteract the negative effect of increased weight. While the frontfilled configuration may compromise the weight-related ballistic performance index of the sandwich structure.
K E Y W O R D Sballistic impact, damage modes, folded sandwich structure, hollow glass beads, micro-bead modified resin
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