Delamination link-ups in composite laminates due to multiple hail impacts

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.

Section: Introductionmentioning

confidence: 99%

Dynamic response of GFRP/Nomex honeycomb sandwich panels subjected to multiple hail impacts – An experimental study

Sun,

Xu,

Deng

2024

“…However, in most practical situations, composites were more likely to be subjected to multiple repeated impacts such as bird strikes, hailstorms, and rubble piles during service. It has been shown that the accumulation of damage due to repeated impacts, even at low energy levels, could result in damaged regions that deteriorate the mechanical properties of the material 19,20 . In addition, experimental evidence suggested that repeated impacts at the same location with low energy may cause more severe damage than a single high‐energy impact 21‐23 .…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that the accumulation of damage due to repeated impacts, even at low energy levels, could result in damaged regions that deteriorate the mechanical properties of the material. 19,20 In addition, experimental evidence suggested that repeated impacts at the same location with low energy may cause more severe damage than a single high-energy impact. [21][22][23] For example, Tian and Zhou 24 investigated the mechanical response of glass fiber-reinforced aluminum alloy laminates under single and multiple impacts with the same total energy (30 J, 20 J + 10 J, 10 J + 20 J, 10 J + 10 J + 10 J), and the results showed that the multiple impact mode of 10 J + 10 J + 10 J caused maximum permanent deformation of the laminates.…”

mentioning

confidence: 99%

Low‐velocity multiple impact damage characteristics and numerical simulation of carbon fiber/epoxy composite laminates

Fang,

Chu,

Zhu

et al. 2023

Low‐velocity impact damage is one of the main defects of composite laminates, which seriously affects the bearing capacity and service life of composite laminates. Multiple impact experiments of carbon fiber/epoxy composite laminates were carried out under different impact energies. The finite‐element model was established according to the experimental conditions. The impact damage mechanism of laminated plates was studied by means of simulated damage cloud image, water immersion ultrasonic C‐scan, and computed tomography. The results showed that the matrix damage occurred mainly during the whole impact process, and the tensile damage of the matrix was dominant. As the number of impacts increased, the impact resistance of composite laminates decreased and the damaged area increased, with the second impact having the greatest influence on the degree of damage to the laminates; multiple impacts with low energy were easy to cause delamination at the top of the laminated plate. With the increase in impact energy, the damage at the bottom of the laminated plate was more serious, and the propagation mode of delamination damage in laminates changed from top‐bottom to bottom‐up.Highlights Establishing a multiple impact finite‐element model for composites. Accurately predicting the impact mechanical response of composites. Revealing multiple impact damage evolution of composites by simulation.

Enhancing impact resistance of fiber‐reinforced polymer composites through bio‐inspired helicoidal structures: A review

Xu,

Feng

2024

One of the primary limitations of fiber‐reinforced polymer composites, particularly carbon fiber, is their low impact resistance. Helicoidal structures, inspired by natural biological materials, are created by rotating each layer at a small angle through the thickness, forming a staircase pattern. These structures have been used as microstructure models to improve impact resistance in composite laminates. This paper provides a comprehensive review of recent progress in the impact resistance of bio‐inspired helicoidal laminates (BIHL). The review begins with an introduction to typical microstructural characteristics of helicoidal architectures, including single‐ and double‐twisted Bouligand structures. The impact damage mechanisms specific to BIHL are then elucidated, particular emphasis is placed on key parameters that affect impact performance, including different forms of helicoidal structures, constituent materials and impact factors. Furthermore, a critical discussion is conducted to highlight the advantages and limitations of manufacturing processes tailored for high‐volume production of BIHL. Finally, after identifying research gaps in the current literature, future directions for BIHL in design, fabrication and application are presented. This review may serve as a practical guide for engineers and researchers interested in developing polymer composite laminates that are highly resistant to impact loads.Highlights Helicoidal structures significantly enhance the impact resistance of composites. The damage pattern and mechanisms of BIHL are identified and summarized. Key parameters influencing the impact behavior of BIHL are discussed in detailed. The advantages and limitations of manufacturing processes for BIHL are examined Contemporary challenges and future research directions for BIHL are outlined.