Search Results (35)

A turboprop aircraft is exposed to the risk of bird strikes during flight, which may have a serious impact on flight safety once the bird is sucked into the engine. In this study, the aerodynamic and bird exclusion characteristics of a branched turboprop inlet were tested on a branched turboprop inlet–bird striking experiment system under ground suction conditions. The ingestion processes of the bird were captured by a high-speed camera system. The static pressure at the inner wall of the inlet during the ingestion process was measured. The results indicate that when a low-speed bird at a large incident angle impacts on the wall of the inlet near the lower lip under ground suction conditions, the bird is easily sucked into the core duct. Conversely, it is more likely to be excluded by the bypass duct. Moreover, when the bird moves into the inlet, the static pressure on the wall of the area where it passes through increases significantly. Full article

The wind turbine blade is subject to multi-source impacts, such as bird strikes, lightning strikes, and hail, throughout its extended service. Accurate localization of those impact sources is a key technical link in structural health monitoring of the wind turbine blade. In this paper, a single-sensor impact source localization method is proposed. Capitalizing on deep learning frameworks, this method innovatively transforms the impact source localization problem into a classification task, thereby eliminating the need for anisotropy compensation and correction required by conventional localization algorithms. Furthermore, it leverages the inherent coding effects of the blade’s material and geometric anisotropy on impact sources originating from different positions, enabling localization using only a single sensor. Experimental results show that the method has a high localization accuracy of 96.9% under single-sensor conditions, which significantly reduces the cost compared to the traditional multi-sensor array scheme. This study provides a cost-effective solution for real-time detection of wind turbine blade impact events. Full article

The use of composite materials in aerospace structures has led to significant weight reductions and improved performance. However, their behavior under low-energy impact remains a critical concern due to the potential initiation of barely visible damage. This study investigates the crack initiation mechanisms in composite airfoil profiles subjected to low-energy impact, simulating real-world scenarios such as hail or bird strikes. Two types of airfoil profiles were fabricated using bidirectional carbon fiber reinforced polymer (CFRP) with epoxy resin and tested under ASTM D7136 impact conditions. Tensile tests following ASTM D3039 were conducted to assess post-impact mechanical behavior. The damage patterns were analyzed using high-resolution microscopy and non-destructive inspection techniques. Results revealed that damage severity and propagation depend on impact energy levels and airfoil geometry, with SC(2)-0714 exhibiting better impact resistance than GOE777-IL. Microscopic analysis confirmed that delamination initiated at 45° fiber orientations, expanding along interlaminar regions, while airfoil curvature influenced the impact energy dissipation. Full article

Bird strikes pose a significant threat to aviation safety, particularly affecting the wing structures of aircraft. This research aims to design and analyze the impact of bird strikes on wing structures using response surface method and metaheuristics (MHs), which are used to explore various risk minimization and damage mitigation techniques. The optimization problem is the minimization of the maximum von Mises stress of aircraft wing structure against bird strike that is subject to displacement and stress constraints. The design variables include skin and rib thickness, as well as sweep angle. Difficulty due to embedded bird strike simulation and optimization design can be alleviated using a response surface method (RSM). The regression technique in the RSM of the data can reach our goal of model fitting with a higher R² until 0.9951 and 0.9919 are obtained for the displacement and von Mises stress model, respectively. The response surface function of the displacement and von Mises stress are related to skin thickness, while sweep angles rather than rib thickness have a greater impact on both design variables. The optimized design of the design variables is performed using MHs, which are TLBO, JADE, and PBIL. The comparative result of MHs can conclude that the PBIL outperformed others in all descriptive statistics. The optimized design results revealed that the optimum solution can release better energy due to bird strike with the highest limit of skin thickness, moderate rib thickness, and less than half of the sweep angle. The results are in accordance with the response surface function analysis. In conclusion, the optimized design of the aircraft wing structure against bird strike can be accomplished with our proposed technique. Full article

The expansion of Urban Air Mobility (UAM) has led to diverse aircraft designs, with piloted systems expected to evolve into remotely piloted and automated operations. Future advancements in Intelligent Transportation Systems (ITSs) will further improve automation capabilities, promising significant benefits to the environment and overall efficiency of UAM aircraft. However, UAM aircraft face unique operational conditions that need to be accounted for when assessing safety risks, such as lower operating altitudes and hazards present in urban settings, thus leading to a potential increased risk of collisions with foreign objects, particularly birds and drones. This paper reviews historical safety data with an aim to better assess the potential risks of UAM aircraft. A survey was conducted to gather quantitative and qualitative insights from subject matter experts, reinforcing findings from existing studies. The results highlight the need for a comprehensive risk assessment framework to guide design improvements and regulatory strategies, ensuring safer UAM operations. Full article

The continuous advancement of urbanization and the expansion of cities inevitably have certain impacts on urban wildlife. Birds are a highly visible group of urban wildlife, widely distributed and sensitive to environmental changes. Birds’ song is an important way of conveying information; the effective conveyance and transmission of bird songs are crucial for attracting mates and successful reproduction. However, the impact of urban development on the songs of many birds remains unknown. This study compared the differences in song characteristics (maximum frequency, minimum frequency, main frequency, and duration) of the Eurasian Nuthatch (Sitta europaea) at six different research sites with different levels of urbanization, in order to explore the song response patterns of birds to urbanization. The results indicate that urbanization leads to a reduction in avian song diversity and a convergence in song parameters. Birds in different life history stages show inconsistent responses to urbanization. During the overwintering period, there are no significant differences in the minimum frequency and duration of the Eurasian Nuthatch’s song, almost no significant differences in the maximum frequency, and the main frequency of the Eurasian Nuthatch’s song, as distributed in the Forest Botanical Garden (FBG) shows some differences compared to other study sites. During the breeding period, there are no significant differences in the main frequency of the Eurasian Nuthatch’s song, while other parameters exhibit varying degrees of differences. Comprehensive analysis reveals that urbanization has varying impacts on the song diversity of the Eurasian Nuthatch across different life history stages. During the overwintering period, there is a significant reduction in song diversity, with a pronounced homogenization effect; during the breeding period, the birds’ songs are more diverse, with only the main frequency showing a significant homogenization effect. It is speculated that birds may strike a certain balance between adapting to urbanization and survival reproduction. Full article

Bird strikes pose one of the most significant threats to aviation safety, often leading to substantial loss of life and economic damage. Many bird strike incidents involve multiple birds. However, in previous bird strike studies, the problem of multiple bird strikes has often been neglected. In this paper, the bird slicing process of a rotating engine fan is examined, and a probability model is introduced to assess the risk of multiple impacts on the fan blades. In addition, this paper utilized an implicit–explicit calculation method. The parameters of blade root stress, tip displacement, plastic deformation, and energy were selected to investigate the effects of the time interval and strike position of a bird strike on the dynamic response of and damage to the blades. The results indicated that the position of bird strikes has a more pronounced effect on blade damage compared to the time interval between impacts. Damage to a blade is most severe when the blade root is struck multiple times. Multiple bird strikes may not always lead to a significant increase in maximum blade tip displacement, and may even have a dampening effect. Full article

It is vital to maximize the safety of outdoor constructions, airplanes, and space vehicles by protecting against the impact of airborne debris from increasing winds due to climate change, or from bird strikes or micrometeoroids. In a widely-used compression-molded short glass fiber polyester bulk-molded compound (SGFRP-BMC) with 55% wt. CaCO₃ filler, the center of the mother panel has lower impact strength than the outer sections with solidification texture angles and short glass fiber (SGF) orientations being random from 0 to 90 degrees. Therefore, a new double-step process of: (1) reducing commercial fiber length without change in molding equipment; followed by a (2) 0.86 MGy dose of homogeneous low-voltage electron beam irradiation (HLEBI) to both sides of the finished samples requiring no chemicals or additives, which is shown to increase the Charpy impact value (a_uc) about 50% from 6.26 to 9.59 kJm⁻² at median-accumulative probability of fracture, P_f = 0.500. Shortening the SGFs results in higher fiber spacing density, S_f, as the thermal compressive stress site proliferation by action of the CTE difference between the matrix and SGF while the composite cools and shrinks. To boost impact strength further, HLEBI provides additional nano-compressive stresses by generating dangling bonds (DBs) creating repulsive forces while increasing SGF/matrix adhesion. Increased internal cracking apparently occurs, raising the a_uc. Full article

Avian coccidiosis, despite advancements in management, nutrition, genetics, and immunology, still remains the most impactful disease, imposing substantial economic losses to the poultry industry. Coccidiosis may strike any avian species, and it may be mild to severe, depending on the pathogenicity of Eimeria spp. and the number of oocysts ingested by the bird. Unlike broilers, low emphasis has been given to laying hens. Coccidiosis in laying hens damages the gastrointestinal tract and causes physiological changes, including oxidative stress, immunosuppression, and inflammatory changes, leading to reduced feed intake and a drastic drop in egg production. Several countries around the world have large numbers of hens raised in cage-free/free-range facilities, and coccidiosis has already become one of the many problems that producers have to face in the future. However, limited research has been conducted on egg-laying hens, and our understanding of the physiological changes following coccidiosis in hens relies heavily on studies conducted on broilers. The aim of this review is to summarize the effect of coccidiosis in laying hens to an extent and correlate it with the physiological changes that occur in broilers following coccidiosis. Additionally, this review tries to explore the nutritional strategies successfully used in broilers to mitigate the negative effects of coccidiosis in improving the gut health and performance of broilers and if they can be used in laying hens. Full article

Sandwich composites are often used as primary load-bearing structures in various industries like aviation, wind, and marine due to their high strength-to-weight and stiffness-to-weight ratios, but they are vulnerable to damage from Low-velocity-impact (LVI) events like dropped tools, hail, and birdstrikes. This often manifests in the form of Facesheet-Core-Debonding (FCD) and is often termed Barely-Visible-Impact-Damage (BVID), which is difficult to detect and can considerably reduce mechanical properties. In general, a balsa core sandwich is especially vulnerable to FCD under LVI as it has poorer adhesion than synthetic core materials. A cork core sandwich does show promise in absorbing LVI with low permanent indentation depth. This paper also reviews surface treatment/modification as a means of improving the adhesion of composite core and fiber materials: key concepts involved, a comparison of surface free energies of various materials, and research literature on surface modification of cork, glass, and carbon fibers. Since both balsa and cork have a relatively low surface free energy compared to other materials, this paper concludes that it may be possible to use surface modification techniques to boost adhesion and thus FCD on balsa or cork sandwich composites under LVI, which has not been covered by existing research literature. Full article

Parrots (Order: Psittaciformes) represent one of the most striking and ecomorphologically diverse avian clades, spanning more than two orders of magnitude in body size with populations occupying six continents. The worldwide diaspora of parrots is largely due to the pet trade, driven by human desire for bright, colorful, and intelligent animals as companions. Some introduced species have aptly inserted themselves into the local ecosystem and established successful breeding colonies all around the globe. Notably, the United States is home to several thriving populations of introduced species including red-masked parakeets (Psittacara erythrogenys), monk parakeets (Myiopsitta monachus), nanday conures (Aratinga nenday), and red-crowned amazons (Amazona viridigenalis). Their incredible success globally begs the question as to how these birds adapt so readily to novel environments. In this commentary, we trace parrots through evolutionary history, contextualize existent naturalized parrot populations within the contiguous United States, and provide a phylogenetic regression analysis of body mass and brain size based on success in establishing breeding populations. The propensity for a parrot species to become established appears to be phylogenetically driven. Notably, parrots in the family Cacatuidae and Neotropical Pyrrhua appear to be poor at establishing themselves in the United States once released. Although brain size among Psittaciformes did not show a significant impact on successful breeding in the continental United States, we propose that the success of parrots can be attributed to their charismatic nature, significant intelligence relative to other avian lineages, and behavioral flexibility. Full article

Smart flexible materials with piezoresistive property are increasingly used in the field of sensors. When embedded in structures, they would allow for in situ structural health monitoring and damage assessment of impact loading, such as crash, bird strikes and ballistic impacts; however, this could not be achieved without a deep characterization of the relation between piezoresistivity and mechanical behavior. The aim of this paper is to study the potential use of the piezoresistivity effect of a conductive foam made of a flexible polyurethane matrix filled with activated carbon for integrated structural health monitoring (SHM) and low-energy impact detection. To do so, polyurethane foam filled with activated carbon, namely PUF-AC, is tested under quasi-static compressions and under a dynamic mechanical analyzer (DMA) with in situ measurements of its electrical resistance. A new relation is proposed for describing the evolution of the resistivity versus strain rate showing that a link exists between electrical sensitivity and viscoelasticity. In addition, a first demonstrative experiment of feasibility of an SHM application using piezoresistive foam embedded in a composite sandwich structure is realized by a low-energy impact (2 J) test. Full article

Bird strikes have long been a source of concern for all airlines across the world. It is the most significant design criterion for aircraft engine fan blades. As it is not practical to manufacture and test aviation engines repeatedly for minor design modifications, simulation analysis can be used to investigate strategies to reduce the influence of a bird strike on a jet engine by employing proper design and manufacturing processes for blades. This study proposes using two fibers (hybrid) instead of the single-fiber composite blade presently in use to address delamination problems. As an idea validation test, the coupon-level analysis results are validated using a four-point bend test of similar-size coupons. Following this validation, dynamic analysis is used to investigate the impact behavior of a rectangular plate subjected to a bird strike. The current research focuses on analyzing bird strikes on a hybrid composite fan blade using blade-level models. This study concentrates on the position of the bird’s impact and the joint region length of two materials. The results show that the joint region with a 40% length of glass composite shows the optimum level of normalized interlaminar shear strain in all three impact locations. Full article

Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (a_uc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]₄[CF]₃. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing a_uc at each accumulative probability, P_f. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron microscopy (SEM) and electron dispersive X-ray (EDS) mapping showed PPS adhering to CF. Electron spin resonance (ESR) of a 5 kGy sample indicated lengthening of PPS chains as evidenced by a reduction in dangling bond peak. It Is assumed that 5 kGy HLEBI creates strong bonds at the interface while strengthening the PPS bulk. A model is proposed to illustrate the possible strengthening mechanism. Full article

Differing from present structural design procedures, most of the existing glass windows and even historic components in traditional/old buildings are not specifically designed to resist possible accidental loads. Rather thin monolithic ordinary annealed glass panels can be found in vertical non-structural envelopes, where they are often arranged to cover large surfaces. As such, an accidental glass fracture could originate even from rather common and moderate impact events and result in severe risk for people, due to propagation of dangerous shards from these vulnerable and fragile building components. To assess potential risks and support possible mitigation strategies, the present study is focused on the bird-strike analysis of existing/historic linearly restrained non-structural glass windows, based on a parametric Smoothed-Particle Hydrodynamics (SPH)–Finite Element (FE) model. Starting from a 1 m–wide and 1.5 m–high configuration, the attention is first given to various influencing parameters, such as impactor features (mass, 0.35–1.81 kg; impact speed, 0–40 m/s; and, thus, impact energy) and the target window (glass thickness, 4–6 mm; impact point; and, thus, glass stiffness). Local and global effects due to parametric localized bird-strikes are discussed based on non-linear dynamic numerical analyses and in terms of expected deflections, tensile stress peaks, and damage extension/severity (i.e., D1 to D3 damage levels). Scale effects are also examined for a case-study historic envelope (≈7 m in total size, 5 mm in thickness), and one of its 2.58 m × 3.3 m large glass components. Furthermore, a simplified empirical approach based on analytical formulations and normalized charts is proposed for a preliminary vulnerability assessment of historic monolithic glass envelopes, including parameters to account for impactor features and glass panel size/thickness, based on vibration-frequency considerations. Full article