Papers by Keyword: Impact

Abstract: Fiber-reinforced polymers (FRP) bars have gained widespread recognition as a viable alternative to steel reinforcement in concrete structures over the past decades due to their advantages in corrosion resistance, durability, and lightweight properties. However, existing research and current design codes do not adequately address the dynamic compressive response of FRP bars under high-impact loading conditions. This gap in knowledge presents a significant challenge in accurately predicting the response of FRP-reinforced structures under extreme loading events. Therefore, it is essential to investigate the response of FRP bars under dynamic loading conditions across a range of strain rates to improve design codes and ensure the reliability and safety of structures subjected to such conditions. This study presents an experimental program conducted on basalt FRP (BFRP) bars subjected to dynamic testing using the Split Hopkinson Pressure Bar (SHPB) apparatus. The 12-mm BFRP bars are subjected to impact loading at high strain rates ranging from 345 to 1300 s^-1. These varying strain rates are achieved by adjusting the pressure of the impact bar. A high-speed camera is employed to capture the failure mechanisms and provide visualization of the deformations during loading. The study focuses on evaluating the stress-strain relationship and failure modes of the tested BFRP bars under various loading rates. The results revealed that at higher strain rates of ∼1300 s^-1, BFRP bars lost 40% of its compressive strength when compared to its quasi-static strength (tested at 3.5 x 10^-4 s^-1). At lower strain rates (∼345 s^-1), 20% of the quasi-static strength is lost. At intermediate strain rates (∼590-740 s^-1), one sample showed a strength reduction of 26%, while another sample showed a strength gain of 10%. This proves that BFRP bars are highly strain-rate dependent. Additionally, the results show relatively significant variation in the behavior of the samples at similar strain rates, indicating microstructural differences between them.

Abstract: Recent research on the progressive collapse of buildings has mainly focused on load redistribution following member failure, commonly referred to as “re-distributional progressive collapse”. However, “impact-type progressive collapse” remains less explored. This mechanism, often triggered by dynamic events such as falling debris or fire scenarios, introduces complex interactions that are difficult to capture using traditional quasi-static models, leaving a significant gap in our understanding of how impact-type progressive collapses occur. This study aims to bridge that gap by investigating the impact forces generated between concrete bodies of various geometries through an experimental campaign. Spherical, semi-spherical, and cubic concrete samples were dropped onto a fiber-reinforced concrete plate from controlled heights. A high-speed camera captured the impact for detailed analysis, while parameters such as impactor mass and velocity, contact radius, and concrete compressive strength were systematically varied. Using advanced data processing techniques, namely Variational Mode Decomposition (VMD), results showed that a 73% increase in impact velocity led to a 75% rise in maximum contact force. Geometry had a significant influence, with spherical and semi-spherical specimens generating up to 64% higher forces than cubes of equal mass. In contrast, compressive strength had a minor effect, raising contact force by only 9% despite a 50% strength increase. High-speed camera footage confirmed more concentrated impacts for spherical shapes, while no notable differences were found between spherical and semi-spherical specimens of equal weight but different contact radii.

Abstract: The article summarizes the results of comprehensive theoretical and experimental studies of ice fracture under shock and explosive loads. Artificial ice and freshwater river ice were considered as objects of research. The results of full-scale underwater explosive tests are presented. Post-explosion analysis of the crushing of a 130-day ice sheet, including the morphology of destruction and diameter and state of the ice edge were obtained. The results of a five-layer ice target impacted by a low-velocity striker showed that a brittle fracture mechanism was dominant. A phenomenological model of ice destruction is briefly described. The model was a complex one of continuum mechanics and was based on fundamental conservation laws. The ice failure concept was based on a deterministic approach and the combined use of several failure criteria. The finite-element Lagrangian method contained a new method for isolating the discontinuity surfaces of materials. The calculations were carried out using the noncommercial software package Udar.Os.1. The impact of an ice cylinder on a rigid wall (aluminum plate) was simulated. Good agreement was obtained in terms of the morphology of the fracture and the velocity of the fracture wave. The contact surface algorithm was illustrated, which helped save computational time when modeling some problems of perforation and penetration, including the detonation process. In the numerical experiment, ice without phase transitions with averaged mechanical properties was considered. The impact response of the ice blocks to the shock and explosive load was simulated. The perforation of structures consisting of ice cubes and thin steel plates above and on them is simulated. Deep penetration of the steel sphere into an ice block and an ice block protected by a metal plate was simulated. Using numerical modeling, the location of explosive substances for the most effective fracture of thick ice was determined.

Abstract: Glass façades have become a prominent feature in modern architecture, offering aesthetic appeal and abundant natural light. However, in regions exposed to severe weather conditions, particularly during storms, glass façades are vulnerable to damage from wind-borne debris. The impact of such debris can compromise the structural integrity of the façade, leading to potential safety hazards. Despite the significant threat posed by wind-borne debris to the safety and performance of glass façades, the behavior of these materials under impact is not extensively studied. This study presents a comprehensive numerical analysis of the impact behavior of laminated glass panels subjected to debris typically propelled by strong wind forces, using LS-DYNA^®. The simulation models the interaction between wind-borne debris and glass panels of varying debris masses. Mechanical behavior of the glass is incorporated using fracture mechanics to simulate cracking and failure under impact. A range of impact scenarios is considered, including variations in debris mass, impact velocity, and impact locations, to replicate real-world conditions as accurately as possible. The numerical model integrates material properties, layer configurations, and impact conditions to closely reflect actual scenarios. In this study, wooden blocks of different masses are impacted on the laminated glass panels at varying locations and impact velocities. The results reveal the critical factors influencing the glass façade's response, such as the velocity of the incoming debris and the material strength of the glass. This study offers valuable insights for improving the safety and durability of glass façades. Thus, by understanding the complex dynamics of glass response to wind-borne debris, the study contributes to the development of more resilient architectural and structural systems, leading to better risk management strategies for buildings in areas prone to extreme weather events.

Abstract: This study examines the performance of hybrid steel-GFRP pipes compared to steel pipes, with a focus on bonding properties and the occurrence of internal corrosion. Some pipes were worn screw-shaped to mimic the effects of corrosion. The hybrid material was manufactured from two steel pipes reinforced with GFRP, bonded with polyester resin and 10% styrene to reduce viscosity and prevent bubble formation. Distortion problems during the manufacture of the specimens are addressed. Results indicate greater deformation in the worn pipes than in the steel-only specimens, whereas the hybrid material showed no significant difference between the two types. The hybrid material supported higher loads in some probes, but only two hybrid probes failed. Strain gauges measured the deformations, and the composite material's behavior was examined under a microscope. The hybrid material presented a lower flexural modulus and greater compliance to cracking. Despite the performance of the proposed hybrid material not being able to stand up to steel’s superior mechanical properties, the study offers useful insights and recommendations for future research, backed by stress-strain graphs.

Abstract: Composite fibers are a significant aspect in changing the mechanical properties through the direction of the fiber. The proposed composite fiber organized by the direction of 90º-45º-90º, 45º-90º-45º, and 90º-90º-90º can add to the substitution of composite fiber that enhances stiffness and impact strength. Thus, the Acrylonitrile-butadiene-styrene ABS arrangement has a place with amorphous polymers that can expand the effect and increase the impact and the mechanical properties, for example, woven ramie utilizing different direction orientations. The outcomes show that the elasticity direction of 45º-90º-45º is 56wt%, 90º-45º-90º is 83wt%, and further increments while utilizing 90º-90º-90º is 94%. The analyses incorporate tensile tests to obtain tensile stress, tensile strain, and elastic modulus, which are performed on the ASTM D3039 utilizing the General Testing Machine Zwick Roell Z020. Findings demonstrated that specimens with various directions demonstrated mechanical characteristics that produce different mechanical properties through stress-strain analysis. The toughness of various directions can endure influence stacking without a fracture with 90º-45º-90º, and toughness for 45º-90º-45º and 90º-90º-90º show the stored energy without having permanent deformation ASTM D256 utilizing Zwick Roell Effect Analyzer HIT 2P. Furthermore, SEM images were also obtained to see the morphological changes on the composite polymer surface due to the tensile test. Overall, the utilization of the tensile test shows the maximum stress that the structure can maintain. Assuming fibers are oriented parallel to the main loading direction 0° and 90° will provide greater strength in that direction, while fibres diagonal 45º more absorb energy. By observing the SEM results, there is no reduction in strength and toughness through the 90º-45º-90º orientation of the layers using the hand laid-up technique.

Abstract: In this study, the low energy impact properties of flax/epoxy, glass/epoxy and hybrid flax-glass/epoxy laminates are evaluated for two different stacking sequences: a unidirectional [0]₈ and a cross-ply [0/90]_2s. For flax laminates, the base reinforcement is made of the combination of a unidirectional flax layer and a flax mat layer, where the mat phase consisted of short flax fibers used as a binder for the unidirectional phase. All laminates were tested under uniaxial tension both before and after impact and were molded at a fiber volume fraction of 40%. The results indicate that the specific stiffness of the flax fiber composite is approximately 7% higher than that of the glass fiber composite, regardless of the stacking sequence used. Concerning low-energy impact resistance, the cross-ply laminate demonstrates superior performance with higher impact resistance and less permanent deformation compared to the unidirectional laminate. The study also explores the hybridization of flax and glass fibers, suggesting a promising approach that leverages the synergistic effects of employing two different types of fibers in the composite. The comparison of energy absorption during impact shows that the hybrid fibers/epoxy composite has a higher energy absorption capacity than the glass fiber/epoxy composite. Additionally, hybridization helps mitigate the degradation of tensile properties caused by impact, representing an effective strategy to enhance the mechanical properties of the flax fiber composite post-impact.

Abstract: This study investigates the impact resistance of Glass Laminate Aluminum Reinforced Epoxy (GLARE) composite laminates by incorporating shape memory alloy (SMA) wires. The influence of varying percentages of pre-strain (0%, 1%, 3%, and 5%) on the SMA wires embedded in the GLARE composites was examined. Laminate composites were made by hand lay-up method using 1100 series aluminum, glass laminate, epoxy resin, and nitinol wire. Impact testing was carried out using the Charpy (un-notched) method. The results demonstrate that the presence of SMA wires significantly enhances the impact resistance of the laminates. The energy absorption capacity of the laminates was found to increase with increasing pre-strain percentage. The highest impact resistance was observed in the specimens with 3% pre-strain, which exhibited a 35.2% increase in energy absorption compared to the specimens without SMA wires. However, a further increase in pre-strain to 5% resulted in a 21.5% decrease in energy absorption due to the higher fraction of stress-induced martensite, limiting the shape memory effect. Additionally, the damage analysis revealed that the absence of SMA wires led to severe debonding and delamination in the GLARE laminates. Conversely, specimens with 3% pre-strain exhibited the least damage, with limited debonding observed only in the front interface of the aluminum and epoxy-laminated fiberglass layers. The higher damage resistance of these specimens is attributed to their optimal energy absorption capability. Based on the findings, it is recommended to further investigate alternative shape memory alloy materials to determine their impact resistance enhancement potential compared to the current SMA wires. Additionally, conducting experiments with pre-strain percentages in the range of 3-5% would provide a better understanding of the maximum achievable performance. Furthermore, microscale observations should be conducted to gain more detailed insights into the damage mechanisms of the tested specimens.

Abstract: Recently, there is a significant increase in the number of people pursuing healthy living and expecting firms to adopt green manufacturing practices leading to improvement in the standard of living. The rapid deterioration of the environment has harmfully affected the socio-economic growth and development across the nations of the world. The severity of this effect is more pronounced among developing nations. The concern for a sustainable environment is thriving as one of the priorities for strategic firms, organization management, manufacturers, and product designers. The study present a critical review of the existing works of literature on green manufacturing,its evolution,definition and concept. The economic, environmental, social impacts from a global perspectives were discussed. The various challenges militating against its implementation and its possible drivers were examined. However, there are numerous opportunities and future research in the area of green manufacturing that are yet to be explored. Keywords: Green Manufacturing; Sustainable; Impact; Opportunities; Performance: Implementation

Abstract: In the current paper, composites with both thin and thick plies are designed to meet specific criteria and tested under both in plane and out of plan critical loading conditions. The tests adopted are bolted joint, drop-weight impact, compression after impact, Charpy impact, bending, and bending after thermal aging. The results of the proposed design are compared with that of the traditional composites and show higher improvement in most of the load cases by using thin plies inside the lamination process with the traditional ones. The results showed that the two proposed alternatives with thin plies are of higher advantage for the bolted joints problem. On the other hand, the alternative with thin plies distributes to be surrounding each traditional ply is of high advantages for both the impact and the bending problems. The alternative with a core of thin plies at the middle of the laminate is of high advantage for the compression after impact.