Search Results (18)

This paper mainly investigates the ice-impact resistance of PVC foam sandwich beams for polar ship protective structures through low-velocity impact experiments and nonlinear finite element simulations. An experimentally validated elastic–plastic coupled model, accounting for ice crushing and large structural deformation, was used to examine the effects of core density and face-sheet thickness distribution on the ice-impact response of sandwich beams. Results show that the upper face sheet undergoes local indentation and global bending, the lower face sheet mainly bends globally, and the foam core exhibits local compression and overall bending, while compressive deformation accompanied by ice crushing and spalling occurs at the front part of the ice impactor. Moreover, the effective structural stiffness decreased during plastic loading as local indentation and core compression developed, whereas the unloading stiffness was higher than the effective stiffness during plastic loading. Energy dissipation primarily comes from ice crushing, face-sheet plasticity, and core compression. Increasing core density reduces deflection and core compression but increases peak force. Among the three face-sheet configurations examined at a constant total thickness, the configuration with a thinner upper face sheet and a thicker lower face sheet produced a smaller final deformation of the lower face sheet. This study provides a useful reference for ice-resistant design of sandwich structures in polar ships. Full article

Integration of composites into the fabrication process of structural assemblies within the aerospace, automotive, marine or civil engineering industries represents a rational solution adopted by leading companies which are guided by the necessity for novel low-weight, high-strength, and high-stiffness materials. During the manufacturing process and throughout the service life, fiber-reinforced polymer structures are subjected to impact loading, either accidentally or as an inherent requirement of the operational cycle. Firstly, general aspects regarding impact loading and some parameters used for its characterization are briefly described. Recent progress regarding the influence of the stacking sequence, fiber type, and impactor geometry on the impact performance of Kevlar and glass fiber reinforced composite materials is emphasized. Additionally, the effects of environmental factors (such as temperature, UV radiation, or humidity) on the impact energy absorbed by polymers reinforced with each of the two types of synthetic fibers are presented. Finally, the importance of directing the researcher’s judgment towards improving the characteristics of materials subjected to impact, from a sustainable perspective, is motivated through the presentation of the impact behavior of polymer composites reinforced with Kevlar fibers or glass fibers hybridized with vegetable fibers. Full article

Type IV composite overwrapped pressure vessels (COPVs) store hydrogen at pressures up to 70 MPa and must meet stringent safety standards through physical testing. However, full-scale burst, plug torque, axial compression, impact, and drop tests are time-consuming and costly. This study proposes a unified finite element analysis (FEA) workflow that replicates these mandatory tests and predicts failure behavior without physical prototypes. Axisymmetric and three-dimensional solid models with reduced-integration elements were constructed for the polyamide liner, aluminum boss, and carbon/epoxy composite. Burst simulations showed that increasing the hoop-to-axial stiffness ratio shifts peak stress to the cylindrical region, promoting a longitudinal rupture—considered structurally safer. Plug torque and axial load simulations revealed critical stresses at the boss–composite interface, which can be reduced through neck boss shaping and layup optimization. A localized impact with a 25 mm sphere generated significantly higher stress than a larger 180 mm impactor under equal energy. Drop tests confirmed that 45° oblique drops cause the most severe dome stresses due to thin walls and the lack of hoop support. The proposed workflow enables early-stage structural validation, supports cost-effective design optimization, and accelerates the development of safe hydrogen storage systems for automotive and aerospace applications. Full article

Evaluating the behavior of materials and their response under low-velocity dynamic impact (less than 30 m/s) is a challenging task in various industries. It requires customized test methods to replicate real-world impact scenarios and capture important material responses accurately. This study introduces a novel spring-actuated testing setup for low-velocity impact (LVI) scenarios, addressing the limitations of existing methods. The setup provides tunable parameters, including adjustable impactor mass (1 to 250 kg), velocity (0.1 to 32 m/s), and spring stiffness (100 N/m to 100 kN/m), allowing for flexible simulation of dynamic impact conditions. Validation experiments on steel plates with a support span of 800 mm and thickness of 5 mm demonstrated the system’s satisfactory accuracy in measuring impact forces (up to 714.2 N), displacements (up to 40.5 mm), and velocities. A calibration procedure is also explored to estimate energy loss using numerical modeling, further enhancing the test setup’s precision and utility. The results underline the effectiveness of the proposed experimental setup in capturing material responses during low-velocity impact events. Full article

This paper studies the behavior of S2-glass woven fabric reinforced polymer composite under low-velocity impact at 18–110 J energy. A macro-homogeneous finite element model for the prediction of their response is implemented, considering the non-linear material behavior and intralaminar and interlaminar failure modes for the prediction of impact damage. The model accurately predicted the permanent indentation caused by impact. By applying the Ramberg-Osgood formulation, different initial stiffness values are examined to assess the post-impact unloading response. This approach reveals the significant role of initial stiffness in inelastic strain accumulation and its consequent effect on permanent indentation depth. A higher initial stiffness correlates with increased inelastic strain, influencing the impactor rebound and resulting in greater permanent indentation. By accurately predicting permanent indentation, and damage accumulation for different impact energies, this study contributes to a better understanding of the impact behavior of composite materials, thereby promoting their wider application. Full article

Curved glass enables designers to achieve unparalleled innovation in creating modern and undulating shapes for building enclosures. However, the curvature of panes changes the static and especially the dynamic behavior of the panes under loading. Studies on low-velocity impacts on curved glass have been limited and have primarily involved numerical studies. This paper experimentally investigates the dynamic response of cylindrically curved glass panes under a low-velocity impact. A flat, 5 mm thick, single-pane geometry with three curvature radii and the lack or presence of movement restraint is considered. Special attention is also paid to the variations caused by impacting bodies involving different stiffness, mass, and geometry parameters. It was found that flat plates have a lower capacity to dampen oscillations, resulting in longer decay times compared to curved panes. For impactors with a lower stiffness, the glass panes experience uneven oscillations at the moment of impact, followed by a chaotic period of transient vibrations before reaching a stationary state. This contrasts bodies with greater deformability in which the main dynamic behavior follows a more predictable pattern. Full article

In the egg industry, fast and highly reliable quality measurements are crucial. This study presents a novel method based on Hertz contact theory that allows for non-destructive determination of eggshell strength. The goal of the study was to evaluate the material strength (Young’s Modulus) and structural strength (stiffness) of eggshells. To this end, an experimental setup was constructed to measure the collision of an eggshell with a small steel ball, which was recorded using a laser vibrometer. The study analyzed a sample of 120 eggs and found a correlation of 0.85 between the traditional static stiffness measured during quasi-static compression tests and the stiffness obtained from the Hertz contact theory. The results show that Hertz contact theory is valid for small steel spheres impacting eggshells, while a sensitivity analysis indicated that the most important factor in determining the strength of the eggshell is the contact duration between the egg and the impactor. These results open up the possibility of grading eggs based on their shell strength in a non-destructive manner. 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

The folded sandwich structure might inevitably be impacted at low velocity when it is working, which will lead to the decline of the mechanical properties. The low-velocity impact resistance of the double-layer V-shaped aluminium folded sandwich structure is researched by the finite element method. It was found that the damage mode and the proportion of energy absorption of the double-layer and single-layer folded sandwich structures are different under low-velocity impact, and the impact stiffness and energy-absorbing capacity of the double-layer structure are better than those of the single-layer structure when the impact energy is small. In addition, in view of the low-velocity impact response characteristics of the double-layer V-shaped aluminum folded sandwich structure, two methods are proposed to improve its impact stiffness. Both methods ensure that the total mass of the structure remains unchanged. One method keeps the inner panel still and changes the wall thickness distribution of the top and bottom cores, and the wall thickness of the top core is increased. The other method keeps the wall thickness of the cores unchanged, and the inner panel is moved upward. From the finite element results, it can be seen that after increasing the wall thickness of the top core from 0.25 mm to 0.4 mm, the maximum impact distance of the impactor decreases by 30.3% when the impact energy is 5 J, and it decreases by 23.1% when the impact energy is 10 J, and with 20 J, it decreases by 14.5%. After reducing the height of the top core from 12.5 mm to 5 mm, the maximum impact distance of the impactor is reduced by 22.86% when the impact energy is 5 J, 21.85% when the impact energy is 10 J, and 20.51% when the impact energy is 40 J. The improvement is obvious. The two methods can increase the equivalent density of the top core, which can increase the stiffness of the top core. For the double-layer structure, the stiffness of the top core near the impact point has a greater influence on the low-velocity impact resistance of the entire structure. Full article

The current study focuses on the impact loading phase characteristic of thin first year ice in inland waterways. We investigate metal grillages, fibre reinforced plastic (FRP) composites and nature-inspired composites using LS Dyna. The impact mode is modelled as (a) simplified impact model with a rigid-body impactor and (b) an experimentally validated ice model represented by cohesive zone elements. The structural concepts are investigated parametrically for strength and stiffness using the simplified model, and an aluminium alloy grillage is analysed with the ice model. The metal–FRP composite was found to be the most favourable concept that offered impact protection as well as being light weight. By weight, FRP composites with a Bouligand ply arrangement were the most favourable but prone to impact damage. Further, aluminium grillage was found to be a significant contender for a range of ice impact velocities. While the ice model is experimentally validated, a drawback of the simplified model is the lack of experimental data. We overcame this by limiting the scope to low velocity impact and investigating only relative structural performance. By doing so, the study identifies significant parameters and parametric trends along with material differences for all structural concepts. The outcomes result in the creation of a viable pool of lightweight variants that fulfil the impact loading phase. Together with outcomes from quasi-static loading phase, it is possible to develop a lightweight ice-going hull concept. Full article

The aim of the work was to investigate the numerical simulations correlation with the experimental behaviour of steel ball high velocity impact onto a 2 × 2 twill woven carbon composite laminate. The experimental set up consisted of a pressurised gas-gun able to shot steel ball projectiles onto two different composite plate layup configurations of plates made of the same composite material fabric. Subsequently, the experiments were replicated using the LSDYNA explicit finite element analysis software package. Progressive failure numerical models of two different fidelity levels were constructed. The higher fidelity model was simulating each of the plys of the composite panels separately, tied together using cohesive zone modelling properties. The lower fidelity model consisted of a single layer plate with artificial integration points for each ply. The simulation results came out to be in satisfactory agreement with the experimental ones. While the delamination extent was moderately under predicted by the higher fidelity model, the general behaviour was complying with the experimental results. The lower fidelity model was consistent in representing the damage of the panel during the impact and better predicted the impactor residual velocities due to the better matching of the pane stiffness. Despite the competency of the higher fidelity model to capture the damage of the laminate in a more detailed level, the computational cost was 80% higher than the lower fidelity case, which rendered that model impractical against the lower fidelity one, to use in larger models representing more substantial or more complex structures. Full article

The structural design of glass curtain walls and facades is a challenging issue, considering that building envelopes can be subjected extreme design loads. Among others, the soft body impact (SBI) test protocol represents a key design step to protect the occupants. While in Europe the standardized protocol based on the pneumatic twin-tire (TT) impactor can be nowadays supported by Finite Element (FE) numerical simulations, cost-time consuming experimental procedures with the spheroconical bag (SB) impactor are still required for facade producers and manufacturers by several technical committees, for the impact assessment of novel systems. At the same time, validated numerical calibrations for SB are still missing in support of designers and manufacturers. In this paper, an enhanced numerical approach is proposed for curtain walls under SB, based on a coupled methodology inclusive of a computationally efficient two Degree of Freedom (2-DOF) and a more geometrically accurate Finite Element (FE) model. As shown, the SB impactor is characterized by stiffness and dissipation properties that hardly match with ideal rigid elastic assumptions, nor with the TT features. Based on a reliable set of experimental investigations and records, the proposed methodology acts on the time history of the imposed load, which is implicitly calibrated to account for the SB impactor features, once the facade features (flexibility and damping parameters) are known. The resulting calibration of the 2-DOF modelling parameters for the derivation of time histories of impact force is achieved with the support of experimental measurements and FE model of the examined facade. The potential and accuracy of the method is emphasized by the collected experimental and numerical comparisons. Successively, the same numerical approach is used to derive a series of iso-damage curves that could support practical design calculations. Full article

The objective of this study was to evaluate rebound characteristics for running-specific prostheses by quantifying their dynamic behavior by an impact experiment. The impact experiment was conducted to produce a typical ground foot strike contact, and to obtain the dynamic behavior of blades during and after impact. The motion of the impactor and displacement of the blade was quantified by tracking markers attached to the surface of the impactor and blade using the digital image correlation method. Impact load was also calculated using the history of acceleration. An average spring stiffness, which was obtained by dividing the maximum impact load by its displacement, was proposed to evaluate the rebound characteristics for prostheses. As a result, the difference between the types of blades can be observed using the proposed stiffness and velocity ratio. This relationship indicates that the stiffness and the ratio may have the potential to be applicable to evaluate the performance of blades. Full article

The conditions of adhesive connections testing can significantly affect the recorded findings. The standards, under which the investigations are conducted, do not take into account numerous factors that can greatly influence the outcome of the tests. Moreover, the research parameters in the standards are not specified. It is not defined in what manner their change, or any failure to comply with the standards, will affect test results. This article presents the results of experimental research, completed with numerical simulations, designed to test to what extent the recorded impact strength of adhesive connections is affected by the stiffness of the test stand, and the speed and energy of the impactor. In the experimental research, the authors used block samples whose substrates were made of an aluminum alloy. The elements of the samples were bonded by means of three different epoxy adhesives. The models used in numerical calculations were built on the basis of the real dimensions of the specimens used in this experimental research. As a result of the performed tests and conducted calculations, it was found that the use of test stands of lesser stiffness resulted in an increased registered impact strength due to an increased energy value of elastic deformations. Full article