Papers by Keyword: Impact

Abstract: The purpose of this research is to develop a vibration isolator using auxetic viscoelastic sheet technology. The procedure for the design and elaboration of the insulator using polymers and by means of fatigue analysis using impacts is exposed, the absorption of energy by cycles is compared and the damage that is produced in the viscoelastic is observed with an optical microscope. This is to compare the variation in the force that the fatigue equipment exerts to deform the sheet in the same magnitude and to be able to establish, through the ratio of absorbed energy and returned energy, criteria on the useful life of the element for future designs.

Abstract: The cervical spine is a complex anatomical structure that mainly stabilizes the head and protects the spinal cord. Injuries of the cervical spine often occur during falls or road accidents and are particularly serious since they generate strong threats of paralysis and death. It should be noted that the ligaments provide cervical stability but their stabilization in case of injury is not yet well investigated. In this context, the objective of the present work is to study the failure of the ligaments by developing a bio-faithful numerical model while using a more realistic geometry of the spinal components and behavior laws that take into account the effect of strain rate and motion amplitudes. In order to validate the results of the study, we conducted a comparison with previous literature studies. It has been found that damage is often supported by intervertebral discs, anterior longitudinal ligaments (ALL) and capsular ligaments (CL) in the case of frontal impact. Indeed, the highest stresses are concentrated in the annulus fibrosus and the capsular ligaments. In this study, we tested the effect of ligament tears on disc behavior, where it was found that the stress rate increased by approximately 6%. The effect of capsular ligament tear orientation was also examined. The obtained results show that the most dangerous inclination was downward at an angle of 45°.

Abstract: Honeycomb structures are frequently used as energy absorption devices in the automotive and aerospace industry. Many studies have been conducted to optimise these structures and improve crashworthiness behaviour. This paper attempts to improve the crashworthiness behaviour of a honeycomb crash box by filling the cells with open-cell aluminium foams. Experimental tests were conducted to develop the honeycomb and aluminium foam material model and, also, to validate the finite element model by experimental data. Foam-filling the crash box allows the control of the densification zone for different impact energies using open-cell aluminium foam, which shows the main novelty of this research. In the end, the optimised structure is presented concerning the optimum number of foam-filled cells and, also, to the aluminium foam’s density that best fits this application.

Abstract: The use of viscoelastic sheets in the hull of vessels built from GFRP has been raised in previous works as an option to protect the vessel from the destructive damage of slamming. The present work proposes its use in boats previously built by adhering to the outside of the hulls of the ships. Its installation process is shown, and this new type of installation is compared. Through impact tests with GFRP panels, it is shown that the viscoelastic material maintains its property of absorbing slamming energy and protecting the interior of the laminate. Fatigue tests on the order of 5x10⁴ cycles are carried out to evaluate the impact force, the accelerations that deform the laminate and the virtual energy work imposed on the panel. This option shows that designers have a new option to protect the hull of already built boats.

Abstract: Concrete is extremely vulnerable against impact loading due to its low tensile strength and pronounced brittleness. The application of thin strengthening layers, containing Textile Reinforced Concrete (TRC) and Strain-Hardening Cement-based Composites (SHCCs) in a ductile cement-based composite, is a promising solution to enhance the impact resistance of existing concrete structures. Three-dimensional (3D) textile structures exhibit numerous advantages over two-dimensional (2D) ones, most importantly higher shear, bending and energy absorption capacity, hence, appear to be instrumental in providing sufficient reinforcement to the target strengthening layers. However, design variability and optimization possibility of available 3D textile reinforcement are restricted. This paper presents the development of novel textile-based 3D truss reinforcement that can overcome these limitations. On the basis of woven 3D cellular structures, innovative pyramidal 3D truss reinforcement with favorable load-bearing capacity as well as notable energy absorption capability is developed and successfully realized. To investigate the feasibility and efficacy, cement-based composite consisting SHCC and newly developed pyramidal 3D truss reinforcement is prepared and tested under high-speed tensile loading as well as transversal impact loading. The experimental results show that woven 3D truss reinforcement is highly compatible with SHCC, and significantly enhances its impact resistance. Furthermore, SHCC reinforced with novel pyramidal 3D truss structure remarkably outperforms that with 2D carbon reinforcing structure approved for commercial use.

Abstract: It is proposed to apply a composite sheet of viscoelastic material encapsulated in ABS plastic to be used in the design of a prototype of vibration isolator in the use of motor bases. The cyclical impact tests presented are carried out with an insulator unit named as a viscoelastic sheet that takes advantage of Hooke's law 3D. Using a vibrating equipment, reproductions of impacts are made to study the ability of the vibration isolator to resist impacts and evaluate its useful life. Through the analysis of force and variation in the response to its natural frequency of vibration, the evaluations and its behavior to the tests are established, and its change to a passive type of isolator. The evolution of the damage in the viscoelastic and the appearance of cracks is also shown.

Abstract: The addition of ceramic nanoparticles to the polymer resin enhances the performance of the composite, enabling the use of such materials in industries such as automobiles and aircraft. This work aims to evaluate the characteristics of epoxy resins by introducing (1%, 3%, 5%, and 7% wt. nano dioxide silica). Using the "hand lay-up " process, about 125 samples were prepared for conducting tests (Hardness, Tensile strength, Impact, Water Absorption) and analyzing results by (SPSS-Scheff). The addition of 7% nano-silica dioxide particles to epoxy considerably raises the hardness values (85.350+.5150 shore D), according to the hardness results. The best average values of the tensile strength and impact (292± 2.828MPa, 54.00 ± 2.828 J/m²) were at the samples (Epoxy- 3% nano-silica dioxide) when compared with other samples. The values of elongation at break reduce through rising concentration, weight fractions of nano-silica dioxide in epoxy, and the best average values of the elongation at break (3.150± .2300 %) were at the samples (Epoxy- 1% nano-silica dioxide). The percentage of water absorption values improved by increasing the weight fraction concentrations of nano-silica dioxide in epoxy, and the best water absorption percentage was (.017 ±.003414%) in the samples (epoxy-1% nano-silica dioxide). Statistically, very large variations were observed of hardness, tensile strength, elongation at break, impact strength, and water absorption (Sig 0.01, 0.04, 0.003, 0.02, and 0.002) respectively, and this indicates an improvement in the properties when addition nano-silica dioxide to the epoxy resin

Abstract: The design of an implant thread plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and stability in cancellous bone. The primary stability of a dental implant is determined by the mechanical engagement between the implant and bone at the time of implant insertion. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. Numerous factors influence load transfer at the bone-implant interface, for example, the type of loading, surface structure, amount of surrounding bone, material properties of the implant and implant design. The purpose of this study was to investigate the effects of the impact two different projectile of implant threads on stress distribution in the jawbone using three-dimensional finite element analysis.

Abstract: Investigation presents an experimental study of mechanical properties of hybrid bio-composites made from man-made cellulose fibres and soft wood microfiller embedded into polypropylene homopolymer matrix at different weight contents. Mechanical properties such as elastic modulus, tensile strength, and impact resistance of the reinforced composites determined for various total weight contents of both biobased fillers were used as the design parameters. The problem was solved by planning the experiments and response surfaces method. The results demonstrate that using the both filler types enhance the mechanical properties. The tensile modulus increases by ~115%. The bio-composite with the highest weight content of man-made cellulose fibres and the lowest content of soft wood microfibers possesses maximum tensile strength (more 66 MPa). Addition of man-made cellulose fibres demonstrate a significant influence on the impact resistance of the investigated composites.

Abstract: For the design of vessels built by GFRP laminates, an insert with a viscoelastic layer is proposed to reduce the spread of damage produced by the vertical impact of the ship's bottom with the sea or slamming phenomenon. Using vertical drops-weight impact machine that reproduce the energy inferred to the panel during navigation, the propagation of the damage of OoA cured prepreg panels is studied comparing it with modified panels with insertion of viscoelastic layer. The use of acceleration data reading allows the benefits of viscoelastic modification during impact to be quantified through the developed formulation. The force, displacement and energy returned by the panel after impact have also been quantified, which does not become intralaminar and interlaminar damage. It is shown that under 40 joules of impact, the viscoelastic sheet has its best ability to return energy and above 130 joules it loses its capacity.