scholarly journals Impact response of different materials for sports mouthguards

2021 ◽  
Vol 15 (57) ◽  
pp. 63-69
Author(s):  
Maria Moreira ◽  
João Carlos Ramos ◽  
Ana Messias ◽  
Maria Augusta Neto ◽  
Ana Paula Amaro ◽  
...  
Keyword(s):  
Contact Time ◽  
Peak Load ◽  
Average Energy ◽  
Ethylene Vinyl Acetate ◽  
Impact Response ◽  
Foam Core ◽  
Absorbed Energy ◽  
Maximum Displacement ◽  
The Impact ◽  
It Structure

Up to this moment, there is no guideline regarding the materials to produce mouthguards. The most used is Ethylene-Vinyl Acetate (EVA). Studies indicate that laminating EVA sheets with rigid components could increase the protection capacities of the mouthguards whereas other studies suggest that only replacement of the material within it structure can increase energy absorption. The aim of this work is to evaluate the impact response of four different foils when compared to a 4 mm thickness EVA sheet. Five groups of different materials were subjected to impact tests with energies of 1.72 J, 2.85 J and 4.40 J. In this context was considered the following materials: EVA foils (G1), EVA foils with an EVA foam core (G2), EVA foils with an acetate core (G3), Foils of Erkoloc-pro (G4) and Foils of Ortho IBT resin (G5). Comparisons between the materials were made by qualitative analysis of the average energy-time and load-displacement curves, as well as by comparison of the peak load, maximum displacement, contact time and absorbed energy using the Kruskal-Wallis test. It was possible to conclude that statistically significant differences were found in the energy absorbed (p=0.001). Laminated foils with a soft core (G2) are a good option to produce mouthguards, while EVA foils with an acetate core (G3) and foils of Ortho IBT resin (G5) were declared unsuitable.

Impact of Storage Integrated Solar Photovoltaics (PV) Power System on Utility Peak Loads

2011 ◽  
Author(s):  
K. Agyenim-Boateng ◽  
R. F. Boehm
Keyword(s):  
Large Scale ◽  
Peak Load ◽  
Average Energy ◽  
Transient Behavior ◽  
Climatic Conditions ◽  
Photovoltaic System ◽  
Solar Pv ◽  
Pv System ◽  
Grid Load ◽  
The Impact

The promise of large-scale use of renewables such as wind and solar for supplying electrical power is tempered by the sources’ transient behavior and the impact this would have on the operation of the grid. One way of addressing this is through the use of supplemental energy storage. While the technology for the latter has not been proven on a large scale or to be economical at the present time, some assessments of what magnitude is required can be made. In performing this work we have used NREL’s Solar Advisor Model (SAM 2010) with TMY3 solar data to estimate the photovoltaic system power generation. Climatic conditions close to load centers were chosen for the simulations. Then the PV output for varying sizes of arrays were examined and the impact of varying amounts of storage investigated. The storage was characterized by maximum limiting energy and power capacities based on annual hourly peak load, as well as its charging and discharging efficiencies. The simulations were performed using hourly time steps with energy withdrawn from, or input to, storage only after considering base generation and the PV system output in serving the grid load. In this work, we examined the load matching capability of solar PV generation (orientated for maximum summer output) for a sample Southwestern US utility grid load of 2008. Specifically we evaluated the daily and seasonal peak load shifting with employing varying storage capacities. The annual average energy penetration based on the usable solar PV output is also examined under these conditions and at different levels of system flexibility.

Effect of Foam Core Density and Facesheet Thickness on the Low Velocity Impact Response of Foam Core Sandwich Composites

2000 ◽  
Author(s):  
M. Motuku ◽  
R. M. Rodgers ◽  
S. Jeelani ◽  
U. K. Vaidya
Keyword(s):  
Impact Energy ◽  
Maximum Load ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Foam Core ◽  
Low Velocity ◽  
Core Density ◽  
Failure Characteristics ◽  
Velocity Impact ◽  
The Impact

Abstract The effect of foam core density and facesheet thickness on the low velocity impact response and damage evolution in homogeneous foam core sandwich composites was studied. The failure characteristics, initiation and evolution of damage as well as the effect of impact energy were investigated. A Dynatup 8210 Impact Test Machine was utilized to conduct the low-velocity impact tests. Characterization of the impact response was performed by comparing the impact load histories, impact plots and failure characteristics. Fractography analysis was conducted through the use of scanning electron microscopy (SEM) and optical microscopy. Three types of foam cores with different densities, namely Airlite B12.5, Rohacell IG-71R63 and Airex R63.5 foam cores, were used to study the effect of core density. Considering four groups of facesheets made of different layers of cross-ply carbon prepregs performed the effect of facesheet thickness. For all the facesheet thicknesses (0.011-0.894-cm thick) and impact energy (11-40 J) range considered in this study, the maximum load (Pm), deflection-at-maximum load (δm) and time-to-maximum load (tm) exhibited strong influence or dependence on the type of foam core as opposed to the facesheet thickness. The energy-to-maximum load (Em), total energy absorbed (Et) and total energy-to-impact energy (Et/Eimp) ratio became less sensitive on the foam core density (or type) with increasing facesheet thickness. A transition point from foam core to facesheet controlled impact behavior as a function of impact energy level was observed. The impact parameters varied either linearly or parabolically with impact energy depending on the impact energy level, type of foam core and facesheet thickness. Excellent repeatability of impact data was generally obtained with increase in foam core density.

Improvement of Energy Absorption of Circular Tubes Subjected to High Velocity Impact

2014 ◽  
Vol 566 ◽  
pp. 575-580
Author(s):  
Masahiro Higuchi ◽  
Shun Suzuki ◽  
Tadaharu Adachi ◽  
Hiroshi Tachiya
Keyword(s):  
Dynamic Behavior ◽  
High Velocity ◽  
Peak Load ◽  
Compressive Deformation ◽  
Straight Tube ◽  
Absorbed Energy ◽  
Velocity Impact ◽  
High Velocity Impacts ◽  
Fixed End ◽  
The Impact

The dynamic behavior of circular straight and stepped tubes made of aluminum alloy under high-velocity impacts was investigated by performing finite element analyses (FEA) and an experiment. The FEA and experiment on the straight tubes suggested that while an increase in the impact velocity enhanced the absorbed energy through compressive deformation just after impact, the peak load at the fixed end was not affected by the velocity. A stepped tube that was thicker near the impacted end was designed on the basis of the results for the straight tubes, and its dynamic behavior was investigated through FEA. The stepped tube absorbed a large amount of impact energy through compressive deformation at the thicker portion during the higher-velocity impact, without increasing the maximum fixed-end load from that of the straight tube.

Low Velocity Penetration Mechanical Behaviors of Aluminum Foam Sandwich Plates at Elevated Temperature

2015 ◽  
Vol 15 (04) ◽  
pp. 1450063 ◽  
Author(s):  
Huifeng Xi ◽  
Liqun Tang ◽  
Jilin Yu ◽  
Xiaoyang Zhang ◽  
Beixin Xie ◽  
...  
Keyword(s):  
Aluminum Foam ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Metal Foam ◽  
Peak Load ◽  
Low Velocity Impact ◽  
Sandwich Plates ◽  
Foam Core ◽  
Absorbed Energy ◽  
Low Velocity

This paper presents the low-velocity impact tests on the sandwich plates with aluminum foam core and aluminum skins at elevated temperatures. A furnace, attached to an Instron Dynatup 9250 HV drop hammer system, was designed to accomplish the penetration tests at temperatures up to 500°C. In order to process the experimental data accurately, the numerical vibration analysis was conducted to determine the threshold frequencies of the fast Fourier transform (FFT) filter for the original impact data. The experimental results showed that the failure modes of the sandwich, peak load and absorbed energy varied obviously with temperatures. Furthermore, the results showed that the failure modes of the top skin and metal foam core showed minor changes with respect to temperatures. Whereas the failure mode of the bottom skin and peak loads changed significantly with respect to temperatures. Also, the absorbed energy revealed a three-stage variation with the change of temperature.

scholarly journals Experimental and numerical study of the response to various impact energy levels for composite sandwich plates with different face thicknesses

2019 ◽  
Vol 21 (5) ◽  
pp. 1654-1682
Author(s):  
Moeen S Rajput ◽  
Magnus Burman ◽  
Fredrik Forsberg ◽  
Stefan Hallström
Keyword(s):  
Impact Energy ◽  
Impact Damage ◽  
Energy Levels ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Absorbed Energy ◽  
Low Velocity ◽  
Composite Sandwich ◽  
The Impact ◽  
Dent Depth

Composite sandwich structures find wide application in the aerospace sector thanks to their lightweight characteristics. However, composite structures are highly susceptible to low-velocity impact damage and therefore thorough characterization of the impact response and damage process for the used material configurations is necessary. The present study investigates the effect of face-sheet thickness on the impact response and damage mechanisms, experimentally and numerically. A uni-directional, non-crimp fabric is used as reinforcement in the face-sheets, and a closed cell Rohacell 200 Hero polymer foam is used as core material. Low-velocity impact tests are performed in a novel instrumented drop-weight rig that is able to capture the true impact response. A range of impact energies are initially utilized in order to identify when low level damage (LLD), barely visible impact damage (BVID) and visible impact damage (VID) occur. A thorough fractography investigation is performed to characterize the impact damage using both destructive and non-destructive testing. The damage from the impacts in terms of dent depth, peak contact force, deflection and absorbed energy is measured. The results show bilinear responses in dent depth vs. impact energy and absorbed energy vs. impact energy. It is found than the BVID energy works well as an indication for the onset of excessive damage. Fractography reveals that there is a failure mode shift between the LLD and the VID energy levels, and that delaminations predominantly grow along the fiber direction and rotate in a spiral pattern through the thickness, following the laminate ply orientations. Finally, a progressive damage finite element model is developed to simulate both the impact response and the delamination extent, incorporating both intra-laminar and inter-laminar damage modes. The simulation shows good agreement with the experiments.

Dynamic impact behavior of syntactic foam core sandwich composites

2019 ◽  
Vol 54 (4) ◽  
pp. 535-547 ◽  
Author(s):  
P Breunig ◽  
V Damodaran ◽  
K Shahapurkar ◽  
S Waddar ◽  
M Doddamani ◽  
...  
Keyword(s):  
Syntactic Foam ◽  
Impact Response ◽  
Sandwich Composite ◽  
Foam Core ◽  
Syntactic Foams ◽  
Sandwich Composites ◽  
Dynamic Impact ◽  
Damage Mechanisms ◽  
The Impact ◽  
Dynamic Impact Loading

Sandwich composites and syntactic foams independently have been used in many engineering applications. However, there has been minimal effort towards taking advantage of the weight saving ability of syntactic foams in the cores of sandwich composites, especially with respect to the impact response of structures. To that end, the goal of this study is to investigate the mechanical response and damage mechanisms associated with syntactic foam core sandwich composites subjected to dynamic impact loading. In particular, this study investigates the influence of varying cenosphere volume fraction in syntactic foam core sandwich composites subjected to varying dynamic impact loading and further elucidates the extent and diversity of corresponding damage mechanisms. The syntactic foam cores are first fabricated using epoxy resin as the matrix and cenospheres as the reinforcement with four cenosphere volume fractions of 0% (pure epoxy), 20%, 40%, and 60%. The sandwich composite panels are then manufactured using the vacuum assisted resin transfer molding process with carbon fiber/vinyl ester facesheets. Dynamic impact tests are performed on the sandwich composite specimens at two energy levels of 80 J and 160 J, upon which the data are post-processed to gain a quantitative understanding of the impact response and damage mechanisms incurred by the specimens. A qualitative understanding is obtained through micro-computed tomography scanning of the impacted specimens. In addition, a finite element model is developed to investigate the causes for different damage mechanisms observed in specimens with different volume fractions.

Impact response of E-glass/epoxy composite bi-directional corrugated core sandwich panels

2020 ◽  
pp. 096739112098275
Author(s):  
A Shahbazi ◽  
A Zeinedini
Keyword(s):  
Finite Element ◽  
Epoxy Composite ◽  
Impact Response ◽  
Impact Behavior ◽  
Absorbed Energy ◽  
Specific Energy Absorption ◽  
Additive Manufacturing Technology ◽  
The Core ◽  
Numerical Predictions ◽  
The Impact

In this paper, the impact response of bi-directional corrugated core sandwich structures was investigated. The core and skins were made of E-glass/epoxy laminated composites. Additive manufacturing technology was used to print the molds applied to fabricate the cores. The influence of different periods, i.e. T = 30, 37.5, 50 and 75 mm, of the double-cosine corrugated core on the impact response of the panels was evaluated. In addition, some other panels with regular corrugated cores were manufactured to evaluate the impact response of the bi-directional corrugated core structures. A finite element modeling was also carried out to analyze the impact behavior of the samples. The empirical measurements and the numerical predictions showed that the panels with the bi-directional corrugated core have a significant improvement in the absorbed energy under impact loading at each given period. It was also manifested that the panel consisting of the bi-directional corrugated core with T = 37.5 mm has the highest specific energy absorption.

Effect of Impact Velocity and Impactor Mass on the Low Velocity Impact Response of Liquid Molding Vinyl Ester-350 Resin and Fiber-Reinforced Plaques

2000 ◽  
Author(s):  
M. Motuku ◽  
U. K. Vaidya ◽  
G. M. Janowski ◽  
G. Basappa ◽  
S. Jeelani
Keyword(s):  
Damage Evolution ◽  
Peak Load ◽  
Maximum Load ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
The Impact ◽  
Total Impact ◽  
Impact Duration

Abstract The influence of test conditions on the low velocity impact (LVI) response and damage evolution in neat resin plaques was investigated and documented. Specifically, the effect of impactor mass, velocity, and corresponding impact energy on the LVI response and damage evolution in unreinforced DERAKANE vinyl ester 411-350-resin system was studied. An instrumented drop weigh test machine was used to conduct the low velocity impact tests. The room temperature response of the material to impact loading and damage evolution was investigated using the impact load histories, impact plots and fractography analysis. This study is built upon previous work by the authors on LVI of neat resin systems, particularly those that have emerged as a new class of resins in liquid molding process. The study was motivated by the need for data and understanding of the failure characteristics of the individual constituents of a composite material such as in modeling of damage propagation and failure criteria analysis. For constant impact velocity, the time-to-maximum load (tm), total impact duration (tt), and the energy-to-maximum load to total energy absorbed (Em/Et) ratio increased, and energy absorbed after peak load (Ep) decreased with the mass of the impactor. For constant impactor mass, the time-to-maximum load and total impact duration decreased, the Em/Et ratio remained fairly the same, and energy absorbed after peak load increased with velocity; i.e., the impact velocity and mass had opposing effects on the time-to-maximum load, the total impact duration, Em/Et and energy absorbed after peak load. A single layer of plain-weave S2-glass fabric was incorporated in some of the unreinforced plaques in order to analyze the influence of reinforcement on the impact response and damage evolution. Insertion of a fabric layer aided in containment of the damage within the bounds of the specimen and to isolate the failure characteristics, which enabled further analysis of the impact response and damage evolution.

scholarly journals Mechanical Behaviour of Pin-Reinforced Foam Core Sandwich Panels Subjected to Low Impact Loading

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3627
Author(s):  
Ali Farokhi Farokhi Nejad ◽  
Seyed Saeid Rahimian Rahimian Koloor ◽  
Syed Mohd Saiful Azwan Syed Hamzah ◽  
Mohd Yazid Yahya
Keyword(s):  
Mechanical Behaviour ◽  
Impact Loading ◽  
Sandwich Panel ◽  
Experimental Testing ◽  
Peak Load ◽  
Sandwich Panels ◽  
Sheet Thickness ◽  
Element Model ◽  
Foam Core ◽  
The Impact

As a light structure, composite sandwich panels are distinguished by their significant bending stiffness that is rapidly used in the manufacture of aircraft bodies. This study focuses on the mechanical behaviour of through-thickness polymer, pin-reinforced foam core sandwich panels subjected to indentation and low impact loading. Experimental and computational approaches are used to study the global and internal behaviour of the sandwich panel. The samples for experimental testing were made from glass/polyester laminates as the face sheets and polyurethane foam as the foam core. To further reinforce the samples against bending, different sizes of polymeric pins were implemented on the sandwich panels. The sandwich panel was fabricated using the vacuum infusion process. Using the experimental data, a finite element model of the sample was generated in LS-DYNA software, and the effect of pin size and loading rate were examined. Results of the simulation were validated through a proper prediction compared to the test data. The results of the study show that using polymeric pins, the flexural strength of the panel significantly increased under impact loading. In addition, the impact resistance of the pin-reinforced foam core panel increased up to 20%. Moreover, the size of pins has a significant influence on the flexural behaviour while the sample was under a moderate strain rate. To design an optimum pin-reinforced sandwich panel a “design of experiment model” was generated to predict energy absorption and the maximum peak load of proposed sandwich panels. The best design of the panel is recommended with 1.8 mm face sheet thickness and 5 mm pins diameter.

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