Bottom Sheet Research Articles

Medical Textiles of Self-Inflating On Air Mattress Bed and Belt for Nursing Physical Therapy Education and Training Performing a Healing Process

Medical textiles of a self-inflating air mattress bed and belt include an air chamber and a foam panel therein. The air chamber is defined by top and bottom sheet panels and a valve allowing air passage into and out of the air chamber. The foam panel includes the field of airflow passage there through, and the top and bottom sheet panels are mechanically coupled directly together via the apertures in the foam panel of the air mattress conducted to improve sleep quality. This study investigated the effect of variations in the surface characteristics of mattress beds and belts on pelvic fracture patients’ sleep quality. The present study developed a mattress bed and belt whose rigidity can be varied by controlling the amount of air in its air cells. To investigate the effect of the variable rigidity of the air mattress bed and belt on pelvic fracture patients’ sleep quality, participants (women, ages 13-45) were instructed to sleep on the air mattress bed and belt under different conditions, and their sleep quality was subjectively and objectively investigated. Subjectively, sleep quality is assessed based on the participants’ evaluations of the depth and length of their sleep. Objectively, medical textiles for pelvic fracture patients and mattress bed and belt specifications are estimated using the sleep stage information obtained by analyzing the movements and brain waves of the participants during their sleep. A subjective assessment of the sleep quality demonstrates that the participants’ sleep was worse with the adjustment of the air mattress bed and belt.

Experimental and numerical study on the flexural properties of RC beams with different CFRP-strengthened schemes

This study conducted a four-point bending experiment investigation on the flexural performances of the RC beams strengthened with various CFRP schemes. Four beams were employed, i.e., the ordinary RC beam (L0), the RC beam bonded with CFRP sheet (L1-C), the CFRP U-wrapped RC beam (L2-U), and the RC beam using CFRP rivets (L3-A). Test results highlighted the obvious improvement in the flexural performances of CFRP-strengthened beams in terms of enhancing load-carrying capacities and limiting overall deformations compared to beam L0. In addition, end anchorage systems, including CFRP U-hoop and CFRP rivets, changed the failure mode, restricted crack propagation, and mitigated the bottom CFRP sheet debonding effectively. The ultimate loads of beams L1-C, L2-U, and L3-A were 27.4 %, 36.4 %, and 41.6 % higher than beam L0, respectively, indicating that CFRP rivets performed the best in improving the beams' flexural properties. Finite element analysis was developed to simulate the bending experiment process. The numerical results comply well with the experiments in terms of the crack distribution pattern and bending force history. Then, parametric studies for the design suggestions with the use of the modes reveal that the implementation of the CFRP rivet with a depth of 80 mm and a diameter of 10 mm seems to be an ideal optimization plan for the beams herein.

Effect of die design on microstructure and mechanical joint strength in friction self-piercing riveted AA7055-T76 and AA7055-T76

In the present study, a unique friction self-piercing riveting (F-SPR) was applied to join high-strength, low-ductility aluminum alloy (AA) 7055-T76 and AA7055-T76 to mitigate a cracking issue. Also, the effect of die design on both joint formation and the mechanical joint performance were investigated. A crack-free joint was achieved when joining AA7055-T76 and AA7055-T76 by F-SPR. As the bottom diameter of the die increased, the mechanical interlocking distance initially increased then became almost saturated. At the same time, the solid-state bonding gradually disappeared, and the lap-shear fracture changed from bottom aluminum fracture to rivet pull-out with partial bottom aluminum fracture. The average maximum lap-shear joint strength of 11.57 kN and cross tension of 5.65 kN were achieved from the D2 die design owing to the combined contributions from high mechanical interlocking distance and good solid-state bonding at the joint interface. Ultrafine grain refinement was observed at the region next to the rivet shank outer surface and along the materials flow line between the top and bottom aluminum sheet in the rivet cavity. Because of the same joint-process parameters, the hardness profile at the joints made by different dies did not show obvious differences. As the distance from the base metal to the rivet outer surface decreased, frictional heat caused the hardness to initially decrease from 190 to 150 HV in the heat-affected zone. Hardness increased up to 175 HV in the thermomechanical affected zone (TMAZ-I) owing to large plastic deformation.

Response of the orthogonal corrugated sandwich panel under low-velocity impact with different shaped impactors

This study aims at investigating the low-velocity impact resistance of the composite orthogonal corrugated sandwich panel through experimental and simulation methods, considering different shaped impactors. To that scope, the progressive damage model with the sandwich panel is developed and numerical investigations are carried out in ABAQUS / Explicit. The results show that as the impactor changes from flat to hemispherical and then to conical shape, the first peak load gradually decreases, and the maximum displacement of the impactor and total energy absorption gradually increase. The high impact energy makes the sandwich panel more compliant. Furthermore, the expansion area of fiber damage, matrix damage and delamination in the top face sheet, core and bottom face sheet depends on the impactor shape and impact energy. Under high impact energy, the damage under the conical impactor mainly expands along the thickness direction of the sandwich panel rather than in the in-plane direction, while the flat impactor causes large damage area in the in-plane direction as well.

Multi-objective optimization of rivet and die for self-piercing riveting using finite element analysis

This study numerically investigated the effects of self-piercing riveting (SPR) process parameters on the quality of joints between steel and aluminum alloy sheets. First, the mechanical properties of each metal were experimentally evaluated, and a single-lap shear test was performed to validate a constructed finite element analysis model. This model was subsequently applied to optimize the die depth, die radius, and rivet length parameters of the SPR process using a multi-objective optimization method considering the shear strength, interlocking distance, and minimum thickness of the bottom sheet as objective functions. The results indicated that the maximum interlock distance was achieved with a longer die depth and larger die radius, and the largest minimum thickness of the bottom sheet was achieved with a shorter rivet length and larger die depth and radius. The die radius and depth were determined to be the most critical variables for all objective functions. The findings of this study can be applied to optimize the SPR of steel and aluminum alloy sheets.

Clinical study of antibacterial medical textiles containing polyhydroxyalkanoate oligomers for reduction of hospital-acquired infections

The prevention and control of hospital-acquired infections remain a significantchallenge worldwide, as textiles used in hospital wards are highly involved in transmission processes. This paper reports a new antibacterial medical fabric used to prepare hospital pillowcases, bottom sheets and quilt covers for controlling and reducing hospital-acquired infections. The medical fabric was composed of blended yarns of staple polyester (PET) and degradable poly(3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV)/polylactic acid (PLA) fibres, which were coated with polylactide oligomers (PLAO), which are environmentally friendly and safe antimicrobial agents with excellent thermal stability in high-temperature laundry. A clinical trial was conducted, with emphasis on the bacterial species that were closely related to the infection cases in the study hospital. After 7 days of use, 94% of PET/PHBV/PLA-PLAO fabric retained <20colony-forming units/100cm2 of the total bacterial amount, meeting hygiene and cleanliness standards. This study demonstrates the potential of fabrics containing polyhydroxyalkanoate oligomers as highly effective, safe and long-lasting antimicrobial medical textiles that can effectively reduce the incidence of hospital-acquired infections.

Vibration Analysis of Damaged Viscoelastic Composite Sandwich Plate

This paper presents a study of free and forced vibration of composite sandwich plate with and without damage using the finite element analysis developed under ANSYS APDL software. This modeling uses the 8-node shell 281 element to modelized the composite laminates of the top and bottom face sheets of the sandwich plate and the 20-node higher order solid 186 element to modelized the viscoelastic core. Two sets of boundaries are considered; Simply supported and clamped boundary conditions at all edges. The effect of damaged face sheets layers on natural frequencies, mode shapes, the frequency and transient responses of the sandwich plate is investigated. Numerical results show remarkable shifts of the natural frequencies, frequency and transient responses due to the presence of damage. It is concluded that the natural frequencies decreasing is due to the loss of structural stiffness. Natural frequencies of the sandwich plates are close to those issued from numerical results available in the literature.

Seismic flexural behavior of CFRP strengthened reinforced concrete beams secured with fiber anchors

An experimental program was conducted to examine the seismic performance of flexural beam members strengthened with carbon fiber-reinforced polymer (CFRP) sheet and anchored using carbon fiber splay anchors. This research study extends the use of carbon fiber anchors to secure the top and bottom CFRP flexural sheets under cyclic loading. In this study, low strength concrete is examined, with lightly reinforced steel ratio (0.0034) to test full-scale rectangular beams. Five reinforced concrete beams were cast, strengthened, and tested under reversed cycles of four-point bending to failure. The beams were categorized into a control specimen, strengthened specimens with thin sheets with and without fiber anchors, and strengthened specimens with thick sheets with and without fiber anchors. They were tested cyclically under displacement control according to the AC 125 loading protocol. The failure modes ranged from classical ultimate failure for the control beam to rupture and intermediate crack (IC) debonding for the beam with unanchored thin CFRP sheets. On the other hand, debonding took place for the thicker sheets with no anchors, while the thicker sheets with fiber anchors underwent cover delamination failure mode despite the fact that the sheets were extended very close to the simple supports. The hysteresis response loops were compared for the different specimens and the analytical envelop curves were predicted resulting in a close agreement to the experimental finding.

Use of sulfur dioxide to reduce postharvest decay and preserve the quality of fresh tomatoes

Tomatoes are an important and versatile crop with a short shelf life. Postharvest losses due to fruit decay and handling are reportedly as high as 30–50% globally; therefore, the agricultural sector would benefit from solutions that target the preservation of crops such as tomatoes. In this study, we investigated the potential use of sulfur dioxide (SO2) to provide postharvest protection against fungal decay in tomatoes whilst maintaining the quality of tomato fruit. Three tomato varieties packed as bulk (3–5 kg) cartons were exposed to SO2-generating sheets applied as either a top sheet over the fruit or a bottom sheet placed on the base of the carton before packing the fruit on the top. The results show that the application of SO2-generating sheets reduced the natural progression of decay on ‘Roma’ tomatoes by up to 60% and up to 80% on ‘Rosa’ tomatoes. Only marginal decay control was observed on ‘Round’ tomatoes. The top sheet application rendered the best results, as the application of the bottom sheet resulted in phytotoxicity in the form of SO2 damage. SO2 application reduced fruit shrivelling, especially when tomatoes were stored at higher temperatures during their shelf life. The application of SO2 on the tomatoes did not have any negative effects on fruit firmness. The results of this study provide a case to further explore the use of SO2-generating sheets on tomatoes to prevent postharvest decay. Differences in varietal physiology may be key to the successful application of this technology. Significance: Tomatoes are a crop that is highly susceptible to postharvest decay. These effects lie mainly with the end consumer. Besides the monetary loss of buying a commodity that rots quickly, pathogens infecting tomatoes are known to produce mycotoxins that pose a risk to human health. With food availability and safety concerns, the application of a product that could reduce these concerns would be beneficial to the agricultural sector.

Mechanical performance of stitched foam-filled honeycomb sandwich panels

Foam-filled Honeycomb Sandwich panels (FHS) are widely used in various industrial applications due to their superior multifunctional properties. However, these sandwich panels fail in some extreme conditions due to interfacial failure between the face sheet and core. To overcome this issue, novel stitched foam-filled honeycomb sandwich panels (SFHS) were fabricated by integrating the top face sheet and bottom face sheet by the stitching technique. Stitching through the face sheet and core is to improve the interfacial strength and increases the mechanical properties of the sandwich panel. FHS and SFHS were prepared by the Vacuum Assisted Resin Transfer molding (VARTM). Flexural, flatwise, and edgewise compression analysis values for SFHS panels are 2.02, 1.28, and 1.25 times higher than for FHS panels. SFHS panel weight increased slightly but had superior mechanical properties than FHS. These innovative SFHS panels can be broadly used for applications including structural, flooring, and body panels.

Innovative stress analysis and machine learning forecasting for semi-trailer truck body durability

This article presents an in-depth analysis of the stress-deformation state (SDS) in the bottom structure of a semi-trailer truck body. Engineering analysis was conducted utilizing the SolidWorks software, focusing on a comprehensive CAD model of the semi-trailer truck body. The study explored variations in SDS parameters resulting from alterations in the geometric parameters of the body bottom elements. The research investigated alterations in static stress and displacement relative to changes in the proportions of the cross-section of the channel while maintaining fixed geometric dimensions of the workpiece, thickness of the workpiece, and the material of the body bottom. Graphical representations were generated to illustrate the variations in static stress, displacement, and safety margin concerning the thickness of the shelf and channel. Additionally, dependencies were derived that correlate static stresses in the channel with the thickness of the channel wall and the thickness of the body bottom sheet. The study results were compiled and summarized, offering valuable insights into the stress-deformation state of the semi-trailer truck body's bottom. Furthermore, machine learning techniques, specifically the RandomForest algorithm, were implemented in a Python environment to predict changes in static stress based on various factors. The model's predictions were validated by comparing predicted static stress values with actual values on a test sample. These findings facilitate efficient selection of appropriately sized elements by predicting static stress values, employing the RandomForest machine learning algorithm.

The relationship between the impact position interference and CAI strength of composite sandwich structures under double impacts

Sandwich structures are susceptible to multiple-impacts, and such multiple-impacts will typically occur at certain distances from each other. Therefore, the influence of five different distances between impact positions (DBIP) and three impact energies on compression after impact (CAI) strength are considered and discussed for honeycomb sandwich structure with composite face sheets in this paper. By comparing two typical impact characteristics, i.e., maximum impact force and displacement, the trend of CAI strength shows a turning-point, which is closely related to the size of the impactor. However, high impact energy (15 J) leads to damage in the bottom face sheet during the second impact, and the presence of damage in both top and bottom face sheet reduces CAI strength, resulting in the turning point of CAI strength not exist. It was observed that there is obvious buckling failure, and some cracks along the width direction from the impact point to the edge after CAI. To provide a more comprehensive understanding of double impacts and CAI behavior, a finite element (FE) model considering different DBIP is developed. In addition, the predicted fraction of energy absorbed by top face sheet, honeycomb core, and bottom face sheet is also obtained to reveal the relationship between the impact position interference and CAI strength.

Experimental and FEM investigation of bending behaviors of S-core sandwich panel composites

Sandwich panel composites have numerous applications in material technology. The sandwich panel composite structure’s mechanical behavior and performance are determined by the material properties and geometry of the relevant components. The top and bottom sheets of the designed sandwich panel composite material are made of stainless steel-316, the core material is aluminum 1050A-0, and the binding element is DP-8405 acrylic adhesive. Three-point bending tests and finite element models were utilized to investigate the bending behavior of S-core composite sandwich panels. Finite element models have been developed to characterize the effect of composite element bending behavior on variations. The specific flexural modulus and strength of composite S-core sandwich structures can be compared to core structures in the literature in general. As a consequence, the minimum weight design was used as a guideline to produce weight and density-efficient hybrid composite sandwich panels. The load-carrying capacity of the composite panel increased as the wall thickness of the S-shaped core increased when the damage loads were examined in the variations. It has been ascertained that as the core height increases, the load-carrying capacity of the composite panel decreases.

Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels (FSP) under high-velocity impact using the explicit non-linear finite element method. Based on the geometric topology of the FSP system, three FSP configurations with the same areal density are derived, namely multi-layer, gradient core and asymmetric face sheet, and three key structural parameters are identified: core thickness (tc), face sheet thickness (tf) and overlap face/core number (no). The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity (BLV), deformation modes, energy dissipation mechanism, and specific penetration energy (SPE). The results show that the FSP system exhibits a significant configuration dependence, whose ballistic performance ranking is: asymmetric face sheet > gradient core > multi-layer. The mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP system. Both BLV and SPE increase with tf, while the raising tc or no leads to an increase in BLV but a decrease in SPE. Further, a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis, based on which the ballistic optimization procedure is also conducted and a design chart is established. This study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

Understanding the formation of “false friends” (hidden lack of fusion defects) in laser beam welding by means of high-speed synchrotron X-ray imaging

This paper provides a fundamental understanding of “false friend” formation, i.e., hidden defects associated with lack of fusion, using an experimental setup that allowed an insight into the processing zone based on high-speed synchrotron X-ray imaging. The setup enabled the welding of a lap joint of AISI 304 high-alloy steel sheets (X5CrNi18-10/1.4301), with the ability to adjust different gap heights between top and bottom sheet (up to 0.20 mm) and to acquire high-speed X-ray images at 100 kHz simultaneously with the welding process. On this basis, a time-resolved description of the “false friend” formation can be provided by visualizing the interaction between keyhole and melt pool during laser welding and solidification processes within the gap area. The bridgeability of the gap was limited due to the gap height and insufficient melt supply leading to the solidification of the bridge. The distance between the solidified bridge and the keyhole increased with time, while the keyhole and melt pool dynamics initiated the formation of new melt bridges whose stability was defined by melt flow conditions, surface tension, and gap heights. The alternating formation and solidification of melt bridges resulted in entrapped areas of lacking fusion within the weld, i.e., “false friends.” Finally, based on the results of this study, a model concept is presented that concludes the main mechanisms of “false friend” formation.

Effect of bottom sheet thickness on weld properties during laser lap welding of aluminum and copper

Effect of bottom sheet thickness on weld properties during laser lap welding of aluminum and copper

Insights into microstructure evolution and interface joining mechanism of ultrasonic spot welded Cu/Cu joint

To understand the underlying microstructure evolution and joining mechanism of ultrasonic spot welded Cu/Cu joint, the microstructure and crystallography analysis were investigated. The grain size, grain boundary, misorientation angle, Kernel Average Misorientation, Schmid factor and crystal orientation along the weld thickness were heterogeneous and unsymmetrical. The changes of corresponding microstructural and crystallographic features were more obvious for the top sheet comparing with the bottom sheet. The {111} <110> texture, nano-sized equiaxed induced by discontinuous dynamic recrystallization and refined elongated grains because of continuous dynamic recrystallization were formed at the welding interface. The nucleated fine grains between the elongated grains attributing to continuous dynamic recrystallization were beneficial to the grain boundary migration and consequent the achievement of the interfacial metallurgical bonding.

Formation mechanism and mechanical strength evaluation of hybrid riveted/solid-state bonded aluminium alloy joint

In this research, an improved friction self-piercing riveting (F-SPR) process with internally threaded rivet and flat die was proposed to achieve hybrid riveted/solid-state bonded connection for low-ductility aluminium alloys. Instead of relying on rivet shank flaring to form mechanical interlock in the existing F-SPR process, a reliable threaded connection was established between the rivet shank and sheets by rapid filling of sheet material into the rivet thread grooves. A perfectly flat joint bottom was formed without inducing large-scale sheet distortion. A series of experimental tests were performed to clarify the joint quality characteristics, formation mechanism and mechanical performance. The results revealed that the quality of newly formed five aluminium threads demonstrated a decline trend from bottom to top. Two kinds of thread formation mechanisms were identified: The mechanism I is solely composed of Filling step and applied to upper four threads; The mechanism II consists of Filling-Fracturing-Welding steps and is applied to the lowest thread. Discontinuous solid-state bonding was formed at the sheet interface around the rivet shank periphery, whilst a bowknot-liked solid-state bonding zone with a weak welded zone and an unwelded zone was formed at the joint centre. Rivet pull-out failure from the bottom sheet was observed for the studied AA7075-T6 joints under both lap-shear and cross-tension loads. The peak loads reached 9.79±0.23 kN and 5.41±0.15 kN in the lap-shear and cross-tension tests, and the corresponding energy absorption was 13.82±0.59 J and 16.42±0.87 J.

Self-Piercing rivet joining of multi-material including CFRP: Experiments and FE modeling

In this study, finite element (FE) analyses based on the arbitrary Lagrangian–Eulerian technique were used to investigate the complex deformation behavior and numerous process variables that arise during the self-piercing riveting (SPR) joining of multi-materials, including carbon-fiber-reinforced polymer, GA590DP, and Al5052-H32 sheets in two- and three-layer combinations. Tensile tests and inverse analysis were conducted to determine the mechanical responses of each joining material, including the rivet, and equivalent strain-based fracture modeling approaches were adopted for a simple but effective crack initiation prediction during the mechanical joining process. The damage distribution and joining characteristics during the SPR joining were then numerically investigated by considering different die profiles. The high predictability of the proposed FE modeling approach in terms of the cross-sectional profile with joint quality indicators, such as the interlock, residual distance between the rivet leg and die, minimum thickness of the bottom sheet, load history, and peak load during mechanical joining, was validated through comparisons between the experiments and FE simulations.

SRR inspired modified psi shaped perfect metamaterial absorber for C-band application

In this research article, a compact and simple design of polarization insensitive perfect metamaterial absorber (PMA) is offered. The design is optimized to target the two mid frequencies of C-band for satellite communication. This novel design is a congress of two modified psi shaped resonators which are surrounded by a split ring resonator (SRR) and an octagonal split ring resonator (OSRR). Dielectric material FR-4 of loss tangent 0.025 and thermal conductivity 0.3 WK-1m−1 is used as substrate whereas the copper (annealed) of thermal conductivity 401 WK-1m−1 and electrical conductivity 5.8 × 107 Sm−1 is used for back copper plate and resonators. This is a compact unit cell of electrical dimension 0.268λ × 0.268λ with 1.6 mm thickness of dielectric substrate and 0.035 mm thickness of bottom copper sheet. The proposed PMA is simulated within the microwave frequency range 5 GHz to 10 GHz with commercially available FIT based high-performance3D EM analyserCST microwave studio suite. The simulation result yields two resonance peaks at 6.15 GHz and 7.36 GHz with fantastic absorption rate 99.99% and 99.40%, respectively. The presented PMA shows polarization insensitivity up to 45° and oblique wide angle incidence up to 75°. Moreover, the simulated outcome is validated by some trusted validation processes; for example- equivalent LC circuit by advanced design software (ADS) and FEM based high-frequency structure simulator (HFSS). A very negligible amount of deviation of resonance frequencies are observed in ADS and HFSS results compared to CST simulated result. Different types of array combinations are also simulated to test the stability of the result and to check the coupling effect. This C-band PMA is recurrently deployed in satellite communication band, defense, security, and stealth coating equipment.