Cushion Performance Research Articles

Directionally arranged flexible bamboo/rubber materials with high cushion performance.

Composites derived from plant fibers are promising reinforcing materials for engineering because of their renewable and easily available characteristics. In this study, a simple pretreatment method was developed to fabricate structurally intact bamboo cellulose scaffolds. Water-stable, flexible, impact-resistant, and high damping ratio bamboo-based rubber composites were synthesized using carboxylated styrene-butadiene latex-impregnated 3D bamboo scaffolds. The composites were prepared by "Ethanol dehydration-delignification-polymer redistribution" strategy. The bamboo cellulose aggregate state structure and multiple crosslinked networks in the composite systems endowed the composites with strong mechanical and damping properties. The prepared composites had a high tensile strength, 67 times that of pure rubber (101.58MPa and 1.25MPa), which is higher than that of reported polymer-based vibration-damping materials, and the hydrostability was also significantly improved. The composites exhibited the characteristic viscoelasticity of polymers, with a recovery angle of 132° after 1000 extreme 180° flexion tests. More importantly, composites maintain a higher effective damping factor (Tan δ=0.5) at room temperature. These bamboo-based rubber composites with excellent comprehensive performances have great potential for engineering applications, particularly for vibration damping, lightweight design, and flexible materials.

Advancements in Bamboo-Based Cushioning Material Manufacturing

The study focuses on producing cushioning packaging material from bamboo fibers. The effects of varying the surface treatment duration and the proportions of foaming agents, adhesives, plasticizers, cross-linking agents, and other components were analyzed in terms of foam density, foaming rate, elasticity, and bubble size. The optimal reagents and the ideal ratios for the different components were identified. The parameters for the foaming process were determined based on a high-efficiency, eco-friendly foaming mechanism. Impact testing was conducted to obtain curves for maximum acceleration versus static stress, dynamic stress versus strain, and dynamic buffering factor versus stress. The study examined the dynamic buffering performance as a function of drop height and compared it to other cushioning materials. The findings indicate that at a height of 450 mm, the bamboo pulp product exhibited a lower peak acceleration value than EPE and EPS in the stress range of 2.8-5.4 kPa, indicating superior cushioning performance under these conditions.

Lightweight and insulation polylactide/poly(butyleneadipate-co-terephthalate) foam with good cushioning performance prepared by supercritical CO2

Herein, biodegradable polylactide (PLA) foams were prepared by supercritical CO2. To address the foaming challenges posed caused by the low crystallization rate and the weak melt strength of PLA, the blending of PLA and poly(butyleneadipate-co-terephthalate) (PBAT) was adopted in this work, the diphenylmethane diisocyanate (MDI) was utilized to boost the compatibility and rheological features of the PLA/PBAT combination. The effects of MDI and PBAT on the crystallization and rheological of the blends were studied. In PLA/PBAT foam, the density prepared was adjustable from 0.02 to 0.025 g/cm3, and the heat-conductivity was a minimum of 0.028 W/(m·K). In addition, the effect of PBAT on PLA cushioning performance was studied, the PLA/PBAT foam prepared has good mechanical properties, which can be used for cushioning packaging and heat insulation. The hardness of the PLA/PBAT blend foam slowly reduced as the PBAT increased, and the elasticity gradually increased. Notably, with 10 phr of PBAT, the compressive strength of the blend foam at 25 ℃ and 60 ℃ was 57 KPa and 55 KPa, respectively. This work broadens the application prospect of PLA and has a positive impact on promoting the high-value utilization of biobased polymers.

Experimental study on the buffering mechanism of EPS bead-sand cushions under single and multiple impacts

As a main functional component of rock sheds in rockfall protection projects, traditional sand cushions have shortcomings such as heavy weight and weak buffering capacity. EPS bead-sand cushion can effectively solve these problems, but its buffering mechanism has not been fully revealed. In this study, a series of impact tests were carried out to investigate the performance of EPS bead-sand cushions with different EPS bead contents, and the evolutions of rockfall impact force, penetration depth, earth pressure, and slab vibration under single impact and multiple impacts were comparatively analyzed. The results show that with the addition of EPS beads, the maximum impact force, the peak earth pressure, and the vibration acceleration are significantly reduced. However, the cushion with high EPS bead content is at risk of being penetrated under high energy or multiple impacts, leading to excessive concentration of impact stresses. Furthermore, the EPS beads can alleviate the hardening of the sand cushion under impact through their deformation coordination, but excessive penetration should be prevented in the design of EPS bead-sand cushions. On this basis, combined with traditional sand cushion design theory, an estimation method for the maximum impact force applicable to EPS bead-sand cushion was proposed. The research results can provide a reference for the design and optimization of cushions in actual projects.

Fluid-structure interaction mechanism in shear thickening fluid/Foam composite for advanced protective structures

Fluid-structure interaction (FSI) between shear thickening fluid (STF) and soft materials is pivotal in designing advanced protective structures. This study delves into the FSI mechanisms within a composite structure known as STF/Foam, which features the infusion of STF into foam. Through comprehensive drop weight tests, the STF/Foam exhibited exceptional cushioning performance. In addition to analyzing FSI from the perspective of structural materials, this study also examines it from the STF standpoint, enabling a multi-faceted understanding of the energy absorption mechanism. To accurately characterize the rheological properties of STF, a novel decoupling method is proposed, accounting for both temporal and spatial inhomogeneities of STF. The research findings indicate that the viscosity variation of STF significantly enhances the energy absorption capabilities of the STF/Foam composite. This study reveals the intricate fluid-solid coupling mechanism between STF and foam. The STF demonstrates a unique combination of shear resistance akin to high-viscosity fluids and the easy flow characteristics of low-viscosity fluids. The modulation of STF viscosity optimizes the structural deformation pattern, thereby rationalizing the energy absorption mechanism of the composite. Consequently, STF/Foam showcases superior cushioning performance. Further investigation into various parameters associated with STF and foam highlights their influence on the structural cushioning performance. These insights lay a theoretical foundation and provide design guidelines for the future development of STF-based controllable protective structures.

Evaluating the Use of Predicted Cushion Curves for Comparing the Performance of Some Sustainable Cushion Systems

ABSTRACTThis paper studies the cushion performance of a range of sustainable cushion systems and applies two methods to estimate cushion curves from limited cushion test data. The methods employed were previously developed to allow for (1) the conversion of cushion curves representing a material's performance for a given drop height and sample thickness to alternative (non‐measured) drop heights and sample thicknesses and (2) generating a complete cushion curve for a given thickness and drop height from a single acceleration (shock) measurement. The results include those generated for medium‐density polyethylene (MDP) closed‐cell foam for benchmarking of the materials and to aid in validating the approach. The results indicate that predicting cushion curves from single shock measurements is generally accurate for polymeric materials (MDP closed‐sell foam and HDPE inflated bag) but much less so for organic materials (sugarcane bagasse and perforated cardboard). Finally, all alternative cushioning materials and systems evaluated are shown to only be effective for very low static stresses. This finding demonstrates that much higher volumes are required when using the alternative materials to achieve the same cushioning effectiveness as MPD foam.

Sustainable lignocellulose bio-based foam with good cushioning performance and thermal insulation for transportation packaging

Bio-based foams have been extensively employed as eco-friendly alternatives for cushioning materials in transportation. Herein, a series of novel bio-based foams with truss-like microstructures are successfully fabricated using lignocellulosic fibers via the Pluronic F127 soft template method. The lignocellulosic fiber-based foams (F-LFFx) exhibit low density (0.055 g/cm3), excellent compressive strength (0.25 MPa at 80% strain), and good recoverable compressibility (80%–90% under 50% strain). Products packaged with F-LFFx undergo a peak impact acceleration of merely 214.5 G after contacting the ground in drop impact testing, which is only 33% of the molded pulp. Additionally, F-LFFx have superior cushioning performance during simulated vibration testing. Furthermore, thermal images reveal the superior efficacy of F-LFFx in mitigating the impact of external temperatures on enclosed spaces compared with commercial expanded polyethylene (EPE) and corrugated cardboard, exhibiting a temperature difference of only 8.7°C in a hot environment at 80°C and −8.5°C in a cold environment at −78°C. Thus, F-LFFx are excellent candidates for vibration and impact protection as well as thermal insulation in transportation.

Simulated logistical transport effects on textural change of wax apple using different packaging types during storage time

The textural damage caused by logistics transport is a major problem during the post-harvest logistics and storage time of agricultural products. To address the issue, this study investigated the impact on the textural change of wax apple with different packaging types by conducting international safe transit association 6-amazon. com-sioc type A (ISTA 6 A) tests and measured the changes in related indicators over the eight-day storage time period at 15 ℃. The results demonstrated that compared to non-vibrated wax apple of the same packaging type, the damage index of the vibration-treated wax apple increased to 0.39 at the end of storage time. This led to more noticeable damage to fruit texture in the vibration-treated wax apple. With the same outer packaging type, different types of expanded polyethylene (EPE) cushioning materials presented varying degrees of textural damage following vibration treatment. The order was double-layer foam net (DL-FN, 0.23) < single-layer foam net (SL-FN, 0.38) < EPE liner (EPE-L, 0.50). The superior cushioning performance of DL-FN could distribute vibratory energy across the entire wax apple to reduce partial textural injury, but SL-FN provided weaker cushioning protection. Furthermore, it was more beneficial for the dissipation of respiratory heat to suppress the related cell-wall enzymes activities and prevented internal cottony softening of wax apple by maintaining an appropriate environment within the packaging, while EPE-L prevented respiratory heat dissipation and water diffusion. Using the same cushioning type, no significant difference was observed in the damage of fruit texture between the wax apple packaging by foam box (FB, 0.25) and corrugated box (CB, 0.23). The finding suggested that when the outer package had sufficient supporting performance, the cushioning type required not only adequate cushioning property, but also excellent vapor and gas permeability in order to facilitate respiratory heat diffusion and better protect the textural integrity of the wax apple in the process of logistics. This protection was crucial for the development of wax apple in e-commerce logistics.

욕창예방 방석의 충격 흡수 시험 장치 개발과 적용

Bedsores mainly occur in bedridden patients who have to lie in the same position for a long period of time, or in people with spinal cord disabilities who use wheelchairs and cannot change positions on their own. In order to prevent excessive pressure on the skin over bone protrusions, which causes circulation problems in peripheral blood vessels and causes bedsores, the Ministry of Food and Drug Safety has designated and operates bedsore prevention cushions as medical devices. ISO, an international standardization organization, established and operates ISO 16840-2 to evaluate the performance of cushions to prevent bedsores for wheelchair users. The purpose of this study is to design and develop a test device to apply this international standard to the test and evaluation of domestic bedsore prevention cushions. In particular, the main purpose was to develop a shock absorption test device to determine how effectively bedsore prevention cushions cushion the shock that occurs when a wheelchair collides with the road surface on a bump or pothole.&#x0D; The impact absorption test device was manufactured by modifying part of the guidelines of ISO 16840-2. In the above international standard, the crash plate is to be supported with a piece of wood block. However, in this study, the time delay that may occur during removal of the block was shortened and convenience was improved by using a roller system instead of wooden block to drop the object. Using the manufactured test device, a shock absorption test was conducted on an air-grid type bedsore prevention cushion and a hybrid bedsore prevention cushion that is a mixture of foam type and air grid type. When the human hip model falls, the falling acceleration was reduced to 63% with the air-grid type cusion compared to the value with no cushion, and it decreased to 42% with the hybrid cushion. However, the occurrence of bedsores is affected not only by the impact force applied to the skin when the wheelchair collides with the ground, but also by the breathability and humidity of the impact area, so it is necessary to comprehensively evaluate various risk factors, including shock absorption tests. The roller-type shock absorption test device will be proposed as an amendment to ISO 16840-2 to the International Standards Committee.

Impacts on Crash Cushions—Analysis of the Safety Performance of Passenger Cars with Improved Safety Equipment Compared with Test Vehicles Based on Assessment Criteria as Defined in EN 1317

To assess the safety performance of crash cushions, guidelines or standards are used. Real-life accident conditions might deviate substantially from the approval test conditions. The objective of this study is to evaluate occupant safety in passenger cars in the event of an impact against a crash cushion. Real-life accident configurations deviate significantly from the impact configurations used in the approval test EN 1317. In four different tests, two vehicles regularly used in EN 1317 and two vehicles with improved safety equipment (airbag, pretensioner, and load limiter) are used. The impact speed is 100 km/h, whereas the crash cushion is designed for an impact speed of 80 km/h. One configuration is defined as a full overlap, and one has a 50% offset. The ASI (Acceleration Severity Index), THIV/OIV (Theoretical Head Impact Velocity/Occupant Impact Velocity), and PHD/ORA (Post Head Deceleration/Occupant Ride down Acceleration) are calculated from the acceleration signals. The offset impact was more serious for both the regularly used vehicle and the vehicle with improved safety equipment. Vehicles with improved safety equipment do not have any influence on these criteria. It is apparent that new occupant safety technologies will not have any influence on occupant safety performance. The criteria currently in use are more likely to be of use for assessing vehicle performance rather than occupant safety.

The buffering performance of a flexible buffer-sand layer composite cushion used for rockfall shed: experimental and numerical investigation

The buffering performance of a flexible buffer-sand layer composite cushion used for rockfall shed: experimental and numerical investigation

Seismic performance of soft rock tunnel under composite support conditions

In order to effectively improve the seismic and impact resistance performance of soft rock tunnels, a composite support method was proposed and validated in the paper. The UDEC (Universal Distinct Element Code) model of soft rock layers was established, and the movement and subsidence characteristics of the roof and floor of the rock layers under impact loads was simulated and calculated. As a result, a composite support scheme with good cushioning performance was proposed. The top and sides of the tunnel were supported by a combination of anchor rods of different lengths and metal mesh, reinforced by steel beams and vibration absorbing filler around. The anchor rod was designed as a segmented loading structure, and can be set to different preloading forces based on the internal deformation of the rock layer. The dynamic response testing scheme was designed, and the results indicate that the segmented loading anchor rod has a significant buffering effect on the response to impact load, and can provide reasonable tension feedback at different stages. Research has found that when the water cement ratio is 0.5-1.5, the curing efficiency and strength are both higher. In order to compare the seismic performance of composite support and traditional constant resistance anchor rod support, local blasting experiments were conducted. Based on a blasting vibration tester, a data detection and transmission system were designed to obtain the vibration speed of the tunnel roof during the vibration process. The research results show that composite support can reduce the maximum vibration by more than 40 %, stabilize the fragmentation coefficient at 1.38, and have a very significant vibration reduction effect.

Bioinspired Structural Composite Flexible Material with High Cushion Performance.

Impacts occur everywhere, and they pose a serious threat to human health and production safety. Flexible materials with efficient cushioning and energy absorption are ideal candidates to provide protection from impacts. Despite the high demand, the cushioning capacity of protective materials is still limited. In this study, an integrated bionic strategy is proposed, and a bioinspired structural composite material with highly cushioning performance is developed on the basis of this strategy. The results demonstrated that the integrated bionic material, an S-spider web-foam, has excellent energy storage and dissipation as well as cushioning performance. Under impact loading, S-spider web-foam can reduce peak impact forces by a factor of 3.5 times better than silicone foam, achieving unprecedented cushioning performance. The results of this study deepen the understanding of flexible cushioning materials and may provide new strategies and inspiration for the preparation of high-performance flexible cushioning materials.

Cushion performance of eco-friendly natural rubber latex foam composite with bamboo leaf fiber for impact protection of guava

This study investigated the performance of an eco-friendly cushion foam net comprised of natural rubber latex and bamboo leaf fiber. It compared this innovative BambooLatex foam net (thickness of 2.52 and 3.57 mm) with a commercial expanded polyethylene foam net (EPE) (thickness of 5.85 and 7.30 mm) as well as a control group with no cushioning. Key cushioning properties including thickness, mass, modulus, compressive strength, damping coefficient, and energy absorption were investigated. To assess cushion performance was conducted a simulated impact test involving guavas dropped from varying heights (200, 300 and 400 mm). The impacted fruits were subsequently stored at 20 ºC and 75% relative humidity for 4 days. During this period, we monitored bruising development using an image analysis technique, evaluating bruise area, fractal dimension, and grayscale as fruit quality parameters. Our findings indicated that thicker cushions offered superior protection, exemplified by the 7.30 mm EPE. However, the cushion material's damping coefficient and energy absorption capacity significantly influenced its ability to reduce impact energy. This resulted in the thinner BambooLatex foam net performing comparably to the EPE foam net. All cushion treatments significantly reduced impact bruising of guava fruit to less than 2% of the bruise area) as compared to the control (4–7% of the bruise area). There was no significant difference in fractal dimension and grayscale values among the four cushioning treatments. The bruise area parameter was recommended as it gave a better resolution for classifying impact fruit bruising severity in the cushion study. Ongoing developments are aimed at further reducing the weight of the eco-friendly natural rubber latex cushion and incorporating additional active functions.

Investigation on dynamic performance of soilbag cushion using shaking table tests

Soilbag cushion is one of the promising base isolation methods to reduce seismic energy transfer from ground to building structure. In this study, a series of shaking table tests were conducted comparatively on foundation models with soilbag cushion and sand cushion to evaluate their dynamic performance. The test results indicate that soilbag cushion could significantly reduce acceleration response and accumulated settlement compared to sand cushion. And the relatively smaller amplitude of dynamic lateral earth pressure measured on contact surface of soilbags within soilbag cushion also indicates its stability during oscillation. The advantages of soilbag cushion for energy dissipation and damping are more easily highlighted under the condition of high-acceleration, high-frequency or high uniformly distributed load. The dynamic performance of soilbag cushion is dependent on embedded depth and thickness. It is most effective for soilbag cushion to be arranged near the rigid footing of building structures; it is suggested that the number of layers of soilbag cushion be controlled on the premise of the designed ratio of the thickness to the width of soilbag cushion ranging from 0.125 to 0.4 for low- or middle-rise masonry buildings in practical engineering.

Effects of extreme cyclic loading on the cushioning performance of human heel pads under engineering test condition.

Human heel pads commonly undergo cyclic loading during daily activities. Low cyclic loadings such as daily human walking tend to have less effect on the mechanical properties of heel pads. However, the impact of cyclic loading on cushion performance, a vital biomechanical property of heel pads, under engineering test condition remains unexplored. Herein, dynamic mechanical measurements and finite element (FE) simulations were employed to explore this phenomenon. It was found that the wavy collagen fibers in the heel pad will be straightened under cycle compression loading, which resulted in increased stiffness of the heel pad. The stiffness of the heel pads demonstrated an inclination to escalate over a span of 50,000 loading cycles, consequently resulting in a corresponding increase in peak impact force over the same loading cycles. Sustained cyclic loading has the potential to result in the fracturing of the straightened collagen fibers, this collagen breakage may diminish the stiffness of the heel pad, leading to a reduction in peak impact force. This work enhances understanding of the biomechanical functions of human heel pad and may provide potential inspirations for the innovative development of healthcare devices for foot complex.

Development of Deproteinized Natural Rubber Latex Foam for Seat Cushions

In the transportation industry, seat cushions are crucial since they are directly responsible for the comfort and safety of the occupant. In this study, recently developed deproteinized natural rubber (DPNR) latex foam is used to make seat cushions for the first time through the Dunlop batch foaming process. A CONFORMat™ pressure sensor system and a mannequin were used to investigate the pressure-relief performance of seat cushions made from DPNR latex foam. Flexible polyurethane (PU) and memory foam (PM) were used as a comparison. The study found that DPNR latex foam has a lower peak pressure value than PU foam, comparable to PM foam. The vibration transmissibility properties of the foam samples were examined using a UCON VT-9008 vibration machine according to ASTM D3580-95. DPNR latex foam has the lowest attenuation frequency, which could be related to the low stiffness and high resilience properties of the material. Overall, the findings suggest that the novel DPNR latex foam has both excellent pressure-relief and vibration isolation performance, making it an ideal candidate material for seat cushions intended for the transportation industry.

Two‐step foaming process for fabrication of flexible polyurethane foam composites with spring‐like air‐layer structure

AbstractDue to its exceptional mechanical properties, polyurethane (PU) foam has found wide application in various fields. Microcellular foaming not only reduces weight but also enhances the cushioning properties of PU. However, current foaming methods have limitations in improving performance. Therefore, this study aimed to construct spring‐like sandwich‐structured flexible PU foam composites (SFFCs). These composites were prepared using a two‐step foaming method, utilizing a precise amount of polyol and isocyanate as raw materials, at room temperature (28–35°C). In the preparation process, warp‐knitted spacer fabrics (WKSFs) with spring‐like structures were encapsulated in the middle layer, while the top and bottom layers consisted of PUF (flexible PU foam with different ring radius differences) formed through the foaming process of polyol and isocyanate. The study focused on investigating the influence of the ring radius difference (r = 1, 1.5, 2) and the two‐layer layout (staggered, diagonal, overlapping) of the WKSFs on the compression and cushioning properties. The experimental results revealed a significant improvement in the mechanical properties of the PU with the incorporation of WKSFs. Particularly noteworthy was the excellent cushioning performance exhibited by the two‐layer WKSFs sample, RPUS‐1, in the dynamic impact test. RPUS‐1 absorbed 94.3% of the energy and reduced the impact value to 3921 N, which is 848 N (17.7%) lower than that of PU foam. Furthermore, even after 20 cycles of compression testing, the SFFCs retained excellent compressive properties, with the compressive stress only decreasing from 0.34 to 0.19 MPa. In conclusion, this study expands the application of PU in cushioning, demonstrating their potential in providing improved cushioning properties.

Research on hierarchical cylindrical negative stiffness structures’ energy absorption characteristics

Negative stiffness (NS) structures possess distinctive mechanical properties and exhibit promising potential for diverse applications. In this paper, we presented an innovative hierarchical design to further enhance the capabilities of NS structures. The dynamic and static performance of the normal and hierarchical cylindrical NS structures were investigated and compared with experiments and numerical simulation. The results demonstrated that the hierarchical structures displayed superior cushioning performance relative to the traditional one. The presented approach offers a novel method to enhance cylindrical NS structures and serves as a valuable reference for future research in this field.

A novel reinforced cylindrical negative stiffness metamaterial for shock isolation: Analysis and application

Negative stiffness (NS) metamaterials have been widely studied in the fields of shock isolation and energy absorption due to their special properties. For various application scenarios, many types of NS metamaterials have been proposed, such as 2D honeycomb, 3D cube, hollow cylinder. However, when installation space is limited, the hollow cylindrical NS metamaterials may not achieve buffering effect due to its weak stiffness. In this paper, a cylindrical negative stiffness structure with inner hollow parts filled by inclined beam elements is proposed, which can obtain enhanced stiffness and energy absorption by improving space utilization. Theoretical analysis, numerical simulation and experimental validation were carried out to study the quasi-static and dynamic mechanical properties of the structure. Finally, the structure was applied as a cushion in a non-pyrotechnic separator, which could achieve good cushion performance. This work is expected to provide more potential for the applications of cylindrical negative stiffness structures.