Synthetic Foam Research Articles

Free vibration analysis of rotating pretwisted composite sandwich conical shells with multiple debonding in hygrothermal environment

This paper presents a finite element based method to study the influence of elevated temperature and moisture absorption on the free vibration behavior of rotating pretwisted sandwich conical shells consisting of two composite face-sheets and a synthetic foam core. The sandwich structure is assumed to contain single or multiple debonding present either in the face-sheets or at the interface between the face-sheets and core. The finite element formulation consists of an eight-noded isoparametric shell element having five degrees of freedom at each node. Lagrange’s equation is employed to derive the governing equation for free vibration analysis at moderate rotational speeds while the multi-point constraint algorithm is used to model the debonding region present in the composite sandwich shells. Numerical results are presented to depict the effects twist angle, thickness ratio of core to face-sheets, rotational speed and single or multiple debonding on the natural frequency of the composite sandwich conical shells at elevated temperature and moisture concentration.

Using Porcine Cadavers as an Alternative to Human Cadavers for Teaching Minimally Invasive Spinal Fusion: Proof of Concept and Anatomical Comparison.

Training surgeons to perform minimally invasive spinal (MIS) surgery is difficult because there are few realistic alternatives to human cadavers which are expensive and require special handling. In this study we report a protocol for performing an MIS training course on a fresh porcine cadaver. We find that the porcine lumbar spine closely resembles the human spine in terms of the vertebral and discal anatomy. Notable differences include a lower disc height and shallower diameter. We obtained fresh porcine cadavers weighing 40-70 kg from local farmers that had been gutted and bled. We position the cadaver prone on a backboard and set up the operating room with biplanar fluoroscopy. During approach and cage insertion, we found that the tactile feedback obtained is realistic and allows surgeons to familiarize themselves with the procedure. Porcine cadavers were also an excellent tool for practicing pedicle screw fixation due to the larger pedicles. Five training courses involving eight surgeons noted that except for anatomical differences the training course was equivalent to training on human cadavers and unanimously preferred training on porcine cadavers to synthetic foam models. We conclude that porcine cadavers are a useful model for training surgeons in MIS surgery. Routine use of porcine cadavers may increase the availability of MIS surgery training.

Mycelium bio-composites in industrial design and architecture: Comparative review and experimental analysis

Recent convergence of biotechnological and design tools has stimulated an emergence of new design practices utilizing natural mechanisms to program matter in a bottom-up approach. In this paper, the fibrous network of mycelium—the vegetative part of fungi—is employed to produce sustainable alternatives for synthetic foams. Current research on mycelium-based materials lacks essential details regarding material compositions, incubation conditions, and fabrication methods . The paper presents the results of ongoing research on employing mycelium to provide cleaner architecture and design products with sustainable lifecycles. The paper opens with a critical review of current projects, products, and scientific literature using mycelium in design and architecture. In the second section, material properties of varied fungi-substrate compositions and fabrication methods are evaluated and compared through changes in essential chemical parameters during fermentation, visual impression, water absorbency , and compression strength tests. Then, potential architecture and design implications related to the material properties are discussed. Results indicate a clear correlation between fungi, substrate, mold properties, and incubation conditions on final material characteristics, depicting a clear effect on material density, water absorbency, and the compressive strength of the final bio-composite. Finally, two primary case studies demonstrate implications for mycelium-based composites for circular design and architectural applications. The study shows that in order to produce desirable designs and performance within an inclusive circular approach, parameters such as material composition and fabrication conditions should be considered according to the target function of the final product throughout the design process. • Mycelium employed to upcycle regional tree-pruning waste into cleaner products. • Materials and methods for fabricating mycelium composites are discussed. • Clear correlation is shown between material composition and material properties. • Implications for sustainable architecture and design products are presented.

Synthetic open cell foams versus a healthy human vertebra: Anisotropy, fluid flow and μ-CT structural studies.

Commercial synthetic open-cell foams are an alternative to human cadaveric bone to simulate in vitro different scenarios of bone infiltration properties. Unfortunately, these artificial foams do not reproduce the anisotropic microstructure of natural bone and, consequently, their suitability in these studies is highly questionable. In order to achieve scaffolds that successfully mimic human bone, microstructural studies of both natural porous media and current synthetic approaches are necessary at different length scales. In this line, the present research was conducted to improve the understanding of local anisotropy in natural vertebral bone and synthetic bone-like porous foams. To attain this objective, small volumes of interest within these materials were reconstructed via micro-computed tomography. The anisotropy of the microstructures was analysed by means of both their main local histomorphometric features and the behaviour of an internal flow computed via computational fluid dynamics. The results showed that the information obtained from each of the micro-volumes of interest could be scaled up to understand not only the macroscopic averaged isotropic and/or anisotropic behaviour of the samples studied, but also to improve the design of macroscopic porous implants better fitting specific local histomorphometric scenarios. The results also clarify the discrepancies in the permeability obtained in the different micro-volumes of interest analysed. STATEMENT OF SIGNIFICANCE: A deep insight comparative study between the porous microstructure of healthy vertebral bone and that of synthetic bone-like open-cell rigid foams used in in vitro permeability studies of bone cement has been performed. The results obtained are of fundamental relevance to computational studies because, in order to achieve convergence values, the computation process should be limited to small computation domains or micro-volumes of interest. This makes the results specific spatial dependent and for this reason computation studies cannot directly capture the macroscopic average behaviour of an anisotropic porous structure such as the one observed in natural bones. The results derived from this study are also important because we have been able to show that the specific spatial information contained in only one healthy vertebra is enough to capture, from a geometric point of view, the same information of "specific surface area vs. porosity" - in other words, the same basic law - that can also be found in other human bones for different patients, even at different biological ages. This is an important finding that, despite the efforts made and the controversies formulated by other authors, should be studied more thoroughly with other bone species and tissues (healthy and/or diseased). Moreover, our results should help to understand that, with the extensive capabilities of current 3D printing technologies, there is an enormous potential in the design of biomimetic porous bone-like scaffolds for bone tissue engineering applications.

Predicting fracture mechanisms in synthetic foam sandwiches with multi-layered cores using extended cohesive damage model

This paper introduces an investigation on fracture mechanisms of synthetic foam sandwiches with graded multi-layered cores. The extended cohesive damage model (ECDM) is used in investigating detailed fracture mechanisms of this kind of synthetic foam sandwich panels under quasi-static 3-point bending. The ECDM prediction shows very good agreements with experimental work on investigating the sandwiches with homogeneous core and the core with four graded layers. This investigation has found that the failure modes of sandwich panels with multi-layered cores are sliding shear failure dominated fracture in the core along the path above the core-bottom sheet interface instead of pure debonding at interfaces. It has been also found an excellent mechanical performance when the core has multiple graded layers in the investigated sandwiches compared to the case of homogenous core. It is the first time that the correlation between loading capacity and number of graded layers in the core of the investigated synthetic foam sandwiches is explored. The ECDM predicted loading capacity of the investigated sandwich panel with an 8-layered core is increased by 70% compared to a homogenous core. This investigation also shows that the ECDM is a robust tool for predicting fracture mechanisms of synthetic foam sandwiches.

ЗАЛЕЖНІСТЬ ВЛАСТИВОСТЕЙ КОМПРЕСІЙНОЇ ПІНИ ВІД РОБОЧИХ ПАРАМЕТРІВ ПРОЦЕСУ ГЕНЕРУВАННЯ ПІНИ

Для системи пожежогасіння компресійною піною наведено результати дослідження залежності властивостей компресійної піни, а саме: стійкості, кратності, адгезії, витрат піноутворювача та води, тривалості гасіння від робочих параметрів процесу генерування піни, таких як тип та концентрація піноутворювача, робочий тиск у системі генерування піни.Наведено результати випробування з визначення тривалості гасіння компресійною піною низької кратності модельного вогнища пожежі 55 В і показника вогнегасної здатності за класом пожежі. У разі гасіння компресійною піною низької кратності та їх порівняння з відповідними показниками ефективності повітряно-механічної піни середньої кратності, одержаної з використанням ежекційних стволів-генераторів піни.

Development of a high-temperature inorganic synthetic foam with recycled fly-ash cenospheres for thermal insulation brick manufacturing

Abstract In this study, a novel inorganic synthetic solid foam composed of recycled fly-ash cenospheres (FACs) is developed with low-density, good thermal insulation performance, and reasonable mechanical strength. The manufacturing process utilizes low-fraction clay binder materials diluted in water, enabling a self-assembling mechanism assisted by natural capillary effect to form minimal contacts among the FACs. The microstructure and minimal contact formation were confirmed by optical and electron microscope imaging. Both thermal and mechanical properties of the fly-ash cenosphere synthetic solid foam (FAC-SSF) materials were experimentally studied as functions of key material parameters including cenosphere particle size and clay content. A numerical model was developed to predict the effective thermal conductivity of FAC-SSF using a three-step homogenization method which takes into account different thermal percolation paths within the material. The inorganic synthetic foam developed has the potential for thermal insulation applications taking advantage of their relatively simple, low-cost, and scalable manufacturing process, minimal use of binder materials, and relatively high mechanical strength and highly tailorable properties.

Glass Microspheres

Glass microspheres are microscopic spheres of glass manufactured for a wide variety of uses in thermal insulation coating, putty, plastic casting polyester, radome, synthetic foam, adhesives, printed circuit board substrate, bowling, fan blades, and caulking materials, emulsion explosives, golf, sealant, pipeline insulation materials, artificial marble, PVC, low density oil drilling, light cement etc. Glass microspheres are usually between 1 and 1000 micrometres in diameter, although the sizes can range from 100 nanometres to 5 millimetres in diameter. Microspheres are spherical particles that can be distinguished into two categories; solid or hollow. This paper presented a general overview of glass microspheres.

A Mechanical Comparison of the Compressive Force Generated by Various Headless Compression Screws and the Impact of Fracture Gap Size.

Background: There is evidence that interfragmentary fracture gap size may affect the compression achievable with a modern headless compression screw (HCS). This mechanical study compared the compression achieved by 3 commercial HCS systems through various fracture gaps: CAPTIVATE Headless (Globus Medical, Inc, Audubon, Pennsylvania), Synthes (DePuy Synthes, Westchester, Pennsylvania), and Acumed Acutrak 2 (Acumed LLC, Hillsboro, Oregon). Methods: Screws were inserted into a custom test fixture composed of polyurethane synthetic bone foam fragments, separated by a layer of easily compressible polyurethane foam simulating a fracture gap. Compression was measured after final insertion and countersinking. The effect of the interfragmentary fracture gap size on the compression generated was also investigated. Results: The CAPTIVATE Headless 3.0 mm screw (70.1 ± 5.7 N) and the Synthes 3.0 mm screw (64.9 ± 7.3 N) achieved similar compressive forces after final countersink. Similar comparisons were found for the CAPTIVATE Headless 2.5 mm and Synthes 2.4 mm screws, and the CAPTIVATE Headless 4.0 mm and Acutrak 2 Standard screws. The final compression of the CAPTIVATE Headless 2.5 mm and Synthes 2.4 mm screws was not significantly affected when the fracture gap was doubled from 2 to 4 mm, but was reduced significantly by 95.9% with the Acutrak 2 Micro screw. Conclusion: When comparing like-sized screws, the CAPTIVATE, Synthes, and Acutrak 2 HCS systems demonstrated similar potential compressive forces. However, compared with the CAPTIVATE Headless and Synthes HCS systems, which are inserted with a compression sleeve that is not gap distance-dependent, the Acutrak 2 HCS system demonstrated less compression when the simulated fracture gap size was increased to 4 mm.

Tibial Implant Fixation Behavior in Total Knee Arthroplasty: A Study With Five Different Bone Cements

BackgroundThe objectives of this study are to (1) evaluate if there is a potential difference in cemented implant fixation strength between tibial components made out of cobalt-chromium (CrCoMo) and of a ceramic zirconium nitride (ZrN) multilayer coating and to (2) test their behavior with 5 different bone cements in a standardized in vitro model for testing of the implant-cement-bone interface conditions. We also analyzed (3) whether initial fixation strength is a function of timing of the cement apposition and component implantation by an early, mid-term, and late usage within the cement-specific processing window. MethodsAn in vitro study using a synthetic polyurethane foam model was performed to investigate the implant fixation strength after cementation of tibial components by a push-out test. A total of 20 groups (n = 5 each) was used: Vega PS CrCoMo tibia and Vega PS ZrN tibia with the bone cements BonOs R, SmartSet HV, Cobalt HV, Palacos R, and Surgical Simplex P, respectively, using mid-term cement apposition. Three different cement apposition times—early, mid-term, and late usage—were tested with a total of 12 groups (n = 5 each) with the bone cements BonOs R and SmartSet HV. ResultsThere was no significant difference in implant-cement-bone fixation strength between CrCoMo and ZrN multilayer-coated Vega tibial trays tested with 5 different commonly used bone cements. ConclusionApposition of bone cements and tibial tray implantation in the early to mid of the cement-specific processing window is beneficial in regard to interface fixation in TKA.

Low Temperature Study on the Behavior of Reinforced Bitumen in Asphalt via Addition of Synthesized Basalt

Abstract In traffic engineering, one of the problems presented by slate pavement, besides being costly to repair and maintain, is the insufficient resistance of bitumen against traffic loads in low temperatures. In this study, the effect of synthesized basalt modifier has been assessed via four different tests to improve bitumen performance. Hence, the enhancement of resistance to traffic loads at low temperatures as an essential problem of asphalt superstructure in traffic engineering has been taken into account. The bending beam rheometer test was conducted at three temperatures of −6°C, −12°C, and −18°C, and the softening point and permeability index tests were performed. A Fourier transform infrared spectroscopy test was carried out to identify the structure of the modifier additives. The prepared samples of synthetic basalt-reinforced foam bitumen and synthetic basalt bitumen were examined, each having three values of 2, 4, and 6 % of reinforcement agent. The results showed that the bitumen mixture including 6 % synthetic basalt has the lowest operating temperature compared with the base counterpart having the same resistance to traffic loads at low temperatures. In addition, the temperature sensitivity of synthetic basalt-reinforced foam bitumen depressed by diminishing the modifier amount because adding the 6 % synthetic basalt to the base bitumen increased it from −0.65 to 0.91. The obtained results indicated that the achieved modified bitumen with optimal temperature sensitivity could be a good choice for employment in road construction.

Sound Absorption Coefficient and Water Content Responses in Acoustic Analysis Based on Renewable Polyurethane Foam Composites

In physiological health, negative effects are felt when unwanted noise is present. Given the negative effects of the unwanted noise, it become important to examine how environmentally-friendly and efficient sound absorbing materials could be developed. Some of the materials associated with acoustic absorption properties entail polymer foams. Particularly, the foams aid in controlling noise. The central purpose of this study was to examine renewable polymer (PU) foam composites’ aspects of moisture content and acoustical properties. Four major parameters that were evaluated included the thickness of the sample, the type of filler, the ratio of the fillers, and the nature of the monomer. A design of experiment (DoE) technique was employed. To prepare the PUs foams, 28 mm and 100 mm were selected as diameters for the cylindrical shapes on focus. Plotting the main effects was achieved through ANOVA, upon which variations in the role and performance of the selected input factors were discerned. From the findings, it was established that when bio-epoxy (B) was used in conjunction with renewable PU foams, the moisture content was greater than the case involving petroleum based PU foam synthesis. Hence, renewable PU foam composite is seen to be realized at 0.9, especially if the filler ratios and size are increased; with the experimental conditions set at 3 kHz. Overall, the study established that the renewable Pus’ state of sound absorption exhibits good agreement with the case of synthetic PU foam.

Ефективність поглинання нафти сорбентами природного та штучного походження

Розглянуто глобальну екологічну проблему контамінації нафтою водних ресурсів та методи боротьби з нею. Досліджено ефективність простих і доступних способів очищення забрудненої нафтою води. Виявлено економічну вигоду від застосування сорбуючого методу боротьби з проблемою порівняно з механічним та диспергуючим методами. Сорбуючий метод є найменш економічно затратний та дуже зручний у застосуванні, оскільки передбачає використання широкого спектра сорбентів нафти. Перспективність цього методу полягає у доступності деяких природних і штучних матеріалів, які можна використати як сорбенти нафти. Проаналізовано практичне значення, переваги та недоліки природних і штучних сорбентів нафти, які широко використовують у різних галузях промисловості та національного господарства. Виявлено максимальну поглинальну здатність бавовни як природного матеріалу, який швидко абсорбує компоненти нафти та не потребує використання додаткових ресурсів для боротьби з контамінацією води. З'ясовано, що природний абсорбент чорне вугілля малоефективне порівняно з іншими методами очищення води від нафти та потребує тривалого часу та додаткових уловлювачів забруднення, що є економічно невигідно. Синтетичний полімер пінопласт і біле вугілля поглинають нафту за короткий час, однак в останньому випадку на поверхні води залишаються незначні плями. Виявлено, що не вся частина білого вугілля прореагувала з нафтовою масою, а випала в осад. Тому за ефективністю поглинання нафти природними та синтетичними матеріалами можна виділити такий ряд досліджених матеріалів: чорне вугілля → пінопласт → біле вугілля → бавовна.

Impact of Different Oil Mixtures on Foam in Porous Media and in Bulk

Foam can be applied to enhance oil recovery from a reservoir. Currently, to understand and model the behavior of foam in an oil reservoir, experiments need to be conducted in the presence of the specific crude oil, and extrapolating from one crude oil to another is not possible. It is therefore desirable to model the impact of a crude oil on foam solely based on the crude-oil composition. This would allow one to efficiently screen reservoirs for foam application. Here we investigate the behavior of foam in the presence of a crude oil and in the presence of mixtures of pure components, which we choose based on the gas chromatography analysis of the crude oil as well as its total acid number and total base number. To analyze the impact of an oil mixture on bulk foam we shake test tubes with surfactant solution and either a mixture of pure oil components or crude oil and analyze foam height and liquid height over time. We also conduct experiments in a porous medium, where we coinject mixtures of pure components, surfactant solution, and gas. We fix the oil injection rate and vary the ratio of the gas to surfactant solution. We use the following organic compounds (OC) to represent the crude oil: toluene (an aromatic), oleic acid (an organic acid), octanol (an organic base), methylcyclohexane (a cycloalkane), dimethyl sulfoxide (an organosulfur), n-octane, and hexadecane. However, when one or all of the first components is added to a 50/50 (vol %) mixture of n-octane and hexadecane, in proportions similar to their presence in the crude oil, the impact of the oil mixture on foam (both in bulk and in porous media) is only slightly different from the impact of the n-octane and hexadecane mixture. We formed a “synthetic” crude oil, with its composition mimicking the composition of a crude oil and its total acid/base number. Although the pure OC and synthetic crude oil weaken foam in bulk and in porous media, their impact on foam was less severe than the impact of the crude oil on the foam. Based on the composition of an oil mixture and the impact of its components, separately, on foam, it is not clear how to predict the impact of the oil mixture on foam in bulk or porous medium. However, in our case we find a good correlation between the foam apparent viscosity in porous media and the product of the bulk foam half-life and initial volume. One implication is that if either the half-life or initial volume of bulk foam is poor, the foam performs poorly in the porous medium.

A Tool to Generate Grain-Resolved Open-Cell Metal Foam Models

The development and use cases of an open-source filter for DREAM.3D that instantiates synthetic, grain-resolved, open-cell metal foam volumes are presented. The new capability allows for both synthetic-grain overlay of X-ray computed tomography data as well as fully synthetic foam geometry and grains. For the latter, a novel technique using Euclidean distances instantiates the 3D open-cell foam morphology, enabling user control of pore size, strut cross-section shape, and strut thickness variability. By integrating this approach into the DREAM.3D architecture, the entire DREAM.3D suite of filters is immediately available; thus, enabling both user control and quantification of grain size, shape, and crystallographic orientation statistics (among other metrics) as well as meshing algorithms to enable subsequent numerical analysis.

Mechanical characterization of bone quality in distal femur fractures using pre-operative computed tomography scans

BackgroundMechanical testing of implant constructs designed to treat distal femur fractures has been hampered by a lack of clinical data on the biomechanical properties of the distal femur in patients who sustain these fractures. Therefore, the purpose of this study was to use quantitative computed tomography (qCT) to investigate the mechanical characteristics of fractured distal femurs to inform the selection of synthetic materials for biomechanical testing. MethodsDistal femur fractures treated at a Level I trauma center were retrospectively reviewed and 43 cases with preoperative CT scans were identified for analysis. Scans were segmented and each bone fragment was reconstructed as a 3D model. The Young's modulus of the distal femur was determined from voxel-based radiodensity. FindingsMedian patient age was 72 years (IQR = 57–81), with 26% males and 74% females. Young's modulus in the distal femur was negatively correlated with patient age (R2 = 0.50, p < 0.001). The distribution of patient-specific modulus values was also compared with the compressive modulus ranges for graded polyurethane foams according to ASTM F1839. Bone quality ranged from Grade 25 in younger individuals to Grade 5 in older individuals. ConclusionNo single grade of synthetic polyurethane foam can be selected to model all clinically important scenarios for biomechanical testing of distal femur fracture fixation devices. Rather, this data can be used to select an appropriate material for a given clinical scenario. A Grade 25 foam is appropriate for implant longevity, whereas for implant stability, Grades 5-15 are more appropriate.

Low-velocity impact responses and CAI properties of synthetic foam sandwiches

This paper presents experimental and analytical studies on impact and compression after impact (CAI) responses of sandwiches with glass fiber reinforced polymer (GFRP) skins and synthetic foam cores under low-velocity impacting. The impact test results showed that the penetration depth of GFRP panels with synthetic foam is much smaller than that of bare synthetic foam panels. The edgewise compression test results indicated the facesheet debonding dominates the failure mode of the sandwich panels without lattice webs, while the failure mode of the sandwich panels with lattice webs is predominated by the wrinkling and delamination of the facesheets and the crushing of foam core. The influences of applied impact energy, GFRP lay-up, synthetic foam density and the existence of webs on the impact and post impact behavior of sandwich panels are discussed herein. Analytical models are proposed to predict the residual ultimate edgewise compressive load capacity of sandwich panels with lattice webs after impacts, using energy principles and variational methods in applied mechanics. The influences from impact damage, the local buckling of the facesheets and the confined strength of the foam core are measured and compared well with proposed analytical models.

Adsorption properties of aqueous methylene blue on mesocellular foam silica: Equilibrium, kinetic, isotherm, and thermodynamic characterization

Mesocellular foam silica was prepared by a hydrothermal synthesis protocol. The surface and pore structure of mesocellular foam silica were characterized by low temperature nitrogen adsorption isotherms, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. The methylene blue was adsorbed by the synthetic mesocellular foam silica; the optimized adsorption conditions were evaluated and the maximum adsorption capacity of methylene blue by mesocellular foam silica was determined to be 215.5 mg g−1. The kinetics of the adsorption of methylene blue by mesocellular foam silica were in accordance with a quasi-second-order kinetic equation. The results were analyzed by Langmuir and Freundlich adsorption isotherm models. The adsorption of methylene blue on mesocellular foam silica was shown to follow the Freundlich adsorption isotherm model. The Gibbs free energy change during adsorption showed that this process was spontaneous. The enthalpy change in the process was –28.868 J·mol−1 K−1, indicating that the adsorption is exothermic. The negative value of entropy –49.296 J·mol−1 K-1 shows that the system disorder decreases due to adsorption.

Effect of fentanyl nasal packing treatment on patients with acute postoperative pain after closed reduction of nasal bone fracture: a randomized double-blind controlled trial

Purpose: Nasal bone fracture reduction surgery is normally followed by nasal packing to control bleeding. Yet, patients suffer from pain and require further analgesic treatments following nasal packing and removal. This study aimed to evaluate the effect of fentanyl-soaked packing as a method of controlling pain after nasal surgeries in a prospective, randomized, double-blind controlled trial.Methods: Sixty-five patients that have undergone closed nasal bone fracture reduction surgery were included in this study. Thirty-two patients were treated postoperatively with 50 mcg fentanyl-soaked Merocel®, a biodegradable synthetic polyurethane foams packing, and the other 33 patients were treated with saline-soaked packings. To analyze the relative nasal pain control effect of fentanyl, Numeric Rating Scale, patient satisfaction and Ramsay Sedation Scale were used. Patients were closely monitored to record relevant cardiopulmonary indicators and degree of adverse symptoms such as headache or sore throat.Results: Fentanyl group had a significantly lower Numeric Rating Scale and higher patient satisfaction for most of the time periods after operation (p < .05). Symptoms of headache and sore throat were also significantly reduced. Ramsay Sedation Scale scores improved compared to the control group (p < .05). No significant differences in cardiopulmonary relevant indicators between the two experimental groups were observed (p > .05).Conclusion: Fentanyl-soaked packing significantly decreased postoperative pain with no observable adverse effects. Our results demonstrate that topical fentanyl application to nasal packing is an effective method of postoperative pain control after closed nasal bone fracture reduction surgery.

Static and dynamic characterization of agglomerated cork and related sandwich structures

The aim of this experimental investigation is to assess the response to low velocity impacts of green sandwich structures made of agglomerated cork encapsulated between two thin flax/epoxy face sheets. Three different cork densities were considered to assess their role on the response to impulsive loading, both in low and high strain rate conditions by Split Hopkinson Pressure Bar (from 90 to 238 1/s). The performance of these structures has been compared to that obtained with similar specimens using a traditional synthetic foam core. Despite the lower quasi-static mechanical properties of high-density cork (modulus and collapse stress of 117.65 ± 4.04 MPa and 4.29 ± 0.06 MPa, respectively), the cork-based structures exhibited a higher perforation threshold (94.41 ± 2.37 J) than synthetic foam-based sandwiches (79.71 ± 2.24 J) for impacts at room temperature. Finally, the material performance was evaluated under different temperatures, namely −40 °C and +80 °C, where perforation thresholds were found to be higher for cork-based structures (113.98 ± 6.04 J and 101.05 ± 2.42 J) compared to synthetic foam-based sandwiches (94.39 ± 2.20 J and 77.64 ± 1.70 J). The results show that the distinctive deformation mechanisms of cork allow to tailor the response to impulsive loading with a tunable damage extension through-the-thickness, despite a pronounced temperature dependent behaviour compared to synthetic foam.