Skin Sheets Research Articles

Mechanical response of pig skin under dynamic tensile loading

Uniaxial tensile experiments were performed on pig skin to investigate the tensile stress–strain response at both quasi-static and dynamic rates of deformation. A Kolsky tension bar, also called a split Hopkinson tension bar (SHTB), was modified to conduct the dynamic experiments. Semiconductor strain gages were used to measure the low levels of the transmitted signal from pig skin. A pulse shaper technique was used for generating a suitable incident pulse to ensure stress equilibrium and approximate constant strain rate in the specimen of a thin skin sheet wrapped around the ends of the bars for minimizing radial inertia. In order to investigate the strain-rate effect over a wide range of strain rates, quasi-static tests were also performed. The experimental results show that pig skin exhibits rate-sensitive, orthotropic, and non-linear behavior. The response along the spine direction is stiffer at lower rate but is less rate sensitive than the perpendicular direction. An Ogden model with two material constants is adopted to describe the rate-sensitive tensile behavior of the pig skin.

The Tensile Reduction Effects of Silicone Gel Sheeting

The Tensile Reduction Effects of Silicone Gel Sheeting

Mechanical Properties of Compound Extruded Aircraft Stringer Profiles Under Cyclic Loading

AbstractThe worldwide competition in the field of aircraft structures leads to an increasing need for functionality and safety as well as for cost and weight reduction. For instance stringers could be directly welded on the aircraft's skin sheet. The requirements to be met are increased safety against crack initiation and crack growth as well as improved residual strength against failure after harmful impact of foreign objects. The application of continuously reinforced aluminium profiles which are manufactured by compound extrusion leads to increased strength and stiffness of the profiles by combining the aluminium matrix with high strength wires. Thus aircraft stringers of such profiles represent an innovative concept with improved properties. The characterisation of compound extrusions based on medium and high strength aircraft aluminium alloys EN AW‐6056 and EN AW‐2099 shows that a good embedding of the reinforcing high strength wires (Co‐based and Fe‐based) can be achieved. Furthermore the mechanical properties under cyclic loading of the profiles were measured and the S/N‐curves for the different compound combinations were determined. Subsequently the crack initiation and propagation was analysed by using metallographic and SEM investigations. The fatigue resistance of reinforced specimens is increased compared to unreinforced ones. The fatigue cracks originate at the surface of unreinforced specimen while the cracks in reinforced specimens are initiated at the wire–matrix interface.

Epidermis‐to‐dermis migration of immature Langerhans cells upon topical irritant exposure is dependent on CCL2 and CCL5

Skin irritation is generally not considered to be an immunological event; however, alterations in the density of Langerhans cells (LC) in the epidermis do occur, which is indicative of LC migration. In this study, we investigated the migration of LC out of the epidermis after skin exposure to contact irritants and identified the chemokines involved. With the aid of ex vivo-intact human skin and epidermal sheets we show that dermal fibroblasts play a role in mediating LC migration towards the dermis. Exposure of ex vivo-intact human skin to a panel of seven irritants (SDS, salicylic acid, phenol, isopropanol, DMSO, TritonX, or benzalkonium chloride) resulted in decreased numbers of CD1a(+) cells in the epidermis and the accumulation of CD1a(+) cells in the dermis. In contrast to allergen exposure, neutralizing antibodies to either CXCL12 or CCL19/CCL21 did not inhibit LC migration out of the epidermis. Exposure of epidermal sheets to the prototypical irritant SDS resulted in a TNF-alpha-dependent LC migration towards dermal fibroblasts. This was a result of CCL2/MCP-1 and CCL5/RANTES chemokine secretion by fibroblasts: injection of CCL2- and CCL5-neutralizing antibodies into intact human skin totally inhibited LC migration into the dermis. We have thus identified a novel role for TNF-alpha-inducible dermis-derived CCL2 and CCL5 in initiating migration of irritant-exposed human LC out of the epidermis.

Perforation of sandwich plates with graded hollow sphere cores under impact loading

In this paper, sandwich plates made from 0.8 mm 2024 T3 aluminium alloy skin sheets and graded polymeric hollow sphere cores (having various density gradients) are studied. The experiments at 45 m/s were performed with an inversed perforation setup using SHPB system. Quasi-static tests using the same clamping system allow for the rate effect investigation. Numerical simulations are performed in order to get the indispensable local information (which is not experimentally available) to better understand the perforation process. With these experimental and numerical tools, it is found that the gradient profiles change the perforation process under studied impact loading, whereas they have no influence under quasi-static loading. Under impact loading, a competition of two deforming scenarios at the early stage governed the whole process afterwards. One is the global crush of the first layer in contact with the incident skin and the other is the piercing of the incident skin sheet. When the first layer is rather strong, the incident skin sheet breaks and the perforator makes a hole in the core afterwards. When the first layer is rather weak, the skin sheet folds into the core and develops a much more energy consuming process. The best gradient profile in terms of the energy absorption capacity as well as the non-sheet breaking criterion should be a weaker first layer and a progressively enhanced core.

Frictional Properties of Electrospun Polyurethane Nanofiber Web

Electrospun nanofiber webs are of increasing interest for a variety of functional goods, not only textiles. The mechanical strength of these nanofiber webs must be evaluated to estimate the effect of rubbing against other fabrics and human skin. Therefore, we analyzed the frictional behavior of polyurethane (PU) nanofiber web against various fabrics and against artificial skin sheets. The present results are summarized as follows:1) The mean friction coefficient of the PU nanofiber web was independent of the load.2) Nanofiber web showed stick-slip motion, the frequency depending on the mating material and applied load.3) The highest observed mean friction coefficients were 0.8 and 0.83 for silk and Flexcare®, respectively, and the lowest were 0.53 to 0.54 for Lorica® and silicone rubber, respectively.

Review of Major Design and Scale-up Considerations for Solar Photocatalytic Reactors

Photocatalytic processes are applicable in wastewater treatment, energy production, chemical synthesis, and greenhouse gas mitigation and thus have the potential to address both the consumption of nonrenewable fossil fuels and global warming, two of the greatest problems facing humankind. The ability to achieve these outcomes using only solar energy as an input is particularly attractive. However, the implementation of most photocatalytic processes at an effective scale requires the use of a photoreactor, a device which brings photons, a photocatalyst and reactants into contact, as well as collecting the reaction products. In this work, we review the state-of-the-art in solar photoreactor design and assess those systems which are most applicable for industrial-scale implementation. Designs for parabolic trough, compound parabolic, inclined plate, double skin sheet, rotating disk, water bell, fiber optic, and fixed/fluidized bed photoreactors are qualitatively discussed and compared. Compound parabolic pho...

Computer Controlled Chamber Measurements for Multiple Contacts for Soil-Skin Adherence from Aluminum and Carpet Surfaces

ABSTRACT A computer-controlled mechanical chamber was used to perform multiple contacts between human cadaver skin or cotton sheet samples and soil-laden carpet or aluminum foil to measure mass soil transfer. The amount transferred was measured with an analytical balance. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 s) were varied for 760 separate multiple contact experiments, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 and ≥ 139.7 < 381 μm) were used. Through parametric and non-parametric tests, this article specifically looks at the influence and interaction of these experimental parameters on the transfer of soil or sand to human skin during multiple contacts. The relationships between the amount of soil or sand that transfers for a first contact, for a second contact, and overall are also presented. On average, a second contact added an additional 8% of soil or sand to the adherence material (i.e., cloth, skin). The experimental variables of pressure, time, soil size, and soil type had less influence on the magnitude of transfer for the second contact as compared to the first contact.

A Study on 3-Layer Roll Projection Welding of Large Area

The metal sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorption, effective thermal insulation and soundproofing. Several bonding methods such as brazing, adhesive bonding, projection welding and adhesive-assisted projection welding are tested for fabrication of the metal sandwich plate. Finally, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metal sandwich plate of large area for the plate width of 270 mm. The new method uses a pair of roll electrodes like in seam welding; however, the workpiece width is much wider than that of seam welding by more than ten times. Projection welding of large area is made at two internal interfaces of the 3-layer weldment, consisting of a structured inner sheet of projection-like shape and a pair of skin sheets, when it passes through the gap between the roll electrodes. The weld quality is inspected by peeling test for various welding conditions, in order to find the optimal welding parameters. The welding sequence is to be synchronized for the given welding speed and pattern type of structured inner sheet to provide the consistent welding condition.

금속 샌드위치 판재 대면적 롤 프로젝션 용접에 관한 연구 : Part 2 - 수치 해석

Metallic sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorptivity, effective thermal insulation and soundproofing. In our study, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metallic sandwich plate. The new method uses a pair of roll electrodes like the seam welding, and projection welding is made at two internal interfaces of the 3-layer weldment consisting of a structured inner sheet and a pair of skin sheets. During the welding process, skin sheet temperature are measured to produce metallic sandwich plate with uniform and good quality. But it is difficult to observe or measure the temperature at the welding points during welding process because the welding points exist at the internal interfaces. Therefore FEM numerical analysis using ABAQUS is conducted to estimate the generated heat at the welding points with different welding conditions.

금속 샌드위치 판재 대면적 롤 프로젝션 용접에 관한 연구 : Part 1 - 공정 모니터링

A roll projection welding machine is introduced to fabricate metallic sandwich plate consisting of a structured inner sheet with projection-like shape and a pair of skin sheets. To fabricate the metallic sandwich plate of consistent and good quality, two process monitoring methods are introduced; dynamic resistance monitoring and skin sheet temperature monitoring. Dynamic resistance monitoring has no time delay but gives only averaged value over plate width. Skin sheet temperature monitoring has certain amount of time delay but is good for predicting weld quality of specified position. By the two complementary monitoring methods, the characteristics of the new welding process is successfully understood.

Properties of Facesheet-reinforced 3-D Spacer Fabric Composites and the Integral Multi-facesheet Structures

3-D spacer fabric is a new sandwich structure textile developed by integrally woven technique. Mono-spacer fabric composite made by 3-D spacer fabric has super-high specific strength and specific stiffness. However, its mechanical properties cannot meet the demand of structural applications. In this article, facesheet-reinforced 3-D spacer fabric composites were investigated by laminating additional glass weave at the skin sheets. Mechanical behavior of this facesheet-reinforced 3-D spacer fabric composite was studied experimentally. Effects of various factors on the mechanical properties were also discussed, such as the additional layer number, the type of glass weave, and the lay-up type. Furthermore, an innovative integral multi-facesheet structure composite was developed by directly weaving three uniformly spaced facesheets in one construction. The mechanical performance was compared with bonded multi-facesheet spacer fabric composite and mono-spacer fabric composite under the same conditions. The results indicated that additional weaves could strengthen the composite facesheets greatly, and the multi-facesheet structure could improve the properties correlated with the piles effectively.

Comparisons of computer-controlled chamber measurements for soil–skin adherence from aluminum and carpet surfaces ,

A computer-controlled mechanical chamber was used to control the contact between carpet and aluminum sheet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. The contact parameters of pressure (10–50 kPa) and time (10–50 s) were varied for 768 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil particle sizes (<139.7 and ⩾139.7<381 μm) were used. Mean soil mass transfer to cadaver skin was higher than mean transfer to cotton sheets for both carpet and aluminum transfers, and also generally higher pressure was associated with larger amounts of soil transfer for all contact scenarios. The mean soil adherence from carpet was 0.37±0.4 mg/cm 2, while the mean soil adherence from aluminum was 0.42±0.6 mg/cm 2. For aluminum, smaller soil particle size was associated with more transfer ( p=0.0349), while for carpet, larger soil size was associated with more transfer ( p<0.0001). Soil type was significant but only for aluminum surface, where sand was associated with higher adherence ( p<0.0001). This data set can be used to improve estimates of dermal exposure to contaminants found in soils and dust present in indoor environments.

Influence of polyester gauze on evaporation capacity and healing of the surface of microskin graft wound after escharectomy

To investigate the influence of polyester gauze on evaporation capacity and its clinical effect after escharectomy of deep burn wound and micro-skin grafting. Twenty patients with deep burn admitted within 24 hours after injury underwent escharectomy and Meek skin grafting. Two surfaces of wound with the area of about 1% as the whole wound surface were used, one covered by Meek skin graft and polyester gauze as inner dressing (polyester gauze group), and the other covered by split-thickness skin sheet 0.3 mm x 0.3 mm in size and vaseline oil gauze as inner dressing (vaseline oil gauze group). Five days after skin grafting, the evaporation capacities of the surface of inner dressing, wound surface without dressing (nude wound), and normal skin near the wound were tested by evaporation test equipment. The complete healing time and survival rate of skin sheet in both groups were observed. The degree of pain during dressing change was evaluated with visual analog scale. The evaporation capacity of the inner dressing surface of polyester gauze group was (24.8 +/- 5.2) ml x h(-1) x m(-2), significantly lower than those of the vaseline oil gauze group [(35.4 +/- 5.0) ml x h(-1) x m(-2), P < 0.01] and nude wound [(41.3 +/- 4.5) ml x h(-1) x m(-2), P < 0.01], and similar to that of the normal skin near the wound [(21.1 +/- 5.1) ml x h(-1) x m(-2), P > 0.05]. The evaporation capacity of the inner dressing surface of vaseline oil gauze group was significantly lower than nude wound [(40.7 +/- 3.6) ml x h(-1) x m(-2), P < 0.01], but significantly higher than the normal skin near the wound [(21.2 +/- 3.8) ml x h(-1) x m(-2), P < 0.01]. The survival rate of skin sheets of the polyester gauze group was 98% +/- 3%, not significantly different from that of the vaseline oil gauze group (98% +/- 2% , P > 0.05). The wound healing rates on days 10, 15, and 20 of the polyester gauze group were 80% +/- 20%, 96% +/- 7%, and 100% respectively, all significantly higher than those of the vaseline oil gauze group (70% +/- 33%, 81% +/- 21%, and 97% +/- 11% respectively, all P < 0.01). The complete healing time of the polyester gauze group was (13.6 +/- 1.9) days, significantly shorter than that of the vaseline oil gauze group [(16.7 +/- 2.6) days, P < 0.01]. The pain scores during dressing change 5 and 10 days after grafting of the polyester gauze group were (3.2 +/- 0.8) and (4.9 +/- 0.4) respectively, both significantly lower than those of the vaseline oil gauze group [(5.1 +/- 0.6) and (8.2 +/- 0.5) respectively, both P < 0.01]. Polyester gauze has quite good abilities to retain moisture and can promote the migration and proliferation of epithelial cells, relieves the pain caused by tearing of dressings off the wound, thus raising its acceptability. It is a relatively ideal carrier of skin grafting, as well as a new type of inner cover for the wound.

103 多孔質積層板の成形性(材料力学I)

103 多孔質積層板の成形性(材料力学I)

BENDING BEHAVIOR OF SIMPLY SUPPOTED METALLIC SANDWICH PLATES WITH DIMPLED CORES

Metallic sandwich plates are lightweight structural materials with load-bearing and multi-functional characteristics. Previous analytic studies have shown that the bendability of these plates increases as the thickness decreases. Due to difficulty in the manufacture of thin sandwich plates, dimpled cores (structures called egg-box cores) are employed as a sandwich core. High-precision dimpled cores are easily fabricated in a sectional forming process. The cores are then bonded with skin sheets by multi-point resistance welding. The bending characteristics of simply supported plates were observed by the defining measure, including the radius ratio of the small dimple, the thickness of a sandwich plate, and the pattern angle (0°/90°, 45°). Experimental results revealed that sandwich plates with a thickness of 2.2 mm and a pattern angle of 0°/90° showed good bendability as the punch stroke under a collapse load was longer than other cases. In addition, the gap between attachment points was found to be an important parameter for the improvement of the bendability. Finally, sandwich plates with dimpled cores were bent with a radius of curvature of 330 mm for the sheet thickness of 2.2 mm using an incremental bending apparatus.

Organotypic modelling as a means of investigating epithelial-stromal interactions during tumourigenesis

The advent of co-culture approaches has allowed researchers to more accurately model the behaviour of epithelial cells in cell culture studies. The initial work on epidermal modelling allowed the development of reconstituted epidermis, growing keratinocytes on top of fibroblasts seeded in a collagen gel at an air-liquid interface to generate terminally differentiated 'skin equivalents'. In addition to developing ex vivo skin sheets for the treatment of burns victims, such cultures have also been used as a means of investigating both the development and repair of the epidermis, in more relevant conditions than simple two-dimensional culture, but without the use of animals. More recently, by varying the cell types used and adjusting the composition of the matrix components, this physiological system can be adapted to allow the study of interactions between tumour cells and their surrounding stroma, particularly with regards to how such interactions regulate invasion. Here we provide a summary of the major themes involved in tumour progression and consider the evolution of the approaches used to study cancer cell behaviour. Finally, we review how organotypic models have facilitated the study of several key pathways in cancer development and invasion, and speculate on the exciting future roles for these models in cancer research.

Soil-skin adherence from carpet: Use of a mechanical chamber to control contact parameters

A computer-controlled mechanical chamber was used to control the contact between carpet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. Mass soil transfers were converted to adherence factors (mg/cm2) for use in models that estimate dermal exposure to contaminants found in soil media. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 sec) were varied for 369 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 μm and ≥139.7 < 381) were used. Chamber probes were used to record temperature and humidity. Log transformation of the sand/soil transfers was performed to normalize the distribution. Estimated adjusted means for experimental conditions were exponentiated in order to express them in the original units. Mean soil mass transfer to cadaver skin (0.74 mg/cm2) was higher than to cotton sheets (0.21 mg/cm2). Higher pressure (p < 0.0001), and larger particle size (p < 0.0001) were also all associated with larger amounts of soil transfer. The original model was simplified into two by adherence material type (i.e., cadaver skin and cotton sheets) in order to investigate the differential effects of pressure, time, soil size, and soil type on transfer. This research can be used to improve estimates of dermal exposure to contaminants found in home carpets.

Fast Analytical Algorithm for Fatigue Crack Life Estimations of Integrally Stiffened Metallic Panels

This work presents the enhancement of a pseudo-numerical tool for fatigue crack growth investigations on integrally stiffened metallic panels. The model is based on an analytical approach that demands compatibility of displacement between skin sheet and stiffener. Since the basis model was presented before, the focus of the present work is on the incorporation of residual stress effects in order to improve simulation results of welded panel configurations that are manufactured by laser beam welding or friction stir welding and exhibit a significant amount of residual stresses. The necessary input parameters for the developed residual stress module are determined from experimental residual stress field measurements. Simulation results using the presented approach are compared with results from finite element simulations on a two stringer panel which show the good accordance of the base model as well as the capability of the tool enhancements to account for the crack retarding effect caused by residual stresses.

The Effect of Adhesion and Tensile Properties on the Formability of Laminated Steels

Laminated steel has been implemented in vehicle structures by several automotive manufacturers to reduce in-cabin noise. This study provides an understanding of how the adhesion between the steel skin and the viscoelastic polymer core affects laminate formability. Material properties, including peel strength, shear strength, and tensile strength were determined. The presence of the viscoelastic core was found to slightly reduce tensile properties of the laminate compared to the skin sheet. Forming limit diagrams were also determined. These indicated that the viscoelastic core properties can significantly affect formability of laminated steel compared to that of solid steel sheet. In general, the formability of laminated steel was found to be similar to or less than that of the much thinner skin sheet material, which indicates that its formability should be less than that of solid steel of the same gauge.