Skin Reinforcement Research Articles

The preparation and axial compressive properties of 3D-printed polymer lattice-reinforced cementitious composite columns

Research on the mechanical properties of 3D-printed lattice-reinforced cementitious materials is becoming increasingly widespread. The bending and compression performances of such materials have been studied from the perspectives of the lattice preparation materials, structural forms, gradient design, and cement-based material types. The extant research has primarily focused on the bending performance of lattice-reinforced specimens, while little research has been conducted on the compressive properties. In addition, the reinforcing effect of the lattice on cementitious materials under lateral constraints has not been considered. This article investigates the compressive performance of cement mortar reinforced by 3D-printed spiral lattices or skin structures with different volume reinforcement ratios (different grid constraint layers). Multi Jet Fusion (MJF) technology was used to print four types of spiral lattices, and six specimens, including a control group, were prepared. The experiment considered the performance differences of polymer-reinforced mortars with different volume reinforcement ratios, bonding performance, and skin reinforcement. The load, displacement, stress, strain and other data of the specimen were measured, and combined with the full field strain measured by DIC technology, the strength, energy absorption performance, ductility, elastic modulus, constraint effect, deformation mechanism, and failure mode of the specimen were comprehensively analyzed. The experimental results indicate that 3D-printed spiral or skin lattices can improve the ductility and energy absorption capacity of cementitious materials. However, the elastic modulus of the raw materials used to reinforce the structure is lower than that of cementitious materials, which will reduce the compressive strength and elastic modulus. In addition, the lateral deformation constraint effect of the lattice or skin structure on the cement mortar under axial compression is not significant. All cementitious specimens were found to exhibit the shear failure of the inclined section under axial compression. This article reveals that 3D printed spiral lattices can improve the deformation ability of cementitious composite materials under compression, providing new ideas for the ideal replacement of stirrups and the development of building energy conservation and emission reduction.

The Effect of Reinforce Powder Size on The Properties of Pineapple Leaf Fiber – Bagasse Sandwich Composites

The growth of ship production in Indonesia encourages the shipping industry to utilize the composite material in order to be more efficient. Natural fibre-reinforced composite (NFRC) is one option that should be considered for use safer than fiberglass. The usage of fiberglass could trigger several health problems. Sugarcane and pineapples are one of the most common agricultural commodities, yet their waste has not been treated optimally. This research is going to analyse the effect of reinforcement powder size on its bending strength in pineapple leaf fibre – bagasse reinforced sandwich composites. Pineapple leaf fibre use as skin reinforcement whereas bagasse use as core reinforcement. Sandwich composites were reviewed for their bending strength on specimens on reinforcement powder size 40, 60, and 100 mesh. The composite was made using the hand lay-up method with skin composition is 20:80% and core composition is 25:75%, each layer of skin and core have 2 mm thickness. The highest bending strength for sandwich composite is 52,72±0,85 MPa as a result of the experiment using 100 mesh of reinforcement powder. The bending strength of sandwich composite increase as finer particle powder use for the reinforcement. The highest bending strength in this study can be used as bulkhead material for the interior of the ship’s accommodation space based on SNI 01-4449-2006.

Analysis of the application of fuselage skin reinforcements with beam element representations in flexible full aircraft models for ditching simulations

The aim of this paper is the application of beam element representations for structural skin reinforcements in flexible full aircraft FE models used in ditching simulations. To verify this approach, it was initially analyzed on flexible reinforced bottom-aircraft panels under guided ditching conditions, considering also structural mesh size variations and partly corresponding fluid mesh densities. For this analysis two different numerical methods were used for comparisons, the coupled Finite Element-Smoothed Particle Hydrodynamics and the Arbitrary Lagrangian Eulerian methods. For the generation of the full aircraft model a multidisciplinary process chain approach and a standardized data format description are used. The beam element representations are considered for the modelling of skin reinforcement as well as other structures like cabin and cargo floor structures. By this approach, first time feasible full aircraft ditching simulations and the subsequent analysis of both global kinematics and the local fuselage structural response could be achieved.

Valorization of date palm wastes as sandwich panels using short rachis fibers in skin and petiole 'wood' as core

Algerian agriculture offers free by-products that can be transformed in biobased-materials. We use one of them, the date palm ’wood’, to locally develop sandwich panels. We demonstrate by tensile tests that rachis fibers are more efficient than petiole fibers. Then, petiole ’wood’ is used as sandwich core and short rachis fibers (5%, 10%, 15%) are used as epoxy skin reinforcement. The skins are tested by tensile and bending tests, 15%Mf untreated short fibers have been selected as a best choice for stiffness of the skins. Three parameters are studied to optimize the design of the core: the orientation (longitudinal, transverse, radial), the length of the pieces of ’wood’ (30 mm, 100 mm), and the thickness (10 mm, 15 mm, 20 mm). The sandwich efficiency are studied by 3-points bending tests combined to linear elastic beam theory and failure mode analysis. The dominant failure modes are bottom skin failure and core shear, the latter being not activated in case of transverse orientation of core. Both other parameters (thickness, pieces of core length) are not really determinant in mechanical point of view, depending on the future use. We conclude that making sandwich board by using untreated short rachis fibers as reinforcement for skins and untreated transverse cut petiole ’wood’ as core is a very efficient choice to give technical and cheap valorization of palm leaf wastes for non-structural use.

On the tensile and compressive behavior of a sandwich panel made of flax fiber and agglomerated cork

Sandwich panels are used in buildings because of their light weight, thermal insulation, sound absorption, and better mechanical properties. Material scientists have been trying their best to replace synthetic materials as these are non-biodegradable. Stringent environmental policies, need for eco-friendly products, and problems in end-of-life disposal have made natural materials in sandwich panels the need of the hour. This research work attempts to replace the synthetic sandwich panels with natural sandwich panels without sacrificing the performance. The natural sandwich panels used in this work had agglomerated cork as the core and flax fiber as skin reinforcement. A vacuum-bagging technique was used to manufacture these panels with three core densities and three skin reinforcements. The performance of these panels was confirmed by conducting flatwise tensile, flatwise compressive, and edgewise compressive tests as per the American Society for Testing and Materials standards and the results are discussed in this article. The specific flatwise tensile strength of natural sandwich panels was 14–21% higher and the specific flatwise compressive strength was 2–10% higher than the synthetic sandwich panels. The edgewise compressive strength was found to be 32–34% lower than synthetic sandwich panels. The results suggest that natural sandwich panel could be a better alternative material for building applications.

Effect of temperature on the low-velocity impact response of environmentally friendly cork sandwich structures

Impact events are common in every-day life and can severely compromise the integrity and reliability of high-performing structures such as sandwich composites that are widespread in different industrial fields. Considering their susceptibility to impact damage and the environmental issues connected with their exploitation of synthetic materials, the present work aims to propose a bio-based sandwich structure with an agglomerated cork core and a flax/basalt intraply fabric as skin reinforcement and to address its main weakness, i.e. its impact response. In-service properties are influenced by temperature, therefore the effect of high (60 °C) and low (−40°C) temperatures on the impact behavior of the proposed structures was investigated and a suitable comparison with traditional (polyvinyl chloride) (PVC) foams was provided. The results highlighted the embrittlement effect of decreasing temperature on the impact resistance of the sole cores and skins and of the overall structures with a reduction in the perforation energy that shifted, in the last case, from 50–60 J at – 40 °C up to more than 180 J at 60 °C. A maleic anhydride coupling agent in the skins hindered fundamental energy dissipation mechanisms such as matrix plasticization, determining a reduction in the perforation threshold of all composites. In particular, neat polypropylene (PP) skins displayed a perforation energy of 20 J higher than compatibilized (PPC) ones at 60 °C, while agglomerated cork sandwich structures at 60 °C were characterized by a perforation threshold higher of at least 50 J.

An experimental study on heat insulaion panels & Brick walls

Like many other experimental study’s, The heat insulation system is a material that replaces the customary divider frameworks, these heat insulation panels are utilized in the construction of inside and outside bearing and non-load bearing walls, roof tops, floors etc. Brick masonry walls requireproper design, detailingand construction to minimize water penetration into or through a wall system. Many aspects of design, construction and maintenance can influence the resistance of a wall to water.How ever little research has been done. This work examines the idea of making, testing and cost estimation for the thermal insulation panels and brick walls comparison. Insulation panels are casted by using thermocol sheet, cement mortar, skin reinforcement where as brick wall is caste by using earth burn bricks and forming a model house with different thermacol sheets with sizes of 25 mm, 50 mm and identifying the heat insulation panels inside and outside temperatures for 25 mm and 50 mm thermocol sheets, comparison with brick wall.

Normal and High-Strength R/C Deep Beams under Pure Torsion and Codes Evaluation.(Dept.C)

Fourteen reinforced concrete deep beams were tested under pure torsion in order to evaluate the torsion design provisions of ACI 318-02 Building Code, the Egyptian code (ECCS-2001), the New Zealand code (NZS 3101-95), and the Eurocode 2 (EC-2) when applied to High Strength Concrete (HSC) deep beams. The results of these tests have been used to compare the torsional behavior of reinforced deep beams constructed from Normal-Strength Concrete (NSC with characteristic cube compressive strength fcu of about 35 MPa) and HSC (with fcu of about 81 MPa). The main parameters examined in this study were the design compressive strength, the provided transverse reinforcement ratio, the quantity of longitudinal and skin reinforcement and the size of the tested beams in the form of the tested span to total height ratio (L/h=1.0, 2.0 and 3.0). The results showed that the reserve in the torsional strength of the HSC deep beams aster cracking is considerably less than that of the similar NSC deep beams. The cracking torsional strength of the tested NSC deep beans is about 38-54% of the measured ultimate torsional strength, while the same ratio for the similar HSC deep beams is about 57-77% of the measured ultimate strength. The design torsional strength equations of the four international codes considered in this study were safe and conservative when applied to NSC and HSC deep beams. The predictions of the ultimate torsional strength of the deep beams according to the method of ACI 318-02 and using a value of the angle between the concrete struts and the longitudinal axis of the beam θ equal to 45 deg may give a conservative results less than that calculated using this angle between 30 and 60 deg.

Evaluating planner hoop steel plates as web reinforcement for deep reinforced concrete beams

An experimental attempt was conducted in this paper, aiming at enhancing the shear and flexural behaviors of deep beams, where steel plates were applied as web reinforcement. Three beams having the same details were prepared using normal concrete strength. Their dimensions were 1250 mm long, 300 mm deep, and 150 mm wide. The specimens were designed to fail in shear, and therefore, they were supplied with two bars with a 20 mm diameter in addition to the top and skin reinforcement. For web reinforcement, the steel plates were cut in dimensions of 4×20 mm and then were applied as closed rectangular stirrups with the longer side (20 mm) aligned in the plane of the beam section. The beams were inspected by applying four-point bending with three shear span to the effective depth ratios (a/d) of 0.75, 1.25 and 1.75. The experimental outcomes revealed that the shear strength, stiffness, and toughness of deep beams enhanced as the a/d ratio dropped.

Cerebrospinal Fluid Leak after Repair of Congenital Spinal Pathologies, Incidence and Management

Objective: To know the incidence of CSF leak and role of tincture benzoyl in the management of CSF leak after the repair of congenital spinal deformities like myelomeningocele, meningocele and tethered cord syndrome.Materials and Methods: All patients who were operated for congenital spinal surgeries in the form of MMC, Meningocele and TCS by a single surgeon were followed for a minimum of 3 months. Patients with already CSF leak/ruptured MMC prior to surgery were not part of the study. The particulars like gender and type of surgery, days since first surgery, associated infection, hydrocephalus and type of management were noted on a proforma.Results: A total of 73 patients with spinal dysraphism were operated during the study period and of them about 13 patients returned with problems of the CSF leak. The mean duration and duration since the CSF leak was from 6 days to 16 days. Among them, 10 patients had an MMC repair and one patient had TCS release, while 2 patients were having meningocele repair. The patients were stitched and one patient was re-operated two times for repair of CSF leak. Two patients had a CSF leak along with post op signs of HCP that settled by placing a shunt along with primary repair of the wound reinforced with tincture benzoyl in a single setting. Conclusion: CSF leak is a common complication following repair of spinal dysraphism and most patients can be managed with the application of tincture benzoyl alone or after simple skin reinforcement.

Use of expanded polystyrene wastes in developing hollow block masonry units

This paper presents the results of an experimental investigation aimed at developing lightweight hollow block masonry units of adequate mechanical and durability characteristics for applications in the construction industry. Five dosages of EPS crumbles were used as partial replacement of the sand in the blocks mixture, namely; 0%, 10%, 15%, 20%, and 26%. Skin reinforcement was added to some of the tested. Three types of EPS blocks were tested: 1 – plain blocks without reinforcement, 2 – blocks reinforced with welded steel wire mesh, and 3 – blocks reinforced with fiberglass mesh. The density of the developed blocks ranged between 2119 and 982 kg/m3 and the net area compressive strength ranged between 9.5 and 1.4 MPa. The presence of EPS in the mixture greatly improved the failure pattern of all the EPS hollow blocks. The durability tests proved that EPS hollow blocks were resilient to acid and salt exposure. The weight loss and compressive strength loss of the hollow blocks due to ettringite leach decreased significantly with the addition of EPS. The presence of the skin reinforcement had minimal effect on the compressive strength, but it improved the failure pattern. The developed EPS hollow blocks are suitable for non-load bearing application of exterior and interior walls within the stated limits of ASTM and the Egyptian Standards.

Shear crack concentration in reinforced concrete beams subjected to shear and flexure

The dual potential capacity model was developed in the authors’ previous studies to estimate the shear strengths of reinforced concrete members, in which the shear crack concentration factor was adopted as the key concept of the proposed approach. In this study, a shear test program was carefully prepared and conducted on five reinforced concrete beam specimens to investigate the crack development, propagation, and merging behavior of critical shear cracks. To this end, concrete cover thickness, diameter of reinforcement, presence of skin reinforcement, and shear reinforcement ratio were taken as the main test variables. From the experiments, the crack merging and concentration phenomena were clearly observed, and the crack concentration factors were estimated from the measured flexural and shear crack widths and spacings. The crack concentration factors were compared to those estimated by the dual potential capacity model, and the shear strengths of the test specimens were also compared with those estimated by the dual potential capacity model and other models in detail.

Experimental study on thermal and morphological analyses of green composite sandwich made of flax and agglomerated cork

The building sector has been showing great interest in incorporating technologically advanced materials with lightweight, ecofriendly, high strength, and stiffness properties in flooring, roofing, and partition walls, etc. In addition to the mechanical properties, these materials should have good thermal properties as well. In response to these requirements, an attempt has been made to study the thermal behavior of green composite sandwich made of flax and agglomerated cork. Composite sandwiches were fabricated by using flax as skin reinforcement and agglomerated cork as core with different densities as 240, 280, and 340 kg m−3 using vacuum bagging method. Glass was also used as skin reinforcement for manufacturing composite sandwiches for comparison purpose. Experiments were conducted to predict thermal properties, viz. thermal conductivity, thermal expansion, flammability, and thermal stability. The experimental results show that the lowest thermal conductivity of 0.03 W m−1 K−1 was observed in flax-based composite sandwich having core density of 240 kg m−3; the lowest thermal expansion of 29.2 × 10−5 °C−1 was observed in glass-based composite sandwich having core density of 340 kg m−3; the highest value of time to ignition was 12 s, and minimum propagation rate was 0.25 mm s−1 in flax-based composite sandwich having core density of 340 kg m−3; The highest initial degradation temperature was 362 °C for glass-based skin and 263 °C for cork having density of 240 kg m−3.

Experimental investigation on impact, sound, and vibration response of natural-based composite sandwich made of flax and agglomerated cork

In recent years, material scientists have been focusing on the utilization of materials from natural resources due to environmental concerns. In the same context, the aim of this work is to evaluate impact response, sound absorption behavior, and vibration damping characteristics of natural-based composite sandwich made of flax as skin reinforcement and agglomerated cork as core. Vacuum bagging method was used for manufacturing composite sandwiches with different cork densities of 240, 280, and 340 kg/m3. Composite sandwiches have also been manufactured by using glass as skin reinforcement for comparison. Low velocity impact test was conducted and found that glass fiber reinforced composite sandwich required 73–77% more energy to perforate when compared to the flax fiber reinforced composite sandwich irrespective of core density. Flax fiber reinforced composite sandwich has 45–96% higher sound absorption capacity and 27–32% higher vibration damping ratio than glass fiber reinforced composite sandwich irrespective of core density. This is due to multiscale structure and cellular nature of the flax fiber and the cork materials, respectively. These enhancements in sound and vibration are accomplished with just little forfeits in perforation energy. This study recommends that, if optimized, the natural-based composite sandwich could be an ecologically appealing answer for automobile and construction applications, where impact behavior is important, along with sound and vibration properties.

Effect of water absorption on the flexural strength of a green sandwich composite

Abstract The main objective of this paper is to study the effect of water absorption on the flexural strength of new green sandwich composite material made of flax as skin reinforcement and agglomerated cork as core. In this work, three different types of skin reinforcements and three different densities of agglomerated cork core have been used for the manufacturing of sandwich composites. The manufactured sandwich composites were subjected to three-point bending tests under both dry and wet conditions. The three-point bending results confirmed a decrease in the specific flexural strength by 14-42 % in wet samples due to water absorption. Also, the increase in core density leads to an increase in flexural strength both in dry and wet conditions. During testing under dry conditions, the specific flexural strength of flax reinforced sandwich composite was found to be superior because of the higher strength to weight ratio factor of flax fiber when compared to a glass reinforced sandwich composite and glass/flax reinforced hybrid sandwich composite. Due to the hydrophilic nature of flax fibers, flax reinforced sandwich composite has a reduced specific flexural strength in wet conditions when compared to glass reinforced sandwich composite and glass/flax reinforced hybrid sandwich composite.

Enhancing Performance of Infill Masonry With Skin reinforcement Subjected To Cyclic Load

Masonry infill has been widely used as building material due to its cost effectiveness and availability. The failure of these masonry infill walls during the past earthquakes have underscored the importance of ensuring the safety of the infill walls when it is subjected to lateral loads. In-plane and out of plane failures have been observed in many reinforced concrete framed building with masonry infill. To prevent the failure of the infill walls researchers have worked on various confinement techniques like, textile reinforced mortar, ferro cement, and diagonal bracings using fiberglass reinforced panels (FRP) etc. In this paper chicken mesh were used as a confinement technique and the experimental investigation is presented for enhancing the in-plane properties of masonry infill walls like diagonal tension and shear thereby improving the in-plane strength of masonry infill wall. For studying the lateral load capacity of the infill wall two specimens are cast namely, i) infill wall without mesh (B2), ii) infill wall with mesh (B3). Single bay, single floor 1:3 scaled down reinforced cement concrete (RCC) frames designed as per codal provisions are cast with scaled down bricks for construction of infill walls and because of incorporation of skin reinforcement for infill walls the ductility, energy dissipation, ultimate loads are improved considerably and reduced the displacements.

Elastic Properties and Failure Behavior of Tiled Laminate Composites

This paper focuses on the elastic properties and the failure behavior of tiled laminate composites. Such laminates, in which the plies are not parallel to the outer surfaces are found in InfraCore® based GFRP panels. This technology is developed for the construction of a robust FRP panel that is applicable for highly loaded structures, e.g. for bridges or lock gates. In general, the drawback in traditional FRP sandwich structures has always been debonding of skin and core. Such a debonding problem may occur after impact, followed by fatigue loading. Through the use of the InfraCore® technology, debonding is no longer possible, as multiple overlapping Z-shaped and two-flanged web structures are alternated with polyurethane foam cores acting as non-structural permanent formwork. Consequently, the fibers in the upper and lower skins as well as in the vertical webs run in all directions, especially in the connection between them, rendering a resin-dominated crack propagation impossible. As a result of the integration of core and skin reinforcement, a skin material is created in which the reinforcement is not parallel to the outer surfaces, but at a small angle. Such stacking is called a tiled laminate (TL), as opposed to plane-parallel (PP) and is not fully described by the classic laminate theory. In the paper, finite element analysis is used to assess the effect of the ply angle and the interlaminar properties on the assessment of stiffness and failure behavior of a tiled laminate.

Soft Tissue and Skin Reinforcement with Acellular Dermal Matrix to Protect Implanted Cardioverters/Defibrillators and Pacemakers.

Summary:Cardiac pacemakers and implantable cardioverters/defibrillators are often placed in older patients with thin skin and scanty subcutaneous tissue. These devices and cardiac leads are at risk for progressive skin erosion and exposure leading to infection. To prevent this severe complication, we developed a reinforcing insertion of acellular dermal matrix. Twenty-two of 24 patients had successful implantation with long-term avoidance of skin erosion

General theory of skin reinforcement

Macroscopic mechanical properties of human skin in vivo cannot be considered independent of adjacent subcutaneous white adipose tissue (sWAT). The layered system skin/sWAT appears as the hierarchical structural composite in which single layers behave as fiber-reinforced structures. Effective macroscopic mechanical properties of such composites are mainly determined either by the properties of the skin or by those of the sWAT, dependent on the conditions of mechanical loading. Mechanical interactions between the skin and the adjacent sWAT associated with a mismatch in the mechanical moduli of these two layers can lead to production of the skin wrinkles. Reinforcement of the composite skin/sWAT can take place in different ways. It can be provided through reorientation of collagen fibers under applied loading, through production of new bonds between existing collagen fibers and through induction of additional collagen structures. Effectiveness of this type of reinforcement is strongly dependent on the type of mechanical loading. Different physical interventions induce the reinforcement of at least one of these two layers, thus increasing the effective macroscopic stiffness of the total composite. At the same time, the standalone reinforcement of the skin appears to be less effective to achieve a delay or a reduction of the apparent signs of skin aging relative to the reinforcement of the sWAT.

Influence of GFRP skin reinforcement on the crack evolution in RC ties

Experimental tests on reinforced concrete ties with skin reinforcement made of Glass Fiber Reinforced Polymers (GFRP) mesh are presented in the paper. The study is a part of a wider research, currently going on at the University of Rome Tor Vergata, aimed at verifying possible solutions for limiting the crack opening, mainly in peculiar typologies of reinforced concrete structures, such as pipes or tunnel segments. Six 150 × 150 × 15000 mm3 specimens, with a steel O24 bar embedded in central position, were cast and tested under pure tension. In four ties a skin GFRP reinforcement was added, in order to analyse its influence on the crack spacing and width. Finally the application of a simple analytical model, suitably adapted for the analysed cases, shows the possibility of forecasting and simulating the crack patterns experimentally found.