Burst Pressure Research Articles

Burst pressure prediction of carbon/natural fiber and hybrid composite pressure vessels by theoretical and numerical analysis

This study utilized finite element modeling to assess the stress and burst strength of a composite pressure vessel (CPV). The fiber type and its sequences were considered while developing the best CPV. The stress produced inside the CPV may cause damage to the vessel as well as loss of life and property. Therefore, it is critical to guarantee that the CPV's stress output does not surpass the vessel material's maximum allowable stress value. The primary goal of this research is to investigate the stresses induced in composite pressure vessels and then examine the stress using three different solutions: von Mises, Tresca, and ASSY. The theoretical burst strength is first established, and then a numerical solution is developed using ABAQUS. To confirm the correctness of FEA, the outcomes of the theoretical technique and the finite element method are compared. The six-layer carbon fiber-reinforced CPV shows twelve times higher burst strength than four layers but an equal thickness of jute fiber-based CPV. On the other hand, the hybrid combination of CPV (jute and carbon) shows a strength improvement over jute fiber based CPV by almost four times. Other jute fiber-based hybrid CPVs with glass, banana, and aluminum foil show very comparable strength relative to only jute CPV. This study's primary goal is to examine the failure phenomena and burst strength of thin, cylindrical pressure vessels.

Effect of ion penetration on the aging of EPDM components used in caustic liquid transfer lines by microscopic analysis

The waste transfer lines at the United States Department of Energy's Hanford Site Tank Farm in Benton County, Washington, USA have flexible sections that are fabricated from ethylene propylene diene monomer (EPDM) hoses. The hoses are of a hose-in-hose design with an inner hose that carries the waste and an outer hose that acts as containment in the event of an inner hose failure. During waste transport, the inner hoses are exposed to several stressors including caustic solutions at high temperatures and high pressures. These hose-in-hose transfer lines (HIHTL) are exposed to several stressors including caustic solutions at high temperatures and high pressures during the waste transport. The aging behavior of the HIHTL inner hose were evaluated by exposure to solutions at 77 °C containing 6.25, 12.50, and 25.00% (v/v) sodium hydroxide (NaOH) for 12-months. After the exposure, the burst pressure of the HIHTL specimens were measured and compared to the unaged samples.The burst pressure of the HIHTL specimens exposed to the 6.25% NaOH solution exhibited the most significant deterioration and those exposed to 25.00% NaOH solution had the least deterioration. Examination of the inside surface of the HIHTL specimens with scanning electron microscopy showed that the surface deterioration for the specimens exposed to 6.25% NaOH solution were the most severe and the samples exposed to 25.00% NaOH solution had the least deterioration. Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS) analysis of the specimens showed that the specimen aged with the 6.25% NaOH solution had that greatest sodium ion penetration into the material with the sodium concentration being significantly higher than those seen with the other specimens. In addition, when the specimens aged with both the 12.50% and the 25.00% NaOH solutions were examined, a white crystalline coating was observed on the inside surfaces of the specimens which appears to have acted as a barrier that protected the EPDM material from attack by the NaOH solutions.

Improvement of Formability in Parallel Double-Branched Tube Hydroforming Combined with Pre-Forming and Crushing Processes.

In hydroforming of parallel double-branch tubes, the material entering the branch zone is obstructed by material accumulation in the main tubes and corners, which decreases the branch height. A tube hydroforming approach is combined with pre-forming and crushing (THPC) to mitigate this problem. A larger diameter tube blank is flattened for pre-forming and then subjected to radial compression for crushing. In the next step, hydroforming forms the parallel double-branch tubes. Experiments and numerical simulations are then carried out to analyze the effect of traditional tube hydroforming (TTH) and the proposed THPC process on the formability of parallel double-branch tubes. The results show that for tubes obtained via THPC, the tube burst pressure increases by 27.5% and the branch height increases 2.37-fold compared to TTH. Additionally, the flattening, pre-forming, and crushing stages cause work hardening of the tube when using the TPHC process. Flattened tubes undergo radial compression to improve the material flowing into the branch tube. The formability of parallel double-branched tubes can be improved by using the TPHC process. Consequently, tube hydroforming, combined with pre-forming and crushing, has been confirmed as a feasible forming process for fabricating parallel double-branch tubes.

Dual-Modified Hyaluronic Acid for Tunable Double Cross-Linked Hydrogel Adhesives.

Conventional techniques for the closure of wounds, such as sutures and staples, have significant drawbacks that can negatively impact wound healing. Tissue adhesives have emerged as promising alternatives, but poor adhesion, low mechanical properties, and toxicity have hindered their widespread clinical adoption. In this work, a dual modified, aldehyde and methacrylate hyaluronic acid (HA) biopolymer (HA-MA-CHO) has been synthesized through a simplified route for use as a double cross-linked network (DCN) hydrogel (HA-MA-CHO-DCN) adhesive for the effective closure and sealing of wounds. HA-MA-CHO-DCN cross-links in two stages: initial cross-linking of the aldehyde functionality (CHO) of HA-MA-CHO using a disulfide-containing cross-linker, 3,3'-dithiobis (propionic hydrazide) (DTPH), leading to the formation of a self-healing injectable gel, followed by further cross-linking via ultraviolet (UV) initiated polymerization of the methacrylate (MA) functionality. This hydrogel adhesive shows a stable swelling behavior and remarkable versatility as the storage modulus (G') has shown to be highly tunable (103-105 Pa) for application to many different wound environments. The new HA-MA-CHO-DCN hydrogel showed excellent adhesive properties by surpassing the burst pressure and lap-shear strength for the widely used bovine serum albumin-glutaraldehyde (BSAG) glue while maintaining excellent cell viability.

Numerical study on the shock wave and vortex and their coupling effect on the behavior of the flame induced by the spontaneous ignition of high-pressure hydrogen release

High-pressure hydrogen storage is currently the mainstream way of hydrogen storage. However, the risk of spontaneous ignition and subsequent jet flame are serious obstacles to the wide application of hydrogen energy. To further reveal the interaction of shock waves, vortices and flame induced by the spontaneous ignition of high-pressure hydrogen release under the effect of release process and burst pressure, a numerical study is conducted by employing LES, RNG, EDC models and detailed hydrogen/air combustion mechanism. The qualitative and quantitative comparison of flow field and flame splitting process outside the tube between this numerical study and previous experimental results validate the numerical results. It is found that an initial vortex is formed at the edge of the jet. Then, several vortices are generated at the edge of the jet and ahead of the Mach disk. The number of vortices in the outer side of the barrel shock is larger when the opening time is shorter. After moving out of the tube, the flame front becomes hemisphere and the lateral edge has a hemispherical bulge which is induced by the initial vortex. The temperature is low and the hydrogen concentration is high in the high-speed region which is induced by the reflected shock wave, leading to the splitting of the flame into two parts: the first and the second half of the flame. However, the flame cannot be formed at the initial stage when the opening time increases to 150 μs and the flame area is larger than with smaller opening times. After splitting, under the affection of the vortices generated at the lateral side, the first half of the flame rotates backward and gradually merges with the second half of the flame, finally forming a complete hydrogen jet flame.

Correlations to estimate the ground loading from small scale propane BLEVE experiments

This paper presents small-scale propane BLEVE (Boiling Liquid Expanding Vapor Explosion) experiments coupled with an investigation into ground loading dynamics. The experiments utilized cylindrical aluminum pressure vessels, with a diameter of 50 mm and a length of 300 mm. The controlled variables included burst pressure, liquid fill level, and weakened length. Both high and low-speed measurements of internal pressure and ground force were conducted during the experiments. The dependent variables analyzed were peak total ground load, force duration, and impulse. The findings from the study show trends in ground force and impulse with alterations in failure pressure, fill level and weakened length. Specifically, ground force and impulse exhibit an upward trend with increasing failure pressure, fill level and weakened length (cut length). For the first time, comprehensive correlations have been developed, incorporating the controlled variables, as well as theoretical boiling wave speed and vapor speed, to estimate the dependent variables, which represents a significant contribution in the field. However, the study does acknowledge the presence of scatter in the data, which are believed to be associated with the intricacies of the vessel opening process. It should be noted that this correlation has not been validated for larger scales. Once validated on a larger scale, these correlations can be directly applied in the design and practice of civil infrastructure to enhance the structural integrity. Additionally, the research has direct implications for industrial applications, allowing for the quantitative assessment of risks associated with bridge collapse during the transportation of PLGs.

A fluid filled MEMS hydrophone

MEMS hydrophones are of interest to provide a small form factor acoustic sensing capability in water. The majority of previous work on MEMS hydrophones (e.g., Bernstein 1997, Moon, 2010, Gu, 2018) use air backed diaphragms in order to provide increased sensitivity. However, this limits the operating depth of the device due to a reduction in the diaphragm burst pressure. In this work we investigate an architecture that has the potential to increase the operating depth by filling the backing cavity with a heavy fluid. We have designed architectures with multiple acoustic ports (Moon, 2010) and coupled piezoelectric diaphragms, in a bid to maintain sufficient sensitivity while incorporating the filling fluid. The sensing elements are Parylene coated, repackaged Vesper VM1000 aluminum nitride MEMS microphones. It was reported (Travaglione, 2018) that such a device can sense underwater sound, but characterization was limited. In our prototypes, the microphone die are co-packaged onto modified printed circuit boards which include the acoustic coupling elements and required preamplifiers. We report on computational predictions of sensitivity and resolution, and provide initial test results as part of our ongoing investigation. Support from OUSD (R&E) Innovation and Modernization Office.

Study on the formation and ignition law of ignition core in ammonia atmosphere diesel cylinder

Ammonia fuel does not contain carbon and is a kind of very good zero-carbon alternative fuel for diesel engines. However, ammonia is difficult to be ignited in diesel engine. The dual-fuel combustion mode of ammonia and diesel is an effective technical means to solve the problem. In this paper, the 186FA diesel engine test bench was built, and the ammonia/diesel dual fuel combustion mode was formed by injecting 0 %, 10 %, 20 %, 30 %, 40 %, and 50 % ammonia into the inlet and direct injection of diesel into the cylinder. The in-cylinder pressure and heat release laws were measured and analyzed at 2700r/min, 25 % load and 75 % load. Based on the analysis of the oxidation in ignition process of ammonia gas and diesel, a computational fluid dynamics model of the ignition process was established. By comparing the temperature contour surface in the cylinder and the concentration contour surface of OH radical, the paper put forward the ignition core evaluation index suitable for diesel/ammonia dual fuel. The formation law of the ignition core of diesel injected in homogeneous low reactive ammonia atmosphere in the cylinder was analyzed, and the influence of ammonia on the ignition process of diesel was revealed. The results show that the ignition delay period is prolonged after adding ammonia, and there is an exponential function relationship between the ignition delay period and the atmospheric concentration of ammonia. At 1200 K, there is an obvious parabolic relationship between ammonia concentration and OH radical concentration. The ignition core area was increased with the increase of ammonia concentration. Compared with pure diesel mode, the single ignition core at 75 % load of 2700 r/min is 3.6 times larger at 50 % ammonia atmosphere concentration. The ignition core will move up the diesel bundle with the increase of ammonia concentration. The study of chemical reaction kinetics showed that the reaction NH3 + OH = NH2 + H2O displayed positive sensitivity when ammonia concentration was less than 10 % and negative sensitivity when ammonia concentration was more than 10 %. The difference in sensitivity is the reason why the phase of the maximum burst pressure in the 10 % ammonia atmosphere is slightly earlier.

Innovative approach: utilizing silver nanoparticles sheet for improved rabbit cecal anastomosis healing.

Anastomotic leakage is a severe complication associated with gastrointestinal surgery. The process of intestinal wound healing is crucial for the successful outcome of digestive tract surgical repair procedures. This research aimed to determine the impact of silver nanoparticles sheet (Acticoat) on the anastomotic healing of the cecum in rabbits. A total of 48 New Zealand male rabbits in good health were used for cecum transection and anastomosis. The animals were randomized into the control group (C) and the silver nanoparticles group (AgNPs). In the C group, the transected cecum was end-to-end anastomosed with a single layer of simple continuous suture pattern using 3-0 polyglyconate. In contrast, a silver nanoparticle sheet (Acticoat) was covered around the sutured anastomotic line in the AgNPs group. Postoperatively, abdominal ultrasound imaging and the Bristol Rabbit Pain Score (BRPS) were measured on days 7, 15, and 30. Eight rabbits from each group were euthanized at each time point to assess macroscopic findings, bursting pressure tests, tensile strength tests, histopathological examinations, and immunohistochemical analyses. The AgNPs group demonstrated a significant increase in the cecal lumen diameter wall (p ≤ 0.001), burst pressure measurement (p ≤ 0.02), and tensile strength (p ≤ 0.01). Conversely, the AgNPs group had significantly lower BRPS scores (p ≤ 0.01). In addition, histopathological examinations revealed that AgNPs significantly reduced inflammatory cell infiltration (neutrophils and macrophages) and enhanced collagen deposition. Immunohistochemical analyses revealed a significant increase (p ≤ 0.01) of α-SMA and a reduction of CD31 in the anastomotic tissue of the AgNPs group. The results of the present study indicate that the utilization of the AgNPs sheet (Acticoat®) effectively enhanced the strength of cecum anastomosis, resulting in a reduction in anastomosis leakages, pain scores, and abdominal adhesions. Additionally, the bursting pressure values in the rabbit model were significantly increased.

A novel design of a low-pressure composite vessel with inspection opening – design, manufacturing and testing

Composite structures, especially pressure vessels, pipelines, and additional components such as tees, reductions, or inspection openings are more and more willingly used in the chemical industry. In this research, a novel design of a low-pressure composite vessel with an inspection opening is presented. The vessels are unsymmetrical considering the domes. On one side the opening is considerably bigger, around half of the cylindrical diameter of the vessel. This design requires a new approach to manufacturing such structures. In this study, a two-step analysis was performed. Firstly, small-size pressure vessels (S) were manufactured and the design of dome reinforcement was validated. Then, the final design of vessel (M) was produced, with a volume of around 700 litres. The vessels were initially calculated for 21 bars of burst pressure. During burst pressure tests, the strains were measured with optical fibres (FBG) and strain gauges. Additionally, the acoustic emission was utilized to predict the damage modes and locations. Finally, a microscopic evaluation of the specific parts of the vessels was performed. Conclusions were drawn, that the proposed novel design of dome reinforcement around the inspection opening fulfilled the strength and stiffness requirements.

Voids in type-IV composite pressure vessels manufactured by a dry filament-winding process

Type-IV high-pressure hydrogen-gas tanks for fuel-cell electric vehicles are made from carbon fiber-reinforced plastic. Their production involves wrapping a carbon-fiber-reinforced thermoset resin towpreg around a plastic liner to form a tank shape, followed by heating in an oven to cure the thermoset resin. The filament-winding process produces many voids in the tank that cause variations in quality and the product lifetime. In this study, the voids in the tank were classified according to their origin. A type-IV high-pressure hydrogen-gas tank with a burst pressure of 70 MPa was fabricated, and the voids produced in the tank were observed. The same filament-winding process was used to fabricate a plate and tank with a simple winding trajectory to identify the voids. The voids produced in the tank by the filament winding were categorized into six groups based on their location, cross-sectional shape, and size, showing the origin of the voids.

Experimental investigation for the effect of bust pressure on hydrogen explosion venting

A series of experiments are carried out to investigate the effect of burst pressure on hydrogen explosion venting in a 20 L square vessel. Pressure buildup and flame evolution are recorded using piezoelectric pressure transducers, high speed camera, high speed infrared camera and schlieren system. The results show that both the maximum explosion pressure (Pmax) inside and outside the vessel increase with the increasing burst pressure, and the Pmax in the external space decreases rapidly with the increase of the distance from the vent port. Compared to the burst pressure of 0 kPa, the Pmax inside the vessel and at 1200 mm increased by 79.1 % and 153.6 %, respectively, when the burst pressure was 325 kPa. The venting flame surface during the propagation is smoother with the increasing burst pressure, the width and area of the flame also increases. There is little effect of burst pressure on the maximum flame propagation distance (Lmax), but with the increase of burst pressure, the flame propagation time is shortened and the average propagation velocity is increased. The venting flame propagation time is shortened from 5.0 ms to 3.5 ms with the burst pressure increases from 0 kPa to 325 kPa. The high temperature zone of venting flame is mainly distributed in the flame front, while the maximum flame temperature (Tmax) gradually increases with the increase of burst pressure. The increase in burst pressure results in an increase in the turbulence intensity inside the vessel and an advance in the time to stabilization inside the vessel. Furthermore, the moment at which flow backflow occurs at the vent port is advanced from 16.5 ms to 8.5 ms with the increase in burst pressure.

Damage-tolerance design method for composite high-pressure hydrogen vessels of fuel cell vehicles and stacking-sequence optimization method based on the design method

An approach was proposed to design high-pressure composite hydrogen vessels for fuel cell vehicles with damage tolerance. In addition, a stacking-sequence optimization method was developed, which was built upon the damage tolerance design. A no-growth approach, damage categorization, and residual strength requirements were proposed for the damage-tolerance design method for high-pressure hydrogen vessels, which were implemented in the damage-tolerance design method for composite aircrafts. The initial burst pressure was set at 180% of normal working pressure (NWP) assuming that the structural health monitoring (SHM) system with acoustic emission (AE) testing would immediately detect the occurrence of fiber failure. Stacking-sequence optimization was then conducted to minimize vessel thickness and meet the residual strength requirements. As a result of the optimization, the calculations confirmed that the vessel thickness could be reduced by approximately 52% of the existing vessel stacking sequence. The results show that the thickness of the vessel can be reduced by introducing a damage-tolerant design. Moreover, the proposed method for an optimal design based on the damage-tolerance design method is effective.

Bioinspired Injectable Polyurethane Underwater Adhesive with Fast Bonding and Hemostatic Properties.

Underwater adhesives with injectable, organic solvent-free, strong, fast adhesion, and hemostatic properties have become an urgent need in biomedical field. Herein, a novel polyurethane underwater adhesive (PUWA) inspired by mussels is developed utilizing the rapid post-cure reaction of isocyanate esterification without organic solvents. The PUWA is created through the injectable two component curing process of component A (biocompatible polyurethane prepolymer) and component B (dopamine modified lysine derivatives: chain extender-LDA and crosslinker-L3DA). The two-component adhesive cures quickly and firmly underwater, with an impressive bonding strength of 40kPa on pork skin and excellent burst pressure of 394mmHg. Moreover, the PUWA exhibits robust adhesion strength in hostile environments with acid, alkali and saline solutions. Combined with excellent biocompatibility and hemostatic performance, the PUWA demonstrates effectively sealing wounds and promoting healing. With the ability to bond diverse substrates rapidly and strongly, the PUWA holds significant potential for application in both biomedical and industrial fields.

A Laparoscopically Compatible Rapid-Adhesion Bioadhesive for Asymmetric Adhesion, Non-Pressing Hemostasis, and Seamless Seal.

Bioadhesive hydrogels offer unprecedented opportunities in hemostatic agents and tissue sealing; however, the application of existing bioadhesive hydrogels through narrow spaces to achieve strong adhesion in fluid-rich physiological environments is challenged either by undesired indiscriminate adhesion or weak wet tissue adhesion. Here, a laparoscopically compatible asymmetric adhesive hydrogel (aAH) composed of sprayable adhesive hydrogel powders and injectable anti-adhesive glue is proposed for hemostasis and to seal the bloody tissues in a non-pressing way, allowing for preventing postoperative adhesion. The powders can seed on the irregular bloody wound to rapidly absorb interfacial fluid, crosslink, and form an adhesive hydrogel to hemostatic seal (blood clotting time and tissue sealing in 10 s, ≈200mm Hg of burst pressure in sealed porcine tissues). The aAH can be simply formed by crosslinking the upper powder with injectable glue to prevent postoperative adhesion (adhesive strength as low as 1kPa). The aAH outperforms commercial hemostatic agents and sealants in the sealing of bleeding organs in live rats, demonstrating superior anti-adhesive efficiency. Further, the hemostatic seamless sealing by aAH succeeds in shortening the time of warm ischemia, decreasing the blood loss, and reducing the possibility of rebleeding in the porcine laparoscopic partial nephrectomy model.

Carotid Artery Stenting for Heavily Calcified Lesions Using a Scoring Balloon: A Report of 2 Cases

Objective Carotid artery stenting for heavily calcified lesions is challenging for interventionists. A calcium burden is associated with suboptimal dilatation, periprocedural complications, high rates of restenosis, and poor outcomes. We describe the first report of 2 cases of successful carotid artery stenting for heavily calcified lesions using a scoring balloon. Case Presentation The patients were both aged 75 years, 1 male and 1 female, who had experienced ipsilateral stroke prior to the procedures. They had dense calcifications at the lesions, stenosis rates of 95% (near occlusion) and 86% according to the North American Symptomatic Carotid Endarterectomy Trial criteria, and calcification arcs of 270° and 360°, respectively. Considering the heavy calcification, predilation with scoring balloons (NSE PTA balloon; Nipro, Osaka, Japan) at the rated burst pressure was performed in both cases. Sufficient dilatation was achieved, followed by carotid stent deployment (Precise Pro RX; Cordis, Miami Lakes, FL, USA). After postdilatation, the stenosis rates decreased to 21% and 23%, respectively. Although 1 patient experienced prolonged bradycardia and hypotension, they were well managed with anticholinergic and vasoconstrictive agents. Both patients remained asymptomatic. Conclusion Carotid artery stenting using a scoring balloon obtained acceptable improvements in severe stenosis with heavily calcified lesions. This method could be a useful option for the revascularization of heavily calcified lesions.

Antioxidant and Trilayered Electrospun Small-Diameter Vascular Grafts Maintain Patency and Promote Endothelialisation in Rat Femoral Artery.

Vascular grafts with a small diameter encounter inadequate patency as a result of intimal hyperplasia development. In the current study, trilayered electrospun small-diameter vascular grafts (PU-PGACL + GA) were fabricated using a poly(glycolic acid) and poly(caprolactone) blend as the middle layer and antioxidant polyurethane with gallic acid as the innermost and outermost layers. The scaffolds exhibited good biocompatibility and mechanical properties, as evidenced by their 6 MPa elastic modulus, 4 N suture retention strength, and 2500 mmHg burst pressure. Additionally, these electrospun grafts attenuated cellular oxidative stress and demonstrated minimal hemolysis (less than 1%). As a proof-of-concept, the preclinical evaluation of the grafts was carried out in the femoral artery of rodents, where the conduits demonstrated satisfactory patency. After 35 days of implantation, ultrasound imaging depicted adequate blood flow through the grafts, and the computed vessel diameter and histological staining showed no significant stenosis issue. Immunohistochemical analysis confirmed matrix deposition (38% collagen I and 16% elastin) and cell infiltration (42% for endothelial cells and 55% for smooth muscle cells) in the explanted grafts. Therefore, PU-PGACL + GA showed characteristics of a clinically relevant small-diameter vascular graft, facilitating re-endothelialization while preserving the anticoagulant properties of the synthetic blood vessels.

Strength and Failure Analysis of Fiber-Wound Composite Gas Cylinder via Numerical Simulation.

Based on the classical grid theory and related regulations, a structure model of a fiber-wound composite gas cylinder was designed in this paper. Based on the design results, a finite element model of a fully wound composite cylinder of an aluminum alloy inner liner with a working pressure of 35 MPa was established based on the ABAQUS software, and its stress distribution under working pressure and minimum burst pressure was analyzed. According to engineering experience, the pressure tolerance of composite cylinders can be improved by proper autofrettage pressure before working pressure, so the influence of autofrettage pressure was analyzed in this paper. The optimum autofrettage pressure was selected by setting the autofrettage gradient, and damage analysis was carried out on the cylinder with nominal working pressure of 35 MPa based on the Hashin failure criterion. The results show the initial damage sequence: matrix stretching occurs before the fiber stretching, and the damage generally starts from the spiral-wound layer. The tensile damage first appears in the transition section between the head and the barrel body, and the damage of the spiral-wound layer develops from the inner layer of the wound layer to the outer layer, while the damage of the circumferentially wound layer develops from the outer layer to the inner layer.

Fabrication and biomechanical characterization of a spider silk reinforced fibrin-based vascular prosthesis

With fibrin-based vascular prostheses, vascular tissue engineering offers a promising approach for the fabrication of biologically active regenerative vascular grafts. As a potentially autologous biomaterial, fibrin exhibits excellent hemo- and biocompatibility. However, the major problem in the use of fibrin constructs in vascular tissue engineering, which has so far prevented their widespread clinical application, is the insufficient biomechanical stability of unprocessed fibrin matrices.In this proof-of-concept study, we investigated to what extent the addition of a spider silk network into the wall structure of fibrin-based vascular prostheses leads to an increase in biomechanical stability and an improvement in the biomimetic elastic behavior of the grafts. For the fabrication of hybrid prostheses composed of fibrin and spider silk, a statically cast tubular fibrin matrix was surrounded with an envelope layer of Trichonephila edulis silk using a custom built coiling machine. The fibrin matrix was then compacted and pressed into the spider silk network by transluminal balloon compression.This manufacturing process resulted in a hybrid prosthesis with a luminal diameter of 4 mm. Biomechanical characterization revealed a significant increase in biomechanical stability of spider silk reinforced grafts compared to exclusively compacted fibrin segments with a mean burst pressure of 362 ± 74 mmHg vs. 213 ± 14 mmHg (p < 0.05). Dynamic elastic behavior of the spider silk reinforced grafts was similar to native arteries. In addition, the coiling with spider silk allowed a significant increase in suture retention strength and resistance to external compression without compromising the endothelialization capacity of the grafts.Thus, spider silk reinforcement using the abluminal coiling technique represents an efficient and reproducible technique to optimize the biomechanical behavior of small-diameter fibrin-based vascular grafts.

Evaluation of damage and failure analysis of CPVC pipes

In this paper, the work we have carried out has focused on the failure analysis of CPVC (chlorinated polyvinyl chloride) pipes. We stimulated the damage by notch effect and evaluated its properties using models available in the literature, specifically, the linear damage of Miner, the normalized damage and the unified theory. Burst tests allowed us to obtain ultimate pressure and time parameters for the virgin specimens and the residual parameters for the damaged ones. Then, we analyzed the effect of defect on the mechanical behavior of the studied structures; we found that the mechanical properties of the material were lost as defects increased. An observation and analysis of the pressure drop and thereafter the residual ultimate resistance brings out acceleration from it around the critical depth. Then, an evaluation of the static damage of the studied CPVC pipes was made according to model based on the experimental results of the burst tests and on the modification of the unified theory concepts and the static damage. Indeed, we evaluated the static damage of blank and notched tubes using mainly burst pressure parameters.