Composite Patch Research Articles

An experimental and parametrical study on repair of cracked titanium airframe structures with single-side bonded carbon fiber-reinforced polymer prepreg patches

The present research aims to investigate efficient repair techniques of cracked Ti-alloy aircraft structures with adhesively bonded carbon fiber-reinforced polymer prepreg patches. The repaired specimens in the configuration of a Ti-alloy butt joint with one-side bonded composite patch were prepared under multiple repair factors including patch thickness, patch length, adhesive thickness, cure pressure, patch layup and surface treatment. The repair efficiency was evaluated by loading behavior, bonded interface microstructure and failure mode. The results reveals that the geometric factors affect the loading performance and alter failure modes by adjusting stress distribution in the repair system, whereas the cure pressure and surface treatment act on the bondline and change interfacial properties. A sensitivity-optimization model based on analysis of variance was established for parametrical study to quantify the contribution of repair factors and obtain optimal values. The optimum parameters were validated by repaired central-cracked specimens via static and fatigue tests, which proved that the repaired structure could restore 90.7% loading capacity of intact ones and endure more than 106 fatigue cycles of 25% ultimate failure load level of center-cracked ones. The proposed experimental and parametrical study possessed good efficacy in refurbishing strength and stiffness of cracked metallic structures.

Pyro-catalysis for refrigerator disinfection via ubiquitous temperature fluctuation

Bacteria breeding in refrigerators can greatly compromise the quality and shelf life of stored food, posing a serious concern. The utilization of disinfection treatments, including ultraviolet irradiation, ozone, and precious metal ions, in refrigerators is constrained by the risk of secondary contamination and the associated high costs. To tackle this matter, we developed a pyro-catalytic disinfection technology that takes advantage of ubiquitous temperature fluctuations to trigger the generation of highly cytotoxic reactive oxygen species for antibacterial. By subjecting the synthesized Ba0.68Sr0.32TiO3 (BST) nanowires or composite patches (BST@C) to temperature fluctuations ranging from 5 to 25 °C for 40 cycles, the survival rates of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were found to be below 5%. More importantly, the survival rates of S. aureus and E. coli were reduced to 19% and 34%, respectively, after only 80 refrigerator opening-closing cycles. This effective demonstration highlights the potential of the safety pyro-catalytic disinfection technology, which does not require additional energy consumption, and exhibits great compatibility with refrigerators.

Asymmetric porous composite hydrogel patch for microenvironment-adapted repair of contaminated abdominal wall defects

Effective antibacterial property and long-term mechanical support are essential for the repair of complex abdominal wall defects associated with infection. However, clinically available repair materials often fail to meet these requirements, resulting in high surgical failure rate and complications. In this study, an asymmetric porous composite hydrogel patch (cCS/PVA@BAC) with antibacterial, anti-adhesion, pro-healing, and durable mechanical support properties is designed for the efficient repair of contaminated abdominal wall defects. By stepwise phase-conversion and soaking method, robust and stable polyvinyl alcohol hydrogel (PVAH) is integrated with the biocompatible multicomponent hydrogel made of chitosan and carboxymethyl chitosan (cCS), and benzalkonium chloride (BAC) is loaded to enhance the antibacterial property. The cCS layer of cCS/PVA@BAC has an extracellular matrix-like porous structure, which can promote fibroblasts adhesion and wound healing. In contrast, the PVAH layer on the other side with a smooth and dense structure, which can reduce fibroblasts adhesion and prevent visceral adhesion. In addition, the composite hydrogel patch has good anti-swelling and anti-deformation properties as well as stable mechanical strength, thus can withstand high intraperitoneal pressure in the wet internal microenvironment. The loaded BAC can efficiently kill bacteria and improve the local inflammatory microenvironment. With these advantages, cCS/PVA@BAC can significantly reduce inflammation, promote tissue remodeling, and accelerate the healing of contaminated abdominal wall defects in the rat model. These findings suggest a potential use of multifunctional hydrogel patch as an ideal material for effective repair of contaminated soft tissue defects.

Outcome of primary ventral hernia repair with monofilament polyester composite ventral patch in a community-based hospital

Background: Ventral hernia repair (VHR) is one of the common surgical procedures carried out in general surgery. This study assessed the post operative outcomes in patients with primary ventral hernia undergoing repair using monofilament polyester composite ventral patch Parietex™ Covidien (PCO-VP). Methods: A prospective single proportion observational study of 54 patients undergoing open VHR for primary ventral hernia with the PCO-VP in a community-based hospital was carried out. The patients were followed up for a period of one year from day of surgery. Primary outcome was recurrence, and secondary outcomes were reoperations and complications including seroma, hematomas, abdominal wall abscess, wound infections, and mesh infections. Results: Our sample size of (n=54) included 35 (65%) females and 19 (35%) males with a mean hernia defect diameter of 3.5±0.4 cm. 83% (45) underwent elective surgery (EL) and 17% (9) underwent emergency surgery with a mean operative time of 98.5 minutes, 11% (n=6) patients needed alteration of the technique and 20% (n=11) patients needed mesh repositioning, 12 adverse events were noted during the hospital stay. No mesh infections, early recurrences, readmissions or revision surgeries were noted. Patients had a average Carolina comfort scale score of 4/115 noted at the end of study. Conclusions: The use of PCO-VP to repair primary ventral hernia yielded nearly nil early recurrence rate, low postoperative complications and high satisfaction ratings, PCO-VP repair is a highly effective method for small and moderate size ventral hernias in both elective and emergency setting.

Three-Dimensional-Printed GelMA-KerMA Composite Patches as an Innovative Platform for Potential Tissue Engineering of Tympanic Membrane Perforations.

Tympanic membrane (TM) perforations, primarily induced by middle ear infections, the introduction of foreign objects into the ear, and acoustic trauma, lead to hearing abnormalities and ear infections. We describe the design and fabrication of a novel composite patch containing photocrosslinkable gelatin methacryloyl (GelMA) and keratin methacryloyl (KerMA) hydrogels. GelMA-KerMA patches containing conical microneedles in their design were developed using the digital light processing (DLP) 3D printing approach. Following this, the patches were biofunctionalized by applying a coaxial coating with PVA nanoparticles loaded with gentamicin (GEN) and fibroblast growth factor (FGF-2) with the Electrohydrodynamic Atomization (EHDA) method. The developed nanoparticle-coated 3D-printed patches were evaluated in terms of their chemical, morphological, mechanical, swelling, and degradation behavior. In addition, the GEN and FGF-2 release profiles, antimicrobial properties, and biocompatibility of the patches were examined in vitro. The morphological assessment verified the successful fabrication and nanoparticle coating of the 3D-printed GelMA-KerMA patches. The outcomes of antibacterial tests demonstrated that GEN@PVA/GelMA-KerMA patches exhibited substantial antibacterial efficacy against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Furthermore, cell culture studies revealed that GelMA-KerMA patches were biocompatible with human adipose-derived mesenchymal stem cells (hADMSC) and supported cell attachment and proliferation without any cytotoxicity. These findings indicated that biofunctional 3D-printed GelMA-KerMA patches have the potential to be a promising therapeutic approach for addressing TM perforations.

Improving the performance of damage repair in thin-walled structures with analytical data and machine learning algorithms

In the last four decades, bonded composite repair has proven to be an effective method for addressing crack damage propagation. On the other hand, machine learning (ML) has made it possible to employ a variety of approaches for mechanical and aerospace problems and such significant approach is the repair mechanism and hence ML algorithms used to enhance in the present work. The current work investigates the effect of the single-sided composite patch bonded on a thin plate under plane stress conditions. An analytical model was formulated for a single-sided composite patch repair using linear elastic fracture mechanics and Rose's analytical modelling. From the analytical model, the stress intensity factors (SIF) were calculated by varying all possible parameters of the model. Next, ML algorithms were selected, and comparative studies were conducted for the best possible performance and to identify the parametric effects on optimum SIF. Also, the analytical model is validated with existing work, and it shows good agreement with less than 10% error. This study is particularly important for designing the single-sided composite patch repair method based on analytical modelling. Also, it is important to compare ML algorithms with analytical solutions in regression applications.

A fibrin patch loaded with mesenchymal stem cells-derived exosomes improves cardiac functions after myocardial infarction

Myocardial infarction (MI) is a typical cardiovascular disease, causing disability and death worldwide. Exosomes secreted by mesenchymal stem cells (MSCs) showed remarkable therapeutic effects in MI by restoring cardiac function. However, the application of exosomes remains a challenge because of their low residence rate in the infarcted myocardium. Herein, a fibrin-based cardiac patch was prepared to deliver MSCs-derived exosomes to the infarcted heart using an MI mouse model, aiming at improvement of cardiac functions. The fibrin patch was optimized for size to minimize the mouse mortality rate. The composite patch showed sustained release of exosomes in vitro and could improve the retention of exosomes in the infarcted heart, inhibiting fibrosis and improving cardiac functions in vivo. Therefore, this combination of natural biomaterial-based cardiac patch and MSCs-derived exosomes may have a promising clinical translational potential for the MI treatment.

Black phosphorus boosts wet-tissue adhesion of composite patches by enhancing water absorption and mechanical properties

Wet-tissue adhesives have long been attractive materials for realizing complicated biomedical functions. However, the hydration film on wet tissues can generate a boundary, forming hydrogen bonds with the adhesives that weaken adhesive strength. Introducing black phosphorus (BP) is believed to enhance the water absorption capacity of tape-type adhesives and effectively eliminate hydration layers between the tissue and adhesive. This study reports a composite patch integrated with BP nanosheets (CPB) for wet-tissue adhesion. The patch’s improved water absorption and mechanical properties ensure its immediate and robust adhesion to wet tissues. Various bioapplications of CPB are demonstrated, such as rapid hemostasis (within ~1-2 seconds), monitoring of physical-activity and prevention of tumour-recurrence, all validated via in vivo studies. Given the good practicability, histocompatibility and biodegradability of CPB, the proposed patches hold significant promise for a wide range of biomedical applications.

Experimental and numerical investigation of patch effect on the bending behavior for hat-shaped carbon fiber composite beams

Abstract In this study, reinforced composite panels with hat-shaped profile were produced from woven carbon fiber fabrics by vacuum infusion method. Holes were drilled on the crown surface of these panels and repaired with composite patches. The mechanical behavior was examined by performing a three-point bending test on the obtained patched and unpatched specimens. The contribution of the repair to the failure load of the damaged specimens under bending load has been clearly determined. In the numerical part, Hashin damage criterion was used for the beginning of damage. For damage progression, both Continuum Damage Mechanics and Material Property Degradation methods were preferred and compared. In the analysis carried out using the finite element package program Workbench, the cohesive zone model (CZM) was added to the model and its effect on the damage behavior and load of the composite structure was determined. As a result of the experiments and analyses, it was seen that the maximum contact force of the specimens under the bending load decreased by 29.8 % by increasing the number of holes on the specimen surface from 1 to 3. The maximum contact force was determined to increase by 18.52 % due to repairing the three-hole specimens with a patch.

Nanofibers and hydrogel composite patch with sandwich structure for prevention post-operative abdominal adhesion

Abdominal adhesions have a high incidence after surgery due to fibrosis and inflammation resulting in damaged tissues caused by trauma, bleeding, infection, foreign body stimulation. The adhesions introduced persistent chronic pain because of attachment and traction seriously affects physical health patients. Recent years, various kinds of membrances, hydrogel, nanofibers were developed to inhibit post-operative abdominal adhesion by physical isolation or drug treatment. However, the integration of physical isolation and pharmaceutical therapy in one platform still has some challenges. For example, the anti-swelling property of hydrogel is not good, membrane is easy prone to displacement. Herein, we developed a nanofiber-hydrogel composite patch (FHCP) with sandwich structure providing effectively anti swelling property and wet adhesion performance. Meanwhile, the nanofiber-hydrogel composite patch achieved combining excellent physical isolation and drug treatment, the sandwich structure of patch provided hierarchical drug release drugs release, and then made the patch realized excellent anti-inflammatory, tissue regeneration, and preventing post-operative abdominal adhesion. Our results showed that the prepared patch has better effects on anti-inflammation, effectively suppressing post-operative adhesion in the abdominal cavity. Therefore, we believe that our nanofiber-hydrogel composite patch has broad clinical application prospects.

Investigation of Stress Intensity Factor Reduction using Steel and GFRP Patches for Repairing Edge Cracks in Steel Plates

The ultimate objective of this study was to compare the performance of repaired edge cracks in steel plates before and after repair with patches made of steel patch and glass fiber-reinforced polymer composite patches (GFRP) in different shapes: circular, rectangular, and trapezoidal, under two conditions: unsymmetric patch (one patch) and symmetric patch (two patches). A three-dimensional finite element model of the one-sided and two-sided repaired examples is used to study how the steel and composite patch affect the stress intensity factor (SIF). Under uniaxial tensile loads, the use of steel patches and GFRP composite patches to repair cracks was studied. The results showed that the steel patch performs better than the GFRP patch because it significantly lowers the stress intensity factor (SIF). The symmetric patch arrangement (two patches) is better than the un-symmetric patch arrangement (one patch) because it significantly reduces the stress intensity factor (SIF).

Effect of fiber orientation-based composite lamina on mitigation of stress intensity factor for a repaired plate: a finite element study

The bonded composite repair has proven to be an effective method for addressing crack damage propagation. Numerous studies have employed experimental and simulation techniques to demonstrate the repair performance through the composites. These studies have explored various parameters related to bonded composites, such as size and properties, to enhance repair effectiveness. However, one aspect that has not been thoroughly investigated is the impact of fiber orientation within the composites. Therefore, the current work investigates the effect of the fiber direction of the composite patch bonded on a thin plate under plane stress conditions. Three types of fiber orientation of composite patch have been considered. In this investigation, the finite element method was used to determine the stress intensity factor using the ANSYS commercial code. The research findings showed that the fiber direction influenced the mitigation of stress intensity factor. This study is particularly important for designing the composite patch based on the fiber direction.

Analysis of water absorption on the efficiency of bonded composite repair of aluminum alloy panels

Abstract Carbon fiber-reinforced polymer (CFRP) exhibits aging effects over time that can degrade its mechanical properties. In this study, a systematic investigation was carried out to investigate the effect of distilled water aging on the mechanical properties of CFRP composite patch bonded on Al 2024-T3 plates. We built a finite element model to analyze the effect of water absorption by the composite and the adhesive on the effectiveness of the composite patch repair. Using the experimentally evaluated mechanical properties of CFRP and Araldite adhesive subjected to distilled water immersion, finite element simulations were validated. The experimental observations deduce that there was a negligible effect of moisture absorption on the bulk mechanical properties of CFRP and adhesive over time. However, a significant effect of moisture absorption was observed on the elasto-plastic behavior of both CFRP and adhesive. Consequently, the numerical simulations suggest that the moisture absorption reduces the bonded composite patch repair efficiency attributed to an increase in the plasticity around the crack front and accordingly increases the damage in the adhesive layer. This study attempts to provide guidelines on the severity of damage caused by water absorption on the performance of structures repaired with composite patches.

Investigating the impact of internal fatigue crack propagation in aluminum alloy plates repaired with a composite patch

Investigating the impact of internal fatigue crack propagation in aluminum alloy plates repaired with a composite patch

Banana fibre-chitosan-guar gum composite as an alternative wound healing material

Bio-composites, which can be obtained from the renewable natural resources, are fascinating material for use as sustainable biomaterials with essential properties like biodegradable, bio-compatibility as well cyto-compatibility etc. These properties are useful for bio-medical including wound healing applications. In this study, fibre obtained banana pseudo stem of banana plant, which is otherwise wasted, was used as a material along with chitosan and guar gum to fabricate a banana fibre-biopolymer composite patch. The physiochemical properties of the patches were examined using Fourier Transformed Infra-red spectrophotometer (FT-IR), tensile tester, Scanning Electron Microscope (SEM), contact angle tester, swelling and degradation studies. We further demonstrated that a herbal drug, Nirgundi could be loaded to the patch showed controlled its release at different pHs. The patch had good antibacterial property and supported proliferation of mouse fibroblast cells. The study thus indicates that banana fibre-chitosan-guar gum composite can be developed into an alternative wound healing material.

Numerical investigation of cracked metal/ceramic FGM plates repaired with bonded composite patch

Numerical investigation of cracked metal/ceramic FGM plates repaired with bonded composite patch

Effect of fibre hybridization and stacking sequence on the low velocity impact response of flax/basalt/aluminum composite-metal joints

A lot of composite materials with better impact resistance and better strength and stiffness can be manufactured these days. Many researchers have been using different materials to form new composites to understand their impact performance. This paper discusses such an attempt to make new composites by utilizing the concept of hybridization and then proposes which among them has better strength and performance under low-velocity impact (LVI) loading. In this work, circular patches of composites made up of a combination of basalt and flax fibers were used while being bonded with aluminum plate Al 2024-T3 of 3 mm thickness. The three different configurations which include asymmetric, symmetric, and sandwich were prepared using vacuum assisted bagging process and their impact performances were investigated using the Drop Weight Impact test. The results obtained were analyzed and they concluded that the asymmetric configuration of basalt/flax composite has better impact resistance, and strength and is better to use in structural components of automobiles, and the defense industry as compared to the other two.

Investigation failure behaviours of notched composite plates repaired with using adhesive and patch

In this study, the damage behaviors of different type-notched composite plates repaired with composite patches were investigated experimentally and numerically. Eight-layer woven glass fiber reinforced epoxy resin matrix composite plates and epoxy-based adhesive were used as materials. Notch type’s variations, adhesive thickness, patch length; double-side repair and single-side repair were used as parameter. Although the same size patch was used, the load values varied due to the different positions of the notches. Notched composite samples with the same area dimensions but different locations have different tensile strength values. Patching and bonding processes have different effects on notched samples with different tensile strength values. A feature of this study is that many parameters were compared for many samples under the same experimental conditions in order to improve repair quality and durability in an understandable way. As a result of the repair process, the failure loads were increased from 47% to 307% ratios according to parameters.

Investigation of patch application failure behaviors according to fiber orientation difference at notched composite plates

In this study, the damage behaviors of different type notched composite plates bonded with external composite patches were investigated experimentally under static tensile test. Eight-layer woven glass fiber reinforced epoxy resin matrix composite plates and epoxy based adhesive were used as materials. Notch type, fiber orientation angle, double side repair and single side repair were used as parameter. Effects of fiber orientation angle was investigated for 0 ° , 15 ° , 30 ° and 45 ° . Radial notch in the center (Type I), semicircular notch on the plate edge (Type II), a circular hole in the plate center (Type III) and U notch at the edges (Type IV) have been examined for 4 different notch types. The outstanding feature of this study is that many parameters were compared for many samples under the same experimental conditions. The composite plates and patches were used from same materials. Reducing of the damage loads has been observed for all notch types depending upon the increasing of fiber orientation angle significantly. In addition, that patch application to different fiber orientation plates is quite effective on damage loads. The extension was changed depending on the notch geometry at unrepaired composite. The load increasing rate is between + % 24 and + % 189 for one-sided bonded repair; + % 60 and + % 349 for two-sided bonded repair compared to the unrepaired samples. The results of this work can serve as a guide for workers to improve repair quality and durability in an understandable way.

PH-responsive, self-sculptured Mg/PLGA composite microfibers for accelerated revascularization and soft tissue regeneration

Biodegradable Mg/polymer composite fibers offer a promising therapeutic option for tissue injury because of bioactive Mg2+ and biomimetic microstructure. However, current studies are limited to the contribution of Mg2+ and the single microstructure. In this study, we designed Mg/poly (lactic-co-glycolic acid) (Mg/PLGA) composite microfibers that significantly enhanced angiogenesis and tissue regeneration synergistically by Mg2+ and self-sculptured microstructure, due to spontaneous in situ microphase separation in response to the weakly alkaline microenvironment. Our composite microfiber patch exhibited superior performance in the adhesion, spreading, and angiogenesis functions of human umbilical vein endothelial cells (HUVECs) due to the joint contribution of the hierarchically porous microstructure and Mg2+. Genomics and proteomics analyses revealed that the Mg/PLGA composite microfibers activated the cell focal adhesion and angiogenesis-related signaling pathways. Furthermore, the repair of typical soft tissue defects, including refractory urethral wounds and easily healed skin wounds, validated that our Mg/PLGA composite microfiber patch could provide favorable surface topography and ions microenvironment for tissue infiltration and accelerated revascularization. It could cause rapid urethral tissue regeneration and recovery of rabbit urethral function within 6 weeks and accelerate rat skin wound closure within 16 days. This work provides new insight into soft tissue regeneration through the bioactive alkaline substance/block copolymer composites interactions.