Composite Patch Research Articles

A ZIF-8-encapsulated interpenetrated hydrogel/nanofiber composite patch for chronic wound treatment.

Designing wound dressings necessitates the crucial considerations of maintaining a moist environment and implementing effective bacterial control. Furthermore, developing a three-dimensional framework emulating the extracellular matrix (ECM) confers advantages in fostering cellular migration and proliferation. Inspired by this, hydrogel/nanofiber composites have been demonstrated as promising materials for wound dressings. The composites also overcome the disadvantages of poor mechanical properties and rapid release of traditional pure hydrogels. In this study, we constructed a calcium alginate hydrogel/polylactic acid nanofiber (CAH/PLANF) composite with an interpenetrated network. Additionally, the synthesis of zeolitic imidazolate framework-8 (ZIF-8) incorporated into the composite system endowed the system with enhanced mechanical properties and photodynamic antibacterial attributes. The obtained composite patch (ZIF-8@CAH/PLANF) exhibited excellent swelling, strong mechanical properties, low cytotoxicity, and durable photodynamic antibacterial effect with an antibacterial efficacy of higher than 99.99%. Finally, bacterial infection and wound healing properties were investigated in vivo, and the ZIF-8@CAH/PLANF patch was proven to have the ability to fight infection and accelerate wound healing.

Quality Inpainting and Region Filling Using a Complete-Composite Patch Sampling Scheme (CCPSS) Based on Statistical Estimation

Research in the field of Inpainting and Region filling has nowadays gained immense momentum to account for historical and ancient mural conservation and the technological advancements as regards the need for image processing applications. This work proposes a complete Composite Patch Sampling Scheme (CCPSS) incorporating four refinements over Criminisi and other state-of-the-art techniques. The earlier Criminisi patch matching approach is supported by adding alien patches generated from independent color components of the existing known or valid patches. The dependency of confidence and data terms used in the priority function had been removed by selecting unknown pixels based on their neighborhood unknowns. The proceeding estimated unknown pixel patches are considered in estimating successive invalid pixel patches. Lastly, the highest similar or consistent known patch concerning an unknown patch is not finalized but retained until all the unknown patches are estimated. The true value of any unknown pixel is computed using the mean and median of all retained values. The inpainting, region filling, and reconstruction quality of the CCPSS scheme is superior in terms of visual perception when tested over high-resolution texture-structure images at the cost of computational overhead.

Cornea‐Inspired Ultrasound‐Responsive Adhesive Hydrogel Patches for Keratitis Treatment

AbstractBiomedical patches offer significant potential for keratitis treatment. Building on advances in multifunctionality and biomimicry, an innovative, multifunctional hydrogel patch with high therapeutic efficacy, inspired by the native architecture and functions of the cornea, is introduced. By engineering a composite patch comprising recombinant human collagen (RHC) hydrogel, near‐field electrospinning (NFES) microfibers, and gold‐nanoparticle‐decorated tetragonal barium titanates (BTO@Au), structural mimicry, mechanical reinforcement, tissue‐specific adhesion, and bacterial inhibition are achieved. The RHC hydrogel recreates a three‐dimensional (3D) microenvironment that emulates the natural structure of the corneal tissue, demonstrating excellent tissue adhesion. Integrated within this hydrogel, the NFES microfibers, designed to emulate the orthogonal arrangement of native corneal stroma, not only reinforce the mechanical strength of the RHC hydrogel but also act as scaffolds to guide the aligned growth of human keratocytes. A unique aspect of this advanced patch is the incorporation of BTO@Au nanoparticles, which generate reactive oxygen species for effective bacterial eradication when subjected to ultrasound stimulation. Through in vivo studies on rat models with infected corneal wounds, this hydrogel patch exhibits superior therapeutic efficacy compared to the current treatment. It is posited that these cornea‐inspired ultrasound‐responsive adhesive hydrogel patches represent a significant scientific advancement with high potential for clinical applications.

Photoelectric-driven conductive composite ionogel patch for effective wound healing

Developing the high biosafety, effective and wearable devices for fast wound healing is highly desired but remains a challenge. Here, we propose a “win–win co-operation” strategy to potentiate effective skin wound healing at the wound site by constructing robust and ecofriendly composite patch under opto-electric stimulation. The wearable patch is composed of ionic gel doped with Ti3C2Tx (MXene), which possesses good photothermal response to kill the bacteria via effective inhibition of the expression of inflammatory factors, preventing wound infection. Importantly, the composite ionogel patch is capable of providing green and on-demand electrical stimulation for wound site, guiding cell migration and proliferation by improved bioenergy and expression up-regulation of growth factor. In mice wound models, the treatment group healed ∼31% more rapidly. Mechanistically, the wearable devices could enable visual and real-time supervising treatment effect due to their good transmittance. The proposed strategy would be promising for future clinical treatment of wound healing.

NUMERICAL STUDY OF MECHANICAL BEHAVIOR OF REPAIRED INCLINED CRACKED UNDER COMPLEX SHEAR-SHEAR LOAD: PERFORMANCE AND DURABILITY OF ALUMINUM 2024-T3 PLATE

In this study, a finite element model was developed to analyze the mechanical behavior of repairing aluminum 2024-T3 structures subjected to complex shear-shear loads using composite patch repair techniques. The study aimed to investigate the effect of different patch sequences on the mechanical behavior of the repaired structure, including the orientation of the fiber patch, to improve durability under complex shear-shear loading conditions. The study demonstrated that the FEM approach is a robust and precise method for optimizing patch repair and studying the effect of mechanical loads on patch repair effectiveness for aluminum 2024-T3 structures.

Schwann Cell-Derived Exosomes and Methylprednisolone Composite Patch for Spinal Cord Injury Repair.

Spinal cord injury (SCI) can cause permanent loss of sensory and motor function, and there is no effective clinical treatment, to date. Due to the complex pathological process involved after injury, synergistic treatments are very urgently needed in clinical practice. We designed a nanofiber scaffold hyaluronic acid hydrogel patch to release both exosomes and methylprednisolone to the injured spinal cord in a non-invasive manner. This composite patch showed good biocompatibility in the stabilization of exosome morphology and toxicity to nerve cells. Meanwhile, the composite patch increased the proportion of M2-type macrophages and reduced neuronal apoptosis in an in vitro study. In vivo, the functional and electrophysiological performance of rats with SCI was significantly improved when the composite patch covered the surface of the hematoma. The composite patch inhibited the inflammatory response through macrophage polarization from M1 type to M2 type and increased the survival of neurons by inhibition neuronal of apoptosis after SCI. The therapeutic effects of this composite patch can be attributed to TLR4/NF-κB, MAPK, and Akt/mTOR pathways. Thus, the composite patch provides a medicine-exosomes dual-release system and may provide a non-invasive method for clinical treatment for individuals with SCI.

Experimental evaluation of interface adhesion of a flax fiber composite patch with epoxy and polyurethane adhesives for the reinforcement of steel structures

Using fiber-reinforced composite patches for repairing damaged structures made of metal or/and concrete is an interesting and widely available solution on the market using synthetic materials. These repairing patches are bonded on the structures’ surfaces to increase their strength against internal stresses, as well as protect them from external physico-chemical attacks, thereby limiting crack propagation. Natural fibers offer a potential alternative to replacing glass or carbon fibers commonly used for bonded repair patches. Similarly, bio-based polymers represent an important sustainable alternative for partially or entirely replacing the petroleum-based polymers. In this study, an epoxy matrix reinforced with flax fiber is proposed as the material for the patches, and bonded to a steel plate using four different types of adhesive materials, including a castor-oil derived polyurethane resin. Floating roller peel tests were performed to assess the adhesion and viability of these new patches. The resulting peeling loads and fracture surface analysis are presented. Polyurethane demonstrates promising performance for epoxy-to-steel joints, but major improvements of the bio-based polyurethane application process and curing conditions may be necessary for its successful industrial implementation.

Advances in Shape Memory Alloy-Based Reinforcement in Steel Structures: A Review

The utilization of shape memory alloys (SMAs) to reinforce steel structures has been proven to be an efficient and reliable method, the structural strengthening needs can be met without the need for tensioning equipment by activating the SMAs to generate restoring stresses. This paper firstly introduces the properties of SMA, and then presents the latest research progress, opportunities and challenges of SMA in the field of steel structural reinforcement, both in terms of basic components and applications. In terms of components, the construction forms and working mechanisms of Fe-SMA strips, SMA/CFRP composite patches and SMA dampers are introduced. On this basis, the application of SMA in steel structures reinforcement is introduced, and its effect is analyzed from three aspects: crack restoration, seismic retrofitting and structural strengthening. Finally, the results of the current research are summarized and the shortcomings are analyzed, hoping to provide a reference for the research of SMA in the field of steel structures reinforcement.

Reinforcement of GFRP Tensile Specimens with Central Holes Using Bonded Composite Patches

The use of bonded composite patches is a promising repair/reinforcement method to extend service live of damaged structures. These patches are non-corroding, lightweight, easy to fabricate and have high specific modulus and strength. In this work, the tensile behavior of a patch-reinforced composite specimen with a central hole is analyzed experimentally. A 10-ply composite tensile specimen is prepared by using bidirectional woven e-glass fabric and epoxy resin as the matrix material. The damage is created in the specimen by drilling three different holes with 3, 6 and 10 mm diameter at the center. The specimen is then reinforced by bonding composite patches or carbon steel patches with different lengths as external patches on both external surfaces. Tensile tests have been carried out on the undamaged, damaged, and repaired specimens. From the tensile tests, it was possible to verify the reduction of the strength (measured by the rupture force) of the specimens with holes of 3 mm, 6 mm and 10 mm. The patches were manufactured using the same glass fiber reinforced plastic, GFRP, used in the specimens or carbon steel. The patches were 25,0 mm wide, 2,5 mm thick. The length was 20 mm, 40 mm or 60 mm. It was found that GFRP patches has better efficiency than carbon steel patches. The repairs with GFRP patches were able to restore between 80% and 90% of the mechanical properties of the intact GFRP specimen without the necessity to replace the composite material.

Comparison of Repair Methods for Cracked Titanium Alloy Aircraft Structures with Single-Sided Adhesively Bonded Composite Patches.

Composite patches are widely accepted as a useful practice for the repair of cracked aircraft components and the repair method is of vital importance to the final performance of the repaired structures. The present research experimentally studied the repair efficiency and processing stability of pre-cured, prepreg (including unidirectional and plain weave prepregs) and wet-layup methods for use on cracked Ti-alloy panels through the configuration of a butt joint bonded with a one-sided composite patch. The efficiency and stability of these repair methods were elaborately evaluated and compared via the load bearing behavior, the microstructure of the bonding interface, and the structural failure morphology through two batches of testing specimens. Typical patterns were found in load-displacement curves where the initial damage and ultimate bearing load points divided them into elastic-linear, damage propagation and complete fracture phases. Although the co-cure process of both unidirectional prepreg and wet-layup methods can form a jigsaw-like demarcation interface between the adhesive layer and the composite patch to achieve a good bonding force and a high recovery of loading performance, the latter presents porous patches with a high coefficient of variation in load-carrying capacity. Conversely, the pre-cured laminate and the plain weave prepreg patches failed to restore the mechanical properties owing to the weak bonding interface and the low axial patch strength, respectively. The unidirectional prepreg patch was proven to be the optimal repair method for the cracked metallic structures when balancing repair efficiency and processing stability.

Numerical simulation for stress analysis of functionally graded adhesively bonded composite patch repair system

Three-dimensional finite element analyses have been carried out for adhesively bonded composite patch repaired an aluminum alloy plate structure with centre circular notch. Presence of defect in the plate causes stress gradients in the bond region which results in reduction of the performance of the patched panel. The patterns of out-of-plane stress components at various interfaces (plate-adhesive-patch) at different angular positions with reference to loading direction are evaluated for mono-modulus adhesive. In the present research work, an attempt has been made to improve the strength of adhesively bonded composite patch repaired system by reducing stress concentration at the critical regions. This has been achieved by smoothening/relieving stresses over the entire bond region by introducing functionally graded adhesive (FGA) material in-lieu of conventional mono-modulus adhesive. Linear material gradation function profile has been used to tailor adhesive layer in the bond region. Effect of material gradation profile with different modulus ratios on out-of-plane stresses at different interfaces of composite patch repaired system have been studied. Numerical simulations based on FE analyses indicates significant reduction in out-of-plane stress levels by which strength of functionally graded composite patch repaired system will be enhanced.

Gain Enhancement of Composite Photonic Crystal Microstrip Patch Antenna Inspired by Maxwell Garnett Model for C‐Band, X‐Band and Ku Band Applications

AbstractThe latest developments in communication systems require an economical, light‐weight, compact size, and excellent performance in microstrip patch antennas in order to meet the requirements of the upcoming implementation. The optical, electrical, and physical properties of different materials have an impact on the design of antennas. An innovative composite photonic crystal microstrip patch antenna with outstanding gain has been developed. For composites of fumed silica embedded in RT‐Duroid dielectric material, the effective permittivity is calculated using the Maxwell‐Garnett model. The performance of composite antennas for different volume fractions and various dielectric substrate thicknesses is studied. The resonance frequencies of composites also shift from the X‐band to the C‐band with an increase in volume concentration, which is suitable for wireless communication systems. This investigation provides a perspective on how composite substrates can represent a communication revolution by providing an alternative to substrates that are readily accessible commercially in situations when the material qualities are insufficient. The photonic crystal composite antenna records the highest gain of 13.89 dB with the coverage of C‐band, X‐band, and Ku‐band, whereas the composite antenna reaches the best gain of 10 dB with the coverage of C‐band and X‐band.

Acoustic Emission-Based Analysis of Damage Mechanisms in Filament Wound Fiber Reinforced Composite Tubes.

This study investigates the mechanical behavior and damage mechanisms of thin-walled glass/epoxy filament wound tubes under quasi-static lateral loads. The novelty is that the tubes are reinforced in critical areas using strip composite patches to provide a topology-optimized tube, and their damage mechanisms and mechanical performance are compared to that of un-reinforced (reference) tubes. To detect the types of damage mechanisms and their progression, the Acoustic Emission (AE) method is employed, accompanied by data clustering analysis. The loading conditions are simulated using the finite element method, and the results are validated through experimental testing. The findings confirm that the inclusion of reinforcing patches improves the stress distribution, leading to enhanced load carrying capacity, stiffness, and energy absorption. Compared to the reference tubes, the reinforced tubes exhibit a remarkable increase of 23.25% in the load carrying capacity, 33.46% in the tube's stiffness, and 23.67% in energy absorption. The analysis of the AE results reveals that both the reference and reinforced tubes experience damage mechanisms such as matrix cracking, fiber-matrix debonding, delamination, and fiber fracture. However, after matrix cracking, delamination becomes dominant in the reinforced tubes, while fiber failure prevails in the reference tubes. Moreover, by combining the AE energy and mechanical energy using the Sentry function, it is observed that the reinforced tubes exhibit a lower rate of damage propagation, indicating superior resistance to damage propagation compared to the reference tubes.

Reliability analysis of composite laminate patch repaired structures based on response surface proxy model

In this paper, the reliability analysis of composite laminate patch repaired structures under unidirectional static load was studied by means of a probability model. First, a proxy model for the maximum static load carrying capacity of the repaired structure was established using quadratic polynomial response surface method (RSM) considering the repair material properties, repair patch design and adhesive layer thickness. Second, the probability distribution input of various basic random parameters including geometric characteristics and material properties were considered based on actual repair data. Finally, both the reliability and sensitivity analysis of the repaired structure were investigated by means of Monte Carlo simulation method. The results show that the reliability analysis model is of great significance for the subsequent design and properties evaluation of composite repaired structures.

Composites for Reinforcement of Damaged Metallic Aircraft Wings

Advanced composites, because of their inherent directional properties and ability to take complex contours are ideally suitable for repairs even in aged metallic aircraft structures. The composite materials can be suitably tailored to suit the strength and stiffness requirement at location of the damage on the parent structure. The laminate patch can be bonded to the structure. This avoids the use of large number of fasteners that are required for repair with metallic repair patch. A composite patch repair has been carried out on a military aircraft wing. The skin and the spar flange near the landing gear part were cut in order to gain access to a loosened bolt. With a request from HAL (Nasik), National Aerospace Laboratories (NAL) has taken the responsibility of designing and realizing composite repair at the damaged locations. The geometry and lay-up of the patches have been arrived at based on the strength requirements. The patches were fabricated at NAL and the repair was implemented on the aircraft. The quality of the patch bonding was checked using non-destructive testing (NDT). The aircraft has completed about 130 hrs flying with the repair. The repair was certified by the regulating authority and has been recommended to be implemented on other twenty aircraft also. This task has been completed successfully and all the aircraft are flying. This is an important achievement both for NAL and HAL (Nasik). This paper discusses the repair design, patch fabrication and implementation of the repair.

Fatigue performance of cracked diaphragm cutouts in steel bridge reinforced employing CFRP/SMA

Under long-term service conditions, fatigue cracking occurs at the diaphragm arc-shape cutouts in the orthotropic steel deck (OSD) bridges subjected to vehicle-induced vibration and cyclical wheel load. To repair cracks of the diaphragm cutouts, this study proposes two repair methods of the carbon fiber reinforced polymer (CFRP) sheets and shape memory alloys (SMA)/CFRP composite patches on the basis of crack-stop holes. The crack-stop hole eliminates the obvious source of fatigue propagation at the crack tip, but it weakens the section and harms the entirety of the diaphragm. The edge of the crack-stop hole in the cracked section becomes a new stress concentration site and the potential crack initiation point. The CFRP sheets can effectively improve the stiffness and reduce the stress amplitude of the cracked part. Moreover, the SMA/CFRP composite patches can further introduce precompression by activating SMA to reduce the stress level. Relative to the reinforcement by the crack-stop hole only, the fatigue notch factor is reduced by 12.28% and 30.76% after bonding CFRP sheets and SMA/CFRP composite patches, respectively. The fatigue tests show that the bonding of CFRP sheets and SMA/CFRP composite patches can effectively postpone the initiation of fatigue cracks and inhibit crack propagation, so they are ideal repair methods for strengthening fatigue cracks of the diaphragm cutouts in the OSD bridges.

Effect of Patch Interface Strengthening on Mechanical Properties of Epoxy/Carbon Fiber Sheet by Double-Sided Patching

To repair the damage to the epoxy/carbon fiber laminate, a single-lap test was performed between sulfuric acid anodized aluminum plate and carbon fiber laminate to study the effect of the anodized layer on the interlaminar shear strength. Then, carbon fiber laminates were prepared by wet-laying method to simulate the damage caused by penetrating cracks, and double-sided adhesive sheets were made from 0.5[Formula: see text]mm thick 2024-T3 aluminum alloy and carbon fiber laminates to match the thickness and material of the simulated damage plate. The adhesive matrix used was E51 bisphenol-A epoxy resin with 1.5[Formula: see text]wt.% nanorubber added for modification and toughening. After double-sided patching, tensile tests were performed to investigate the effect of different materials on the tensile strength of double-sided adhesive patches. We observed SEM images of the fracture surface of the patch after tensile failure and analyzed the strengthening mechanisms of different material patches. The results show that the shear strength between the single-layer sulfuric acid anodized aluminum plate and the carbon fiber laminate is 9.792 MPa, which is 61.5% higher than the shear strength of the nonanodized aluminum plate. The tensile strength of the 2024-T3 aluminum patch specimen is 271.83 MPa, which is 48.43% and 23.97% higher than the perforated specimen without patch and the specimen with carbon fiber laminate patch, respectively, and reaches 72.56% of the undamaged carbon fiber laminate. The specimens with aluminum plate patches showed a maximum bending strength of 616.47 MPa, which increased by 70.83% compared to the 360.875 MPa of the perforated specimens. The maximum bending strength of the aluminum plate patch specimen reached 74.76% of that of the undamaged specimen. However, the maximum bending strength of the composite patch specimen is as high as 1101.9 MPa, far exceeding that of other samples. Due to the poor toughness of the sample, it cannot withstand large strains. The addition of 1.5[Formula: see text]wt.% nanorubber results in shear yield bands and induces silver grains to absorb a large amount of energy during stress deformation.

Quasi-static and fatigue analyses of aluminium structures repaired by CFRP patch bonding

In this work, quasi-static and fatigue analyses of the three most common adhesive repair geometries were performed considering composite patches and aluminium as parent material. Experimental three-point bending tests were accomplished on single-strap, double-strap and scarf repairs in order to obtain the load–displacement curves for quasi-static analysis, and compliance versus number of cycles curves for the fatigue studies. The main goals are to identify the static strength and fatigue lives for each type of adhesive repair. In addition, progressive damage analyses that rely on two cohesive zone models appropriate for quasi-static and high-cycle fatigue under mixed-mode I + II loading were performed. These models allow the simulation of damage initiation and propagation in the repairs under quasi-static and fatigue loading. It was found that both models are able to replicate the fundamental trends observed experimentally, thus establishing their effectiveness.

Chitosan-Collagen Electrospun Nanofibers Loaded with Curcumin as Wound-Healing Patches.

Composite chitosan-collagen nanofibrous mats embedded with curcumin were prepared via a single-step electrospinning procedure and explored as wound-healing patches with superior biological activity. A mild crosslinking protocol consisting of a short exposure to ammonia vapor and UV radiation was developed to ensure proper stability in physiological-like conditions without affecting the intrinsic biocompatibility of chitosan and collagen. The fabricated composite patches displayed a highly porous, homogeneous nanostructure consisting of fibers with an average diameter of 200 nm, thermal stability up to 200 °C, mechanical features able to ensure protection and support to the new tissues, and water-related properties in the ideal range to allow exudate removal and gas exchange. The release kinetic studies carried out in a simulated physiological environment demonstrated that curcumin release was sustained for 72 h when the mats are crosslinked hence providing prolonged bioactivity reflected by the displayed antioxidant properties. Remarkably, combining chitosan and collagen not only ensures prolonged stability and optimal physical-chemical properties but also allows for better-promoting cell adhesion and proliferation and enhanced anti-bacteriostatic capabilities with the addition of curcumin, owing to its beneficial anti-inflammatory effect, ameliorating the attachment and survival/proliferation rates of keratinocytes and fibroblasts to the fabricated patches.

Taguchi Optimization of Geometrical Factors of a Polymer Composite Patch in Crack Repair

For the repair of a crack in thin aluminium sheets, polymer composite patching is one of the better repair techniques. During service, when the load acts, the patch separates from the substrate due to the stresses developed at the interface. This separation of the patch from the substrate largely depends on the geometrical factors of the patch, i.e. length, width and thickness. The optimum geometrical factors need to be incorporated for the effective and economical repair of the cracks. In this work, the optimum combination of the geometrical factors, i.e. length, width and thickness of the polymer composite patch, is obtained using the Taguchi technique with the help of the results generated in the numerical analyses.