Composite Repair Research Articles

Incorporating Hydrogel (with Low Polymeric Content) into 3D-Printed PLGA Scaffolds for Local and Sustained Release of BMP2 in Repairing Large Segmental Bone Defects.

Treating large bone defects remains a considerable challenge for clinicians: bone repair requires scaffolds with mechanical properties and bioactivities. Herein, based on crosslinking o-phthalaldehyde (OPA) with amine groups, 4-arm polyethylene glycol (4armPEG)-OPA/Gelatin hydrogel loaded with bone morphogenetic protein 2 (BMP2) is prepared and a three dimensional (3D)-printed poly (lactic-co-glycolic acid) (PLGA) porous scaffold is filled with the hydrogel solution. The composite scaffold, with a compression modulus of 0.68 ±0.097GPa similar to the cancellous bone, has a porosity of 56.67 ± 4.72% and a pore size of about 380µm, promoting bone growth. The hydrogel forms a porous network at low concentrations, aiding protein release and cell migration. The hydrogel degrades in approximately three weeks, and the scaffold takes five months, matching bone repair timelines. BMP2 release experiment shows a sustained BMP2 release with a 72.4 ± 0.53% release ratio. The ALP activity test and alizarin red staining shows effective osteogenic promotion, while RT-PCR confirms BMP2@Gel enhanced COL-1 and OPN expression. Animal experiments further validate the composite scaffold's bone repair efficacy. This study demonstrates the effectiveness of the hydrogel in releasing BMP2 and the mechanical support of the 3D-printed PLGA porous scaffold, providing a new treatment for bone defects.

Reliability-based multi-objective optimization design of composite patch repair structure using artificial neural networks

Due to the parameter differences and the existence of random factors, the performance of composite repair structure shows a large dispersion. In order to obtain stronger, lighter and more reliable repair structure, multi-objective optimization design of carbon fiber reinforced polymers (CFRP) laminate repair structure is investigated by combining the reliability theory, artificial neural networks and the genetic algorithm. First, a 3D simulation model of the composite laminate patch repair structures is established using the 3D Hashin criterion and the cohesive region model. Then, the Latin Hypercube sampling (LHS) method is used to realize the random sampling, and the strength proxy model of the repair structure is established by using Back-propagation artificial neural network, further a multi-objective optimization model with tensile strength, reliability and weight as objective functions is built considering the design parameters and the random parameters. Finally, NSGAⅡalgorithm is used to solve the multi-objective optimization problem, and a set of solutions on the Pareto front surface are obtained, also the optimal design parameters of the composite repair structure meets the requirements is obtained.

Research on damage repair and high-velocity impact characteristics of thermoplastic composites

Low-velocity impact (LVI) can result in imperceptible damage to carbon fiber reinforced thermoplastic composites (CFRTP) laminates during service, leading to a reduction in structural strength. The thermal repair of damaged CFRTP laminates is conducted using the repairability of thermoplastic resin at high temperatures. However, the high-velocity impact characteristics of CFRTP laminates following thermal repair remain uncertain. This study examines CFRTP laminates made of two different materials (CF/PEEK and CF/PPS) with varying levels of low-velocity impact damage, and investigates the thermal repair process. A comparative experimental analysis examined the high-speed impact characteristics of CFRTP laminates under varying conditions. The results indicate that CF/PEEK laminates consistently exhibit superior compressive properties and impact resistance compared to CF/PPS laminates under similar conditions. Following damage from low-velocity impact, the compressive properties and high-velocity impact resistance of CFRTP laminates decrease, with CF/PPS laminates typically showing a lower performance retention rate. However, the thermal repair process proposed in this study significantly enhances the performance of CF/PPS laminates. Moreover, the degree of performance healing in CF/PPS laminates is consistently higher than that in CF/PEEK laminates, which is closely related to the semi-crystalline nature of PEEK resin.

New Prediction Of Cracks Propagation In Repaired Steel Plate With Bonded Composite Patch At Cyclic Loading

Abstract This study presents a numerical prediction of the fatigue life of steel panels repaired by a composite patch. The effect of length cracks, the stress ratio R and properties of the patch is presented. The obtained results show that the bonded composite repair significantly reduces the stress intensity factors at the tip of repaired cracks. The results are in a good agreement with those in the literature. The Monte Carlo method is used to predict the distribution function governing crack propagation in fatigue analysis. In computing the failure probability of the structure, we consider the statistical uncertainty associated with key variables, along with the previously discussed model uncertainty. The results obtained highlight the considerable impact of variations in crack length and stress ratio on the distribution function. Notably, uncertainty in these parameters significantly amplifies the probability of structural failure in plates, thereby diminishing overall structural durability.

Characterization of thin-walled self-healing microcapsules reinforced with multi-walled carbon nanotubes

This study presents a novel approach to fabricating thinner shells and significantly enhancing the fracture strength of melamine-urea-formaldehyde (M-U-F) microcapsules reinforced with multi-walled carbon nanotubes (MWCNTs). Unlike previous studies that primarily focused on single-walled carbon nanotubes (SWCNTs) or MWCNTs in polyurea-formaldehyde (PUF) shells, this research advances microcapsule technology by exploring MWCNT reinforcement in M-U-F shells. We employed a dual experimental-numerical approach, combining the precision of micro-compression tests with the predictive capabilities of finite element analysis (FEA) to determine the elastic modulus of MWCNT-reinforced M-U-F microcapsules. This method offers new insights into the mechanical behavior of these microcapsules. Our findings indicate an 8.8% increase in fracture load and a 14.6% reduction in fracture displacement for MWCNT-reinforced microcapsules compared to conventional M-U-F microcapsules. Additionally, FEA confirmed the results of the micro-compression tests, showing that MWCNT-reinforced microcapsules had the best correlation with an elastic modulus of 4.00 GPa. Conventional M-U-F microcapsules corresponded to an elastic modulus of 2.25 GPa. These results provide a comprehensive understanding of how nano-reinforcement influences the structural properties of thin-walled microcapsules, with potential applications in composite damage repair and beyond.

Development of an Open-Source Robotic NDT Solution for Automated Composite Repair Testing

Abstract Non-destructive testing (NDT) plays an important role in aircraft maintenance and repair processes, ensuring the structural integrity necessary for safe operation. The paper presents the design and evaluation of an animated, low-cost robotic NDT system tailored for inspecting composite bonding agents. The system integrates commercially available components, including a three-degree-of-freedom robotic arm and a Raspberry Pi 4B, managed by custom Python software with a user-friendly graphical interface. Mechanical Impedance Analysis (MIA) and Eddy Current Testing (ET) methods were employed to assess the system’s performance on representative test specimens. Results indicate that the system delivers reliable and accurate measurements comparable to commercial tools like the MAUS V, while offering simplicity and modularity. Limitations such as scanning speed and handling of complex geometries are acknowledged, with potential solutions proposed for future enhancement. The system provides an affordable and customizable alternative for NDT automation in the aerospace industry.

The effect of different treatment protocols on shear bond strength in resin composite restoration repair

BackgroundIt was aimed to investigate the effect of sandblasting and laser surface treatment on shear bond strength in composite restoration repair in vitro.MethodsA micro-hybrid composite (Filtek Z250, 3 M-ESPE, USA) was used to prepare 120 samples. The samples were subjected to a thermal cycle test 5,000 times between 5 and 55 0C, and they were randomly divided into 12 groups (n = 10). No surface treatment was performed in Groups 1 to 4, which were designed as control groups. The surfaces of the samples in Groups 5 to 8 were sandblasted with a Cojet device, and the surfaces of the samples in Groups 9 to 12 were applied Er, Cr: YSGG laser. After the sample surfaces were divided into groups with and without acid etching, universal adhesive was applied, and the repair process was performed using Filtek Z250 or nano-filled resin composite (Filtek Ultimate, 3 M-ESPE, USA). The thermal cycle test was repeated 5,000 times between 5 and 55 0C on all repaired samples. The repair shear bond strength of the samples was measured using a universal testing device (Shimadzu IG-IS, Kyoto, Japan). The fracture types were evaluated by optical microscopy and scanning electron microscopy (SEM). Statistical analyses of the findings were evaluated by the Kruskal Wallis test and Mann Whitney U test at 0.05 significance degree.ResultsThe highest mean shear bond strength values were obtained from the samples sandblasted with CoJet, followed by Er, Cr: YSGG laser, and the control group. It was determined that there was a significant difference between the mean shear bond strength values obtained from the control group and the other surface treatment groups (p < 0.05). In general, significantly higher mean shear bond strength values were obtained when the universal adhesive was applied in total-etch mode compared to the application in self-etch mode (p < 0.05). Additionally, it was determined that higher shear bond strength values were obtained with Filtek Ultimate compared to Filtek Z250 (p < 0.05).ConclusionWithin the limitations of this study, it can be concluded that the use of universal adhesive in total-etch mode, in addition to surface treatments on the resin composite surface in the repair protocol and the use of nano-filled resin composite as repair material can increase the mean shear bond values in repair.

3D-printed magnesium-doped micro-nano bioactive glass composite scaffolds repair critical bone defects by promoting osteogenesis, angiogenesis, and immunomodulation

Magnesium ions play an important immune-regulatory role during bone repair. For this study, we prepared micro-nano bioactive glass (MNBG) containing magnesium, which can release magnesium, silicon, and calcium ions and has a positive impact on osteogenic differentiation and vascular regeneration. In this study, MgMNBG was compounded and combined with poly(lactic-co-glycolic acid (PLGA) and polycaprolactone (PCL) for 3D printing. Afterwards, the physicochemical properties and bone repair performance of the scaffolds were evaluated throughin vitroandin vivoexperiments. We also investigated the effects of MgMNBG on osteogenic differentiation, immune regulation, and vascular regeneration. The results showed that MgMNBG can inhibit inflammation and promote osteogenesis and angiogenesis by regulating macrophages. PLGA/PCL/MgMNBG scaffolds have good osteogenic and angiogenic effects, and the composite scaffolds have excellent bone repair performance and potential application value.

Effect of temperature and adhesive defect on repaired structure using composite patch

In structural engineering, composite patch repairs are widely used to address cracked structures. However, their behavior under thermo-mechanical loading remains complex and less understood. This study examines the repair of a center-cracked plate subjected to both mechanical and thermo-mechanical environments, using finite element analysis in ANSYS. The repair effectiveness is evaluated using the Stress Intensity Factor (SIF) at the crack tip. Findings reveal that increased temperature substantially elevates SIF values. Boron/epoxy patches are most effective under mechanical loading, yielding the lowest SIF, while graphite/epoxy patches excel under thermo-mechanical loading due to their lower Coefficient of Thermal Expansion (CTE). Patch thickness influences SIF differently based on loading conditions; thicker patches decrease SIF under mechanical loading but increase it under thermo-mechanical loading. Furthermore, adhesive defects, particularly at the crack tip, markedly increase the risk of adhesive failure, especially under thermo-mechanical conditions. This research underscores the significant impact of temperature variations on the efficiency of structural repairs, contributing to a deeper understanding of composite patch repair performance in cracked structures.

Crack monitoring and repair model of SMA composite material based on strain transfer

In the process of using composite materials, crack damage is unavoidable. These cracks may cause a decrease in the structural performance of the material and may even pose a threat to the safety of the entire structure. In this paper, the shape memory alloy (SMA) is embedded into the composite material, and the strain transfer effect of the interface layer is considered. The crack monitoring and repair model of SMA composite material based on strain transfer are established using SMA resistance-sensing characteristics and SMA constitutive model. Based on this monitoring and repair model, the crack monitoring behavior of SMA under different initial states and temperature conditions is discussed, and the crack repair behavior of SMA under specific initial states and temperature conditions is also discussed. The research results show that the change in SMA resistance and the strain of the composite material crack are linearly segmented, and as the temperature increases, the composite material crack is gradually repaired. This study can provide theoretical guidance for the further engineering application of SMA composite material crack monitoring and repair theory.

Experimental investigation on composite patch repair for cracked aluminum structures

Experimental investigation on composite patch repair for cracked aluminum structures

The current attitudes and practices of dentists in Australia towards composite repair: A cross-sectional survey study.

Whether to replace or repair a composite restoration is controversial and varies among clinicians. This study was designed to collect information on the attitudes and practices of Australian dentists towards composite repair. An electronic 16-item questionnaire was distributed online on Australian clinicians' dental forum with a URL address and instructions on completing the survey. The questionnaire remained accessible for 2 months. The data collected were analysed statistically using descriptive, average rank, Pearson chi-square and Kruskal-Wallis tests at α = 0.05. Repair of composite restorations was a widely accepted treatment modality among surveyed dentists. Despite this, approximately half of clinicians reported the prognosis of repaired restorations to be worse when compared to replacement. The most cited indications for repair were partial loss or fracture of the restoration, while the most common reason for repair was because this treatment modality was more conservative in terms of tooth structure removal. Most important patient factor influencing decision to repair composite restoration was caries risk of the patient (n = 50). Most significant situational factor to consider in decision whether to repair was previous (failed) attempts to repair (n = 74). The most important tooth level factor was the proximity of restoration to pulp (mean statistic rank 2.22). The most common composite surface treatment employed by participants bonding to old composite was acid etching (n = 87), and the main reason participants employed their chosen surface treatment was based on personal experience (n = 72). The repair of composite restorations was a commonly performed procedure that is well accepted but may still be viewed as an inferior treatment to replacement by many Australian dentists. Most dentists agreed on indications for repair restorations and surface conditioning techniques, but there was wide variation in opinions overall. Due to the lack of high-quality evidence regarding composite repair techniques, dentists tend to rely on personal experience to guide their clinical decisions.

The effect of different surface treatments on composite repair

The effect of different surface treatments on composite repair

Adhesive systems' effect on aged composite repair bond strength

Adhesive systems' effect on aged composite repair bond strength

Silane and acid etch cross contamination of dentin and composite reduced µ-tensile bond strength.

To investigate whether acid etch contamination of silane-treated composite influenced repair bond strength and whether silane contamination on dentin influenced composite bond strength to dentin. Forty composite blocks stored in water for 4 weeks were divided into four groups. Specimens in groups 1-3 were coated with Bis-Silane and contaminated with acid etch + water spray (group 1) or water spray (group 2). Group 3 was not contaminated. Group 4 was untreated. The occlusal third of 60 third molars was cut off, ground flat, and divided into three groups. After etching, the surfaces in groups A and B were contaminated with Bis-silane. The contaminated surfaces in group A were re-etched.Each composite repair group and composite-dentin group was divided into two subgroups receiving Adper Scotchbond 1 XT or Clearfil SE Bond 2 adhesives followed by a composite build up. After ageing for 3 months, specimens were sectioned into 1.1 mm × 1.1 mm rods for tensile testing and strength calculated at fracture. The fracture was examined using microscope. Bis-Silane surface treatment increased the repair bond strength. Contamination with acid reduced the strength of the repair bond. Similar results were obtained for both adhesives. Tooth surface contamination with silane reduced the bond strength between dentin and composite. Additional acid etching or water spray on silane contaminated dentin did not influence the weakened bond strength. Most fractures were adhesive type. Silane contamination on etched dentin and acid etch contamination on silanized composite surfaces significantly reduced tensile bond strength.

511. IS IT SAFE TO USE NONABSORBABLE MESH IMPLANTATION FOR HIATAL REINFORCEMENT DURING PRIMARY ANTIREFLUX PROCEDURES?

Abstract Background Laparoscopic Fundoplication (LF) is highly effective in surgical treatment of GERD and the prevention of disease progression. Currently it is the gold standard of treatment and allows to achieve good and excellent postoperative results in majority patients. However, despite the gained experience, failures of primary LF and hiatus repair like hiatal hernia recurrence demonstrate that current surgical techniques are not optimal. One of the decisions is mesh implantation for hiatal reinforcement in GERD. However, due to the different types of complications (mesh erosion, scarring, dysphagia) safety use of mesh are still controversial. Method Laparoscopic Total Fundoplication (LTF) with nonabsorbable and composite light mesh implantation for hiatal reinforcement during 2022 – 2023 years were performed in 71 patients. We use macroporous nonabsorbable polypropylene or composite (polypropylene/monocryl) light mesh repair routinely by own proposed surgical technique. Our decision did not depend on size of hiatal hernia and hiatal surface area. We use U-shaped mesh posteriorly on the approximated crura by previous interrupted suturing not around the esophagus (Fig. 1). The mesh fixes with staples to the muscular and ligamentous structures of crura. We compared our results with the group of LTF without mesh implantation. Result All patients underwent completed validated questionnaires, esophagogasroduodenoscopy, contrast video esophagram, 24-hour impedance-pH monitoring after surgery. Some patients underwent computed tomography. Along with the disappearance of GERD symptoms, no mesh erosion and long (&amp;gt;3 month) postoperative follow-up dysphagia were marked in any patient with mesh repair. There are no significant difference in comparison with these results of LTF without mesh implantation. During the early postoperative period (&amp;lt; 12 months) no recurrence of hiatal hernia was diagnosed in the group with mesh implantation. Conclusion According to our study, in comparison with no-mesh repair, the proposed surgical technique is safe. Nonabsorbable and composite light mesh implantation for hiatal enforcement during primary antireflux procedures may be used routinely to prevent hiatal hernia recurrence effectively. Further, longer-term follow-up will be continued to confirm this position.

Dynamics of hiatal hernia recurrence: how important is a composite crural repair?

Hiatal hernia recurrence rates vary widely. The true causes of recurrences are not fully understood but likely multifactorial. Surgical approaches and techniques have evolved over time to try and reduce recurrence rates after hiatal hernia repair. Our objective is to provide a current review on the physiology of hiatal hernias and the importance of a composite crural repair on hiatal hernia recurrence rates; more specifically, for this review, a composite repair is defined as a repair requiring more than primary closure of the crura. A recent review of the literature was conducted to identify studies reporting on hiatal hernia pathophysiology, stress, and tension, as well as the role of composite repair. There is a paucity of studies focusing on the pathophysiology of hiatal hernias and recurrence rates. Articles that report on the pathophysiology of the hiatus were found to have alterations of the extracellular matrix, collagen composition, changes in metalloproteinases (MMPs), and differences in genetic composition. The role of composite repair on reducing recurrence rates is not well studied. Hiatal hernias remain a complex problem with no ideal surgical technique. It is likely that the pathophysiology of hiatal hernias is multifactorial, and more studies need to be done to better understand the potential underlying mechanisms for hiatal hernias so this may also further identify the ideal surgical repair.

Repair strength of 3D-printed denture base resins: Effect of surface treatment and repair material type.

The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D-printed denture base resins after thermal aging. Bar-shape specimens (64×10×3.3mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles-abrasion, or (3) both methods (aluminum oxide particles-abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3-point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p<0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p<0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p>0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p<0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto-polymerized resin (p<0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto-polymerized while cohesive and mixed were dominant with composite repair groups. Surface treatment improved the repair strength of 3D-printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D-printed denture base repair.

StrainNet-LD: Large Displacement digital image correlation based on deep learning and displacement-field decomposition

First, a displacement-field decomposition strategy is proposed that effectively enhances the accuracy of digital image correlation (DIC) algorithms under large displacement or deformation conditions. The implementation methodologies of displacement-field decomposition under both Lagrangian and Eulerian descriptions are derived and presented. Second, displacement-field decomposition is applied to speckle image correlation algorithms based on deep learning, resolving the contradiction between registration capability of large displacement and the accuracy. A CUDA-accelerated and residual learning-based strain fitting algorithm is proposed for high-precision and real-time strain computation. This method is named “StrainNet for Large Displacement” (StrainNet-LD). StrainNet-LD achieves a calculation speed of 768 × 768 × 6 fps (768 × 768 × 3 fps with strain calculated simultaneously) on GPU with displacement MAE < 0.05 pixels and strain MAE < 0.002ε. Finally, rubber tensile tests, 3D motion measurement of composite shells, and morphology reconstruction experiments of speckle-free composite repair structures are conducted to validate the algorithm's robustness and efficiency. Some vital discussions of displacement-field decomposition are given in the Appendixes. The code and dataset are available at https://github.com/GW-Wang-thu/StrainNet-LD.

A design method for continuous fiber-reinforced composite patches

The urgent need for lightweight and high-strength patches in the field of aircraft structural repair has propelled continuous fiber-reinforced thermoset composites into a research hotspot. However, constrained by manufacturing processes, the designs of composite repair structures primarily focus on external shape and ply layup. These approaches presently lack design methods for the internal fiber adaptability of patches driven by in-service loads. In this paper, we proposed a method for fiber distribution and orientation design based on maximum normal stress. The composite simulation model was established based on fracture toughness. The influence of tensile-shear coupling effects on the mechanical response of composites and the fiber orientation design were examined in the study. The orientation-density coupling effects on the enhancement of patch strength were also analyzed. Furthermore, additive manufacturing technology was employed to fabricate thermoset composite patches. The results show that the composite patches designed in this paper exhibit a 10.50 % improvement in strength compared to traditional unidirectional patches.