Repair Of Composite Materials Research Articles

Effects of fly ash and silica fume on the rheological properties of magnesium phosphate cement-emulsified asphalt (MPC-EA) composite repair materials

Effects of fly ash and silica fume on the rheological properties of magnesium phosphate cement-emulsified asphalt (MPC-EA) composite repair materials

Optimization of Composite Material Repair Patch Shape Based on Strength Analysis

With the increasing use of composite materials in aircraft structures and the extension of their service life, the selection of repair patch shapes for composite material damage repair has become a significant engineering concern. The ultimate strength of the repaired structure is among the main evaluation criteria for selecting optimal patch shapes. In this study, strength analysis is conducted along with the use of the Digital Image Correlation (DIC) method to assess the quality of the repaired components, making the evaluation method more rational. Early studies often focused on simplified models, which diverged significantly from the practicalities of maintenance engineering in civil aviation. Therefore, it is essential to research full-scale composite material repair patches, as this will provide a more reliable basis for the optimal selection of patch shapes in composite material maintenance engineering for civil aircraft.

A Review of Waterborne Polymer–Cementitious Composite Repair Materials for Application in Saline Soil Environments: Properties and Progress

The properties of a large number of concrete infrastructures in China are deteriorating year by year, raising the need for repairing and strengthening these infrastructures. By introducing waterborne polymers into a cement concrete system, brittle cracks and easy bonding performance defects of concrete can be compensated for to form a long-life, semi rigid, waterborne polymer-modified cementitious repair material with a promising development prospect. This paper investigates the modification effect of polymer emulsions on ordinary cement mortar. Our research mainly focused on the physical and mechanical properties, durability, microstructure and application status of waterborne polymer-modified cementitious composites. Literature studies show that with the increase in waterborne polymer content (0 wt%~20 wt%), the performance of cement mortar significantly improves, which in turn expands its application range. Compared with ordinary cement mortar, the introduction of waterborne polymers blocks some of the pores in the cement to a certain extent, thus improving its permeability, freeze–thaw resistance and durability. Finally, this paper describes the application of waterborne polymer–cementitious composites in western saline soil environments, as well as discusses the prospects of their development.

Mechanical properties and microstructure of waterborne polyurethane-modified cement composites as concrete repair mortar

With the increase in service life, the durability of a large number of concrete structures deteriorates year by year under the influence of the external environment, requiring urgent repair and reinforcement. Ordinary cement concrete materials have disadvantages such as high brittleness, low tensile strength, poor bonding ability, and insufficient durability, making it difficult to meet the repair needs of high-quality building structures. Therefore, self-synthesized anion WPU was used to study its effect on the mechanical properties of cement-based repair mortar. The research found that waterborne polyurethane (WPU)-modified cementitious composite repair materials exhibit better bonding strength with old concrete substrates compared to traditional cement-based materials. Additionally, the incorporation of WPU significantly reduces the brittleness of the repair material, ensuring enhanced efficiency in the repair process. However, according to the hydration heat test results, the addition of WPU delays the hydration process of the composite repair materials. In addition, the addition of WPU enhances the flexibility and bonding ability of the materials, with flexural strength and tensile strength at the age of 28 days reaching 13 MPa and 6 MPa, respectively. Through stress‒strain curve analysis, it was found that the maximum strain amplification of WPU cement mortar can reach 134 %. Combined with SEM testing, it was observed that cured WPU films were present in specimens aged 28 days with P/C ratios of 10 % and 15 %. WPU and cement hydration products permeate each other, forming a three-dimensional polymer network structure, improving the pore structure, and fully exerting the flexibility of WPU. This also validates the experimental results of increased ultimate tensile strain. WPU cement-based composite repair materials have higher bonding strength at a high P/C ratio (15 %), and WPU alone, used as an interface agent for pretreating the interface of old concrete, can improve the interface bonding strength, up to twice that of the group without the surface agent.

The tensile properties and repair behavior of glass fiber reinforced polymer using resin pre-coating technology

Resin pre-coating technology is widely used in all aspects of composite materials, especially in the repair of composite materials. The pre-coating is formed by combining acetone with the resin, which is diffused and cured by the epoxy adhesive at the same time. It acts as an interlock to prevent the interface from debonding and to fill in the damaged cracks. The capillary action of acetone allows the resin to permeate the cracks in the fiber damage layers, thus filling the cracks and completing the repair. The pre-coating solutions of 10 wt%, 20 wt%, 25 wt%, 35 wt%, and 45 wt% resin were applied to damaged areas respectively, and cured at 60°C for 7 days. The crack filling effect was observed by scanning electronic microscopy (SEM). At the same concentration, the effect of prolonged repair time was also studied. The other two repair times were 14 days and 30 days respectively. In addition, the tensile properties of the materials before and after repair were tested and compared. The results showed that 25 wt% resin pre-coating had the best repair performance after 7 days, with a repair rate of 27%, which was 22% higher than the conventional repair without resin pre-coating. However, the repair effect became more obvious after the extension of repair time, and the repair effect of 25 wt% resin pre-coating reached 44% after 30 days curing. Therefore, it was found that the resin can fully penetrate the cracks in the damaged area with resin pre-coating technology, and 25 wt% resin pre-coating solution is the best choice.

Restoration of rolled equipment using composite materials

In recent years, polymer materials with various adhesive compounds based on epoxy resins, polyesters, polyurethanes, polyacrylics, and others enriched with fine-dispersed metallic and other fillers have found wide application in various industrial sectors for equipment repair. These composite repair materials have excellent adhesive properties when applied to metal surfaces, and when combined with their high strength and the ability to transition from a plastic to a solid state without shrinkage in a short period of time, they provide a broad range of applications in solving repair problems. A technology for restoring the original dimensions of equipment parts using composite materials has been developed, eliminating the need for welding and milling. Numerous industrial tests have shown that composite materials allow solving a range of serious repair problems in rolling production, particularly on heavily loaded sheet rolling stands and blooming mills when restoring worn contact surfaces of this equipment. An original technology for the application of composite materials was developed at the Pryazovskyi State Technical University (Mariupol, Ukraine), which allowed for a unique repair operation at one of the metallurgical plants, involving the installation of a new blooming mill housing onto old worn plates with wear of up to 7 mm at certain points. These composite repair materials have excellent adhesion properties when applied to metal surfaces, which, in combination with their high strength and the ability to transition from a plastic to a solid state without shrinkage in a short period of time, provide a wide range of applications in solving repair problems. Additionally, there are cases of damage to certain types of machinery that are either impossible to repair using traditional methods or require significant material and time investments for restoration

Unveiling the Effects of Quicklime on the Properties of Sulfoaluminate Cement-Ordinary Portland Cement-Mineral Admixture Repairing Composites and Their Sulphate Resistance.

Aiming at the problem of repeated repair of concrete caused by the damage of concrete structure repair system in a sulphate environment, the quicklime modified sulphoaluminate cement (CSA)-ordinary Portland cement (OPC) -mineral admixture composite repair material was utilised to obtain the law and mechanism of quicklime, improving the mechanical properties and sulphate resistance of composite repair materials. In this paper, the effects of quicklime on the mechanical properties, as well as sulphate resistance of CSA-OPC-ground granulated blast furnace slag (SPB) and CSA-OPC-silica fume (SPF) composites, were studied. The findings reveal that the addition of quicklime improves the stability of ettringite in SPB and SPF composite systems, promotes the pozzolanic reaction of mineral admixtures in composite systems, and significantly increases the compressive strength of both SPB and SPF systems. The 8 h compressive strength of SPB and SPF composite systems increased by 154% and 107%, and the 28 d compressive strength enhanced by 32% and 40%. After the quicklime was added, the formation of C-S-H gel and calcium carbonate in SPB and SPF composite systems was promoted, the porosity was reduced, and the pore structure was refined. The porosity was reduced by 2.68% and 0.48%, respectively. The mass change rate of various composite systems under sulphate attack was reduced, and the mass change rate of the SPCB30 and SPCF9 composite systems decreased to 0.11% and -0.76% after 150 dry-wet cycles. Additionally, the mechanical strength of different composite systems under sulphate attack was improved, so that the sulphate resistance of different ground granulated blast furnace slag and silica fume composite systems was improved.

Comparison of Bond Strength of Bulkfill and Conventional Composites as Composite Repair Materials

Amaç: Bu in vitro çalışmanın amacı mikrohibrit, submikrohibrit ve bulkfill kompozitin kompozit tamir materyali olarak mikro gerilme bağlanma dayanımının ve kırılma yüzeylerindeki başarısızlık tipinin karşılaştırmalı olarak değerlendirilmesidir. Gereç ve Yöntem: Standart Teflon kalıplarda supranano kompozit rezinden (Estelite Sigma Quick) silindirik (4x4 mm) örnekler hazırlandı ve 3.000 termal döngüye maruz bırakıldı. Örneklerin bir yüzeyi abraze hale getirilerek mikrohibrit kompozit (Arabesk), submikrohibrit kompozit (Charisma Smart) ve bulkfill kompozit (Filtek Bulk-Fill Posterior) ile restore edilip 4x8 mm boyutlarında bloklar oluşturuldu. Kompozit bloklardan kesme cihazı ile her grup için 12 adet olmak üzere 1x1x8 mm3 ölçülerinde dikdörtgenler prizması şeklinde çubuklar elde edilerek mikro gerilim test cihazı ile bağlanma dayanımları test edildi. Ayrıca test sonrası her örneğin kopma yüzeyi stereo mikroskopta incelendi. Tamir bağlanma dayanımı verileri tek yönlü varyans analizi (ANOVA) ile karşılaştırıldı ve çoklu karşılaştırmalar Tukey HSD testi ile değerlendirildi. Bütün p<0.05 değerleri istatistiksel olarak anlamlı kabul edildi. Bulgular: Bulkfill kompozit grubu en yüksek ortalama mikro gerilim tamir bağlanma dayanımı değeri gösterirken en düşük ortalama değer mikrohibrit kompozit grubunda görüldü (p<0.05). Koheziv tip başarısızlık yüzdesi ise tamir bağlanma dayanımı değerlerine paralel şekilde tespit edildi (Bulkfill> Submikrohibrit>Mikrohibrit). Sonuç: Supranano kompozit rezinin tamirinde submikrohibrit ve mikrohibrit kompozite göre bulkfill kompozit ile daha iyi bir bağlanma sağlanabilir.

Poly(methyl methacrylate) as Healing Agent for Carbon Fibre Reinforced Epoxy Composites.

Self-healing materials offer a potential solution to the problem of damage to fibre-reinforced plastics (FRPs) by allowing for the in-service repair of composite materials at a lower cost, in less time, and with improved mechanical properties compared to traditional repair methods. This study investigates for the first time the use of poly(methyl methacrylate) (PMMA) as a self-healing agent in FRPs and evaluates its effectiveness both when blended with the matrix and when applied as a coating to carbon fibres. The self-healing properties of the material are evaluated using double cantilever beam (DCB) tests for up to three healing cycles. The blending strategy does not impart a healing capacity to the FRP due to its discrete and confined morphology; meanwhile, coating the fibres with the PMMA results in healing efficiencies of up to 53% in terms of fracture toughness recovery. This efficiency remains constant, with a slight decrease over three subsequent healing cycles. It has been demonstrated that spray coating is a simple and scalable method of incorporating a thermoplastic agent into an FRP. This study also compares the healing efficiency of specimens with and without a transesterification catalyst and finds that the catalyst does not increase the healing efficiency, but it does improve the interlaminar properties of the material.

Repairing of damaged composite materials and self-healing composites

Repairing any damage in composite materials is very important in terms of the mechanical strength of the structure in which they are used. Therefore, the damage needs to be detected and repaired quickly. The increasing use of composite materials in various industries makes it more important to repair damage in composites both quickly and cost effectively. Patch repair method is one of the most preferred methods for repairing damaged composites because it does not create a new tension on the structure it is applied, does not damage the damaged area and is light. In addition, thanks to the embedded microcapsules placed in its matrix, self-healing composites have been studied in recent years. In this study, both the repair of composite materials and self-healing composites are discussed.

Design and Heating Simulation of Continuous Laser Welding Curing Device for Carbon Fiber Composite Repair

Rapid repair of composite materials is a major challenge in composite applications. At present, the mainstream method is to use the heat repair instrument and the prefabricated patch bonding, but there are some problems, such as slow heating, uncontrolled temperature gradient and long curing time. Laser curing is a new type of carbon fiber composite material with fast curing time and good curing effect. The laser heating technology curing equipment designed in this paper consists of laser heating device, mobile device, rotating device, etc. The specific curing method is to use semiconductor fiber laser to cure the composite material when the laser and carbon fiber material are moving. Simulation software of laser heating process is simulated, and the resin base carbon fiber composite material as the research object, established three-dimensional physical model of laser heating carbon fiber composite materials, simulation and calculate the temperature field distribution in the laser heating process of carbon fiber composite materials and rule, a preliminary analysis of the laser parameters on the influence law of temperature of carbon fiber composite materials. As the laser power of the heating device laser increases, the average temperature and the maximum temperature achieved by the carbon fiber composite will be increased. With the acceleration of the laser moving speed of heating equipment, the maximum temperature that carbon fiber composite material can achieve will decrease, but the average temperature will rise in a certain range, which can have a certain insulation effect. The research results can provide certain reference for the temperature field simulation in the process of laser carbon fiber composite material.

Enlargement of geo polymer compound material for the renovation of conventional concrete structures

Abstract Ordinary Portland cement (OPC) concrete undergoes deterioration due to the simultaneous action of mechanical (service) and thermal loads. Concrete deterioration is manifested primarily through cracking and spalling of concrete and de-bonding of rebars. In all such cases, deteriorated structural elements require efficient and successful repair materials in order to improve their serviceability. The objective of this study is to examine the efficiency of geopolymer mortar/concrete based composite as a repair material for OPC structures. In this study, geopolymer composite was prepared by mixing fly ash, ground granulated blast furnace slag (GGBS), chopped alkali resistant chopped E-glass fibers and reaction generating liquid (RGL) comprising of sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and distilled water. Three weight fractions of chopped E-glass fiber (0.5%, 1%, and 1.5%) were used in the geopolymer composites, which were used in this study. The performance of these composite repair materials was examined in terms of compressive strength, split tensile strength, modulus of rupture, bond strength, impact abrasion resistance, notch beams bending test and durability test. Bond strength of the repair material with substrate concrete was determined according to ASTM C882 and the impact abrasion resistance of the repair material was evaluated using ASTM C1747 standard.

Composite patch repair of damaged tubular members from flare boom structures subjected to compressive loads

Conventional repair method for steel structures requires cutting and welding processes, which in offshore platforms may impose several disadvantages. Composite material repair has become an alternative for the rehabilitation of damaged structures and has been widely applied in other industries. In this work a numerical-experimental investigation evidences the effectiveness of the composite patch repair for flare boom corroded tubular elements subjected to axial compressive loads. A finite element model developed to determine the minimum composite laminate thickness that recovers the structural element strength is validated through numerical simulations. Twelve API 5L grade B reduced scale steel tubes with central perforations and similar longitudinal and transverse slenderness, respectively defined by length to radius of gyration of the cross-section area and diameter to thickness ratios, are tested covering the range of interest for full scale members. The composite material consists of a hybrid fabric made of carbon and glass fibers impregnated with epoxy resin. Severe localized corrosion is considered conservatively, idealized as a circular perforation in half the element length. In many cases the maximum load of the repaired tube even exceeded the intact tube capacity. Moreover, it is shown that sufficient load capacity recovery is achieved for the conditions assumed.

Failure loads analysis of corroded pipe repaired by composite material under tension and internal pressure

ABSTRACT Pipeline repair plays an important role in safe pipeline operation. Composite material repair technology has been widely used in pipeline repair due to its advantage of light weight and low cost. In this paper, the failure loads of repaired pipe with composite under tension and internal pressure are analysed by experiments, Finite Element Method (FEM) and theoretical method, and simple formula of failure loads is obtained based on theoretical analysis and verified by FEM and experiments. First, the tension experiment shows that debonding happens in the repaired pipe before its fracture, and then the debonding details are showed in FEM results considering the adhesive debonding criteria, finally a simple formula expression is obtained for the failure tension loads based on the analysis of interface stresses, and the results are almost consistent with the experimental method and FEM. Similarly, for the case under internal pressure, the blasting failure loads are obtained for the repaired pipe based on the theoretical analysis, which are consistent with FEM results.

The debonding failure analysis of corroded pipes repaired with CFRP under tension and the bending moment

Under the influence of environmental and transmission mediums, marine pipes are threatened by corrosion. The composite material repair method is very practical and efficient for external corroded pipes, and it has been widely used in recent years. In this paper, to study the interfacial stresses of a corroded pipe repaired with carbon fiber reinforced polymers (CFRP), a theoretical mechanical model of a perfect pipe repaired with CFRP is constructed firstly, and then the interface stresses are obtained for the reinforced pipe under tension and bending, with a modification of stresses using the residual strength factor. the interface stresses are obtained for the reinforced pipe under tension and bending, with a modification of stresses using the residual strength factor. The debonding load for the corroded pipe repaired with CFRP is calculated based on the damage failure criteria of the adhesive layer. A finite element model (FEM) for corroded pipes repaired with CFRP is constructed to achieve the interface stresses and the debonding load, and the tension experiment is also done to achieve the initial debonding loads. The theoretical results and FEM results are found to have good coherence with the experimental results. Finally, the relationship between the debonding load and the aging time is obtained based on the degradation rules of adhesive peeling and shear strength.

Summary and application analysis of clinical herniorrhaphy mesh materials

It is widely believed in the medical community that the pathological and anatomical basis for the occurrence of external abdominal hernia is the fascia defect, and how to correctly deal with this kind of fascia defect is the key point in the treatment of external abdominal hernia. Theodore Billorth famously said that if we could artificially create dense and tough tissues like fascia and tendons, the secret to the complete healing of hernia would be solved. These similar theories largely guide the research and practice in the treatment of external abdominal hernia. along with the breakthrough progress in the mesh treatment of external abdominal hernia, According to the chemical composition and biological characteristics, the patch materials can be divided into non-absorbable materials, absorbable materials, composite repair materials and biological materials. Methods In this paper, Pubmed database and Chinese journal full-text database literatures were searched,and all mesh materials used in inguinal hernia repair were comprehensively studied, summarized and analyzed in clinical application.
 Keywords: external abdominal hernia; patch material; conclusion; application

Cohesive zone method for failure analysis of scarf patch-repaired composite laminates under bending load

The repair of composite materials has received much attention in recent decades because these materials are used in a wide range of industrial applications owing to their excellent mechanical properties. In this work, the failure of scarf patch-repaired composite laminates subjected to bending loads was experimentally and numerically investigated. Thirty repaired laminates with a scarf angle of 5.7° or 3.8° were prepared and tested under different bending loads. Three-dimensional finite element models implementing cohesive elements were created to examine crack initiation and propagation in the specimens during loading. Experimental results revealed that a combination of adhesive, intralaminar, and interlaminar failure occurred in the bonding surface area. Compared to the failure of repair under tensile loading, additional failure occurred in the patch. Simulations reproduced these failure modes well with cohesive elements. The failure loads were also accurately predicted with a maximum prediction error of 9.7%.

Plasmonic nanoparticle-based epoxy photocuring: A deeper look

Abstract Many epoxy adhesives require high temperatures to bond composite materials. However, oven heating severely restricts what may be attached or enclosed within composite material-based structures and greatly limits the possibilities for repair. Inspired by initial reports of photothermal epoxy curing using plasmonic nanoparticles, we examine how laser-illuminated Au nanoparticles embedded within high-temperature epoxy films convert the conventional thermal curing process into a photothermally driven one. Our theoretical investigations reveal that plasmonic nanoparticle-based epoxy photocuring proceeds through a four-stage process: a rapid, plasmon-induced temperature increase, a slow localized initialization of the curing chemistry that increases the optical absorption of the epoxy film, a subsequent temperature increase as the epoxy absorbs the laser radiation directly, and a final stage that completes the chemical transformation of the epoxy film to its cured state. Our experimental studies validate this model, and also reveal that highly local photocuring can create a stronger bond between composite materials than thermal curing without nanoparticles, at times even stronger than the composite material itself, substantially reducing the time needed for the curing process. Our findings support key advances in our understanding of this approach to the rapid, highly efficient bonding and repair of composite materials.

The Effect of Various Composite Resin Types, Surface Treatments, and Repaired Materials on the Shear Bond Strength of Composite Resin Repair

Background and Objectives: Composite resin are widely used in the field of restorative dentistry, as the time passes, composite resin restoration are subjected to failure. This in vitro study conducted to evaluate the effect of two types of composite resin, surface treatment, and three types of repaired materials on shear bond strength. Methods: Total of 120 undercut cylindrical cavities 8 mm in diameter in 2.5 mm in depth were cut at the center of self-cured acrylic resin blocks, the samples divided randomly according to the types of composite resin into 2 groups; microfilled and hybrid, the samples in each groups subdivided according to surface treatment; diamond bur and phosphoric acid. Then all the samples received bonding agent, these groups were subdivided into subgroups according to three composite repair materials. After that the samples were thermocycled manually 500 times, and then each bonded sample subjected to shear bond testing with a universal testing machine. Results: The results showed that groups filled with hybrid composite had higher mean shear bond strength than groups filled with microfilled. Groups received surface roughness with diamond bur had higher mean shear bond strength than groups roughened by phosphoric acid. Conclusion: The highest repair bond strength was obtained by roughening the hybrid composite surface with diamond bur. There was no any significant difference in shear bond strength among groups repaired with different repaired materials, while combination of surface roughness with diamond bur and repaired with microfilled composite had higher mean shear bond strength.

Finite element analysis of a repaired thin-walled aluminum tube containing a longitudinal crack with composite patches under internal dynamic loading

One of the main issues with the cylindrical tubes is the propagation of cracks during their operational life wherein most of the cracks happen along the axial direction of the tube. This paper reports a 3D finite element simulation of the mechanical responses of an aluminum tube containing a longitudinal crack repaired with composite patches. After several loading-unloading cycles of the dynamic load, mechanical stresses at the crack tips may result in unstable crack propagation. Therefore, it is necessary to use a repair process to prevent the structure from final rupture. Glass/epoxy and boron/epoxy composite patches, with different number of patch layers, are considered in the analysis of the composite material repair effect on the crack tips stress distribution, evaluating the possibilities of crack propagation and patch delamination onset. Numerical simulations were partially compared with literature results to verify the modeling procedure, while a parametric study on the patch thickness was performed to verify the repair effectiveness. In general, boron and longer (140 mm) repair patches presented better performance than glass and shorter (70 mm) patches. Although thinner patches (2 layers) do not present the required resistance, thicker patches (16 layers) may precipitate delamination onset and thus should be avoided.