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The structural damage repair of composite material is an important issue that needs to be addressed during the service life of composite materials. To investigate the effects of a scarf structure and scarf angle on the repair quality of composite material, this paper proposes a mixed-scarf (MS) repair structure that combines ramped-scarf (RS) and stepped-scarf (SS) repair structures. The effect of the repair structure on the mechanical properties was analyzed, as well as the quality of the adhesive interface. The results show that at a scarf angle of 10°, the repair efficiency and the quality of adhesive interface are better than that of scarf angles of 20° and 30°. At a scarf angle of 10°, the recovery degree of the flexural strength of the MS repair structure is 79.72%, which is 6.77% and 38.24% higher than that of the RS and SS repair structures, respectively. However, in terms of flexural modulus, regardless of repair structure, the flexural modulus is highest at a scarf angle of 20°. Furthermore, the impact strength of the MS repair structure is approximately 87.60% that of the RS repair structure; additionally, it exhibits an increase of 45.83% compared to the SS repair structure. Overall, the quality of the adhesive interface for the RS and MS repair structures is similar and better than that of the SS repair structure. In conclusion, the MS repair structure is well suited for small-angle scarf repairs, whereas the RS repair structure is more appropriate for large-angle repairs; in contrast, the SS repair structure demonstrates the least effective performance in terms of repair outcomes.

Previous studies show that the adhesive strength can be expressed as a constant value of the critical ISSF (Intensity of Singular Stress Field) for several butt joints and lap joints. This study deals with the scarf joints where two distinct singular stress fields appear at the interface end. How to evaluate the scarf joint strength is described in comparison with the lap joint where two singular stress fields appear but the second singular stress field is weak. It is found that the adhesive strength of the scraf joints can also be expressed as a constant value of one of the ISSF like other joints. When two singular stress fields are comparable, the debonding strength of the scarf joints can be expressed at a certain point of the sum of the two singular stress fields as σ θ c ( 10 μ m ) = const.

A progressive damage model was developed to study the damage and failure behavior of CFRP/Ti double-bolt scarf joints under quasi-static loading. The three-dimensional Hashin failure criterion was integrated into a finite element model via the ABAQUS user-defined material subroutine. Quasi-static tensile tests were conducted to investigate failure mechanisms and validate the model. The predicted failure modes match the experimental results with an error of 11.8% in the prediction of ultimate load. The effect of helicoidal layup on the composite joint was studied for the application of a helicoidal composite. The results show that the helicoidal layup configuration with a 45/−45 layup on the surface had the highest failure load, and the helicoidal layup introduced more tensile damage in the matrix. This study offers practical failure prediction methods and comprehensive failure mode analysis for composite bolted scarf joints.

A potential repair alternative to restoring the mechanical properties of lightweight fiber-reinforced polymer (FRP) structures is to locally patch these areas with scarf joints. The effects of such repair methods on the structural integrity, however, are still largely unknown. In this paper, the mechanical property restoration, failure mechanism, and influence of fiber orientation mismatch between parent and repair materials of 1:50 scarf joints are studied on monolithic glass fiber-reinforced polymer (GFRP) specimens under tensile load. Two different parent orientations of [−45/+45]2S and [0/90]2S are exemplarily examined, and control specimens are taken as a baseline for the tensile strength and stiffness property recovery assessment. Using a layer-wise stress analysis with finite element simulations conducted with ANSYS Composite PrepPost to support the experimental investigation, the fiber orientation with respect to load direction is shown to affect the critical regions and thereby failure mechanism of the scarf joint specimens.

The paper presents the results of an experimental investigation of stop-splayed scarf joints, which was carried out as part of a research programme at the Wroclaw University of Science and Technology. A brief description and the characteristics of scarf and splice joints appearing in historical buildings are provided, with special reference to stop-splayed scarf joints (so-called ‘Bolt of lightning’) which were widely used, for example, in Italian renaissance architecture. Analyses and studies of scarf and splice joints in bent elements presented in the literature are reviewed, along with selected examples of analyses and research on tensile joints. It is worth noting that the authors in practically all the cited literature draw attention to the need for further research in this area. Next, the results of the authors’ own research on beams with stop-splayed scarf joints, strengthened using various methods, e.g., by means of drawbolts (metal screws), steel clamps and steel clamps with wooden pegs, which were subjected to four-point bending tests are presented. Load-deflection plots were obtained for load-bearing to bending of each beam in relation to the load-bearing of a continuous reference beam. A comparative analysis of the results obtained for each beam series is presented, along with conclusions and directions for further research.

In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was used and effect of pin profiles was investigated on this type of joint configuration. The effect of pin profiles on microstructure, micro-hardness, impact and tensile properties of friction stir welded Al 6063-T6 was investigated. Scanning electron and optical microscopy were employed to characterize the different zones of welded joints. A thorough discussion on correlation between mechanical properties and microstructure has been made. In addition, the formation of various defects during the FSW was discussed with the help of fractography of the fractured surfaces.

Sisal and jute woven mat epoxy composites offer uniform fiber distribution and ease of fabrication, with the mat structure significantly enhancing wear resistance. This study compares the adhesive bond strength of these composites using sisal, jute, and hybrid mats joined with single lap, butt, and scarf configurations (ASTM D5868‐01R14) and two epoxy adhesives: LY‐556/HY951 and XIN‐100 IN/XIN‐900. Results demonstrate that enhanced fiber/matrix interfacial bonding increases joint strength, with both fibers exhibiting superior adhesion to XIN‐100 IN/XIN‐900. The hybrid mat achieved the highest tensile strength in both matrices compared to sisal or jute alone. Tensile tests and Field Emission Scanning Electron Microscopy (FE‐SEM) conducted at room temperature revealed the failure mechanisms of the bonded laminates. This study experimentally investigates the development and properties of sisal and jute woven mat epoxy composites that offer uniform fiber distribution and ease of fabrication, with the mat structure significantly enhancing wear resistance. This study compares the adhesive bond strength of these composites using sisal, jute, and hybrid mats joined with single lap, butt, and scarf configurations (ASTM D5868‐01R14) and two epoxy adhesives: LY‐556/HY951 and XIN‐100 IN/XIN‐900. Results demonstrate that enhanced fiber/matrix interfacial bonding increases joint strength, with both fibers exhibiting superior adhesion to XIN‐100 IN/XIN‐900. The hybrid mat achieved the highest tensile strength in both matrices compared to sisal or jute alone. Tensile tests and Field Emission Scanning Electron Microscopy (FE‐SEM) conducted at room temperature revealed the failure mechanisms of the bonded laminates.

Failure to clear apoptotic cells can lead to autoinflammatory disease. Means and colleagues demonstrate that the receptor SCARF1 recognizes C1q-bound apoptotic cells, which leads to their clearance and prevents lupus-like symptoms. The clearance of apoptotic cells is critical for the control of tissue homeostasis; however, the full range of receptors on phagocytes responsible for the recognition of apoptotic cells remains to be identified. Here we found that dendritic cells (DCs), macrophages and endothelial cells used the scavenger receptor SCARF1 to recognize and engulf apoptotic cells via the complement component C1q. Loss of SCARF1 impaired the uptake of apoptotic cells. Consequently, in SCARF1-deficient mice, dying cells accumulated in tissues, which led to a lupus-like disease, with the spontaneous generation of autoantibodies to DNA-containing antigens, activation of cells of the immune system, dermatitis and nephritis. The discovery of such interactions of SCARF1 with C1q and apoptotic cells provides insight into the molecular mechanisms involved in the maintenance of tolerance and prevention of autoimmune disease.

Bonded composite scarf joints with bonding flaws were tested to study their tensile behaviors. Based on the failure modes obtained by various observation methods, an improved numerical methodology with appropriate model width was developed, considering the marginal low stiffness regions in ± 45° plies. The results show that the modelling approach provides accurate predictions on the strength, stiffness, and the failure modes considering variations in scarf angle, flaw size, and flaw location. Marginal low stiffness regions in ± 45° plies influence the stress distributions in the adhesive layer and the failure mode. Adhesive layer failure is the main cause of the final fracture of the pristine and the defective scarf joints, and damages within composite adherend especially interlaminar delamination, may accelerate the growth of the bondline stress at an early stage. The traditional damage tolerance design approach for bonded composite joints needs to be improved to avoid confusing and adventurous results.

Purpose The purpose of this paper is to evaluate and exploit the combination of additive manufacturing polymeric technology and structural adhesives. The main advantage is to expand the maximum dimension of the 3D printed parts, which is typically limited, by joining the parts with structural adhesive, without losing strength and stiffness and keeping the major asset of polymeric 3 D printing: freedom of shape of the system and low cost of parts. Design/methodology/approach The materials used in the paper are the following. The adhesive considered is a commercial inexpensive acrylic, quite similar to superglue, applicable with almost no surface preparation and fast curing, as time constraint is one of the key problems that affects industrial adhesive applications. The 3D printed parts were in acrylonitrile butadiene styrene (ABS), obtained with a Fortus 250mc FDM machine, from Stratasys. The work first compares flat overlap joint with joints designed to permit mechanical interlocking of the adherends and then to a monolithic component with the same geometry. Single lap, joggle lap and double lap joints are the configurations experimentally characterized following a design of experiment approach. Findings The results show a failure in the substrate, due to the low strength of the polymeric adherends for the first batch of typical bonded configurations, single lap, joggle lap and double lap. The central bonded area, with an increased global thickness, never does fail, and the adhesive is able to transfer the load both with and without mechanical interlocking. An additional set of scarf joints was also tested to promote adhesive failure as well as to retrieve the adhesive strength in this application. The results shows that bonding of polymeric AM parts is able to express its full potential compared with a monolithic solution even though the joint fails prematurely in the adherend due to the bending stresses and the notches present in the lap joints. Research limitations/implications Because of the 3D printed polymeric material adopted, the results may be generalized only when the elastic properties of the adherends and of the adhesive are similar, so it is not possible to extend the findings of the work to metallic additive manufactured components. Practical implications The paper shows that the adhesives are feasible way to expand the potentiality of 3 D printed equipment to obtain larger parts with equivalent mechanical properties. The paper also shows that the scarf joint, which fails in the adhesive first, can be used to extract information about the adhesive strength, useful for the designers which have to combine adhesive and additive manufactured polymeric parts. Originality/value To the best of the researchers’ knowledge, there are scarce quantitative information in technical literature about the performance of additive manufactured parts in combination with structural adhesives and this work provides an insight on this interesting subject. This manuscript provides a feasible way of using rapid prototyping techniques in combination with adhesive bonding to fully exploit the additive manufacturing capability and to create large and cost-effective 3 D printed parts.