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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.

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.

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.

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.

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.

The stress distribution of timber tenoned scarf joint subjected to tension force was analysed by means of finite element method. This analysis was compared and validated with results from an experimental work on 42 specimens of Scots pine wood ( Pinus sylvestris L.) with 48 × 148 mm in cross-section and 1932 mm, in length, manufactured with a tenoned scarf joint in the middle of its length. Specimens were divided in eight groups corresponding to different joint geometries. A plane finite element analysis using ANSYS software was made considering the elasticity moduli, Poisson ratios and friction coefficients obtained in previous research works for the same material. Three different failure modes were analysed: compression parallel to the grain in the notch area, shear parallel to the grain in the heel surface, and the combination of tension and bending moment in the effective cross-section of the piece, which is limited by the crack initiation due to tension perpendicular to the grain. Equations for the verification of this joint are proposed as a practical conclusion.

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.

With the increasing use of structures with adhesive bonds at the industrial level, several authors in the last decades have been conducting studies concerning the behaviour and strength of adhesive joints. Between the available strength prediction methods, cohesive zone models, which have shown good results, are particularly relevant. This work consists of a validation of cohesive laws in traction and shear, estimated by the application of the direct method, in the strength prediction of joints under a mixed-mode loading. In this context, scarf joints with different scarf angles ( α ) and adhesives of different ductility were tested. Pure-mode cohesive laws served as the basis for the creation of simplified triangular, trapezoidal and exponential laws for all adhesives. Their validation was accomplished by comparing the numerical maximum load ( P m ) predictions with the experimental results. An analysis of peel ( σ ) and shear ( τ ) stresses in the adhesive layer was also performed to understand the influence of stresses on P m . The use of the direct method allowed obtaining very precise P m predictions. For the geometric and material conditions considered, this study has led to the conclusion that no significant P m errors are incurred by the choice of a less appropriate law or by uncoupling the loading modes.

In the present study, elastic properties of scarf-jointed oak (Quercus castaneifolia) timbers with the application of two different types of adhesives (polyvinyl acetate and isocyanate) were evaluated using free flexural vibration of free–free beam method in different flexural directions of vibration, i.e., tangential and redial directions. Samples were taken from trees of Hyrcanian forests in Iran with nominal dimensions of 20 × 20 × 360 mm³. Comparing the results of elastic properties of clear oak wood beams with scarf-jointed samples wood showed that scarf joints with the bonding angles of 70° and 75°, covered by polyvinyl acetate adhesive, did not demonstrate any significant effect on modules of elasticity. Scarf-jointed beams with smaller joint angles (60° and 65°) were considerably weaker or totally unreliable in their moduli of elasticity. It is also shown that the magnitude of effect gets worst by using isocyanate rather than polyvinyl acetate adhesive.