Experimental Testing of Scarf Joints and Laminated Timber for Wooden Boatbuilding Applications

Timber construction has recently seen a significant regain of interest across a range of industries, owing to contemporary concerns for sustainability. In the marine industry, historic principles of traditional wooden boatbuilding remain present, with empirical rules still common practice, as is the case for scarf joints. Moreover, laminated wood is made more attractive and efficient thanks to modern adhesives. However, with the progress made in structural analysis, these assemblies can now be refined based on scientifically informed evidence. This paper employs destructive testing to tackle two distinct cases. On the one hand, the strength of plain scarf joints as a function of their slope is evaluated. On the other hand, the effectiveness of a range of adhesives is ascertained for the purpose of laminated manufacturing. The results are compared to both solid wood and the mechanical properties assumed by modern scantling regulations, revealing significant differences. The novel research findings provide a better understanding of these fundamental timber construction principles, supporting designers and builders alike in making informed choices while promoting safer regulatory compliance and enabling the future development of structural small craft standards. Applications beyond the structural design of wooden boats are also anticipated, for instance in sustainable buildings and architecture.

A nonlinear viscoelastic–viscoplastic constitutive model for adhesives under creep

In this study, we consider the nonlinear viscoelastic–viscoplastic behavior of adhesive films in scarf joints. We develop a three-dimensional nonlinear model, which combines a nonlinear viscoelastic model with a viscoplastic model using the von Mises yield criterion and nonlinear kinematic hardening. We implement an iterative scheme for the viscoplastic solution and a numerical algorithm with stress correction for the combined viscoelastic–viscoplastic model into finite element analysis. The viscoelastic component of the model is calibrated using creep-recovery data from adhesive films in scarf joints. The viscoplastic parameters are calibrated from the residual strains of recovered creep tests with varying load durations. A two-dimensional form of the model shows good agreement with the three-dimensional model for the scarf joint considered in this work and is compared with experiment. The numerical results show favorable agreement with the experimental creep and recovery responses of two epoxy adhesive systems. We also discuss the contribution of nonlinear viscoelasticity and viscoplasticity to the stress/strain distribution along the adhesive center lines. Viscoplasticity tends to lower the stress concentration.

SCARF JOINTS IN GLUED LAMINATED TIMBER OF PARICÁ

Glued Laminated Timber (GLULAM) is manufactured by joining wood lamellae glued in parallel to each other. GLULAM with larger longitudinal dimensions can be obtained by gluing the tops of two wood lamellae. The gluing of the tops can be done using wedge-shaped scarf joints. However, the joints produce a discontinuity in the wood, being areas considered as susceptible to rupture. In this way, the objectives were to evaluate four slopes (1:6; 1:8; 1:10 and 1:12) in scarf joints of Schizolobium parahyba var. amazonicum timber for use with structural purposes; and glued laminated timber beams – GLULAM manufactured with the scarf joint with the best performance by the modulus of elasticity – MOE (theoretical and analytical MOE values). Each laminated timber used to produce the test specimens was classified by visual inspection that aimed at the absence of defects, such as knots. The test specimens were adapted to the four-point static bending test and to the tensile strength test in parallel to the grain direction, in accordance to the NBR 7190 (1997). The slope of 1:12 showed the best results, while the slope of 1:6 presented the lowest results when compared with the control. The beams of 5 x 9.5 x 220 cm, composed of joints with slopes of 1:12, showed MOE values statistically equal to those of beams without joints. The scarf joint proved to be an alternative for use in glulam beams of paricá, as it presents stiffness and strength comparable with those of beams without a joint.

Modelling of Harmonic Response of Scarf Adhesive Joints

Adhesives are used for attaching structures to various spacers such as tubular and scarf joints to replace the traditional joining methods of welding, brazing, soldering, etc. Many of the unique features associated with adhesives are low manufacturing cost, long component life, and lightweight. Accordingly, a considerable amount of study has been carried out and is still underway to develop. The main objective of this study is to investigate the response of the scarf joints when exposed to a harmonic load. The finite element method (FEM) using ANSYS is availed to study and analysis the natural frequencies, mode shape, and frequency response. Additionally, the influence of the adhesion angle is examined.

Failure Mechanisms of GFRP Scarf Joints under Tensile Load

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.

Timber Construction: An Experimental Assessment of the Strength of Scarf Joints and the Effectiveness of Various Adhesives for Laminated Wood

Timber construction has recently seen a significant regain of interest across a range of industries, owing to contemporary concerns for sustainability. In the marine industry, historic principles of traditional wooden boatbuilding remain present, with empirical rules still common practice, as is the case for scarf joints. Moreover, laminated wood is made more attractive and efficient thanks to modern adhesives. However, with the progresses made in structural analysis, these assemblies can now be refined based on scientifically informed evidence. Consequently, this paper will employ destructive testing to tackle two distinct cases. On the one hand, the strength of feathered (plain) scarf joints as a function of their slope will be evaluated. On the other hand, the effectiveness of a range of adhesives will be ascertained for the purpose of laminated manufacturing. Ultimately, the results will be compared to both the strength of solid wood and the mechanical properties assumed by modern scantling regulations, revealing significant differences. The research findings provide a better understanding of these fundamental timber construction principles, supporting designers and builders alike in making informed choices and promoting safer regulatory compliance. It is also anticipated these findings will impact structural design beyond the wooden boatbuilding field, with applications in sustainable buildings and architecture.