Bolting technologies have been commonly used to assemble structural members in order to carry loads. However, the main drawback of these joints is the local reduction of the strength-to-stress ratio. Compared to the bolted joints, adhesive bonding technology allows for the increase of static and fatigue strength while reducing the weight. The Finite Element (FE) method is able to address the stress analysis of bonded joints. Nevertheless, analyses based on FE models are computationally expensive. Therefore, it is profitable to develop new simplified approaches enabling extensive parametric studies. A semi-analytical technique was developed to model the joints based on the formulation of 4-node special elements, termed macro-elements, which is able to simulate an entire bonded overlap at low computational costs. In this paper, a multilayered bonded-bars and a multilayered bonded-beams macro-elements are derived from bonded-bar and bonded-beam macro-elements. 1D-bar and 1Dbeam simplified stress analyses of such multilayered joints are presented in order to predict the adhesive stress distributions along the overlap. For validation purpose, the results obtained by the simplified 1D-bar and 1Dbeam model are compared with the results predicted by 1D-FE models. Good agreements are shown. Finally, the parametric studies are performed in order to understand the mechanical behavior of multilayered adhesively bonded structures. This presented simplified stress analysis can be used to deduce the sizing guidelines as a consequence of these parametric studies.

In the present paper, the degree of cure-dependent viscoelastic properties of a commercial photopolymer resin (Loctite$$^{\textregistered }$$ ® 3D 3830) used in digital light processing (DLP) 3D printing are investigated experimentally and described by suitable model equations. To do this, tests are carried out both on the liquid resin and printed specimens under various conditions. The experimental methods include photo-DSC, UV rheometry, and dynamic mechanical analysis. A commercial digital light processing (DLP) printer (Loctite$$^{\textregistered }$$ ® EQ PR10.1) is used for the printing of the samples. Model equations are proposed to describe the behavior of the material during and after the printing process. For the representation of the degree of cure depending on temperature and light intensity, the one-dimensional differential equation proposed in a previous paper is extended to capture a temperature-dependent threshold value. The change of the viscoelastic properties during crosslinking is captured macroscopically by time-temperature and time-cure superposition principles. The parameters of the model equations are identified using nonlinear optimization algorithms. A good representation of the experimental data is achieved by the proposed model equations. The findings of this paper help users in additive manufacturing of photopolymers to predict the material properties depending on the degree of cure and temperature of printed components.