Additive manufacturing (AM), as one of the most powerful manufacturing methods, is fabricating a three-dimensional (3D) structure using computer-aided design (CAD) data by adding material layer by layer. In contrast to traditional manufacturing processes that start from raw block material and remove waste materials, the AM process can demonstrate better aspects such as freedom of design, reduced postprocessing, and waste reduction. With emerging smart materials such as shape memory polymers, the 3D printing technology has upgraded to a technology that is called four-dimensional (4D) printing, in which the fourth dimension expresses time. In this technology, by using active materials, the printed structure can reshape its configuration and also change its mechanical properties in the presence of external stimuli such as temperature, magnetic field, and/or electric field. The fabrication and modeling of 4D-printed structures are considered due to their extensive applications in various areas such as biomedical and robotic. In this chapter, initially based on thermomechanical properties of smart materials, the constitutive modeling is presented for the shape memory feature. Subsequently, the fabrication of 4D-printed elements based on the FDM process is described, and a simple finite element method (FEM) is introduced to predict their self-morphing features. Finally, the fabricated self-morphing and adaptive structures are presented and the proposed model is calibrated based on them. Following model calibration, some smart structures such as grippers, adaptive dynamic structures, and smart composites are presented as case studies, and their behavior under external stimuli is investigated.

The authors regret to inform that unfortunately, there is a minor typo in the original version of the article. Authors apologize for this shortcoming and are aimed to report the correct data herein. In Table 1 of the original manuscript, a6 must be considered to be equal with +2.71 (instead of −2.71). The authors would like to apologise for any inconvenience caused.

Magnetorheological elastomers (MREs) are polymers reinforced by ferromagnetic particles that show magnetic dependent behavior. Mixing MREs with reinforcing fibers can create a new class of material so-called “MRE composites, MRECs” with additional functionalities and properties. Here, using a Generalized Maxwell model, we proposed a new magnetic-dependent rheological model by considering the hysteresis phenomenon for MREs to predict the dynamic damping responses of MREC plates reinforced by fibers in the frequency domain. We also investigated the influence of magnetic flux intensity, the volume fraction of the fiber, the orientation angle of the fibers, the number of layers, as well as the fiber-to-matrix stiffness ratio on the natural frequency, loss factor, and mode shapes of MRECs plates. Our results suggest that homogenously increasing the elastic properties of the MRECs through the spatial distribution of fibers and changing the fiber-to-matrix stiffness ratio can effectively tailor the dynamic properties of MRECs. Tailoring these properties can provide additional freedom for the fabrication of 4D-printed MRE-based composites.

Modeling and analyzing the sports equipment for injury prevention, reduction in cost, and performance enhancement have gained considerable attention in the sports engineering community. In this regard, the structure study of on-water sports board (surfboard, kiteboard, and skimboard) is vital due to its close relation with environmental and human health as well as performance and safety of the board. The aim of this paper is to advance the on-water sports board through various bio-inspired core structure designs such as honeycomb, spiderweb, pinecone, and carbon atom configuration fabricated by three-dimensional (3D) printing technology. Fused deposition modeling was employed to fabricate complex structures from polylactic acid (PLA) materials. A 3D-printed sample board with a uniform honeycomb structure was designed, 3D printed, and tested under three-point bending conditions. A geometrically linear analytical method was developed for the honeycomb core structure using the energy method and considering the equivalent section for honeycombs. A geometrically non-linear finite element method based on the ABAQUS software was also employed to simulate the boards with various core designs. Experiments were conducted to verify the analytical and numerical results. After validation, various patterns were simulated, and it was found that bio-inspired functionally graded honeycomb structure had the best bending performance. Due to the absence of similar designs and results in the literature, this paper is expected to advance the state of the art of on-water sports boards and provide designers with structures that could enhance the performance of sports equipment.