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Additive Manufacturing (AM) empowers the creation of high‐performance cellular materials, underscoring the increasing need for programmable and predictable energy absorption capabilities. This study evaluates the impact of a precisely tuned fused filament fabrication (FFF) process on the energy absorption and failure characteristics of 2D‐thermoplastic lattice materials through multiscale experiments and predictive modeling. Macroscale in‐plane compression testing of both thick‐ and thin‐walled lattices, along with their µ‐CT imaging, reveal relative density‐dependent damage mechanisms and failure modes, prompting the development of a robust predictive modeling framework to capture process‐induced performance variation and damage. For lower relative density lattices, an FE model based on the extended Drucker–Prager material model, incorporating Bridgman's correction with crazing failure criteria, accurately captures the crushing response. As lattice density increases, interfacial damage along bead‐bead interfaces becomes predominant, necessitating the enrichment of the model with a microscale cohesive zone model to capture interfacial debonding. The predictive modeling introduces an enhancement factor, offering a straightforward method to assess the impact of the AM process on energy absorption performance, thereby facilitating the inverse design of FFF‐printed lattices. This approach provides a critical evaluation of how FFF processes can be optimized to achieve the highest attainable performance and mitigate failures in architected materials. [ABSTRACT FROM AUTHOR]

A feasibility study of an innovative apparatus for dynamic characterization of materials at intermediate strain rates is presented. The working principle is based on the Split Hopkinson bar, but the wave propagation occurs through properly sized springs. The system is designed to generate and transmit tension or compression waves having a low propagation speed, in order to reduce the specimen strain rate at the impact. At first, a simplified theory is presented for the estimation of longitudinal wave speed in springs as a function of the main engineering parameters of the coil dimensioning. Then, a preliminary sizing of the apparatus is proposed based on basic considerations of wave propagation theory. Finally, a numerical model of a compression test is presented as a proof-of-concept.

The increasing interest to improve the description of the plastic behavior and the fracture prediction for ductile materials under complex loading conditions conducted the researchers to overcome the J2 plasticity theory. To do this more sophisticated plasticity model base on ductile damage have been implemented. Material model parameters must be identified by means of proper testing and calibration procedures requiring different loading conditions. Different types of tests must be performed, imposing multiaxial stress paths to the specimens. Tensile tests on smooth and round notched bars, plane strain tests, torsion tests, compression and combined tension–torsion tests on hollow and solid cylindrical bars must be executed. While multiple works are present in literature for model assessment and validation in quasi-static conditions, nothing can be found at high strain rate in biaxial conditions (tension-torsion). Biaxial tests in dynamic conditions are very difficult to carry out especially if you are interested to register the entire story of stress and strain. In this work, analytical and numerical study to evaluate the feasibility to carry out dynamic tension, dynamic torsion, dynamic torsion-static tension/compression and dynamic tension–dynamic torsion tests is discussed. The tests will be performed using a properly designed Split Hopkinson Bar.

Shape memory polymers (SMPs) represent a materials class capable of recovering their initial shape, when submitted to deformations, through an external stimulus. This paper focuses on a Shape Memory Thermoplastic Polyurethane (SMPU), characterized by a one-way shape memory effect (SME) activated by temperature. The material was characterized by Differential Scanning Calorimetry (DSC) to find transition temperature; then, it was manufactured by an injection molding machine to perform a campaign of characterization tests. Thermomechanical tests were conducted varying the prescribed strain (up to 25%, 50%, and 80%), imposed at both different strain rates ( 10 − 3 , 10 − 2 , and 10 − 1 s−1), and temperatures (50°C, 60°C, and 70°C); the results were investigated in terms of shape fixity and shape recovery ratios. An excellent memory capability was observed for all the tested conditions; otherwise, the shape recoverability is strongly influenced by all investigated parameters, especially by the strain rate, resulted to be the most effective one. In fact, the shape recovery ratio can increase as much as 20%, when the strain rate is increased from 10 − 3 to 10 − 1 s−1. An opposite effect was observed with the variation of prescribed strain and temperature, the increase of which reduces the ability of the material to return to its original shape. [ABSTRACT FROM AUTHOR]