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Composite materials are increasingly used in the structural and mechanical fields, thanks to their high strength‐to‐weight ratios and the possibility of tailoring them to meet specific requirements. This study is focused on the damage to a glass fiber reinforced composite under different loading conditions. The aim is to find, by coupling mechanical tests with thermal analyses, a damage parameter, able to define the damage initiation in the studied material.

The object of this work is a glass‐fiber reinforced plastic (GFRP) laminate. To study the damage of this material under different loading conditions, static, dynamic and fatigue tests were carried out. During these tests, the surface temperature of the specimens was monitored by means of an IR‐camera. In the dynamic tests, a D‐mode (dissipation mode) analysis was also performed allowing the dissipated energy to be determined.

In the literature, thermography is an experimental technique which has always been applied to the study of homogeneous materials. Results obtained from the proposed experimental tests on this GFRP composite show how this practice can be applied also to this kinds of materials, to identify their damage initiation. From these observations, the results can be used to definite a stress corresponding to the damage initiation, which can be related to the fatigue behavior, and useful in design stage with these materials.

This paper provides for a useful tool to understand and predict fatigue behavior of a GFRP composite, from thermographic observations. Applications of thermography to the study of composite materials is an innovative research field, and the presented results seems satisfactory and promising for further experimental investigations.

This study aims to investigate the behaviour of soft lattices, i.e. lattices capable of reaching large deformations, and the influence of the printing process on it. The authors focused on two cell topologies, the body-centred cubic (BCC) and the Kelvin, characterized by a bending-dominated behaviour relevant to the design of energy-absorbing applications.

The authors analysed the experimental and numerical behaviour of multiple BCC and Kelvin structures. The authors designed homogenous and graded arrays of different dimensions. The authors compared their technical feasibility with two three-dimensional-printed technologies, such as the fused filament fabrication and the selective laser sintering, choosing thermoplastic polyurethane as the base material.

The results demonstrate that multiple design aspects determine how the printing process influences the behaviour of soft lattices. Besides, a graded distribution of the material could contribute to fine-tuning this behaviour and mitigating the influence of the printing process.

Despite being less explored than their rigid counterpart, soft lattices are now becoming of great interest, especially when lightweight, wearable and customizable solutions are needed. This study contributes to filling this gap.

Only a few studies analyse design and printing issues of soft lattices due to the intrinsic complexity of printing flexible materials.

Natural elements in the biological organs of plants and animals consist of repetitive geometries, which often form the basis for the new lattice structure design with improved performance. The purpose of this study is to investigate the energy absorption capabilities and deformation behavior of lattice structures inspired by Helleborus petticoat flower and fish scale patterns.

The authors designed arc-shaped strut lattice structures by incorporating the geometrical features of Helleborus petticoat flower and fish scale pattern into lattice strut configuration. The structures were printed from thermoplastic polyurethane (TPU) material using fused deposition modeling process and tested under uniaxial compression. The energy absorption parameters, such as specific energy absorption (SEA), mean plateau stress, onset densification strain and absorption efficiency were determined, and deformation mechanism under static compression was analyzed. The SEA of proposed structures was compared with other TPU structures in the reported literature.

The results show that the lattice strut configuration affects the mechanical properties, energy absorption characteristics and deformation behavior of the proposed bio-inspired structures. The SEA was found to be in the range of 0.34–0.97 kJ / kg. Overall, the novel flower-inspired structure displayed significantly higher SEA (+185%), compared to fish scale-derived structure.

To the best of the authors’ knowledge, the authors have designed the proposed lattice structures for the first time. The energy absorption characteristics and deformation behavior of proposed lattice structures had never been reported previously.

The purpose of this study is to investigate the bending behaviour of three-dimensional (3D) thermoplastic polyurethane (TPU) structures printed onto the fabric.

TPU parts with varying infill patterns and raster angles were 3D-printed onto both woven and knitted fabrics. The resulting hybrid structures’ bending behaviours were evaluated using three test methods: cantilever bending, three-point bending and circular compression. Besides, both sides of the hybrid structures were tested to capture the influence of test direction.

The fabric structure is effective on adhesion force and greater values were observed for woven fabrics. The infill structures, raster angle and test directions were observed effective on the bending behaviour of the hybrid structures. The 45° raster angle resulted in greater bending resistance in three test methods. For knitted fabric structures, gyroid infill generally exhibits superior bending resistance. A case of fabricating a personal elbow brace for cubital tunnel syndrome was also introduced.

This study provides experimental information about the effects of 3D printing parameters on the bending behaviour of the hybrid structures and supports the development of special-purpose designs with tailored functionalities for various applications.

The purpose of this paper is to compare the influence of relative density (RD) and strain rates on failure mechanism and specific energy absorption (SEA) of polyamide lattices ranging from bending to stretch-dominated structures using selective laser sintering (SLS).

Three bending and two stretch-dominated unit cells were selected based on the Maxwell stability criterion. Lattices were designed with three RD and fabricated by SLS technique using PA12 material. Quasi-static compression tests with three strain rates were carried out using Taguchi's L9 experiments. The lattice compressive behaviour was verified with the Gibson–Ashby analytical model.

It has been observed that RD and strain rates played a vital role in lattice compressive properties by controlling failure mechanisms, resulting in distinct post-yielding responses as fluctuating and stable hardening in the plateau region. Analysis of variance (ANOVA) displayed the significant impact of RD and emphasised dissimilar influences of strain rate that vary to cell topology. Bending-dominated lattices showed better compressive properties than stretch-dominated lattices. The interesting observation is that stretch-dominated lattices with over-stiff topology exhibited less compressive properties contrary to the Maxwell stability criterion, whereas strain rate has less influence on the SEA of face-centered and body-centered cubic unit cells with vertical and horizontal struts (FBCCXYZ).

This comparative study is expected to provide new prospects for designing end-user parts that undergo various impact conditions like automotive bumpers and evolving techniques like hybrid and functionally graded lattices.

To the best of the authors' knowledge, this is the first work that relates the strain rate with compressive properties and also highlights the lattice behaviour transformation from ductile to brittle while the increase of RD and strain rate analytically using the Gibson–Ashby analytical model.

This study highlights the demand for low-cost and high accuracy products through the design and development of new 3D printing technologies. Besides, significant progress has been made in this field. A comparative study helps to understand the latest development in materials and future prospect of this technology.

Nevertheless, a large amount of progress still remains to be made. While some of the works have focused on the performances of the materials, the rest have focused on the development of new methods and techniques in additive manufacturing.

This paper critically evaluates the current 3D printing technologies, including the development and optimizations made to the printing methods, as well as the printed objects. Meanwhile, previous developments in this area and contributions to the modern trend in manufacturing technology are summarized briefly.

The paper can be summarized in three sections. Firstly, the existing printing methods along with the frequently used printing materials, as well as the processing parameters, and the factors which influence the quality and mechanical performances of the printed objects are discussed. Secondly, the optimization techniques, such as topology, shape, structure and mechanical property, are described. Thirdly, the latest development and applications of additive manufacturing are depicted, and the scope of future research in the relevant area is put forward.

Additive Manufacturing (AM) conventionally necessitates an intermediary slicing procedure using the standard tessellation language (STL) data, which can be computationally burdensome, especially for intricate microcellular architectures. This study aims to propose a direct slicing method tailored for digital light processing-type AM processes for the efficient generation of slicing data for microcellular structures.

The authors proposed a direct slicing method designed for microcellular structures, encompassing micro-lattice and triply periodic minimal surface (TPMS) structures. The sliced data of these structures were represented mathematically and then convert into 2D monochromatic images, bypassing the time-consuming slicing procedures required by 3D STL data. The efficiency of the proposed method was validated through data preparations for lattice-based nasopharyngeal swabs and TPMS-based ellipsoid components. Furthermore, its adaptability was highlighted by incorporating 2D images of additional features, eliminating the requirement for complex 3D Boolean operations.

The direct slicing method offered significant benefits upon implementation for microcellular structures. For lattice-based nasopharyngeal swabs, it reduced data size by a factor of 1/300 and data preparation time by a factor of 1/8. Similarly, for TPMS-based ellipsoid components, it reduced data size by a factor of 1/60 and preparation time by a factor of 1/16.

The direct slicing method allows for bypasses the computational burdens associated with traditional indirect slicing from 3D STL data, by directly translating complex cellular structures into 2D sliced images. This method not only reduces data volume and processing time significantly but also demonstrates the versatility of sliced data preparation by integrating supplementary features using 2D operations.

This paper develops a neural network surrogate model based on a discrete lattice approach to investigate the influence of complex microstructures on the emergent behavior of biological networks.

The adaptability of network-forming organisms, such as, slime molds, relies on fluid-to-solid state transitions and dynamic behaviors at the level of the discrete microstructure, which continuum modeling methods struggle to capture effectively. To address this challenge, we present an optimized approach that combines lattice spring modeling with machine learning to capture dynamic behavior and develop nonlinear constitutive relationships.

This integrated approach allows us to predict the dynamic response of biological materials with heterogeneous microstructures, overcoming the limitations of conventional trial-and-error lattice design. The study investigates the microstructural behavior of biological materials using a neural network-based surrogate model. The results indicate that our surrogate model is effective in capturing the behavior of discrete lattice microstructures in biological materials.

The combination of numerical simulations and machine learning endows simulations of the slime mold Physarum polycephalum with a more accurate description of its emergent behavior and offers a pathway for the development of more effective lattice structures across a wide range of applications.

The novelty of this research lies in integrating lattice spring modeling and machine learning to explore the dynamic behavior of biological materials. This combined approach surpasses conventional methods, providing a more holistic and accurate representation of emergent behaviors in organisms.

The purpose of this study is to develop a novel approach to designing locally programmed multi-material distribution in a three-dimensional (3D) model, with the goal of producing a biomimetic robot that could mimic the locomotion of living organisms.

A voxelized representation is used to design the multi-material digital model and the material distribution in the model is optimized with the aims of mimicking the deflection dynamics of a real-life biological structure (i.e. inchworms) during its locomotion and achieving smooth deflection between adjacent regions. The design is validated post-fabrication by comparing the bending profiles of the printed robot with the deflection reference images of the real-life organism.

The proposed design framework in this study provides a foundation for multi-material multi-functional design for biomimicry and a wide range of applications in the manufacturing field and many other fields such as robotics and biomedical fields. The final optimized material design was 3D printed using a novel multi-material additive manufacturing method, magnetic field-assisted projection stereolithography. From the experimental tests, it was observed that the deflection curve and the deflection gradient of the printed robot within the adjacent regions of the body agreed well with the profiles taken from the real-life inchworm.

This paper presents a voxelized digital representation of the material distribution in printed parts, allowing spatially varied programming of material properties. The incorporation of reference images from living organisms into the design approach is a novel approach to transform image domain knowledge into the domain of engineering mechanical and material properties. Furthermore, the novel multi-material distribution design approach was validated through designing, 3D printing and prototyping an inchworm-inspired soft robot, which showed superior locomotion capability by mimicking the observed locomotion of the real inchworm.

The purpose of this paper is to study if it is possible applying infrared thermography (both vibro and pulsed) to detect and localise material discontinuities as well as to find the place where the inclusion was introduced.

The experimental investigation is performed on samples manufactured during infusion process. The measurements were performed on three four-layered rectangular composite samples with discontinuities. The discontinuities introduced in the samples were as follow: all three samples between first and second layer counting form the bottom two optical fibres (OFs) were embedded and additionally: sample no. 1 – one of the OF was broken, sample no. 2 – the drop of water was introduced, and sample no. 3 – the little amount of dust was introduced.

For some discontinuities, the vibrothermography is excellent tool (placement of broken OF, drop of water), for same is not sufficient (healthy OFs or dust). For dust, the pulsed thermography seems to be the required tool. Different approaches (vibrothermography and pulsed thermography) for the same sample will confirm that for same defects vibrothermograpy is better and for some pulsed thermography – complex combination of different thermography approaches is needed to have complex response about sample structural condition.

The presented paper is an original research work. There are very limited literature papers applying both vibro and pulsed thermography for one problem. The assessment of different discontinuities (inclusions) and detailed analysis is presented.