The poly(lactic acid) (PLA) biodegradable polymer, as well as natural, siliceous reinforcement in the form of diatomaceous earth, fit perfectly into the circular economy trend. In this study, various kinds of commercial PLA have been reinforced with diatomaceous earth (DE) to prepare biodegradable composites via the extrusion process. The structure of the manufactured composites as well as adhesion between the matrix and the filler were investigated using scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) analyses were carried out to determine crystallinity of PLA matrix as function of DE additions. Additionally, the effect of the ceramic-based reinforcement on the mechanical properties (Young’s modulus, elongation to failure, ultimate tensile strength) of PLA has been investigated. The results are discussed in terms of possible applications of PLA + DE composites.

Numerous engineering applications require lightweight structures with excellent absorption capacity. The problem of obtaining such structures may be solved by nature and especially biological structures with such properties. The paper concerns an attempt to develop a new energy-absorbing material using a biomimetic approach. The lightweight structure investigated here is mimicking geometry of diatom shells, which are known to be optimized by nature in terms of the resistance to mechanical loading. The structures mimicking frustule of diatoms, retaining the similarity with the natural shell, were 3D printed and subjected to compression tests. As required, the bio-inspired structure deformed continuously with the increase in deformation force. Finite element analysis (FEA) was carried out to gain insight into the mechanism of damage of the samples mimicking diatoms shells. The experimental results showed a good agreement with the numerical results. The results are discussed in the context of further investigations which need to be conducted as well as possible applications in the energy absorbing structures.

Three-dimensional printing enables rapid prototyping, customization, and on-demand production. Polylactide is a popular biopolymer filament used in 3D printing. However, due to its brittleness and low mechanical strength, it often needs to be reinforced with filler particles. Diatomaceous earth shows great potential as a filler material due to its abundant and natural occurrence, biocompatibility, and environmental friendliness, as well as its excellent mechanical properties. Cold hydrostatic extrusion was used to improve the compressive strength of 3D-printed parts. Both neat and reinforced with 10% diatomaceous earth filaments were used to 3D print cylindrical billets, followed by post-processing using hydrostatic extrusion. X-ray microtomography showed a significant reduction in total and open porosity and average pore size, from ~20 µm to less than 10 µm in the Polylactide (PLA) and Diatomaceous (DE) composite. Compression tests showed a significant improvement in the compressive strength of PLA from ~60 MPa to ~100 MPa, while PLA with DE achieved an impressive almost twofold increase to 80–120 MPa. This was attributed to a reduction in pore size, as well as pore closure, which mitigates crack initiation in semi-brittle PLA. In addition, it has been proposed that hydro extrusion-induced structural rearrangement is an important strengthening factor.

The development of additive manufacturing (AM) techniques has sparked interest in porous structures that can be customized in terms of size, shape, and arrangement of pores. Porous lattice structure (LS, called also lattice struct) offer superior specific stiffness and strength, making them ideal components for lightweight products with energy absorption and heat transfer capabilities. They find applications in industries such as aerospace, aeronautics, automotive, and bone ingrowth applications. One of the main advantages of additive manufacturing is the freedom of design, control over geometry and architecture, cost and time savings, waste reduction, and product customization. However, the designation of appropriate struct/pore geometry to achieve the desired properties and structure remains a challenge. In this part of the study, five lattice structs with various pore sizes, with two volume fractions for each, and shapes (ellipsoidal, helical, X-shape, trapezoidal, and triangular) were designed and manufactured using selective laser sintering (SLS) additive manufacturing technology. Mechanical properties were tested through uniaxial compression, and the apparent stress-strain curves were analyzed. The results showed that the compression tests revealed both monotonic and non-monotonic stress-strain curves, indicating different compression behaviors among the structures. The helical structure exhibited the highest resistance to compression, while other structures showed similarities in their mechanical properties. In Part II of this study provides a comprehensive analysis of these findings, emphasizing the potential of purpose-designed porous structures for various engineering applications.

In this study, thermal deformation in non-planar, large-scale additive manufacturing (LSAM) was experimentally and numerically investigated. A Bézier-based non-planar build surface was fabricated by CNC machining, and a single layer of ABS was deposited using a hybrid LSAM system. Toolpaths with raster angles of 0° and 45° were generated for surface-conformal printing. Infrared thermography was employed to monitor the thermal history during deposition. A three-dimensional finite element model was developed to simulate transient heat transfer and thermally induced deformation. Experimental deformation was quantified by 3D scanning and compared with simulation results. The results show that the slope geometry strongly influences deformation direction: negative slopes promote contraction, whereas positive slopes lead to upward deflection. Maintaining the material temperature above the glass transition temperature significantly reduces skew deformation. The finite element method predictions demonstrate strong agreement with experimental measurements, with normalized root mean square errors (NRMSEs) of approximately 11% for thermal deformation and 10% for temperature history. The proposed framework enables prediction and mitigation of thermal warping in non-planar polymer additive manufacturing.

Polylactide (PLA) that is reinforced with diatomaceous earth (DE) is a promising and eco-friendly material with high engineering potential. This article provides a comprehensive overview of various PLA types and processing methods for PLA + DE composites. This study aimed to determine the mechanical strength limits of PLA + DE composites using two PLA grades—amorphous PLE 005-A and semi-crystalline Ingeo 4043D—that are each filled with Perma-Guard DE 5, 10, and 15% by weight, and two manufacturing methods, injection molding (IM) and additive manufacturing (3DP), using fused filament fabrication (FFF). The mechanical properties were assessed through static tensile tests in accordance with ISO 527-1 and compared with values reported in the literature. The results indicate a linear increase in stiffness (Young’s modulus) with increasing DE content. This is accompanied by a reduction in maximum tensile strength (σ_max) and elongation at break (ε_b). The highest Young’s modulus, around 4.65 GPa, was observed for injection-molded, semi-crystalline PLA with a 15% by weight DE. The greatest tensile strength, approx. 72 MPa, was achieved for printed, semi-crystalline PLA without filler. Furthermore, 3D printing achieved a tensile strength and stiffness comparable to injection molding, though the latter ensured significantly better ductility. These findings provide a basis for adjusting the PLA + DE composite properties to specific applications by selecting the matrix type, DE content, and manufacturing method.