Functionally Graded Polymer Lattice Structures Enabled by Multi-Material Fused Deposition Modeling: Current Progress, Challenges, and Future Perspectives.
Functionally graded lattice structures can potentially enhance energy absorption, but the actual benefits may be modest and depend on specific configurations.
Where it sits
this study against the rest of the fgl (fg loop peptide) corpusSummary and findings
This review examines functionally graded lattice (FGL) structures created through multi-material fused deposition modeling (MM-FDM). It evaluates 65 primary studies on the performance of these structures, particularly in terms of stiffness, strength, and energy absorption. The findings indicate that pairing rigid thermoplastics with hyperelastic TPU can increase specific energy absorption by up to two- to threefold compared to single-material lattices.
Abstract
Functionally graded lattice (FGL) structures can decouple stiffness, strength and energy absorption. Multi-material fused deposition modeling (MM-FDM) is an accessible route to lattices that vary in composition and topology within one print. This review examines MM-FDM polymer FGLs through a PRISMA 2020-informed screening of 610 records. Of the 126 screened references, 65 primary studies meet all eligibility criteria and form the core evidence, and 20 are supporting studies. Four grading strategies were identified: material-based zoning, geometry-induced grading, combined material-geometry grading and process-induced grading, applied mainly to strut-based, triply periodic minimal surface (TPMS) and hybrid plate-TPMS architectures. Pairing rigid thermoplastics (PLA, ABS, PETG) with hyperelastic TPU increased specific energy absorption by up to two- to threefold over single-material lattices, but the gain over the rigid constituent alone was smaller and, in several quasi-static studies, negative; it depends on configuration, baseline and loading rate. Graded lattices collapse layer by layer, yet their energy gain over uniform lattices of equal mass is often modest. TPMS architectures are reported to reduce nodal stress concentrations. Most evidence remains at the specimen level. The main limitations are weak interfaces between incompatible polymers, process-induced defects, models that neglect manufacturing effects and the lack of standardized test protocols.
Background
This review addresses the development of functionally graded lattice structures (FGLs) using multi-material fused deposition modeling (MM-FDM). Prior knowledge indicates that FGLs can decouple stiffness, strength, and energy absorption, but challenges remain in their practical application. The study is significant as it consolidates current research and identifies strategies to improve the performance of FGLs.
Methods
The review employs a PRISMA 2020-informed screening of 610 records, narrowing down to 126 screened references, of which 65 primary studies met eligibility criteria. It discusses various grading strategies, including material-based zoning and geometry-induced grading, primarily focusing on strut-based and triply periodic minimal surface (TPMS) architectures. No specific doses or treatment durations are reported.
Results
The review highlights that pairing rigid thermoplastics with hyperelastic TPU can increase specific energy absorption by up to two- to threefold. However, the gain over the rigid constituent alone was smaller and, in several quasi-static studies, negative. The review also notes that graded lattices often exhibit modest energy gain over uniform lattices of equal mass.
Interpretation
The findings suggest that while there are potential benefits to using graded lattices, the effect sizes may not be clinically meaningful due to the modest gains observed. The review emphasizes that most evidence is at the specimen level, which limits broader applicability. Additionally, confounding factors such as weak polymer interfaces and process-induced defects may impact the reliability of the results.
Key findings
- Increased specific energy absorption by up to two- to threefold over single-material lattices.
- The gain over the rigid constituent alone was smaller and, in several quasi-static studies, negative.
- Most evidence remains at the specimen level.
- Weak interfaces between incompatible polymers are a main limitation.
- Graded lattices collapse layer by layer.
Limitations
- Most evidence remains at the specimen level.
- Weak interfaces between incompatible polymers.
- Process-induced defects may affect results.
- Lack of standardized test protocols.