Influence of Infill Structures and Process Parameters on the Tensile Strength of 3Dprinted PEEK Parts Polyetheretherketone (PEEK) is a high performance semi crystalline polymer used in technical applications as well as for medical purposes. Its mechanical properties and its temperature resistance often allow its use instead of metal for lightweight applications. In the medical field, its biocompatibility and the modulus of elasticity similar to this of bones make it a good choice for implants. For this purpose, additive manufacturing is a technology that allows the economic production of patientspecific implants. Until now, only few 3D printers for PEEK are available on the market and only few process knowledge is available so far. In this paper, PEEK parts are fabricated using a 3Dprinter based on the Fused Layer Manufacturing (FLM) technology. The influence of different process parameters on the mechanical properties of the specimens is investigated. For this, printing speed, local part cooling, filling degree and infill geometry are varied and the tensile strength of the corresponding specimens is investigated. Fracture surfaces are analyzed using optical microscopy and scanning electron microscopy. Results show a slightly increase of tensile strength at lower printing speed. Filling degree as expected has great influence on the mechanical properties. Optical investigation often shows insufficient adhesion between the single layers. Also a filament with carbon fiber reinforcement is used and compared to the standard material. This material shows a significant increase in tensile strength and stiffness.

Material characterization and precise finite element analysis of fiber reinforced thermoplastic composites for 4D printing Abstract   Fourdimensional (4D) printing, a new technology emerged from additive manufacturing (3D printing), is widely known for its capability of programming postfabrication shapechanging into artifacts. Fused deposition modeling (FDM)based 4D printing, in particular, uses thermoplastics to produce artifacts and requires computational analysis to assist the design processes of complex geometries. However, these artifacts are weak against structural loads, and the design quality can be limited by less accurate material models and numerical simulations. To address these issues, this paper propounds a composite structure design made of two materials  polylactic acid (PLA) and carbon fiber reinforced PLA (CFPLA)  to increase the structural strength of 4D printed artifacts and a workflow composed of several physical experiments and series of dynamic mechanical analysis (DMA) to characterize materials. We apply this workflow to 3D printed samples fabricated with different printed parameters to accurately characterize the materials and implement a sequential finite element analysis (FEA) to achieve accurate simulations. The accuracy of deformation induced by the triggering process is both computationally and experimentally verified with several creative design examples and is measured to be at least 95%, with a confidence interval of     (  0  .  972  ,  0  .  985  )    . We believe the presented workflow is essential to the combination of geometry, material mechanism and design, and has various potential applications.