Lattice structures are currently of high interest, especially for lightweight design. They generally have better structural performance per weight than parts made of bulk material. With conventional manufacturing techniques they are difficult to produce, but with additive manufacturing (AM) fabricationisfeasible. To better understand their behaviour under various loading conditions two lattice structures in different configurations were observed. For each structure three different test specimens were designed and manufactured using selective laser sintering (SLS). To investigate the mechanical performance under large deformations the specimens were made of a thermoplastic polyurethane(TPU), which shows a hyperelastic material behaviour. Beside the experimental observations also finite element analyses (FEA) were conducted to investigate the deformation behaviour in more detail.

Based on lightweight design concepts, lattices are increasingly considered as internal structures. This work deals with the simulation of periodically constructed lattices to characterize their behaviour under different loadings considering various material models. A thermo-mechanical analysis was done, which is resulting in negative CLTE-values (Coefficient of Linear Thermal Expansion). Simulations with linear-elastic behaviour were evaluated regarding the tensile, compression and shear modulus and the Poisson’s ratio. Some of the investigated structures behave auxetic. Beside the linear elastic behaviour, also the hyper-elastic and visco-elastic behaviour of some structures were investigated. Furthermore, elasto-plastic simulations were performed where the applied loading was biaxial. As a result the initial yield surfaces were presented. The individual RVEs (Representative Volume Elements) can be utilized for different areas of application dependent on the used materials.

Instrumented puncture tests according to ISO 6603-2 and ASTMD3763 were executed for five different Polypropylene compounds (talcum-, glass fibre- and elastomer modified) with specimen thicknesses ranging from 1mm to 4 mm. Over 1500 puncture tests were executed at the Impact & Long-term Behaviour laboratory of the company Borealisr in Linz. This serves as strong foundation for statistical evaluations of the ductile/brittle transition temperature. For different materials and ductile/brittle transition determination methods, similar trends have been observed, which were characterized by introducing shift factors.

Nowadays short fibre reinforced polymers are often used in load carrying structural parts. Compared to continuous fibre reinforced polymers they exhibit a more complex morphology. Hence the determination of the strength is a difficult but important task. Therefore this was the objective of this research. The strength of short fibre reinforced polymers was numerically determined for low-speed to high-speed strain rates for specimens with different fibre orientations. For the failure modelling the micromechanical approach “First pseudo grain failure” in Digimat was used. The parameters for the material and failure description were determined with the reverse engineering method. Integrated finite element simulations<br />were performed to validate the material and failure models by tensile and bending tests with different specimens. The comparison of the results of the experiments and simulations showed low deviation.