Polylactic acid (PLA) is one of the most extensively used biodegradable aliphatic polyester produced from renewable resources, such as corn starch. Due to its qualities, PLA is a leading biomaterial for numerous applications in medicine as well as in industry, replacing conventional petrochemical–based polymers. The purpose of this paper is to highlight the fracture behavior of pure PLA specimens in comparison with PLA particle insertions, (copper, aluminum and Graphene), after evaluation the mechanical properties, as well as the influence of filament angle deposition on these properties. In order to check if the filling density of the specimen influences the ultimate tensile stress (UTS), three different filling percentages (60%, 80%, and 100%) have been chosen in the experimental tests. A hierarchy concerning elongation / fiber heights after tensile testing was done. So, the highest elongation values were for simple PLA (about 4.1%), followed by PLA + Al insertion (3.2%–4%), PLA + graphene insertion (2.6%–4%) and the lowest values being for PLA with copper insertion (1.8%–2.7%). Regarding the fiber heights after fracture, the hierarchy was: the highest values was for PLA, then PLA + Al, PLA + grapheme and PLA + Cu. Finally, a correlation between fracture surfaces appearance and mechanical properties were established, being formulated the mechanism of fracture in according with filament angle deposition. Also, it was proposed a new method of evaluation of the fractured surface by measuring the dimensions of the filaments after printing Fused Deposition Modeling (FDM) and tensile testing.

Several procedures in medicine (such as anesthesia, injections, biopsies and percutaneous treatments) involve a needle insertion. Such procedures operate without vision of the internal involved areas. Physicians and anesthetists rely on manual (force and tactile) feedback to guide their movements, so a number of medical practice is strongly based on manual skill. In order to be expert in the execution of such procedures the medical students must practice a number of times, but before practice in a real patient they must be trained in some place and a virtual environment, using Virtual Reality (VR) or Augmented Reality (AR) is the best possible solution for such training. In a virtual environment the success of user practices is improved by the addition of force output using haptic device to improve the manual sensations in the interactions between user and computer. Haptic devices enable simulate the physical restriction of the diverse tissues and force reactions to movements of operator hands. The trainees can effectively “feel” the reactions to theirs movements and receive immediate feedback from the actions executed by them in the implemented environment. However, in order to implement such systems, the tissue reaction to penetration and cutting must be modeled. A proper model must emulate the physical sensations of the needle action in the skin, fat, muscle, and so one, as if it really done in a patient that is as they are holding a real needle and feeling each tissue resistance when inserting it through the body. For example an average force value for human skin puncture is 6.0 N, it is 2.0 N for subcutaneous fat tissue and 4.4 N for muscles: this difference of sensations to penetration of each layers trespassed by the needle makes possible to suppose the correct position inside the body. This work presents a model for tissues before and after the cutting that with proper assumptions of proprieties can model any part of human body. It was based on experiments and used in embryonic system for epidural anesthesia having good evaluation as presented in the last section “Preliminary Results”.

A sandwich composite represents a special class of composite materials that is manufactured by bonding two thin but stiff faces to a low density and low strength but thick core. The distance between the skins given by the core increases the flexural modulus of the panel with a low mass increase, producing an efficient structure able to resist at flexural and buckling loads. The strength of sandwich panels depends on the size of the panel, skins material and number or density of the cells within it. Sandwich composites are used widely in several industries, such as aerospace, automotive, medical and leisure industries. The behavior of composite sandwich panels with different core designs under different impact velocities are analyzed in this paper by numerical simulations performed on sandwich panels. The modeling was done in ANSYS and the analysis was performed through LS-DYNA.

The purpose of this article is to present the modeling of the dynamic behaviour of unsymmetrical rotors in relatively simple quantitative terms. Numerical simulations show that the shaft orthotropy produces a peak of resonant vibration about half the regular critical speed and, for small damping, a range of possible unstable behavior between the two critical speeds. Rotors having the shaft and/or the disks with unequal diametral moments of inertia (e.g., two-bladed small airplane propellers, wind turbines and fans) are dynamically unstable above a certain speed and some of these may return to a stable condition at a sufficiently high speed, depending on the particular magnitudes of the gyroscopic coupling and the inertia inequality.

Honeycomb cores used in engineering applications are subjected to compressive and bending loads. One of the most important elastic properties allowing the accurate design of the structural components which contain honeycomb cores is the out-of-plane Young modulus. The present paper provides analytical and numerical analysis, allowing an accurate design of the structural components containing honeycomb cores.