No abstract

A joint using a metal pin is one possibility of how to achieve a removable joint of composites. The load capacity of a wrapped pin joint depends on many parameters, especially on the types of fibres and resin, and geometric properties of the joint. The composite part of a wrapped pin joint is exposed to a combination of the tension in the longitudinal direction and local compression in the transverse direction. The values of the compressive stress in the transverse direction can exceed several times the uniaxial compressive strength. In this work, CFRP (carbon-fibre-reinforced plastic) and GFRP (glass-fibre-reinforced plastic) parts of wrapped pin joints were tested. Experimental specimens with different geometries were exposed to a quasi-static loading. A Zwick/Roell Z050 testing machine was used for the tensile tests. Moreover, the load capacities of the carbon or glass composite parts were determined using a finite-element analysis. A new measure based on the LaRC04 criterion was proposed for the prediction of the load capacity. The numerical and experimental results were compared. Keywords: composite, finite-element method, load capacity, loop criterion, wrapped pin joint Spoji z uporabo kovinskega zati~a so ena od mo`nosti, kako dose~i odstranljivo kompozitno povezavo. Nosilnost zavite sti~ne povezave je odvisna od mnogih parametrov, posebno od vrste vlaken in smole ter geometrijskih lastnosti povezave. Kompozitni del zavite zati~ne povezave je izpostavljen kombinaciji napetosti v vzdol`ni smeri in lokalnim tlakom v pre~ni smeri. Vrednosti tla~nih napetosti v pre~ni smeri lahko ve~krat prese`ejo enoosno tla~no trdnost. V tem delu so bili preizku{eni zaviti zati~ni spoji z deli iz CFRP (plastika, oja~ana z ogljikovimi vlakni) in GFRP (plastika, oja~ana s steklenimi vlakni). Preizkusni vzorci z razli~no geometrijo so bili izpostavljeni kvazistati~ni obremenitvi. Za natezne preizkuse je bila uporabljena naprava Zwick/Roell Z050. Poleg tega je bila nosilnost kompozitnih delov z ogljikovimi ali steklastimi vlakni dolo~ena z uporabo analize kon~nih elementov. Novo merilo, ki temelji na merilu LaRC04, je bilo predlagano za napovedovanje nosilnosti. Primerjani so numeri~ni in eksperimentalni rezultati. Klju~ne besede: kompozit, metoda kon~nih elementov, nosilnost, merilo zanke, zavit spoj s kovinskim zati~em

The analysis is performed on a hydraulic press which is intended for use in the automotive industry and is a part of a production line. The final phase of manufacture of interior and acoustic parts takes place in this press. These interior and acoustic parts are made of sandwich fabric which is inserted into the heated mould of the press and by treatment with a defined pressure (or, more precisely, a defined compression) and temperature, it is formed into its final shape. This press has a frame with four columns and it is not preloaded. Two double acting hydraulic cylinders placed on an upper cross beam exert the compressive force. Due to continuously increasing demands on the accuracy and quality of products not only in the automotive industry, it is necessary to ensure compliance with the accuracy of certain values of machine operation. Especially in this case, the value of accuracy substantially depends on the clamping plates of the press, for which a certain value of flatness is required, both at room temperature and at elevated temperatures. To achieve this accuracy, it is necessary to guarantee sufficient stiffness of the machine to resist the pressing force with the smallest deformation possible. Another crucial factor affecting the accuracy of the machine is heating of the heated clamping plates. Unequal heating of parts of the frame causes additional deformation that has to be quantified and eliminated. The main aim was to verify the design of the press by numerical computation and gather knowledge for modifying the topological design of the press so that it fulfils the required customer parameters of flatness and parallelism for different types of loading. A computational model of the press was created for the numerical solution of a coupled temperature-displacement numerical analysis. The analysis was performed using the finite element method in Abaqus software. The press is symmetrical in two orthogonal planes and the load of the press is considered to be centric. On the basis of these two factors it was possible to carry out the analysis by considering only a quarter of the press. The analysis was used to investigate the effects of static and combined loads from the pressing force and heat on the press. The influence of a cooling circuit located in the press frame for the reduction of frame deformation (and deformation of clamping plates) was investigated. Contacts were defined among individual parts to ensure the computational model had characteristics as close as possible to the real press. The analysis was solved as stationary, on the basis that the cooling of the tool between individual pressing cycles is negligible. The insulating plates are made of a particulate composite material which was considered to have isotropic properties depending on the temperature. For strength evaluation of composite materials all individual components of the stress tensor were examined according to the maximum stress criterion. Hook’s law was considered to be valid for the metallic materials. Von Mises criterion was used to evaluate the strength of the metallic materials. The geometry of the press was discretized using 3D linear thermally coupled brick elements with 8 nodes and full integration (C3D8T). There were approximately 174,000 elements in total. Design procedures for designing a press frame with higher work accuracy (flatness) were proposed with the example of the simplified model of the press table. With these methods it is possible to achieve times higher accuracy than is achieved with conventional method.

Current industrial trends bring new challenges in energy absorbing systems. Polymer materials as the traditional packaging materials seem to be promising due to their low weight, structure, and production price. Based on the review, the linear low-density polyethylene (LLDPE) material was identified as the most promising material for absorbing impact energy. The current paper addresses the identification of the material parameters and the development of a constitutive material model to be used in future designs by virtual prototyping. The paper deals with the experimental measurement of the stress-strain relations of linear low-density polyethylene under static and dynamic loading. The quasi-static measurement was realized in two perpendicular principal directions and was supplemented by a test measurement in the 45° direction, i.e., exactly between the principal directions. The quasi-static stress-strain curves were analyzed as an initial step for dynamic strain rate-dependent material behavior. The dynamic response was tested in a drop tower using a spherical impactor hitting a flat material multi-layered specimen at two different energy levels. The strain rate-dependent material model was identified by optimizing the static material response obtained in the dynamic experiments. The material model was validated by the virtual reconstruction of the experiments and by comparing the numerical results to the experimental ones.

Abstract. This paper deals with material property identification of a helmet lining consisting of an outer layer of an expanded polystyrene (EPS) and inner layer of an open-closed cell foam (OCCF). A combined numerical simulation and experimental testing was used for the material property identification. Compression and drop tests were performed. The ABAQUS finite element commercial code was used for numerical simulations in which the OOCF was modelled as a rate dependent viscoelastic material, while the EPS as a crushable foam. The reaction force time histories coming from the numerical simulation and the experiment have been used as a criterion for material parameter determination. After the identification of the material properties, numerical drop-tests were used to study the behaviour of a plate and a conical composite OOCF and EPS liners to decide which of them suits more for the helmet.