Аналитическая зависимость для послойной деформации металлофторопластовой полосы

Тез. докл. VIII Междунар. науч.-техн. конф. (науч. чтения, посвящ. П. О. Сухому), Гомель, 28–29 окт. 2010 г

Structural-Acoustic Optimization of Sandwich Panels

NR 2014080

Integrated cost/weight optimization of composite skin/stringer elements

In this paper, a methodology for a combined cost/weight optimization of composite elements is proposed. The methodology is similar to the work of Curran et al. [1], where the objective function is formed by manufacturing costs and a so-called weight penalty. This weight penalty could include the effect of fuel burn, environmental impact or con-tractual penalties due to overweight, and depends on the view of the "optimizer". In our approach, the analytical cost model is replaced by a commercial software package that allows a more realistic model of the manufacturing costs. In the spotlight is a parameter study, in which the weight penalty is varied from zero to infinity, literally varying from pure cost to pure weight opti-mization. This is done for three material configura-tions: a metal/metal, a composite/metal and a com-posite/composite skin/stringer panel. It is shown that the design solution depends on the magnitude of the weight penalty and that - depending on this magni-tude - another material configuration has to be re-garded as the optimum.QC 20101112</p

Multi-objective optimisation of vehicle bodies made of FRP sandwich structures

An optimisation methodology is developed and applied on a FRP sandwich body of an electric vehicle - ZBee, where single-objective and multi-objective optimisation studies are performed stepwise using a commercially available software package. The single-objective optimisation allows the identification of the load paths within the composite body, according to the loading conditions previously defined. Within the multi-objective optimisation, the optimum thickness and distribution for each of the layers that form the composite body are searched within the design space so as to obtain the best performance with respect to weight, material cost, global and local stiffness. Strength requirements are also considered as constraints within the optimisation. A conflict situation appears when several objectives are considered within the optimisation, meaning that an increased performance in one objective may often lead to a decreased performance for the others. Therefore, a trade-off between objectives is needed. The interpretation of results is partially made by using trade-off plots, the so-called Pareto frontiers. A method for the overall selection of the most beneficial solutions is proposed and applied in order to choose between the best obtained solutions according to the importance of the objectives.QC 20140602</p

Integrated cost/weight optimization of aircraft structures

A methodology for a combined cost/weight optimization of aircraft components is proposed. The objective function is formed by a simplified form of direct operating cost, i.e. by a weighted sum of the manufacturing costs and the component weight. Hence, the structural engineer can perform the evaluation of a design solution based on economical values rather than pure cost or weight targets.The parameter that governs the balance between manufacturing cost and weight is called weight penalty and incorporates the effect of fuel burn, environmental impact or contractual penalties due to overweight. Unlike previous work, the analytical cost model and structural models are replaced by commercially available software packages that allow a more realistic model of the manufacturing costs; further, arbitrary constraints for the structural analysis can be implemented. By means of parametric studies it is shown that the design solution strongly depends on the magnitude of the weight penalty.Parts of this paper have been presented as: Kaufmann M, Zenkert D, Wennhage W. "Integrated cost/weight optimization of composite skin/stringer elements", Proceedings of ICCM-16, Kyoto (2007). QC 20100723.European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS

A Statistical Porosity Characterization Approach of Carbon-Fiber-Reinforced Polymer Material Using Optical Microscopy and Neural Network

The intensified pursuit for lightweight solutions in the commercial vehicle industry increases the demand for method development of more advanced lightweight materials such as Carbon-Fiber-Reinforced Composites (CFRP). The behavior of these anisotropic materials is challenging to understand and manufacturing defects could dramatically change the mechanical properties. Voids are one of the most common manufacturing defects; they can affect mechanical properties and work as initiation sites for damage. It is essential to know the micromechanical composition of the material to understand the material behavior. Void characterization is commonly conducted using optical microscopy, which is a reliable technique. In the current study, an approach based on optical microscopy, statistically characterizing a CFRP laminate with regard to porosity, is proposed. A neural network is implemented to efficiently segment micrographs and label the constituents: void, matrix, and fiber. A neural network minimizes the manual labor automating the process and shows great potential to be implemented in repetitive tasks in a design process to save time. The constituent fractions are determined and they show that constituent characterization can be performed with high accuracy for a very low number of training images. The extracted data are statistically analyzed. If significant differences are found, they can reveal and explain differences in the material behavior. The global and local void fraction show significant differences for the material used in this study and are good candidates to explain differences in material behavior

An Experimentally Based Micromechanical Framework Exploring Effects of Void Shape on Macromechanical Properties

A micromechanical simulation approach in a Multi-Scale Modeling (MSM) framework with the ability to consider manufacturing defects is proposed. The study includes a case study where the framework is implemented exploring a cross-ply laminate. The proposed framework highlights the importance of correct input regarding micromechanical geometry and void characteristics. A Representative Volume Element (RVE) model is developed utilizing true micromechanical geometry extracted from micrographs. Voids, based on statistical experimental data, are implemented in the RVE model, and the effects on the fiber distribution and effective macromechanical properties are evaluated. The RVE algorithm is robust and maintains a good surrounding fiber distribution around the implemented void. The local void fraction, void size, and void shape affect the effective micromechanical properties, and it is important to consider the phenomena of the effective mechanical properties with regard to the overall void fraction of an RVE and the actual laminate. The proposed framework has a good prediction of the macromechanical properties and shows great potential to be used in an industrial implementation. For an industrial implementation, weak spots and critical areas for a laminate on a macro-level are found through combining local RVEs

Bearing strength performance of mixed thin/thick-ply, quasi-isotropiccomposite laminates

The effect of using thin plies to increase the bearing strength of composite laminates has been investigated. A series of 5 laminates of theoretically identical stiffness with varying proportions of thin plies were manufactured using a single material system. Four specimens from each plate were tested for bearing strength and damage was subsequently characterized using an optical microscope. The results show that performance in terms of bearing stiffness, strength at onset of damage, and ultimate bearing stress increase proportionally with the increasing amount of thin plies within the stack. Shifting from a 100% conventional ply laminate to a 100% thin-ply laminate gave an increase of 47% in the strength at onset of damage. Placement of the thin plies within the stack was also shown to be important for strength at initial onset of damage. Microscopic examination of the failure modes for all samples showed fiber kinking, localized to the center of the hole, to be the dominant failure mode regardless of the stacking sequence

A material selection approach to evaluate material substitution for minimizing the life cycle environmental impact of vehicles

Weight reduction is commonly adopted in vehicle design as a means for energy and emissions savings. However, selection of lightweight materials is often focused on performance characteristics, which may lead to sub optimizations of life cycle environmental impact. Therefore systematic material selection processes are needed that integrate weight optimization and environmental life cycle assessment. This paper presents such an approach and its application to design of an automotive component. Materials from the metal, hybrid and polymer families were assessed, along with a novel self-reinforced composite material that is a potential lightweight alternative to non-recyclable composites. It was shown that materials offering the highest weight saving potential offer limited life cycle environmental benefit due to energy demanding manufacturing. Selection of the preferable alternative is not a straightforward process since results may be sensitive to critical but uncertain aspects of the life cycle. Such aspects need to be evaluated to determine the actual benefits of lightweight design and to base material selection on more informed choices.QC 20150911</p