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A case study for the cost optimization of aircraft structures based on the operating cost as an objective function is presented. The proposed optimization framework contains modules for estimation of the weight, manufacturing cost, nondestructive inspection cost, and structural performance; the latter is enhanced by a kinematic draping model that a...
Citations
... The embodied energy of CFRPs is estimated to range from 183-286 MJ/kg [12,13], which is significantly higher than the embodied energies of steel and aluminium [14,15]. Additionally, the cost per kilogram of high-performance CFRPs is often higher than that of metals (110 e/kg [3,16,17] vs. 30 e/kg [8]). This is due in part to the complex and energy-intensive processes required to extract resources and process materials for CFRPs (Fig. 1). ...
... Through constructing the fabric without crimp, mechanical properties inline with prepregs can be reached, offering a balanced solution. versions with fibres in the 0° and 90° directions referred to as L and T, given the longitudinal and transverse fibre directions [13,14]. Biaxial NCFs, whose fibres are ± 45° are termed DB or 'double bias' and can also be referred to as bidiagonal by manufacturers. ...
... 14: Shirley cantilever experiment schematic with the NCF (black), cantilever boards (yellow) ...
Non-crimp fabric (NCF) composites are increasingly regarded as a viable alternative to pre-impregnated composite materials. Favoured for their ability to streamline productivity, whilst offering comparable mechanical properties, these materials are first formed and subsequently infused with a resin matrix. Drape forming processes are typical in production, yet, offer little opportunity to influence deformation. Existing research in the area has focused on laboratory scale processes, with very little work looking at scalability for industrial parts. These concerns not only decrease productivity, but create inflexibility in the design and manufacture of composite components. Coupled with the continuous development of new NCFs, industry demands processes that are adaptable, scalable and purpose-built for predictive modelling.
This thesis first considers the deformation mechanics of a complex NCF, interply
shear stiffness, intraply shear stiffness and out-of-plane bending stiffness. Here, the presence of a “veil” layer revealed important characteristics that further exacerbated the material anisotropy. Subsequently, an FEA model using coupled shell and membrane elements was validated. This macroscale model allowed efficient designation of in- and out-of-plane properties via experimental characterisation.
A novel preforming process that can generate in-plane tension through discontinuous blank boundary conditions was established. Distributed Magnetic Clamping allows for highly flexible process control. This method was designed to reduce the human factor in production, and work towards an off-the-roll, intelligent resin transfer system. An efficient two-stage optimisation routine deployed a Gaussian process model for preform deformation, and Bayesian optimisation to find the optimal clamping locations. Results demonstrate that surrogate modelling is viable for magnetic distributed clamping. This lays the foundation for the development of large, translatable data sets that can maximise the impact of statistical tools.
Finally, productivity requirements motivate industrialists to form multiple plies in one stroke. Therefore, DIMAC was employed to experimentally investigate the feasibility of multiple-ply preforms. An increased number of biaxial plies formed in one stroke was possible through DIMAC, after using the key insights developed through predictive modelling and single-ply experiments. Similarly, the process was able to influence individual ply deformation for stacks with diverse fibre orientations toward the goal of high-rate manufacture.
... The goal of most of the developed models of the vacuum infusion process is to understand the evolving dynamics of the formation of a resin flow pattern in a porous preform. Only a small part of the developed models was used in algorithms for inverse problems of optimization of quality [38][39][40][41] and (or) process productivity [42,43], and also to accept the tradeoff between quality and cost [44,45]. Two classes of parameters are most often used as the design variables: parameters of the process layout (number and location of injection gates and vacuum vents, their throughput) and process modes (temperatures of injected resin and preform heating, pressure in the vacuum line and in the resin injection gate). ...
The increasingly widespread use of vacuum assisted technologies in the manufacture of polymer-composite structures does not always provide the required product quality and repeatability. Deterioration of quality most often appears itself in the form of incomplete filling of the preform with resin as a result of the inner and outer dry spot formation, as well as due to premature gelation of the resin and blockage of the vacuum port. As experience shows, these undesirable phenomena are significantly dependent on the location of the resin and vacuum ports. This article presents a method for making a decision on the rational design of a process layout. It is based on early forecasting of its objectives in terms of quality and reliability when simulating its finite element model, on the correlation analysis of the preliminary and final quality assessments, as well as on the study of the cross-correlation of a group of early calculated sub-criteria. The effectiveness of the proposed method is demonstrated by the example of vacuum infusion of a 3D thin-walled structure of complex geometry.
... Providing such a forecast is necessary to reduce the computation time and minimise the cost of simulationbased optimisation. Optimization of any technology, including the one considered here, always implies achieving the best indicators of quality [27][28][29][30][31][32][33], productivity [34,35], cost [36]. To solve the multiobjective optimization problem of the process quality, the list of particular criteria given in [29]: -Maximum final degree of cure; -Minimum curing internal stresses; -Minimum cooling stresses; -Minimum exothermic peak temperature; -Constant through-thickness degree of cure and minimum through-thickness curing gradients after gelation point, should be supplemented with the requirements for providing: -Maximum and evenly distributed fiber volume fraction, -Minimum void volume in filled perform and -Absence of inner and outer separate dry spots. ...
Vacuum assisted molding technologies for the manufacture of composite structures have become more and more popular in the last decade in many industries due to their simplicity, relatively low cost and speed of preparation for production. However, their distribution is limited due to the low stability of the achieved quality indicators (limited porosity, the required proportion of the reinforcing
component, geometry accuracy), which requires a large number of experimental tests of the process, as well as the use of very complex and laborious computer modeling methods to obtain information on a rational strategy (number and location of gates and runners for resin injection and vacuum vents) and process conditions (temperature, pressure, time). The presented work proposes a technology for computer modeling of the process, based on the formulation and the finite elements implementation of a coupled problem, including the Cahn-
Hilliard, Richards, thermal kinetics-convection-diffusion and heat transfer equations to describe evolution of the porous perform filling by the resin taking into account its cure with a preliminary assessment of the process quality sub-objectives before the start of the post-filling stage, when the
thermosetting resin begins to solidify. After analyzing a large group of process variants, the time instant for performing such a forecast and the composition of sub-objectives were determined, the values of which allow obtaining with sufficient accuracy valid estimates of the resin filling, fiber volume fraction of the preform, the spatial distribution and the average value of porosity in the molded part just before the transition of the resin from a liquid to a gelatinous state. A significant reduction in the computation time for the simulation, achieved through the use of preliminary estimates of partial quality criteria, ensures the effective use of the developed product in optimization systems to minimize the unfilled preform volume during vacuum infusion processes before the resin solidification.
... Providing such a forecast is necessary to reduce the computation time and minimise the cost of simulationbased optimisation. Optimization of any technology, including the one considered here, always implies achieving the best indicators of quality [27][28][29][30][31][32][33], productivity [34,35], cost [36]. To solve the multiobjective optimization problem of the process quality, the list of particular criteria given in [29]: -Maximum final degree of cure; -Minimum curing internal stresses; -Minimum cooling stresses; -Minimum exothermic peak temperature; -Constant through-thickness degree of cure and minimum through-thickness curing gradients after gelation point, should be supplemented with the requirements for providing: -Maximum and evenly distributed fiber volume fraction, -Minimum void volume in filled perform and -Absence of inner and outer separate dry spots. ...
... M ATERIALS selection is a key portion of the aircraft design process, and indeed engineering design in general [1][2][3]. A designer must first make choices about the broad families of materials to consider, then make tradeoffs between specific materials, and must ultimately select a supplier to produce a chosen material. ...
Materials selection is a key part of aircraft design. The materials index is used to numerically rank materials for a particular function, for example, the strength-to-weight ratio selects minimum-weight structural ties that satisfy a strength constraint. However, the ordinary materials index uses nominal or allowable material properties and does not reliably propagate manufacturing variability or statistical characterization. This work introduces the precision materials index (PMI) to rigorously account for both factors. Counterintuitive results from the PMI are demonstrated. Several case studies demonstrate new analyses enabled by the PMI (making supplier comparisons and exploring materials and process scenarios) and how the analytic PMI concept can be complemented with statistical modeling to analyze more complex structures, namely, a composite laminate plate.
... Aeronautical stiffened plates have shown to be more cost-efficient if densely populated by several smaller stiffeners [20,21,22]. Automotive stiffened geometries on the other hand, have shown more cost-and weight-promise through implementing more automotive-friendly manufacturing methods such as compression moulding and hot stamping [23]. ...
The design of a composite material structure is often challenging as it is driven by the trade-off between lightweight performance and production costs. In this paper, the boundaries of this design trade-off and its implications on material selection, geometrical design and manufacturability are analysed for a number of design strategies and composite material systems. The analysis is founded on a methodology that couples weight-optimization and technical cost modelling through an application-bound design cost. Each design strategy is evaluated for three levels of bending and torsional stiffness. The resulting stiffness-versus cost-range together constructs the design envelope and provides guidelines on the suitability and improvement potential of each case. Design strategies researched include monolithic, u-beam-, sandwich-insert- and sandwich-stiffened plates. Considered material systems include carbon-, glass, recycled carbon-, lignin- and hemp-fibre reinforced composites. Optimized sandwich designs are shown to have lowest design cost. Glass-, recycled carbon-, lignin- and hemp-fibre reinforced composite materials are all shown to reduce costs but at lower stiffness performance. Ultimately, the case study demonstrates the importance of early structural design trade-off studies and material selection and justifies introducing novel fibre systems in low-cost applications of moderate stiffness levels.
... Fibre-reinforced composite materials, such as carbon-reinforced epoxy, are used extensively for demanding high-stiffness applications in aeronautical and aerospace adaptions where their low structural weight potential leads to increased fuel efficiency, and thereby to reduced usage phase costs, and environment benefits (Kaufmann et al., 2011;Timmis et al., 2015;European Commission, 2014a). More recently, the potential to reduce these usage phase costs and the overall environmental impact has attracted also the automotive industry. ...
This paper presents a novel recyclate value model derived from the retained mechanical performance of retrieved fibres in fibre-reinforced composites. The proposed recyclate value model was used to perform an economic analysis for establishing the future closed-loop material usage of fibre-reinforced composite materials. State-of-the-art recycling of carbon and glass-reinforced thermosets was adopted and resulted in a proposed recycling hierarchy in order to achieve a more sustainable environment and raw material cost reduction. The recyclate value model showed that approximately 50% material cost reductions can be achieved at comparable mechanical performance by using recycled fibre instead of virgin fibre in appropriate applications. From the aspect of lightweight design this cost reduction provides the designer with new material choices, appropriate for lower cost and diverse stiffness designs. The proposed closed-loop hierarchy documents the importance of further improvement of fibrous material recycling, including sorting according to mechanical performance, in order to identify application areas previously not utilised and to maximise material sustainability and value throughout the material's lifetime.
... The use of composite materials therefore ultimately presents a trade-off between potential weight save and higher production cost. Research has been devoted to this trade-off through multi-dimensional optimization [1], knowledge-based engineering [2] as well as the development of performance indices [3]. However, more focus on the estimation of production costs during the development phase of a composite structure is needed to further study the relationship between weight reduction and production cost. ...
This paper presents a novel composite production cost estimation model. The strength of the model is its modular construction, allowing for easy implementation of different production methods and case studies. The cost model is exemplified by evaluating the costs of a generic aeronautical wing, consisting of skin, stiffeners and rib feet. Several common aeronautical manufacturing methods are studied. For studied structure, hand layup is the most cost-effective method for annual volumes of less than 150 structures per year. For higher production volumes automatic tape layup (ATL) followed by hot drape forming (HDF) is the most cost-effective choice.
This paper presents an integrated design and costing method for large stiffened panels for the purpose of investigating the influence and interaction of lay-up technology and production rate on manufacturing cost. A series of wing cover panels (≈586kg, 19·9m
2
) have been sized with realistic requirements considering manual and automated lay-up routes. The integrated method has enabled the quantification of component unit cost sensitivity to changes in annual production rate and employed equipment maximum deposition rate. Moreover the results demonstrate the interconnected relationship between lay-up process and panel design, and unit cost. The optimum unit cost solution when using automated lay-up is a combination of the minimum deposition rate and minimum number of lay-up machines to meet the required production rate. However, the location of the optimum unit cost, at the boundaries between the number of lay-up machines required, can make unit cost very sensitive to small changes in component design, production rate, and equipment maximum deposition rate.
