Optimum Structural and Manufacturing Design of a Braided Hollow Composite Part

Abstract

Simultaneous material consolidation and shaping, as performed in manufacturing of composite materials, causes a strong interconnection between structural and manufacturing parameters which makes the design process complicated. In this paper, the design of a carbon fiber bicycle stem is examined through the application of a multi-objective optimization method to illustrate the interconnection between structural and manufacturing objectives. To demonstrate the proposed method, a test case dealing with the design of composite part with complex geometry, small size and hollow structure is described. Bladder-assisted Resin Transfer Molding is chosen as the manufacturing method. A finite element model of the stem is created to evaluate the objectives of the structural design, while a simplified 2D model is used to simulate the flow inside the preform during the injection process. Both models are formulated to take into account the variation of fiber orientation, thickness and fiber volume fraction as a function of braid diameters, injection pressure and bladder pressure. Finally, a multiobjective optimization method, called Normalized Normal Constraint Method, is used to find a set of solutions that simultaneously optimizes weight, filling time and strength. The solution to the problem is a set of optimum designs which represent the Pareto frontier of the problem. Pareto frontier helps to gain insight into the trade-off among objectives, whose presence and importance is confirmed by the numerical results presented in this paper.

Design of a Motorcycle Composite Swing-Arm by Means of Multi-objective Optimisation

“…The application of multi-objective optimization to parts manufactured by means of RTM processes is described in [10,20]. Both works takes into account the possibility to optimize the mechanical properties and the manufacturing process, by a minimization of mold filling time, on composite plates [20] and on an hollow composite part [10].…”

“…In such innovative vehicles, one-piece monocoque passengers cells can be produced by using fully automated RTM or VaRTM processes in very fast production cycles [8]. The application of RTM methodology to the production of a bicycle stem is described in detail in [10]. This paper moves from these two considerations: on one end the increasing trend of replacing high performance metal parts with composite ones; on the other, the emerging manufacturing techniques such as RTM and VaRTM, which allow faster and less expensive production.…”

A methodology for determining preform compaction in bladder-assisted resin transfer molding with elastomeric bladders for tubular composite parts

“…In contrast to process variants that solely use rigid mold components, BARTM typically uses a rigid, two-part outer mold and an internal flexible bladder. The latter can be inflated by air or fluid pressure in order to compress the externally positioned fabrics against the outer mold [2,3]. After ensuring a certain degree of preform compaction, the injection of the impregnating resin is conducted in a subsequent process step.…”

“…Under-sized bladders need to be radially expanded to enable preform compaction, either based on an elastic or plastic deformation of the membrane (Fig. 2a) [3,5]. If the tubular fabrics are directly applied to the bladder surface, a sufficiently high degree of preform drapability is required.…”

Multi-criteria optimization of an aircraft propeller considering manufacturing

“…Further underpinning this, the mechanical focal point is lying on designing as light as possible, yet this may induce conflicts in technical criteria, where high manufacturing effort may be observed (Schatz and Baier 2014a). Manufacturing effort is frequently considered by numerical process simulations or analytics (Ghiasi et al 2010). However, either of those approaches might be applicable, since numerics can be computationally expensive or analytics not comprehensive enough.…”