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

Abstract

A common approach for the manufacturing of hollow composite parts based on textile reinforcement materials is the utilization of bladder-assisted resin transfer molding (BARTM). Here, the process-induced compaction of the preform is a decisive factor in the injection stage as it significantly influences filling times and part qualities. However, the use of expandable elastomeric bladders impedes the determination of local compaction pressures and thicknesses of compliant preforms during BARTM. This paper therefore presents an efficient methodology for evaluating the compaction state of tubular fabrics during preform compaction and subsequent resin injection by considering the membrane stiffness of an elastomeric bladder as well as the compressibility of the textile preform. First, different process models are developed to describe preform compaction based on single-point and full preform compaction data. The acquisition of exemplary model data for bladder expansion and preform compaction is accomplished through experimental methods. A specifically developed test rig comprising optical measurement techniques is used to directly characterize the radial expansion behavior of tubular silicone rubber bladders. The compaction behavior of single-and multi-layered braided preforms is evaluated by means of dry compression experiments. The resulting measurement data is used to create an integral model-based process window for combined bladder expansion and preform compaction. Lastly, a prediction of relevant local compaction pressures and preform thicknesses is conducted for an exemplary BARTM process.

Optimizing Bladder Resin Transfer Molding Process to Manufacture Complex, Thin-Ply Thermoplastic Tubular Composite Structures: An Experimental Case Study

“…Although there exist some solutions such as bonding the structures together, it reduces the mechanical performance of the structure, due to existing joining lines, and there is no structural continuity. These processes are effective but do not fulfill There is some research carried out on investigating the B-RTM process, but it is mostly focused on woven fabrics or bi-axial braided fabrics, which have high permeability [9][10][11][12]. The B-RTM process depends on a number of factors that affect the final manufactured part such as process parameters, such as injection pressure, bladder pressure, and consolidation pressure, and the intrinsic parameters including resin viscosity and the fiber permeability [9,10,[13][14][15].…”

“…This research work presents a first attempt to carry out a detailed experimental case study to manufacture a composite tube mimicking a section of a racket shaft using thin-ply NCFs [8,[16][17][18] as a reinforcement with novel thermoplastic Elium ® [19][20][21][22][23][24][25][26][27][28] and thermoset epoxy resin. The details of the effective mold design and the development of injection There is some research carried out on investigating the B-RTM process, but it is mostly focused on woven fabrics or bi-axial braided fabrics, which have high permeability [9][10][11][12]. The B-RTM process depends on a number of factors that affect the final manufactured part such as process parameters, such as injection pressure, bladder pressure, and consolidation pressure, and the intrinsic parameters including resin viscosity and the fiber permeability [9,10,[13][14][15].…”

“…There is some research carried out on investigating the B-RTM process, but it is mostly focused on woven fabrics or bi-axial braided fabrics, which have high permeability [ 9 , 10 , 11 , 12 ]. The B-RTM process depends on a number of factors that affect the final manufactured part such as process parameters, such as injection pressure, bladder pressure, and consolidation pressure, and the intrinsic parameters including resin viscosity and the fiber permeability [ 9 , 10 , 13 , 14 , 15 ].…”

“…The moldability zone for the study with Toho Tenax HTS40 carbon/corn oil was described as the one where the consolidation pressure was greater than the minimum bladder compaction pressure, and the initial bladder compaction pressure should be greater than the minimum bladder pressure required for full compaction [ 10 ]. In another study, Schillfahrt et al presented a methodology to determine the preform compaction behavior with an undersized elastomeric bladder during the B-RTM process [ 11 ].…”