Novel epoxy powder for manufacturing thick-section composite parts under vacuum-bag-only conditions. Part I: Through-thickness process modelling

Thick-section composite parts are difficult to manufacture using thermosetting resins due to their exothermic curing reaction. If processing is not carefully controlled, the build-up of heat can lead to warpage or material degradation. This risk can be reduced or removed with the use of a low-exotherm resin system. Material and process models are presented which describe vacuum-bag-only processing of thick-section composites using a novel, low-exotherm epoxy powder. One-dimensional resin flow and heat transfer models are presented which govern the fabric impregnation and temperature evolution, respectively. A semi-empirical equation is presented which describes the sintering of the epoxy powder. The models are coupled via laminate thickness change, which is determined for a simplified ply microstructure. The resulting system of equations are discretised and solved numerically using a finite difference code. A case study is performed on a 100-ply laminate, and the advantages and disadvantages of using epoxy powders are discussed

A non-local void dynamics modeling and simulation using the Proper Generalized Decomposition

In this work we develop a void filling and void motion dynamics model using volatile pressure and squeeze flow during tape placement process. The void motion and filling are simulated using a non-local model where their presence is reflected in the global macroscale behavior. Local pressure gradients during compression do play a critical role in void dynamics, and hence the need for a non-local model. Deriving a non-local model accounting for all the void motion and dynamics entails a prohibitive number of degrees of freedom, leading to unrealistic computation times with classical solution techniques. Hence, Proper Generalized Decomposition – PGD – is used to solve the aforementioned model. In fact, PGD circumvents the curse of dimensionality by using separated representation of the space coordinates. For example, a 2D problem can be solved as a sequence of 1D problems to find the 2D solution. The non-local model solution sheds light on the fundamental of the void dynamics including their pressure variation, motion and closure mechanisms. Finally, a post treatment of the transient compression of the voids is used to derive conclusions regarding the physics of the void dynamics

Simulation and validation of injection-compression filling stage of liquid moulding with fast curing resins

Very short manufacture cycle times are required if continuous carbon fibre and epoxy composite components are to be economically viable solutions for high volume composite production for the automotive industry. Here, a manufacturing process variant of resin transfer moulding (RTM), targets a reduction of in-mould manufacture time by reducing the time to inject and cure components. The process involves two stages; resin injection followed by compression. A flow simulation methodology using an RTM solver for the process has been developed. This paper compares the simulation prediction to experiments performed using industrial equipment. The issues encountered during the manufacturing are included in the simulation and their sensitivity to the process is explored

Modeling Flow in Compression Resin Transfer Molding for Manufacturing of Complex Lightweight HighPerformance Automotive Parts

ABSTRACT: Lightweight vehicles for energy savings encourages the use of compo-sites in the new generation of vehicles. The compression resin transfer molding process (CRTM) is a novel variation of liquid composite molding (LCM) which offers fast manufacturing cycle for net-shape complex parts with excellent perfor-mance, ideal for the automotive industry. The process combines features of resin transfer molding (RTM) and compression molding. The process stages are identified and compared to other LCM processes to take advantage of existing simulation tools. A numerical model that simulates the resin flow in this process is proposed. Several first-order analyses are developed to estimate important process parameters to simplify modeling. Finally, this approach is used to model and simulate the process and is applied to a complex automotive part (the Automotive Composites Consortium B-pillar) with qualitative experimental validation

Prediction of process-induced void formation in anisotropic Fiber-reinforced autoclave composite parts

Abstract A numerical methodology is proposed to predict void content and evolution during autoclave processing of thermoset prepregs. Starting with the initial prepreg void content, the void evolution model implements mechanisms for void compaction under the effect of the applied pressure, including Ideal Gas law compaction, and squeeze flow for single curvature geometries. Pressure variability in the prepreg stack due to interactions between applied autoclave pressure and anisotropic material response are considered and implemented. A parametric study is conducted to investigate the role of material anisotropy, initial void content, and applied autoclave pressure on void evolution during consolidation of prepregs on a tool with single curvatures. The ability of the model to predict pressure gradient through the thickness of the laminate and its impact on void evolution is discussed

A methodology to characterize fiber preform permeability by using Kardar-Parisi-Zhang equation

Permeability tensor describes the resistance to fluid flow through the fibrous porous media, which may not be spatially uniform. This nonuniformity in fiber architecture causes variation in the permeability value of the fibrous domain. The time evolution and geometry of the rough interfaces of the fluid flow in fibrous porous medium are analyzed using the concepts of dynamic scaling and self-affine fractal geometry, and they are shown to belong to the Kardar–Parisi– Zhang (KPZ) universality class. The resulting growth exponent, β is found to match the 1 + 1 KPZ values, and the roughness exponent, α, describes the standard deviation of the variation in fiber preform permeability. Additionally, this characterization is used to develop a tool to quantify the percentage and strength of defects within the fibrous porous media from flow front profile analysis

Wind Turbine Manufacturing Process Monitoring

To develop a practical inline inspection that could be used in combination with automated composite material placement equipment to economically manufacture high performance and reliable carbon composite wind turbine blade spar caps. The approach technical feasibility and cost benefit will be assessed to provide a solid basis for further development and implementation in the wind turbine industry. The program is focused on the following technology development: (1) Develop in-line monitoring methods, using optical metrology and ultrasound inspection, and perform a demonstration in the lab. This includes development of the approach and performing appropriate demonstration in the lab; (2) Develop methods to predict composite strength reduction due to defects; and (3) Develop process models to predict defects from leading indicators found in the uncured composites