Email: icrc@uwo.ca
Core research idea: The primary research objective of the IGS program is to develop a robust, integrated engineering strategy for CoDiCoFRP material design, manufacture and optimization of thermoplastic and thermoset-based materials where closer linkages between material characterization and process systems operation are made, leading to greater quality control of the final product. The potential scope of this research effort is described in the context of an automotive material life-cycle. Below, we describe the key research and development questions in each of the four research areas (RA): Materials, Processing, Simulation, and Design.
RA Materials: The appraisal of the properties of CoDiCoFRP requires a holistic approach covering the impacts of the physical, chemical and mechanical properties of the raw materials on the primary and secondary manufacturing process(es) and the resulting mechanical properties of the molded part including the interface between the constituents. The challenging question in CoDiCoFRP is how the continuous fiber reinforcement affects the material behavior of such long-fibre thermoplastic (LFT) and Sheet Molding Compound (SMC) based materials. In this context, non-destructive characterization methods in combination with mechanical testing, i.e. an in-situ approach, open new perspectives for understanding the damage evolution in composites and will be under consideration. Beyond macromechanical characterization, considering the global inhomogeneity of CoDiCoFRP, micromechanical testing and characterization of interfacial effects is important for bottom-up modeling on scales from atomic-layer interfaces up to macroscopic material properties.
RA Processing: There are very limited scientific activities to combine DiCoFRP and CoFRP in compression molding. In the field of thermoplastic FRP, it is common to attach organo-sheets (CoFRP) by injection molding. Hereby the fiber length of the DiCoFRP is small and the fiber orientation of the CoFRP unsatisfactory. Individual CoFRP tapes, combined with long fiber reinforced LFT material, promise a significant improvement in lightweight design. For thermoset CoDiCoFRP, mechanical properties and preforming of the intermediate material were evaluated. But there is no holistic approach addressing the whole process chain of CoDiCoFRP. Therefore, the RA Processing considers issues related to both primary and secondary processing technologies. Here, CoDiCoFRP research questions of characterizing and predicting the evolution of microstructure through the primary processing operations will be answered as functions of processing parameters, part geometry and placement of CoFRP reinforcements. These achievements will be complemented by investigations in the field of intermediate material handling, machining and joining of molded parts in subsequent assembly operations. Finally, this will lead to overall optimized lightweight structures.
RA Simulation spans the entire manufacturing cycle. Research issues revolve around developing and validating fluid-flow models describing the primary processing operations with micro and macro-thermo-mechanical models describing the properties of the CoFRP and DiCoFRP sub-structures and their interaction including a functionally graded interface. The definition and standardization of interfaces between numerical tools for the fluid and solid type simulations are a prerequisite for simulation of the full process chain. The interface standardization follows the principles of ICME well established in the context of metals but still missing for FRP. While there is considerable literature on short fiber modeling and commercial software (e.g. Moldflow from Autodesk and Moldex 3D), implementation of long fiber deformation during flow with validation is still very much in early stage development. Simulation of the in-mold filling process, either in compression or injection molding, requires capturing long and continuous fiber deformation. Here, new mechanism-based models are to be developed which consider micro-mechanical information and simultaneously can be implemented in commercial software solution. Additionally, efficient estimates of the effective thermo-viscoelastic properties of the final FRP components and parts (SMC and LFT) are necessarily based on mold flow data, µCT data and micromechanical analysis in order to perform robust finite element simulations of the component behavior, especially in optimization. Phenomenological elastic modeling would be oversimplified; therefore, scale-bridging methods that consider previous process steps are crucial. Establishing, documenting and benchmarking standard models for CoDiCoFRP is of utmost importance for the Canadian and German institutes.
RA Design: Contrary to the traditional design with metals, the mechanical properties of composite materials are highly dependent on the part geometry throughout the manufacturing process. For efficient design of thin-walled structures, several algorithms for numerical shape optimization exist. Over the last few years, the spectrum of topology optimization methods has been extended to more and more application fields. So far, only a few simple methods have been developed on dimensioning local patches of CoFRP. First approaches have been made to consider manufacturing constraints. Johrendt’s group has performed research concerning optimization strategies for hydroforming process parameters using genetic algorithms and neural networks that may be transferred to CoDiCoFRP manufacturing techniques. CFRP models were developed for automotive suspension components to optimize their dynamic performance properties. Johrendt has also worked with Western and FPC to develop a neural network model to predict LFT material properties with process control parameters. Cooperation between Johrendt and KIT brings additional value to the current research regarding shape optimization aspects of DiCoFRP structures. Herein the integration of mold-filling simulations into the optimization procedure will be an important aspect to account for production constraints and realistic material behavior. Furthermore, the RA Design will focus on CoDiCoFRP component design regarding shape and CoFRP material placement.
Other Topics: The IGS team recognizes the importance of repair and recycling in the product life-cycle and fully expects to incorporate these topics as research areas in the future. At present, however, industry research focus on CoDiCoFRPs is on the development of structural components and related processing technologies. When these hurdles are overcome, repair and recycling will increase in industrial importance.
