Compaction, Curing and Consolidation Simulation
During consolidation and cure the final material properties of a composite component are determined. Ideally after this production step the part would look and perform as designed. However in reality this is not the case: thermal, mechanical as well as flow and compaction related phenomena lead to deviations in terms of geometry - process induced deformations (PID) - and the materials architecture such as residual porosity content.
Our team is working on development and industrialization of modeling and simulation tools to predict component’s behavior and internal structure in order to optimize the process during consolidation and cure.
Porosity, Void Formation and Transport
Curing under low pressures (“Out of Autoclave”, OoA) i.e. curing under vacuum in an oven provides a cost cost-effective alternative over conventional autoclave processing where high external pressure is applied. One of the major challenges, especially for manufacturing of high performance aerospace composite components, is to ensure that OoA cured parts meet porosity targets set.
The simulation of void formation and transport provides a tool to optimize parameters on the virtual consolidation process and simultaneously achieve an acceptable limit on porosity content in the finished part while minimizing processing time. It requires a multi-physics approach, addressing the following phenomena: compaction, resin and air flow as well as their interaction and dependency on cure-related parameters such as resin viscosity.
Process Induced Deformations (PID)
Prior knowledge of a component’s final shape after processing is required for cost effective manufacturing of highly integrative CFRP structures. Whether or not residual deformations - spring-in, warpage etc - pose a problem depends on the tolerances for component’s integration. In the worst case PID can prevent assembly due to deformed components.
A major goal at the LCC is to provide composite manufacturers with a basis for a cost-benefit analyseis for the utilization of different methods for the determination of PIDs. Such methods range from analytical to finite element based phenomenological and detailed multi-physics approaches, and are compared to the traditional iterative tool-adaption process.
The fraction of cross-linked monomers in thermoset matrix materials is the central state variable for describing the resin properties during cure such as exotherm, shrinkage, viscosity, heat capacity and conductivity, modulus development etc. The results of a thermal analysis serve both as a key input for detailed investigations of mechanical response of the structure during processing and residual stress build up, but can also be utilized for virtual process optimization (for example determination of minimum cycle for dimensional stability, minimal processing time and parameters for achieving specified material properties such as Tg). The main research areas are the characterization of property development models (cure kinetics, modulus development, etc.) and the enhancement of the scope of multi-physics simulation platforms for current and new process technologies (for instance electrically heated tools).