Effect of Double Bag and Distribution Medium in Vacuum Infusion Process

Abstract

Composite materials especially CFRP have shown promise to the aerospace and automotive industry for improved strength / weight ratio. However, manufacturing processes are posing hindrances for the induction of composite materials in the main stream production. Prepreg materials are capable of producing aerospace quality products but are not feasible for higher production rates with lower cost. On the contrary, engineers are looking forward to vacuum infusion process as the solution to their problems due to its lower cost and higher production rate. However, this process requires an improvement to achieve better mechanical properties so that the production of industrial products may be made with this technique. Efforts are being employed at improving the vacuum infusion process by engineers where most of them are trying to improve the compaction, vacuum integrity, fill time, fibre volume fraction, reduce void content and resin waste. The purpose to improve these parameters is to improve mechanical characteristics of the material. Furthermore, CFD simulations are also being done to avoid cost and time consuming experimentation in order to study flow dynamics for, effects of vacuum pressure variation, lead lag and resin starvation. ILSS is also an important parameter for design engineers and is critical for modeling and analysis of composite materials. Keeping in view the above mentioned requirements an experimental analysis is presented here aiming at improvement of vacuum infusion process. A technique named as Double Bag Vacuum Infusion process is analyzed for comparison with conventional vacuum infusion process employing single bag. This technique was aimed at improving vacuum integrity and compaction for improving mechanical properties. Experiments are presented to observe its improvement effect on ILSS, Flexural Strength and void content. Another primary objective was to develop trends and database for effect of vacuum regulation in inner and outer bags on above mentioned mechanical properties. Samples are prepared for structural testing as per ASTM standards. Image analysis is performed to quantify the void content in samples prepared with different vacuum regulation combinations. CFD model is developed in commercial software and validated with the experimental data which showed good agreement. Analysis of fill time and lead lag of vacuum infusion process is vii presented to improve flow dynamics in the process. Comparison of fill time is made in vacuum infusion process with single and double distribution model. Lead Lag shape is validated with reported data for single distribution medium and shape of lead lag is reported for double distribution medium. This data can be useful for manufacturers interesting in using double distribution medium for improving fill time in vacuum infusion process. Structural simulations are also an important tool for design engineers. Macro mechanical models are mostly used in modeling of the composite structures. However, micro mechanical models can be used to improve the modeling process by better predictions of failure, mechanical properties and response to certain loadings. Therefore, a micromechanical model is developed to predict ILSS which showed good agreement with the experimental results.