Micromechanical characterization of Carbon/PEEK thermoplastic composite material in-situ consolidated by automated fiber placement: Stiffness prediction

Abstract

Despite manufacturing challenges, Automated Fiber Placement (AFP) offers a viable alternative to conventional manufacturing methods, allowing for time and cost savings. Creating a Representative Volume Element (RVE) that realistically represents long-fiber-reinforced composites with high fiber volume fraction is a challenging task in modeling their response. The present research aims to predict effective stiffness properties of in-situ-consolidated Carbon/PEEK thermoplastic composite material by considering the effect of fiber volume fraction, void content, degree of crystallinity, and interlaminar resin pocket resulting from AFP in-situ consolidation manufacturing process. In this regard, two sets of samples were manufactured by AFP in-situ consolidation and autoclave re-consolidation methods. Both of them were evaluated by micrographic study and thermoanalytical Differential Scanning Calorimetry (DSC) technique to obtain inputs required for micromechanical analysis. The 2D RVEs on a micro-scale are developed to predict the transverse elastic modulus, out-of-plane Poisson's ratio and out-of-plane shear modulus of the composite material by applying Periodic Boundary Conditions (PBCs) and using Asymptotic Homogenization Theory (AHT). Results show that AFP in-situ consolidation may lead the transverse elastic and out-of-plane shear moduli of Carbon/PEEK thermoplastic composite material to be reduced by about 10 % and 20 %, respectively, compared to autoclave re-consolidation whereas the out-of-plane Poisson's ratio remains unchanged. The findings of the present work confirm that the mechanical performance of Carbon/PEEK thermoplastic composite material could be remarkably influenced by AFP in-situ consolidation manufacturing process, particularly in the transverse direction, which must be taken into account in finite element modeling, analyses, and design of AFP-manufactured composite laminates and structures.