Prediction of transverse tensile strength of in-situ-consolidated Carbon/PEEK thermoplastic composite material based on micromechanical modeling and simulation

Thermoplastic composite laminates have emerged as a compelling alternative to thermoset laminates for primary aerospace applications, following the industrial development of automated manufacturing technologies, such as the Automated Fiber Placement (AFP) process. The present research aims to predict the transverse tensile strength of in-situ-consolidated Carbon/PEEK thermoplastic composite material, considering inherent variations caused by the AFP process in fiber volume fraction, void content, interlaminar resin pocket and degree of crystallinity. To achieve this, two-dimensional Representative Volume Elements (RVEs) with randomly distributed fibers were developed at the micro-scale level. The Drucker-Prager model, combined with a ductile failure criterion, was used to capture the plastic behavior and damage accumulation in the PEEK resin during the numerical analysis. In order to acquire the necessary data for micromechanical modeling and analysis, two sets of specimens, manufactured using AFP in-situ consolidation and autoclave re-consolidation techniques, underwent micrographic examination and thermoanalytical Differential Scanning Calorimetry (DSC) analysis. The results reveal that AFP in-situ consolidation can reduce the transverse tensile strength of Carbon/PEEK thermoplastic composite material up to approximately 44%, compared to the autoclave re-consolidation technique. Due to the lack of experimental data caused by warpage occurring in the manufactured laminate in the absence of a heated mandrel, the present work proposes a simulation methodology to predict the transverse tensile strength resulting from the in-situ consolidation process. This crucial difference in strength values, most notably in the transverse direction, must be carefully considered in finite element analyses, analytical evaluations, and design procedures involving AFP-manufactured thermoplastic composite laminates and structures.