We present a fully coupled thermomechanical simulation of the hot forming process of composite materials. The raw material is a mixture of resin powders, strengthening particles and reinforcing fibers. Complex material responses in the process, such as phase change (melting and polymerization) and reorientation of the fibers, determine the microstructure and the performance of the final product. A phase-aware incremental mesh-free Lagrangian method is presented to overcome the challenges, which combines the Optimal Transportation Meshfree (OTM) method and the variational thermomechanical constitutive updates, and simulation results including the compression ratio, material properties of the final product and orientation distribution of fibers are recorded. By comparing the simulation results with the experimental measurements, the computational framework is validated, which enables robust and efficient analysis of the sensitivity of the performance of composite materials on their processing parameters.