This study examines the thermal deformation behavior of a fiberglass composite polymer material, specifically a phenol-formaldehyde matrix, under various heating conditions. The material is subjected to uniform and one-sided heating at rates up to 600°C/min, with a high-temperature gas flow reaching 2500°C. The research focuses on the kinetics of thermal deformation, assessing how different heating rates and temperatures impact the composite material. The analysis involves computing the stressed-deformed state of reinforced plastic samples to measure their expansion under one-sided heating. Findings reveal that the coefficient of thermal deformation (αT\alpha_TαT) shows a linear dependence on temperature and stresses, which helps in preventing bending in free samples. Conversely, for bent samples, the absence of a stress gradient (Δσ=0\Delta\sigma = 0Δσ=0) at higher heating rates results in increased stress gradient values. Comparative data from dilatometry tests, conducted across a temperature range of 20 to 1100°C, corroborate these observations, providing insights into the material's response to thermal and mechanical loads.