Investigation on the mechanical properties and damage mechanisms of plain-woven composites at elevated temperatures through a newly-designed testing system

In this paper, the mechanical properties and damage mechanisms of T800/epoxy plain-woven composites at elevated temperatures are investigated by using a newly-designed testing system, including improved digital image correlation (DIC) equipment, modified fixture and dedicated environmental chamber. The molecular structure, glass transition temperature (T_g) and thermal stability of the composites and epoxy resin are separately characterized. The tensile and compressive experiments of plain-woven composites are conducted at 20 °C, 60 °C, 100 °C and 150 °C. The full-field strain distributions of plain-woven composites at elevated temperatures can be accurately measured by the newly-designed testing system. The experimental results indicate that the modulus, failure strengths and damage mechanisms of plain-woven composites are highly temperature dependent. In general, the tensile and compressive moduli decrease slightly with increasing temperature, and the temperature exhibits a more pronounced weakening effect on compressive strength. When the temperature exceeds T_g, the resin attached to fiber yarns is gelatinous. High temperatures severely degrade the interlayer performance of plain-woven composites, resulting in severe delamination accumulation. Particularly, a modified Gibson model is proposed to predict the failure strengths of plain-woven composites at elevated temperatures, which is in high agreement with the experimental results.