This paper deals with an experimental study of a relaxation behaviour of fibreglass/epoxy composite material subjected to tensile stress. The small tensile testing machine including the heating chamber with the temperature controller is designed and manufactured to perform the stress relief testing at different operating conditions. The influence of the operating temperature onto both the relief time and the number of the loading cycles is considered. The test specimens having a different number of layers of fibreglass tissues are prepared in the laboratory. The effect of the fiberglass tissue volume fraction on the relief behaviour of the fibreglass/epoxy composite is investigated. The constant of the relief time is evaluated for various operating temperature. The obtained results showed that the relief time and the number of relaxation cycles are highly increased by increasing the fibreglass layers. The total number of relief cycles was increased by about 34% when increasing the volume fraction of the fibreglass tissue by about 15%. The relief time of the first cycle was increased by about 83% when increasing the volume fraction of the fibreglass tissue from 30% to 45 % at operating temperature equal to 〖60〗^o C. The time taken to fracture the specimens decreased significantly by increasing the operating temperature as it decreased by about 88% and 73% for volume fraction 30% and 40% respectively when raising the operating temperature by about〖30〗^o C. The material relief time constant is strongly affected by both the operating temperature and the volume fraction of the fibreglass tissue.