Abstract: Temperature gradient distribution of thick composite along the thickness direction in curing process was measured using a method of setting Teflon film and thermocouple monitor in different position. The relationship between temperature non-uniformity and mechanical performance was studied by means of tensile test and shear test. And, laminate micro-structural fracture surface was analyzed by SEM. The results show that there are obvious temperature gradient along the thickness direction in the curing process of thick composite, and the mechanical properties of tensile strength and inter-layer shear strength show a downward trend with the increase of temperature difference. Employing the top laminate as reference, when there is 20.6 degree inner temperature difference in composite laminate tensile, the strength difference is 7.4%, and the shear strength difference is 6.8%. Likewise, when there is 10.2 degree inner temperature difference, the tensile strength difference is 3.8%, and the shear strength difference is 3.4%. This is due to the high curing temperature, and inter-facial strength between resin and carbon fiber reduces. This study provides significant experimental evidence and theoretical reference for the necessity of controlling the composite temperature distribution uniformty for the thick section parts of the composite materials during the autoclave curing.

Key words: thick composite, laminate, temperature gradient, mechanical properties