The current study focuses on curing kinetics and influence of temperature on thermal, physical, and mechanical properties of epoxy-based composite materials. The bloom test and DSC were used to study the curing kinetics of resin. For the bloom test, resin samples were made using two different curing cycles and two different resin-to-hardener mixing ratios (100:24, 100:28). The bloom test was carried out by indenting the 30 g of partially cured epoxy resin in silicone mold using a 12.7 mm flat cylindrical probe and found that force is increasing with increase in curing time and hardener content, and this could be due to the increase in cross-linking density. Correlation was established between the bloom strength and residual enthalpy of cure obtained from DSC. Neat epoxy resin blocks and T800 carbon fiber-epoxy composite samples are prepared using a resin-to-hardener ratio 100:28 (wt.%), wherein composites were processed by filament winding followed by the vacuum oven curing at 160 °C–5 h. The density of neat resins and composites was measured, and no change in data was observed between −20 and 150 °C. The composite thermal conductivity and CTE were also measured from −20 to 150 °C, and no change in CTE values was found, but a 23% increase in longitudinal thermal conductivity was reported for 150 °C compared to −20 °C. Neat resin dog-bone specimens were made using silicone molds and subjected to tensile testing at different temperatures. It was concluded that epoxy resin strength and stiffness decrease with an increase in temperature from −20 to 150 °C. Based on the results, it is concluded that carbon–epoxy composites can be used at sub-zero temperatures if high thermal conductivity in longitudinal direction is not the criteria.