The curing process of composites is well researched for thin walled composite structures [1]. However, the use of thick walled composite structures has increased over the last decade [2]. The thickness makes the manufacturing of these thick composites more challenging compared to thin composites [3]. This study investigates the Resin Transfer Moulding (RTM) manufacturing process of thick composite beams using virtual manufacturing. In contrast to thin composites, thick composites exhibit through-thickness heat effects that play an important role in curing and manufacturing induced stress and damage. A thick composite brace shown below is used as a reference case for this study. A cross-section of this brace is modelled using the finite element software Abaqus. This model uses a validated subroutine that calculates the state of cure and the generated heat in each step [4]. Results show that changing the cure cycle has a profound effect on the cure rate in different locations of the part. This directly affects the internal stresses caused by curing, as shown in the graph below. This result forms a basis on which the cure cycle can be optimised for a specific part or structure to minimise stress and damage caused by the manufacturing.