Fiber reinforced composites (FRCs) are materials consist of three components, fiber, matrix and interphase. These materials are used widely in different areas because of their high strength to weight ratio. However, residual stress has always been an intrinsic problem to these materials and can cause failures such as warping and delamination. We here propose a new post cure method of changing the stress state inside the polymer matrix by using dynamic covalent crosslink network. Dynamic covalent network allows covalent bonds to break and reform at the same time without losing network integrity while also relaxing the material to a more stable topology. Thermosetting polymer with this network is called ”vitrimers” and the dynamic reactions are called bond exchange reactions (BERs). With fiber bragg sensors, strain inside vitrimer matrix was measured and changes in stress state was observed before and after thermal loading cycles. Physical aging of the vitrimer is also studied to understand the effect of BER in aging.