Low‐temperature 3D printing and curing process of continuous fiber‐reinforced thermosetting polymer composites

The reported work has developed a methodology of printing and curing continuous fiber-reinforced thermosetting polymer composites (CFRTPCs) with excellent mechanical properties at low temperatures. First, to print and cure CFRTPCs at low temperatures, a thermosetting polymer system was proposed, consisting of phenol based epoxy resin and curing agent (F-44/2E4MZ). The rheological properties of the polymer system were analyzed to determine a reasonable printing temperature. Second, the non-linear Vyazovkin integral method was applied to establish the model-free kinetics (MFK) of the resin system. MFK can predict the curing degree curves at the characteristic temperatures obtained by extrapolation. Reasonable curing process parameters were determined by analyzing the predicted curing degree curves. Then, CFRTPC samples were prepared with the low-temperature 3D printing process and the low-temperature curing process, and the fiber content was found to be 53 wt.%. At last, the mechanical property measurements revealed that the tensile and flexural strengths were 1012 MPa and 929 MPa, respectively. This work can further expand the potential applications of 3D printed CFRTPCs in aerospace and defense industries which require high mechanical properties and temperature safety simultaneously.