Processing and properties of co-injected resin transfer molded vinyl esterand phenolic composites

Vacuum Assisted Resin Transfer Molding type processes have been proven to b e cost effective manufacturing techniques for large composite structures. H owever, their use has been limited to a single resin system. A large variet y of composite structures require multiple resins to serve different purpos es while being integrated into a single structure. Go-Injection Resin Trans fer Molding (CIRTM) is a new manufacturing process, developed at the Univer sity of Delaware's Center for Composite Materials in collaboration with the U.S. Army Research Laboratory, that enables the user to manufacture multi- layer hybrid composite parts in a single processing step (1). In this paper , CIRTM is used to manufacture a dual layered structure consisting of a vin yl ester layer for structural integrity and a phenolic layer for fire, smok e, and toxicity protection. The two resins are simultaneously injected into a mold filled with a stationary fiber bed and are co-cured. Resin separati on is maintained by a 0.0254 mm (0.001 in) thick polysulfone film sandwiche d between two layers of 0.165 mm (0.0065 in) thick adhesive. A Differential Scanning Calorimeter (DSC) is used to select the optimum cure cycle for al l of the materials, Mechanical testing is used to evaluate the performance of the interphase formed between dissimilar materials. Short beam shear (SB S) is used to evaluate the overall quality of the part produced. Double can tilever beam (DCB) is used to quantify the fracture toughness of the interp hase, and the wedge test is used to evaluate the durability of the interpha se. Experimental results show that co-injected, co-cured materials offer pr operties equivalent, or in some cases, superior, to those provided by singl e injection resin composites. This case is used to develop and present a me thodology that can be followed to co-inject different resins.