Comparison of Tensile Properties of Triaxial Braided Carbon Fiber Composites Made from Vacuum Assisted Resin Transfer Molding (VARTM) and Autoclave Molding

Triaxially braided fiber composites are increasingly being used in aerospace, ballistic, and sporting good applications due to their inherent damage tolerance, torsional stability, and cost compared to woven fabrics and unidirectional preforms. There have been numerous publications over the past 15-20 years on the mechanical properties and failure mechanisms of triaxial braided composites. However, most of these have involved panels made with autoclave curing. In the present study, braided carbon fiber composites were made using autoclave curing and vacuum assisted resin transfer molding (VARTM). The goal of the study was to compare the physical and tensile properties of quasi-isotropic panels produced from these two methods while keeping the fiber and matrix materials constant. Material characterizations included density and fiber volume fraction (Vf), tensile modulus and strength in both the 0° and 90° directions, and microstructure via optical microscopy and scanning electron microscopy. The results revealed that the 0° vs. 90° tensile properties of QISO composites are equivalent or very close is most respects regardless of processing technique. The VARTM panels had slightly lower Vf autoclave. However, the tensile properties of the VARTM panels compared favorably with autoclave cured panels when normalized for fiber volume fraction. Overall this study represents a very good side-by-side comparison of braided carbon fiber composites made with two significantly different processes.