Rule of mixtures model for 3d printed kevlar reinforced nylon: Determination of volume fraction using thermal gravimetric analysis

An experimental procedure to determine the elastic modulus and tensile strength of kevlar reinforced nylon composites is discussed. Thermal Gravimetric Analysis (TGA), has been performed to determine the volume fraction of fiber and matrix components. TGA is a robust method to determine the volume fraction. It is also less labor intensive as compared to other methods. Samples with varying kevlar-nylon layer ratio were additively manufactured using fused deposition modelling (FDM) based on ASTM D3039 standards. MarkForged Mark X7 3D printer was used to manufacture samples. Elastic and tensile tests of the samples were conducted. The relation between volume fraction and elastic modulus of the composite can indeed be fit into the rule of mixtures model. However, its applicability for ultimate tensile strength for high fiber ratio composites has been put to question. The direction of fibers in the additively manufactured samples has been kept parallel to the loading direction. In this paper we will give the readers a deeper understanding of how additively manufactured composite samples behave under loading, further facilitating the design process for materials produced by additive manufacturing.