## 1 Introduction  
Additive manufacturing (AM) is gathering significant interest in a variety of industries, such as aerospace, automotive, and medical, among many others. Fused filament fabrication (FFF), or fusion-based material extrusion additive manufacturing, is one of the most common methods of AM for producing functional polymer and polymer composite AM components. Due to its increased application and use in industry, the quality and performance of the manufactured component have become increasingly important factors. To date, the mechanical performance of FFF components has proven to be inferior to traditionally manufactured components, with a significant contributing factor being the reliability concerns from part to part. The development and use of nondestructive testing (NDT) technologies, tuned for FFF components, will further enable the use of FFF components in critical, end-use applications. The work herein garners insights into the nondestructive testing of FFF components, providing an effective means of estimating component performance using ultrasonic testing (UT) to quantify the internal, as-manufactured, raster orientation layer-by-layer. Process parameters, one of the most significant being the raster orientation, have been shown to have a significant impact on the final component performance [1, 2]. The orientation of the internal raster path, or raster orientation, of an FFF component refersto the direction of material deposition, with respect to a given axis within the FFF printer, which often varies layer by layer. [PERSON] discussed that small raster angles offer more resistance to flexural strength and failure as the deposited rasters are more aligned along the load direction, resulting in improved strength [2]. Research indicates raster orientation plays a fundamental role in determining the mechanical properties of additively manufactured components [3; 4]. Among the numerous works investigating the effects of raster orientation, [PERSON] et al. [3] explored the impact of varying raster orientations, including \(0^{\circ}/90^{\circ}\), \(30^{\circ}/-60^{\circ}\), and \(45^{\circ}/-45^{\circ}\), on the mechanical properties of a 3D-printed polyether-ether-ketone (PEEK) by testing their tensile, compressive, and bending strength. The highest tensile strength recorded was 56.6 MPa with the \(0^{\circ}/90^{\circ}\) orientation when the filaments were aligned parallel to the load direction. The tensile strengths of 41.8 MPa and 43.3 MPa were noted when the raster orientations were \(30^{\circ}/-60^{\circ}\) and \(45^{\circ}/-45^{\circ}\). Several additional studies have highlighted the substantial influence of raster orientation on the tensile strength of additively manufactured parts [5; 6]. Acrylonitrile Butadiene Styrene (ABS) test coupons fabricated with \(0^{\circ}\) and \(90^{\circ}\) orientations, respectively, underwent the tensile test procedure, resulting in a decrease in the ultimate strength ranging from 81% to 26% [5]. [PERSON] et al. [7] conducted additional investigations on the influence of raster orientations on the mechanical properties of 3D-printed PLA specimens. Their findings proved \(45^{\circ}/-45^{\circ}\) oriented specimens exhibited a 41.20% increase in impact strength compared to those specimens oriented at \(0^{\circ}/90^{\circ}\). Several dogbone specimens featuring \(45^{\circ}/-45^{\circ}\) and \(0^{\circ}/90^{\circ}\) raster orientations manufactured with ABS were subjected to fatigue analysis [8]. It was observed with the increasing percentage of mean ultimate tensile strength that both orientations failed at an equivalent number of cycles. On the other hand, when subjected to identical absolute stress levels, the \(45^{\circ}/-45^{\circ}\) orientation exhibited an increased number of cycles to failure by 63.5%. In addition to affecting the strength of the object, raster orientation influences the fracture mechanism as well [9; 10; 11]. [PERSON] et al.