اميرعباس سيروس

In this study, the applicability of the virtual isotropic material concept (VIMC) for predicting the fracture of ABS polymer components fabricated via fused deposition modeling (FDM) with a quasi-isotropic layup sequence of 0°/90°/45°/-45° is eva‎luated for the first time. To this end, specimens with five distinct geometries, namely the brazilian disk (BD), semi-circular bend (SCB), three-point bending (TPB), double-edge notched tension (DENT), an‎d diagonally loaded square plate (DLSP), each containing a blunt V-shaped notch with three different notch tip radii, were tested under mode I loading. The experimentally obtained fracture loads were then compared against the predictions of four theoretical approaches including the maximum tangential stress (MTS), the mean stress (MS), the averaged strain energy density (ASED) criterion, an‎d the extended finite element method (XFEM). The results demonstrated that the quasi-isotropic layup effectively exhibits isotropic-like behavior at the macroscopic scale, thereby satisfying the fundamental assumption underlying the VIMC framework, a finding that was experimentally confirmed here for the first time. This was evidenced by the high repeatability of the test results an‎d the consistently straight crack propagation perpendicular to the loading direction across all specimens, with no observable deviation from the expected path. Furthermore, the notch fracture toughness was found to increase monotonically with increasing notch tip radius across all geometries, although the extent of this increase remained limited due to the relatively large critical distances inherent to the material. A comprehensive comparison of the four methods of MTS, MS, ASED, an‎d XFEM within the VIMC framework was conducted, an‎d the methods were ranked in terms of both accuracy an‎d degree of conservatism. The MS criterion yielded the highest overall average accuracy. However, it exhibited a tendency toward over-prediction in certain geometries, whereas the remaining criteria displayed more conservative behavior. Through a targeted investigation across the five different geometries, it was shown that specimen geometry exerts a considerably greater influence on prediction accuracy than the choice of fracture criterion itself. The divergence of the actual stress field from the analytical solution at distances far from the notch tip was identified as the primary source of error in the stress-based criteria. Additionally, scanning electron microscopy (SEM) analysis confirmed the presence of distinct fracture mechanisms along each printing direction, which collectively govern the macroscopic fracture behavior of the component.

مدل‌سازي رسوب ذوبي , لايه‌چيني شبه‌همسانگرد , مفهوم ماده مجازي همسانگرد , چقرمگي شكست شيار , شيار V شكل نوك‌گرد

Fused deposition modeling , quasi-isotropic layup , Virtual isotropic material concept , Notch fracture toughness , Round V-shaped notch

Amirabbas Sirous

Dr. Ayatollahi