Estimation of Load Bearing Capacity in 3D Printed PLA Notched Plates Using the Theory of Critical Distances

Abstract

Abstract This paper provides a simple safe approach to obtain estimations of the load-bearing capacity of 3D printed PLA (polylactic acid) plates containing U-notches. The plates are subjected to pure tensile loading and combine different types of notch lengths. The estimations are obtained defining the stress field ahead of the notch tip by the Creager-Paris stress distribution, and establishing the fracture criterion through the Theory of Critical Distances (TCD). This theory requires an additional material parameter, the critical distance (L), to determine failure conditions. Particularly, in fracture evaluations, the TCD provides several failure criteria, among which the Point Method (PM) is particularly simple and has been validated in a number of more conventional materials, such as structural steels, aluminum alloys, different types of polymers and composites. The PM states that fracture occurs when the stress level reaches the inherent strength (σ0) at a distance from the notch tip equal to L/2. L and σ0 are related to each other through the material fracture toughness (Kc), so σ0 is not an additional (second) parameter required for the assessments. In any case, the results obtained in the present work demonstrate the capacity of the proposed methodology for estimating the load-bearing capacity in this specific 3D printed material and for the component geometry and loading conditions analyzed here, which implies low constraint conditions, providing safe reasonably conservative predictions.