Session: MF-05-01 Fitness-For-Service and Failure Assessment-1

Paper Number: 152706

152706 - Predicting Critical Loads in U-Notched 3d-Printed Asa and Carbon Fiber Reinforced Asa Specimens Using Failure Assessment Diagrams 

Abstract: 

The mechanical behavior of 3D printed polymeric materials, and particularly those obtained through Fused Filament Fabrication (FFF), is being increasingly investigated in the last years with the aim of scaling the use of such materials from prototyping purposes to structural applications. In this regard, acrylonitrile-styrene-acrylate (ASA) terpolymer emerges as a promising option, printed alone or being the matrix in diverse composite materials. ASA polymer displays outstanding resistance to weathering agents and, interestingly, to ultraviolet (UV) light, making it more appropriate for outdoors applications than other extended alternatives such as acrylonitrile butadiene styrene (ABS) that could degrade faster. ASA also presents heat and oil resistance (preventing discoloration), reasonable mechanical properties, both dimensional and thermal stability and relatively greater resistance to environmental stress cracking (when compared to ABS), among other properties.

This being said, one of the necessary requirements when studying the structural use of a given material is to have tools for evaluating its structural integrity in the presence of defects, regardless of their origin (e.g., material manufacturing, structural design, construction process, operational use, etc.) and their severity (from sharp cracks to blunt notches). In this sense, this paper provides an analysis of fracture loads in 3D printed (FFF) single edge notched bending (SENB) specimens containing U-notches and made of pure ASA and carbon fiber reinforced (10 wt.%) ASA. The specimens cover three different raster orientations (0/90, 45/−45 and 30/−60) and contain four different notch radii (0 mm – corresponding to crack-like defects-, 0.5 mm, 1 mm and 2 mm). Additionally, six specimens per combination of material, raster orientation and notch radius were tested in order to capture the scatter of the fracture results. The fracture loads were predicted using the FAD (Failure Assessment Diagram, BS7910 Option 1) methodology in conjunction with the Theory of Critical Distances (TCD, that evaluates the material sensitivity to the notch effect), leading to the FAD-TCD approach. The results show how this FAD-TCD approach, in spite of FADs were originally proposed for the analysis of metallic materials and crack-like defects, is capable of providing accurate predictions of fracture loads for this type of 3D printed polymeric and composite materials when containing notch-type defects. The safety of the predictions relies directly on the standard used for the characterization of the fracture toughness (ASTM D5045 vs ASTM D6068), a choice that it is not evident in this type of materials, and also on the criterion (in terms of probability of failure) assumed to define the fracture toughness level included in the FAD approach.

Presenting Author: Sergio Cicero University of Cantabria

Presenting Author Biography: Professor of Materials Science and Metallurgical Engineering at University of Cantabria, he is vice-Chair of ASME Spain Section and Vice-president of the Spanish Structural Integrity Society.
Works on structural integrity, with particular emphasis on fracture analyses and fatigue phenomena.

Authors:

Sergio Cicero University of Cantabria
Sergio Arrieta University of Cantabria
Borja Arroyo University of Cantabria
Fabrizia Devito Politecnico di Bari