Buckling Strength of 3-D Printed Thermoplastic Thin Shells: Notes on an Exploratory Study of As-Printed and Reinforced Cases

Tais Rocha Pereira,Sherri L Messimer,Albert E Patterson

doi:10.3390/app10175863

Abstract

Additively-manufactured (AM) materials have a defined mesostructure and natural voids which impact their structural stability; thin shells, which do not have the bulk to support or absorb the effects of the variances in properties, are particularly affected. Thin shells are a common feature in many designs, providing good strength-to-weight ratios for many applications, particularly in the aerospace and structural design domains. The use of AM to fabricate thin structures could both expand the use of AM and improve the application space for thin structures in design, but this problem has not yet been widely discussed for buckling cases. This short technical note explored this problem for thermoplastic thin shells fabricated by fused deposition modeling (FDM), providing insight into the problem, some initial experimental results, and discussion of design implications. A designed 2(4−1) factorial experiment was used to study the buckling behavior, examining the impact of wall thickness, material, and two methods for internal reinforcement (soft infill and polyurethane foam). Analysis of variance (ANOVA) (including model adequacy testing and proof of Fisher Assumption validity) was completed on data from two replications (32 total tests), providing useful information on the significance of the factors and their interactions.

Highlights

Thin-walled structures are common in engineering design, often seen in the form of domes, shells, plates, and membranes
As additive manufacturing (AM) becomes more widely accepted and used, it is increasingly important to understand the behavior of additively-fabricated structures
All p-values were above the level of significance, so the use of Analysis of variance (ANOVA) (Table 3) was valid

Summary

Introduction

Thin-walled structures are common in engineering design, often seen in the form of domes, shells, plates, and membranes. There are numerous advantages to using these structures, but there are trade-offs; the mass and strength must be balanced, making the thin structures optimal relative to both but neither individually [7,8]. This has a significant impact on their performance, especially on buckling behavior since thin-wall buckling failure often occurs long before the yield point of the material [9,10,11]. AM materials are highly anisotropic [13,14] and have a well-defined mesostructure that greatly affects the mechanical

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Results

Conclusion