Experimental analysis of heterogeneous shape recovery in 4d printed honeycomb structures. (July 2018)

• Record Type: Journal Article
• Authors: Abuzaid, Wael; Alkhader, Maen; Omari, Mohamed
• Is Part Of: Polymer testing. Volume 68(2018)
• Page Start: 100
• Page End: 109
• Publication Date: 2018-07
• Subjects: 4D printing -- Shape memory polymers -- Recovery strains -- Honeycomb structure -- Strain recovery rate; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2018.03.050
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: Additive manufacturing of complex structures with functional and programmable attributes ( i.e., 4D printing) enables complex and innovative designs with tunable, adaptable or shape memory properties. To capitalize on the potential of 4D printing, it is instrumental to establish the knowledge base needed to predict the behavior of 4D printed structures. Accordingly, this work is dedicated to study the stability and shape recovery properties of 4D printed honeycomb structures using thermoplastic shape memory polymer (SMP). In particular, the dimensional stability of samples subjected to heat at temperatures around the glass transition temperature of the SMP material was assessed. In addition, the local shape recovery properties were investigated in samples programed into various temporary shapes with highly heterogeneous stored strain fields. The as-printed samples experienced dimensional instability manifested through a time dependent and heat induced strain accumulation when subjected to temperatures of ±10 °C around the SMP glass transition temperature. The rate of strain accumulation was temperature dependent and exhibited a high strain accumulation rate initially, followed by a relatively saturated response after about 10 min of temperature exposure. The total strain accumulation in the honeycomb samples was heterogeneous due to local variation in the deposition direction during printing. In the recovery experiments, despite the dissimilar levels of stored strain during programing, full local recovery was achieved independent of magnitude or nature of the stored strains. However, the local strain recovery rates varied in different regions and was attributed to different levels of stored strain and variation in the deposition direction. Overall, the work sheds important quantitative insight into the heterogeneous material response, dimensional stability and shape recovery of 4D printed structures manufactured using fused deposition and thermoplastic SMP. Highlights: 4D printed structures manufactured using thermoplastic SMP undergo a time dependent shape change during heat exposure. The heterogeneous heat induced strain accumulation in 4D printed honeycomb structures depends on the deposition direction. In honeycomb samples, structure complexity results in heterogeneities in the stored strains during SMP shape programing. Despite heterogeneities in the stored strains, full recovery was achieved independent of strain magnitude and nature. The local strain recovery rates were shown to vary depending on the level of stored strains and deposition direction.