Probing the complex thermo-mechanical properties of a 3D-printed polylactide-hydroxyapatite composite using in situ synchrotron X-ray scattering

Journal article

Polylactide (PLA)-hydroxyapatite (HAp) composite components have attracted extensive attentions for a variety of biomedical applications. This study seeks to explore how the biocompatible PLA matrix and the bioactive HAp fillers respond to thermo-mechanical environment of a PLA-HAp composite manufactured by 3D printing using Fused Filament Fabrication (FFF). The insight is obtained by in situ synchrotron small- and wide- angle X-ray scattering (SAXS/WAXS) techniques. The thermo-mechanical cyclic loading tests (0–20 MPa, 22–56 °C) revealed strain softening (Mullins effect) of PLA-HAp composite at both room and elevated temperatures (<56 °C), which can be attributed primarily to the non-linear deformation of PLA nanometre-scale lamellar structure. In contrast, the strain softening of the PLA amorphous matrix appeared only at elevated temperatures (>50 °C) due to the increased chain mobility. Above this temperature the deformation behaviour of the soft PLA lamella changes drastically. The thermal test (0–110 °C) identified multiple crystallisation mechanisms of the PLA amorphous matrix, including reversible stress-induced large crystal formation at room temperature, reversible coupled stress-temperature-induced PLA crystal formation appearing at around 60 °C, as well as irreversible heating-induced crystallisation above 92 °C. The shape memory test (0–3.75 MPa, 0–70 °C) of the PLA-HAp composite demonstrates a fixing ratio (strain upon unloading/strain before unloading) of 65% and rather a ∼100% recovery ratio, showing an improved shape memory property. These findings provide a new framework for systematic characterisation of the thermo-mechanical response of composites, and open up ways towards improved material design and enhanced functionality for biomedical applications.

Authors: Sui, T; Salvati, E; Zhang, H; Nyaza, K; Senatov, FS

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Journal of Advanced Research
• Volume: 16
• Pages: 113-122
• Publication date: 2018-11-16
• Acceptance date: 2018-11-07
• DOI: 10.1016/j.jare.2018.11.002
• EISSN: 2090-1224
• ISSN: 2090-1232
• Pmid: 30899594
• Language: English
• Keywords: FFR