Title: 3D Printing of Liquid Crystal Elastomer Foams for Enhanced Energy Dissipation Under Mechanical Insult

Abstract

Polymer foams are an essential class of lightweight materials used to protect assets against mechanical insults, such as shock and vibration. Two features are important to enhance their energy absorption characteristics: the foam structure and the matrix phase mechanical behavior. This study investigates novel approaches to control both of these features to enhance the energy absorption capability of flexible lattice foams. First, we consider 3D printing via digital light processing (DLP) as a method to control the foam mesostructure across a suite of periodic unit cells. Second, we introduce an additional energy dissipation mechanism in the solid matrix phase material by 3D printing the lattice foams with polydomain liquid crystal elastomer (LCE), which undergo a mechanically induced phase transition under large strains. This phase transition is associated with LC mesogen rotation and alignment and provides a second mechanism for mechanical energy dissipation in addition to the viscoelastic relaxation of the polymer network. Here, we contrast the 3D printed LCE lattices with conventional, thermomechanically near-equivalent elastomer lattice foams to quantify the energy-absorbing enhancement the LCE matrix phase provides. Under cyclic quasi-static uniaxial compression conditions, the LCE lattices show dramatically enhanced energy dissipation in uniaxial compression compared to the non-LCE equivalent foamsmore » printed with a commercially available photocurable elastomer resin. The lattice geometry also plays a prominent role in determining the energy dissipation ratio between the LCE and non-LCE foams. We show that when increasing the lattice connectivity, the foam deformation transitions from bending-dominated to stretching-dominated deformations, which generates higher axial strains in the struts and higher energy dissipation in the lattice foam, as stretching allows greater mesogen rotation than bending. The LCE foams demonstrate superior energy absorption during the repeated dynamic loading during drop testing compared with the non-LCE equivalent foams, demonstrating the potential of LCEs to enhance physical protection systems against mechanical impact.« less

Authors:

Luo, Chaoqian ^[1]; Chung, Christopher ^[1]; Traugutt, Nicholas A. ^[1]; Yakacki, Christopher M. ^[1]; Long, Kevin N. ^[2]; Yu, Kai  ^[1]

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+ Show Author Affiliations

1. Univ. of Colorado, Denver, CO (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

Mon Dec 28 00:00:00 EST 2020

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program; US Army Research Office (ARO); National Science Foundation (NSF)

OSTI Identifier:

1760444

Report Number(s):

SAND-2021-0030J
Journal ID: ISSN 1944-8244; 693176

Grant/Contract Number:  

AC04-94AL85000; NA0003525; W911NF1710165; CMMI-1350436

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 13; Journal Issue: 11; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; liquid crystal elastomer; digital light processing; 3D printing; polymer foam; energy dissipation