The one-dimensional deformation of shape memory alloy (SMA) wires and springs can be implemented into different types of functional structures with three-dimensional deformations. These structures can be classified based on the type of structure and how the SMA element has been implemented into the following categories: rigid mechanical joints, semi-rigid flexural hinges, SMA elements externally attached to a soft structure, and embedded into the soft structure. These structures have a wide range of properties and implementation requirements, and they have been used to produce a variety of robots with rigid and soft motions. The different research efforts to develop actuators and robots related to each type of structure are presented along with their respective strengths and weaknesses. A model is then developed to discuss the performance and applicability of SMA wires versus SMA springs for actuators with a polymeric matrix to see the effect of each type of SMA on the selection of design parameters. A comparison of the different types of structures and the applicability of different types of SMA elements for different types of structures is then presented.

An Overview of Shape Memory Alloy-Coupled Actuators and Robots

A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.

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Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature

Impact localisation with FBG for a self-healing carbon fibre composite structure

Experimental and numerical investigation on the macroscopic mechanical behavior of shape memory alloy hybrid composite with weak interface

This study develops a fiber-optic-based technique for in situ characterization of direction-dependent cure-induced shrinkage in thermoset fiber-reinforced composites. A procedure is established to ...

http://journals.sagepub.com/doi/pdf/10.1177/0021998314528735

In situ characterization of direction-dependent cure-induced shrinkage in thermoset composite laminates with fiber-optic sensors embedded in through-thickness and in-plane directions:

Integrating smart materials such as fibre optic sensors or actuating shape memory alloy (SMA) wires with the host composites during manufacturing is one of the most fundamental aspects in the technology of smart structures. Sensing or actuating needs often dictate at what depth and how many sensors or wires should be embedded in the host composites. Thus manufacturing defects like resin pockets or poor interfacial bonding occur and could affect interlaminar shear (ILS) and flexural mechanical behaviour of smart composite structures. Limited information on these through-the-thickness mechanical properties is available from smart quasi-isotropic (QI) laminates of less than 8-ply thick, but no such data exists for thicker smart QI laminates. Therefore in the present research, both ILS and flexural mechanical properties of smart QI carbon/epoxy beams have been determined by using short beam shear (SBS) and Iosipescu methods as well as three-point and four-point bending methods. While SMA wires were embedded at selected interfaces of two different lay-ups in the longitudinal direction, optical fibres (OFs) were embedded at six different ply interfaces in both the longitudinal and transverse directions. It was found that neither ILS properties nor flexural modulus was affected, irrespective of the smart materials, their orientation, or through-the-thickness location. The flexural strengths did not suffer any noticeable degradation when the OFs or SMA wires were embedded either in the longitudinal direction or in the transverse direction in the tensile region. It was shown that the flexural strength degraded significantly when the OFs embedded in the transverse direction were in the compressive region.

A.R. Giles

Papers

Through-the-thickness mechanical properties of smart quasi-isotropic carbon/epoxy laminates