Shape memory polymer composite unit with embedded heater

Abstract

A shape memory polymer composite (SMPC) unit has been manufactured with embedded heater. The structure of the SMPC unit has been designed to allow reaching high recovery loads with a reduced size of the functional device. The unit is a composite sandwich with four carbon fibre reinforced (CFR) plies, two SMP foam cores, and one SMP interlayer. In the mid-plane of the sandwich the heater is integrated, being immersed in the SMP interlayer. The adopted manufacturing procedure was able to provide the necessary consolidation in one step moulding thanks to the use, during lamination, of pre-formed SMP cores, and uncured SMP powder for the interlayer. The SMP cores were manufactured by solid state foaming of the same SM epoxy powder. SMPC laminates, without the embedded heater, were also manufactured for testing as well as traditional four-ply CFR laminates. Several tests were carried out for temperature calibration and for investigating SM properties of the SMPC laminates and unit. Dynamic mechanical analyses, hot bending tests, and microscopic observations were performed on CFR and SMPC laminates. It was found that the SMP layers reduce the glass transition temperature of the laminates as well as the transition onset temperature and, above all, the extension of the transition range thus providing the trigger effect to the SMPC transition. Double-cycle SM tests were carried on the SMPC unit at different temperatures from 160 °C to 190 °C. The unit (20 × 45 mm2) was able to exert recovery loads over 7.4 N almost independently from the temperature and without any evidence of failure after several repeated tests. High values were measured also for the shape fixity and shape recovery which were, on average, higher than 96% and 95%, respectively.

Electro‐responsive shape‐memory composites obtained via dual‐curing processing

“…Bilayer shape‐memory composites developed by Zheng et al 35 took around 220 s to recover their shape under 5 V voltage applied. Higher actuation speed can be found in the literature but at significantly higher voltage (around 20–40 V) 17,21,36,37 . The comparison in terms of power (W) is not always possible due to insufficient data available.…”

“…Higher actuation speed can be found in the literature but at significantly higher voltage (around 20-40 V). 17,21,36,37 The comparison in terms of power (W) is not always possible due to insufficient data available. In this investigation, electro-activated SM experiments were conducted applying 0.84, 1.8, and 3.5 W (respectively slow, medium and fast) depending on the heating strategies.…”

Shape Memory Composite Sandwich Structures with Self-Healing Properties

“…In terms of durability, the shape memory efficiency in multiple cyclic tests of SMPC skins has been already evaluated in previous works [38]. Results show that negligible effects are present for the SMPC laminate of the skin at least for limited number of cycles if the elastic range is not crossed during the memory steps.…”

Design of a Morphing Skin with Shape Memory Alloy Based on Equivalent Thermal Stress Approach

“…Corrugated skin had a better out-of-plane load-carrying capacity and could provide a large deformation in a specific direction. A variable stiffness deformable skin based on corrugated structure and SMP was developed [7,8]. One side of the ridged design was filled with SMP to guarantee a smooth aerodynamic surface.…”