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Additive manufacturing (AM) has drawn significant attention in the fabrication of soft actuators due to its unique capability of printing geometrically complex parts. This research presents the design and development of an AM process for bioinspired, deformable, and magnetic stimuli-responsive actuator arms. The actuator arms were fabricated via the material extrusion-based AM process with magnetic particle-polymer composite filaments. Inspired by the rhombus cellular structure found in nature, different design parameters, such as the line width of the interior rhombus sides, and 3D printing parameters were studied and optimized to fabricate actuator arms that exhibit enhanced flexibility while being magnetically actuated. The trigger distance and deformation experiments revealed that the width of the rhomboids' sides played a critical role in magnetic and bending properties. It was found that the sample with a line width of 550 µm and printing layer thickness of 0.05 mm had the maximum deflection with a measured bending angle of 34 degrees. The magnetic property measurement exhibited that the sample with a line width of 550 µm showed the maximum magnetic flux density of 3.2 mT. The trigger distance results also supported this result. A maximum trigger distance of 8.25 mm was measured for the arm with a line width of 550 µm. Additionally, tensile tests showed that the sample exhibited a 17.7 MPa tensile strength, 1.8 GPa elastic modulus, and 1.3% elongation. Based on these results, we successfully fabricated a 3D printed magnetic gripper with two rhombus cellular structured arms which showed grasping and extensive load lifting capability (up to ∼140 times its weight).

Many engineering structures, especially defense applications, need to be reinforced against blast loads due to a nearby explosion. Today, much more attention needs to be given to this issue because of increased exposure to explosions, and natural disasters. Different solutions have been used in the literature to mitigate blast-loading effects. One of these applications, sandwich panels, are a good candidate for blast-loading applications. In a sandwich panel structure, several parameters have considerable effects on deflections, deformations, and energy absorption capability. The most important of these parameters are: (i) the material and thickness of the front and back face sheets and core; (ii) core density and grading; (iii) core and face sheet types; (iv) filling and stiffening strategies of the core; (v) radius of curvature of the panel; (vi) mass of explosive charge; and (vii) standoff distance. The aim of this paper is to review these critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application.

A dynamic mechanical thermal analyser operating in the single cantilever mode was used to examine the dynamic mechanical properties of unaged and hygrothermally aged discontinuous asymmetric helicoidal (Bouligand) carbon fibre reinforced plastic (CFRP) composites as a function of fibre architecture. The discontinuous Bouligand was manufactured using two major pitch angles as independent variables: 90° and 120° and from each major pitch angle, minor interply pitch angles were used as independent variables ranging 5°–25°. The composites were tested as either dry unaged specimens or following hygrothermal ageing in seawater at the constant temperatures of 40 °C and 60 °C for over 2000 h. We find that the viscoelastic properties E' and E'' are adversely affected by both hygrothermal aging and the minor pitch angle, but not the major pitch angle. Higher hygrothermal ageing temperatures and increasing minor pitch angles are found to decrease the energy absorption and dissipation capacities of discontinuous Bouligand structured CFRP composites. The tan-δ curves also indicate that hygrothermal ageing increases the heterogeneity of discontinuous Bouligand structured composites, with separate viscoelastic phases and glass transition temperatures.

The purpose of this project was to introduce a way to improve the mechanical properties of dissimilar welded material, which provides benefits such as affordability, high speed, and a suitable bond property. This experimental project applies the friction welding method, including combining parameters, such as a numerical control machine, two different speeds, and three different cross sections, including flat, cone, and step surfaces. When the welding process was done, samples were implemented and prepared via a bending test of materials. The results have shown that, besides increasing the machining velocity, the surface friction increased, and so did the temperature. Considering the stated experimental facts, the melting temperature of composite materials increased. This provides the possibility of having a better blend of nanomaterial compared to the base melted plastics. Thus, the result showed that, besides increasing the weight percentage of nanomaterial contents and machining velocity, the mechanical properties increased on the welded area for all three types of samples. This enhancement is due to the better melting process on the welded area with the attendance of various nanoparticle contents. Also, the results showed that the shape of the welding area could play a significant role, and the results also change drastically where the shape changes. Optimum shape in the welding process has been dedicated to the step surface. The temperature causes the melting process, which is a significant factor in the friction welding process.

Coarse-grained molecular dynamics simulations are a widely accepted methodology in the field of studying the viscoelasticity of elastomers. In this paper, a thermophysically balanced multiscale coarse-grained potential for glass-forming polymers is presented with the energy renormalization (ER) method by redefining temperature transferable correlation effects between rescaling factors for energy parameter and length-scale parameter. The correlation effects have not been investigated in the literature, to the best knowledge of authors. The coarse-grained potential was demonstrated for the polyisoprene model generated from the anionic polymerization. The ER enables temperature transferability by adopting renormalization parameters as function of the temperature. Considering the correlation effects, a multi objective-optimization algorithm was adopted to find proper solution sets of $\alpha$ and $\beta$ matching mean square displacement (MSD) and density to the all-atom model simultaneously. Meanwhile, shear stress was matched to find $\alpha$ first, then, density was fitted in the low-temperature regime. To verify the coarse-grained potential in the middle-temperature regime, MSD was compared to those from the all-atom model, and it was successfully matched.

Carbon nanomaterials including, but not limited to, carbon nanotubes (CNTs) and graphene have attracted considerable attention due to their nanoscale electrical conductivity. Flexible sensors have experienced a growing demand due to several potential applications, such as personalized health monitoring and robots. In this study, CNT/cellulose composite sheets were manufactured using spray methods for flexible sensors. MWCNTs were ultrasonically dispersed in an acetone solvent and flexible plain paper was used as a substrate on which the CNT suspension was sprayed. At the end of the coating process, to remove the acetone solvent, the specimens were dried in an oven. Electrical resistance (ER) three-dimensional-mapping and optical observation were used to confirm and evaluate the dispersion of CNTs on the paper. To access the wettability of CNT/cellulose sheets, the changes of static contact angle of distilled water droplets on the sheets were measured. The critical point of the CNT coating numbers was determined using the ER method as well as the change of wettability using the static contact angle measurements.