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Thermoplastic composites offer the potential for reducing the overall manufacturing costs of aircraft structures by allowing continuous production methods to be applied without the ancillary need f...

We present a case of D-lactic acidosis presenting as a metabolic encephalopathy secondary to small intestinal bacterial overgrowth. This patient had a known history of short bowel syndrome. Of note, this case required the alteration of treatment to promote a sustained clinical and biochemical improvement. We discuss the pathophysiological mechanisms thought to be involved. We also review the current therapies as well as potential future strategies. This case highlights the importance of the prompt clinical recognition of signs and symptoms as well as the rapid initiation of management strategies to ameliorate this condition.

As materials and engineering design tools become more complex, engineers are looking to mimic structures and systems, occurring in nature, to design more efficient mechanical structures. One such structure is a morphing composite lattice structure, whose design was inspired by the tail of the bacteriophage T4 virus [1]. To date the morphing behavior of the tail structure of the virus has been simplified by neglecting the intermolecular mechanisms that actuate the bistable behavior of the tail. This behavior has been achieved using prestressed composite flanges that are mechanically joined in alternating clockwise and anti-clockwise chiralities. The composite lattice structure has previously been proposed as an actuator for aerospace structures, replacing more complex and heavier traditional actuator structures. McHale et al. [2] have shown that the composite lattice is capable of greatly improving upon the state-of-the-art in the form of a telescopic boom for CubeSat systems. This utility provides validity in studying further enhancements on the capabilities of the structure to enhance its potential applications in the aerospace industry. This work proposes a mechanism for replicating the inter-molecular behavior that occurs in the bacteriophage T4 tail. The bonds between the inner and outer tail structures are broken and reformed, thus, driving the actuation process. This method will form a variable topology morphing system. As such, a novel category of morphing structure is presented here for the first time. The morphing topology behavior is proposed by replacing mechanical fasteners in the traditional lattice structure in select locations with a series of permanent magnets. Finite element analysis is used to calculate the difference in energies between the states before and after discrete topology changes occur, allowing the associated change in energy to be converted to a required actuation force. Varying the topology of the lattice structure allows the lattice to transition from a linear morphing actuator system to a bespoke and tunable curved actuator with potential applications in satellite dish actuation, for example.

Automated manufacturing of thermoplastic composites has found increased interest in aerospace applications over the past three decades because of its great potential in low-cost, high rate, repeatable production of high performance composite structures. Experimental validation is a key element in the development of structures made using this emerging technology. In this work, a $750\times640\times240$ mm variable-stiffness unitised integrated-stiffener out-of-autoclave thermoplastic composite wingbox is tested for a combined shear-bending-torsion induced buckling load. The wingbox is manufactured by in-situ consolidation using a laser-assisted automated tape placement technique. It is made and tested as a demonstrator section located at 85% of the wing semi-span of a B-737/A320 sized aircraft. A bespoke in-house test rig and two aluminium dummy wingboxes are also designed and manufactured for testing the wingbox assembly which spans more than 3m. Prior to testing, the wingbox assembly and the test rig were analysed using a high fidelity finite element method to minimise the failure risk due to the applied load case. The experimental test results of the wingbox are also compared with the predictions made by a numerical study performed by nonlinear finite element analysis showing less than 5% difference in load-displacement behaviour and buckling load and full agreement in predicting the buckling mode shape.

Morphing composites are relatively new types of structure that change their shape due to inherent combinations of anisotropy, pre-stress and curvature. They have found use in deployable spacecraft structures, including booms and solar generators. However, little work has been completed on the utilisation of morphing composites in the design of curved space structures, e.g. parabolic dish antennae. This study focuses on the development and testing of a morphing composite cylindrical lattice that deploys along a toroidal (curved) path, which has potential to be used in future deployable antennae. This structure achieves its curved deployment through the tailoring of lattice fastener pitch, where the fasteners are more closely spaced on the inside of the curve and further apart on the outside. A numerical model of this new structure is developed and compared with a straight cylindrical lattice of similar configuration, to determine the effect that curving a lattice has on the stability landscape. The numerical model shows that the curving lattice produces a larger longitudinal curvature during deployment and smaller transverse and twisting curvatures, than the equivalent straight lattice. It also produces a marginally smaller force and extends to a slightly shorter deployed state. This numerical model is verified by comparison with experimental testing, which shows good agreement in key areas of the stability landscape.

Morphing composite structures are of significant interest due to the fact that they exhibit superior mass-to-stiffness ratios and a large degree of tailorability in comparison to traditional materials and structures. One such morphing composite structure is the multistable composite cylindrical lattice. Current work introduces a novel variable-topology morphing mechanism to it through the use of both permanent magnets and electromagnets. By replacing a set of mechanical fasteners from the central intersection of the lattice strips with a bespoke variable-topology mechanism introduces a controllable and replicable semi-autonomous means for topology morphing. The variable-topology mechanism allows the structure to transition from being a linear deployment actuator to one that deploys along a curved path, without need for external mechanical input. The behaviour of both the variable-topology mechanism and the topology-changing cylindrical lattice are thoroughly characterised through a combination of mechanical and virtual tests.

peer-reviewed Structures used in space applications demand the highest levels of stiffness for their mass whilst also performing in a hostile environment. To partly address these requirements and so as to also pack efficiently for stowage during launch we propose a new type of compact telescopic morphing lattice space boom. This boom stows within a 1U CubeSat volume and is lightweight being only 0.4 kg. The boom has a total length of 2 m in its deployed state which is 20 times its stowed height. The device comprises two multi-stable cylindrical composite lattices that are joined telescopically. These lattices nest inside one another in the stowed configuration, with the objective of improving packaging efficiency. Notably, prestress and lamina orientation are used to smoothly change shape from being compact when stowed to being extended when deployed. The lattices in the boom have been designed to maximise deployment force and to be self-deploying by tuning manufacturing parameters. As a result, only a small, lightweight mechanism is required to regulate deployment speed of the lattice boom. By reversing its direction, this mechanism can be used to retract the lattice boom to its stowed configuration, thereby enabling two-way reconfigurability.

This paper reports on the design and manufacture of a compact telescopic morphing lattice (CTML) space boom. This boom stows within a 1U CubeSat volume and weighs only 0.475kg. Once deployed, the CTML has a total length of 2m, 20 times the stowed height. The device consists of three multi-stable cylindrical composite lattices connected in series. To improve packaging efficiency, these lattices nest inside one another in the stowed configuration. The morphing lattice is a structure that uses prestress and lamina orientation to seamlessly morph from a short stowed state to a long deployed state. By tailoring the manufacturing parameters, the lattices in the boom have been designed to maximize the deployment force and to be self-deploying. Therefore, the CTML only requires a small, lightweight mechanism to regulate the deployment speed. The deployment speed regulator can also potentially retract the boom back to the stowed state, facilitating reconfigurability.

Morphing technologies use large, seamless changes in the shape of a structure to enable multi-functionality and reconfigurability. Several industrial sectors could benefit from morphing structures, including medical, energy and aerospace which require lightweight, simple and reliable solutions. Composite materials are key to lightweight morphing technologies due to their increased strength- and stiffness-to-mass ratios, stiffness tailorability and excellent fatigue properties, all of which reduce the mass and complexity of these types of structures. By accounting for thermal effects in their analytical description, we enhance the viability of multi-stable composite helical structures. This consideration improves predictions of existing analytical models in comparison with experiments, while also vastly expanding the design space to include antisymmetric and non-symmetric flange lay-up sequences. The developed analytical model is presented and verified using both finite-element models and experiments. By including thermal effects, we show that beneficial new morphing behaviours can be obtained.

Deployable spacecraft technology should be both lightweight and compact for storage while also being rigid and expansive once deployed. A new type of structure that can meet both of these requirements is the morphing cylindrical lattice. This multi-stable structure can morph from a compact stowed state, to a long and slender deployed beam. It comprises narrow strips of carbon fibre composite material, making it particularly suitable for deployable booms, solar arrays and antennae. While existing modelling techniques focus on predicting the stability of lattices using symmetrical laminates, current work extends upon state-of-the-art by including the effects of thermal strains and curvatures that arise in non-symmetrical laminates when cured at elevated temperatures. As non-symmetrical laminates cool during post-cure, thermal stresses increasingly develop due to the variation of in-plane thermal expansion coefficient through the thickness. The model developed in this work, includes thermal stress effects, allowing for the design of thermally actuating lattices. This model is verified through comparison with finite element analysis and experimental data, both of which show excellent agreement.

Advanced composite materials enable the development of lightweight and stiff deployable structures that have significant potential for the space sector. In particular, a morphing cylindrical lattice can deploy from a small cylinder to one that is substantially thinner and longer and is particularly suited for deploying solar arrays or antennae. The morphing behaviour of the lattice stems from the nonlinear strain energy state obtained from prestressing strips of orthotropic material. Current analytical models used to describe the behaviour of morphing lattices only consider bending strains in the strain energy formulation. This paper extends state-of-the-art modelling techniques by including both transverse curvature and membrane strains, associated with non-zero Gaussian curvature, in the strain energy formulation. Transverse curvatures in tandem with longitudinal curvatures lead to the development of membrane strains, giving a complex interplay between membrane and bending strain energies and their combined effect on morphing properties of the lattice providing a rich tailorable nonlinear response. The analytical model developed is compared against finite element modelling and the first experimental results reported for such multi-stable composite helical lattices, showing good agreement over a range of designs.

peer-reviewed The proof of an aircraft’s structural integrity and safety is typically provided by analysis and supported by structural test evidence. The experimental test of a wingbox, which is the main structural component of a wing, can provide useful data on assessment of its structural performance in an actual airplane for the design objectives. To this end, a testing fixture was designed and manufactured to introduce a prescribed shear force and bending moment at one end of a variable stiffness thermoplastic composite wingbox and react the load at the other end. We report experimental results and compare them with detailed finite element data.

Automated fiber/tow placement (AFP/ATP) techniques can provide cost-effective, reduced waste, and repeatable high rate production of laminated composite structures with some unprecedented capabilities such as in-situ consolidation and fiber/tow steering. In fiber steering, the fiber orientation angles are continuously changed in-plane to make composites with optimum path between the loading points and supports in a structure. Thermoplastic composites (TPC) have gained increasing interest from the aerospace sector for their increased formability, weldability, recyclability and their superior toughness and fatigue performance in comparison with their thermoset counterparts.. Their potential for out-of-autoclave manufacture (OOA) also makes them an excellent candidate for low cost production of large structures for aerospace applications. To investigate the potential for aerospace structures, an OOA variable stiffness, unitized, integrated-stiffener thermoplastic wingbox demonstrator was recently built at the University of Limerick. A number of different techniques were targeted: fiber steering to achieve the variable stiffness skin, in-situ consolidation to weld the stiffeners to the wingbox skin, and as manufacturing methodology a laser-assisted tape placement (LATP) in combination with winding was used. In the design process, the wingbox loads were determined by assuming its location to be at 85% of the wing semi-span of a B737/A320 size aircraft. Previously we reported on a full-scale structural test using a bespoke testing frame with representative bending moment and shear load. Indeed, the wingbox buckled elastically at a load close to that predicted numerically. Our results highlight the potential advances that become possible in primary aerospace structures by combining fiber steering and in-situ consolidation of carbon fiber thermoplastic composites together with new blended, unitized structural concepts. Herein, we report on the results of a new test that include torsion as well as bending moment and shear. An overview of the design against buckling, manufacture and structural testing for load carrying capability is given.