From new chemical capsules for treating water to advances in aeronautics, the inaugural volume of Composites Part C: Open Access brings together original, high-quality research into composite materials.
The journal, a newly launched sister to Composites Part A: Applied Science and Manufacturing and Composites Part B: Engineering, is publishing all its articles as gold open access. Every article, and related content, will be freely available on the journal’s home page for anyone to view.
The journal, which is open to submissions of original and high-quality research, has three sections. The first, focussing on composite structures, explores the modelling and mechanics of existing composite designs, as well as novel design formulations and concepts. Multi-functional composites, their behaviour and use are investigated in the second section, while the third covers the relatively new area of sustainable composites.
New developments in composite structures
In Volume 1, papers in the journal’s first section detail new developments in modelling shear and tensile stresses in composite material structures, and explore composite structures in aeronautics, reflecting the demanding nature of this environment.
‘Flutter’ can be a major problem when designing structures exposed to strong winds, for example planes or bridges. Such winds cause parts of a structure to self-vibrate uncontrollably – one bridge in the US shook itself apart this way in 1940. A paper by Aleksander Muc from the Cracow University of Technology, Poland, examines ‘flutter’ in layered composite plates when they are exposed to supersonic conditions. Muc was able to develop an analytical method to evaluate the flutter characteristics of rectangular laminated multi-layered plates, and thus the influence of transverse shear effects. The new method, he claims, can then also help to investigate the influence of the stacking sequence, thermal effects and compressive forces on these plates.
A paper by a team from the Ernst-Mach-Institut in Germany looks at a current aerospace standard when designing lightweight composite laminates. Polymer matrix composite materials are often used in passenger aircraft to keep them as light and fuel-efficient as possible. Usually the aerospace industry prefers these laminates to have symmetrical layers (that is, the arranged layers in the first half mirror the layers arranged in the second half). However, researchers experimented with two symmetrical and two non-symmetrical layers to see if either made any difference when replicating a bird flying into part of an airplane’s engine covering. They found that no stacking sequence was significantly superior to the others evaluated.
Staying with aeronautics, a paper from researchers at the Université de Toulouse and Elixir Aircraft in France reviews the history and applications of ‘sandwich structures’ – two ‘skin’ layers covering a core structure – in aircraft. These structures have the advantage of being strong enough to be load-carrying while having low density. Starting from their earliest incarnation in 1849 to the present, the paper covers issues such as manufacturing, maintenance and design. The authors explore the future of aeronautic sandwich structures, noting that many new cores have been developed or rediscovered in recent years. These new components could add extra functions, such as electrical conductivity.
In the Netherlands, a team at the Delft University of Technology explored the damage caused to carbon fibre polymer laminates when they experience tensile loading. Using acoustic emission and digital image correlation, the researchers monitored transversal cracks in real time and investigated how inter-laminal cracks could influence the transverse matrix density. They were able to see that cracks across the matrix distributed more uniformly under lower loading rates, with the cracks usually measuring between 0-10mm. Under higher loading rates, the cracks range from 0-28mm.
Meanwhile, a study from the Universidade de Lisboa, Portugal, aimed to reduce the amount of errors when testing the tension damage of a composite material in computer simulations. Objects recreated digitally for simulations are typically drawn in polygons or ‘meshes’. If these polygons are drawn too wide to properly represent the little faults within an object, the simulation may show an unrealistic result – a victim of ‘mesh dependency’. M.R.T. Arruda and colleagues were able to fine-tune their damage simulation model to minimise this mesh dependency.
Exploring the possibilities of multi-functional composites
The second section of the volume is dedicated to multi-functional composites: highly versatile materials capable of both providing strength to a structure while also performing another function, for example harvesting energy, sensing or self-repair.
One such ground-breaking application, which could ultimately help clean up industrial wastewater, is described in a paper by researchers from Hirosaki University in Japan. They show how a novel composite can encapsulate particles of magnetite, a mineral that is attracted to magnets and can be magnetised itself. These composite particles can then be used to selectively remove trace amounts of fluorinated aromatic compounds from water using only the compound’s magnetic field. One such compound they were able to easily remove from water was bisphenol A, a common component in plastic bottles and sports equipment. The composite, the researchers believe, has a lot of potential to be used in the future to remove fluorinated micropollutants from industrial wastewater.
Sustainable composites for a greener future
With its focus on sustainable composites, the volume’s third section showcases research that could help industries reduce the environmental impact of their work.
Research led by Yousef Saadati at the École de Technologie Supérieure in Canada offers insight into how sustainable composite materials behave when under stress. Composites reinforced with natural flax fibres are increasingly being used in construction, for example replacing glass fibres in wind turbines. They are low cost and sustainable, but there has been little research into their translaminar fracture toughness, that is, how easily they crack. Saadati and his team were able to characterise the translaminar fracture toughness parameters in the fibre direction when it was pulled and compressed. These values are the most reliable data ever obtained for use in engineering design and numerical simulation studies.
In another article, researchers based at the University of Auckland, New Zealand, and KTH Royal Institute of Technology, Sweden, attempted to find a more fire-resistant composite also based on natural fibres and biopolymers. They found a high-strength composite made of wool fibre and wheat gluten polymer that, when burned, minimised the rate at which the highest amount of heat from the flame was released. Using a scanning electron micrograph, the researchers were also able to see that the fibre and polymer still had good adhesion after they had been on fire. The resulting compact char also prevented heat and oxygen transfer, thus preventing the spread of the flame.
The final paper describes how researchers at the University of Waterloo in Canada took polychloroprene rubber – used in materials such as weather seals and diving suits – and reinforced it with cellulose nanocrystals chemically modified to better adhere to the rubber. When testing the resulting film, the researchers found that the treated rubber showed a substantial increase in its tensile strength and tear resistance, stretching to six times its size without tearing. Overall, the researchers believe that the constructed polychloroprene rubber-based nanocomposite films have great potential for high performance medical gloves and other ‘dipped’ products treated with an extra polymer layer.
Following on from this inaugural volume, the journal aims to continue bringing diverse, novel research on composites to the community through open access.