Epoxy Vitrimer Materials by Lipase-Catalyzed Network Formation and Exchange Reactions.

The preparation and reprocessing of an epoxy vitrimer material is performed in a fully biocatalyzed process wherein network formation and exchange reactions are promoted by a lipase enzyme. Binary phase diagrams are introduced to select suitable diacid/diepoxide monomer compositions overcoming the limitations (phase separation/sedimentation) imposed by curing temperature inferior than 100 °C, to protect the enzyme. The ability of lipase TL, embedded in the chemical network, to catalyze efficiently exchange reactions (transesterification) is demonstrated by combining multiple stress relaxation experiments at 70-100 °C and complete recovery of mechanical strength after several reprocessing assays (up to 3 times).

Lipase-Catalyzed Epoxy-Acid Addition and Transesterification: from Model Molecule Studies to Network Build-Up.

Commercially available lipase from (lipase TL) is investigated as a biocatalyst for the formation of an acid-epoxy chemical network. Molecular model reactions are performed by reacting 2-phenyl glycidyl ether and hexanoic acid in bulk, varying two parameters: temperature and water content. Characterizations of the formed products by H NMR spectroscopy and gas chromatography-mass spectrometry combined with enzymatic assays confirm that lipase TL is able to simultaneously promote acid-epoxy addition and transesterification reactions below 100 °C and solely the acid-epoxy addition after denaturation at > 100 °C.

Direct-Write Piezoelectric Transducers on Carbon-Fiber-Reinforced Polymer Structures for Exciting and Receiving Guided Ultrasonic Waves.

Advancements in the structural health monitoring (SHM) technology of composite materials are of paramount importance for early detection of critical damage. In this work, direct-write transducers (DWTs) were designed for the excitation and reception of selective ultrasonic guided waves and fabricated by spraying 25- [Formula: see text]-thick piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TRFE)] coating with a comb-shaped electrode on carbon fiber-reinforced polymer (CFRP) plates. The characteristics and performance of the ultrasonic DWTs were benchmarked with the state-of-the-art devices, discrete lead zirconate titanate (PZT) ceramic transducers surface-mounted on the same CFRP plates.

Patterned, morphing composites via maskless photo-click lithography.

Morphing materials, also known as smart materials are attracting increasing attention as sensors, actuators and in soft robotic applications. In this work bilayered morphing composites were created by exploiting the thiol-ene photoclick reaction via maskless digital light processing (DLP). This technique allows for gradients and patterns of near infrared (nIR)-triggered materials to be efficiently crosslinked to substrates, with suitable interfacial adhesion to realise complex morphing.

Graphene-aramid nanocomposite fibres via superacid co-processing.

The development of graphene-polymer nanocomposite materials has been hindered by issues such as poor colloidal stability of graphene in liquid media, weak interactions between graphene and the host polymers as well as the lack of scalable and economical graphene synthesis routes. Chlorosulfonic acid (CSA) can spontaneously disperse graphene without the need for mechanical agitation, chemical functionalisation or surfactant stabilisation,1 however is incompatible with most polymers and organic materials. Here, we demonstrate how poly(p-phenylene terephthalamide) (PPTA) - the polymer which constitutes Kevlar - can be co-processed with graphene in CSA and wet-spun into nanocomposite fibres with minimal aggregation of graphene.

Transverse Crack Detection in 3D Angle Interlock Glass Fibre Composites Using Acoustic Emission.

In addition to manufacturing cost and production rates, damage resistance has become a major issue for the composites industry. Three-dimensional (3D) woven composites have superior through-thickness properties compared to two-dimensional (2D) laminates, for example, improved impact damage resistance, high interlaminar fracture toughness and reduced notch sensitivity. The performance of 3D woven preforms is dependent on the fabric architecture, which is determined by the binding pattern.

Early Damage Detection in Composites during Fabrication and Mechanical Testing.

Fully integrated monitoring systems have shown promise in improving confidence in composite materials while reducing lifecycle costs. A distributed optical fibre sensor is embedded in a fibre reinforced composite laminate, to give three sensing regions at different levels through-the-thickness of the plate. This study follows the resin infusion process during fabrication of the composite, monitoring the development of strain in-situ and in real time, and to gain better understanding of the resin rheology during curing.

Thermal Diffusivity Mapping of Graphene Based Polymer Nanocomposites.

Nanoparticle dispersion is widely recognised as a challenge in polymer nanocomposites fabrication. The dispersion quality can affect the physical and thermomechanical properties of the material system. Qualitative transmission electronic microscopy, often cumbersome, remains as the 'gold standard' for dispersion characterisation.