‘Resin welding’: A novel route to joining acrylic composite components at room temperature

The solubility of acrylic polymer in its own liquid monomer creates the opportunity to ‘weld’ acrylic-matrix (Elium®) composites without the application of heat. In this method, termed resin welding, acrylic monomeric resin is infused between acrylic-matrix composite parts. The resin dissolves and diffuses into the acrylic matrix and creates a continuous material, and a strong bond, when it polymerises, without the sensitivities of traditional welding methods to adherend or bondline thickness. Single lap shear testing was conducted on resin-welded and adhesively-bonded coupons with varying bondline thicknesses and filling fibres, and the bonding and fracture mechanisms were investigated using SEM and the diffusion of dyed acrylic resin. The highest bond strength of resin-welded coupons reached 27.9 MPa, which is 24 % higher than the strongest weld reported in the literature, indicating that resin welding is a promising alternative to traditional bonding and welding methods for acrylic-matrix composites

Repair of acrylic/glass composites by liquid resin injection and press moulding

This paper presents repair methods for in-situ polymerised acrylic (Elium®)/glass composites focusing on mode-I fracture toughness recovery. Acrylic/glass composites were first subjected to double cantilever beam (DCB) tests to measure their Mode-I fracture toughness. The delaminated samples after DCB tests were repaired and rejoined. Two repair methods were performed: liquid resin injection and press moulding at two different temperatures (130°C and 160°C). The repaired samples were subjected to a second set of DCB tests. The fracture behaviours of the four specimen groups (virgin, resin-injected, pressed at 130°C, and pressed at 160°C) were evaluated in terms of strain energy release rates (GIC) during crack initiation and propagation. The results showed that specimens repaired by resin injection exhibited highest GIC values, about 30% higher than the virgin state, due to the formation of a semi-interpenetrating polymer network (semi-IPN) at the joining interface. Scanning electron microscopy images provided insight into distinctive fracture behaviours for each test group

Seawater ageing of thermoplastic acrylic hybrid matrix composites for marine applications

Increasing usage of polymer composite materials necessitates the development of recyclable alternatives to traditional thermoset matrices or new techniques for recycling these materials. One family of promising recyclable matrices are the room temperature infusible acrylic resins, known commercially as Elium®. If these new materials are to be used in the tidal stream energy and shipping sectors, they must be able to withstand long-term immersion in seawater without significant losses in mechanical properties. In this study, accelerated seawater ageing is applied to acrylic/glass fibre and modified acrylic/glass fibre composites along with a traditional epoxy/glass fibre baseline. The mechanical properties (tensile, flexural, and short beam) are compared before and after ageing, and electron microscopy is used to examine fracture surfaces to determine the effects of water ingress on fracture propagation. In addition, the diffusion coefficients of the composites in seawater are compared and the changes in glass transition temperatures are used to determine the effects of plasticisation

Enhancing fracture toughness of carbon fiber/epoxy composites using polyphenylene ether as a modifier

In this study, carbon fiber/epoxy composites (CFRP) were fabricated by vacuum-assisted resin infusion molding (VARIM) with polyphenylene ether (PPE) as a toughening agent. The PPE contained hydroxyl end groups that facilitated chemical bonding with epoxy during curing. PPE was incorporated into the epoxy matrix by dissolution, and spreading in the interlaminar regions. The presence of PPE as a toughener exhibited significant improvement in the Mode-I fracture toughness of the composites. The CFRP samples, which were toughened with 5 wt.% and 10 wt.% PPE, showed about 191% to 380% enhancement, respectively, in the critical energy release rate (GIC) compared to the unmodified sample. Dynamic mechanical analysis (DMA) showed about a 6°C increase in the glass transition temperature of the toughened composites, which is an interesting aspect of this work. These results indicate the potential of using PPE as a toughening agent in CFRP composites

Active chiral plasmonics: flexoelectric control of nanoscale chirality

The ability to electrically control the optical properties of metamaterials is an essential capability required for technological innovation. The creation of dynamic electrically tuneable metamaterials in the visible and near IR region are important for a range of imaging and fibre optic technologies. However current approaches require complex nanofabrication processes which are incompatible for low cost device production. Here, we report a novel simple approach for electrical control of optical properties which utilises a flexoelectric dielectric element to electromechanically manipulate the form factor of a chiral nanostructure. By altering the dimensions of the chiral nanostructure, we allow the polarisation properties of light to be electrically controlled. The flexoelectric element is part of a composite metafilm that is templated on to a nanostructured polymer substrate. Since the flexoelectric element does not require in situ high temperature annealing it can be readily combined with polymer‐based substrates produced by high throughput methods. This is not the case for piezoelectric elements, routinely used in microelectromechanical (MEM) devices which require high temperature processing. Consequently, combining amorphous flexoelectric dielectric and low‐cost polymer‐based materials provides a route to the high throughput production of electrically responsive disposable metadevices

Thermal reshaping as a route for reuse of end-of-life glass fibre-reinforced acrylic composites

Thermal reshaping has been employed to simulate the end-of-life reuse of liquid-resin-infused thermoplastic acrylic composite laminates, and the associated effects on matrix-dominated mechanical performance and microstructure have been studied. L-shaped laminates were infused at room temperature and subjected to 1 or 4 hot-press flattening cycles (25 min at 120 °C; 11 bar). Compared to the original references, up to 13% higher transverse flexural strengths were measured for the reprocessed laminates. Such a scheme may be readily implemented for high-value reuse without sacrificing fibre length scales, and with minimal cumulative mass loss over successive reheating cycles (10 cycles: 2% and 15 cycles: 2.6%). This study provides important insights to foster a greater understanding of the performance limits of hot-press reprocessing to inform the practical reuse and re-application of sustainable composites in a circular economy