Continuous fibre-reinforced thermoplastic acrylic-matrix composites prepared by liquid resin infusion – a review

Increasing demand for lightweight materials is a major driving force for the steady growth of the continuous fibre-reinforced polymer composite industry. In recent years, strict global targets demanding greater environmental responsibility have led to a shift in research focus to address the end-of-life challenges posed by the use of thermoset matrices. Thermosets offer lower-cost processibility than thermoplastics, which historically required cost- and energy-intensive production methodologies. Consequently, despite their well-demonstrated recyclability, thermoformability and weldability, thermoplastics are yet to attain the same technological maturity as thermosets. In situ polymerisable thermoplastic resins have been identified as attractive emerging solutions for improving the processibility of thermoplastics. Thus, are essential materials in meeting the demand for fibre-reinforced thermoplastic composites. This review presents a comprehensive summary of recent works on room-temperature-processible liquid thermoplastic acrylic resins and their composites. Moreover, open problems and research opportunities are identified and discussed

Polyolefins and Polyethylene Terephthalate Package Wastes: Recycling and Use in Composites

Plastics are versatile materials used in a variety of sectors that have seen a rapid increase in their global production. Millions of tonnes of plastic wastes are generated each year, which puts pressure on plastic waste management methods to prevent their accumulation within the environment. Recycling is an attractive disposal method and aids the initiative of a circular plastic economy, but recycling still has challenges to overcome. This review starts with an overview of the current European recycling strategies for solid plastic waste and the challenges faced. Emphasis lies on the recycling of polyolefins (POs) and polyethylene terephthalate (PET) which are found in plastic packaging, as packaging contributes a signification proportion to solid plastic wastes. Both sections, the recycling of POs and PET, discuss the sources of wastes, chemical and mechanical recycling, effects of recycling on the material properties, strategies to improve the performance of recycled POs and PET, and finally the applications of recycled POs and PET. The review concludes with a discussion of the future potential and opportunities of recycled POs and PET

Thermoplastic hybrid-matrix composites prepared by a room-temperature vacuum infusion and in-situ polymerisation process

This work explores a novel route for the fabrication of hybrid-matrix composites based on a recently developed liquid thermoplastic acrylic resin. This resin was modified using a poly(phenylene ether) (PPE) oligomer with vinyl functionality. Glass fibre-reinforced laminates based on acrylic and PPE-modified acrylic matrices were produced by a room-temperature vacuum infusion and in-situ polymerisation process. Comparative assessments of their mechanical performance and mode-I interlaminar fracture behaviour revealed enhanced matrix ductility, transverse flexural properties and initiation fracture toughness. Crazing was identified as the dominant mechanism for improved resistance to crack initiation

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

‘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

Education and labour market: estimating future skill gap in India

Demographic transition creates a small window for countries when the population pyramid shows signs of maturity and bulges in the middle, indicating a relatively larger share of working age population. Key to reaping this demographic dividend lies in using the working age population to fullest potential and enhance production to the maximum possible. However, this can become a nightmare if skill demand and supply in the labour market do not match, keeping large portion of the working age population out of productive engagement while at the same time some productive sectors suffer from labour shortage in key areas. In this paper we look at the issue of estimating skill gap in the Indian labour market starting with the methods currently available globally. It then attempts to project both future labour demand and labour supply by sector and skill group and study the expected surplus/shortages in labour market. Results indicate that methodologies are still in the nascent stage and surplus and shortages are likely to coexist in the labour market. While some specific skills are scarce, others are in surplus, indicating the importance of taking a hard look at the manpower policy, including the education policy. It is crucial to bridge the gap between education, training and employment so that promised demographic dividend can actually materialise

Education and labour market: estimating future skill gap in India

Demographic transition creates a small window for countries when the population pyramid shows signs of maturity and bulges in the middle, indicating a relatively larger share of working age population. Key to reaping this demographic dividend lies in using the working age population to fullest potential and enhance production to the maximum possible. However, this can become a nightmare if skill demand and supply in the labour market do not match, keeping large portion of the working age population out of productive engagement while at the same time some productive sectors suffer from labour shortage in key areas. In this paper we look at the issue of estimating skill gap in the Indian labour market starting with the methods currently available globally. It then attempts to project both future labour demand and labour supply by sector and skill group and study the expected surplus/shortages in labour market. Results indicate that methodologies are still in the nascent stage and surplus and shortages are likely to coexist in the labour market. While some specific skills are scarce, others are in surplus, indicating the importance of taking a hard look at the manpower policy, including the education policy. It is crucial to bridge the gap between education, training and employment so that promised demographic dividend can actually materialise