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Liquid composite molding (LCM) suffers from multiple factors that contribute to pronounced uncertainty of process characteristics. This results in compromised reproducibility which is associated to high scrap or the unpredictable behavior of approved parts. However, LCM is still attractive for Fiber-reinforced polymeric composites (FRPC) production due to its economic advantage (i.e. in relation to Autoclave), the capability of some of its variants to produce high performance parts and its potential for process optimization. This review analyzes each uncertainty with respect to its origins and its impact in part or process, based on a combination of past literature and original numerical results. The possible methods to counteract uncertainties are critically discussed, with an eye on both the scientific and feasibility (technical/economical) aspects. The overall aim is to provide to future LCM implementations a roadmap of the most critical challenges and solutions regarding the establishment of a reproducible process.

Fibre-reinforced polymer (FRP) matrix composites are widely used in large marine structures, and in wind turbines where blade lengths are now over 100 m. Composites are the material of choice for small vessels due to ease of manufacture, high hull girder stiffness, buckling resistance, corrosion resistance and underwater shock resistance. Ships over 100 m are still built using traditional steel and/or aluminium, but so far not FRP. Composite ship lengths have increased over the past 50 years, but fundamental technical challenges remain for the 100 m composite ship. Preliminary studies suggest a possible 30% saving in structural weight, a 7–21% reduction in full load displacement, and a cost saving of 15%. However, economic considerations, design codes, manufacturing limits, safety and end of life scenarios need to be addressed before a 100 m ship is built. Innovative materials and structures, notably carbon fibre composite skinned sandwich construction, or aramid fibres with vinylester modified epoxy resin, should result in increased mechanical performance and consequent improvements in economics and manufacturing processes. A linear extrapolation of length vs. launch dates predicts the first 100 m ship would be launched in 2042.

Fibres in different textile forms (woven, knitted, stitched, and non-crimp) are used to reinforce composites for multifaced applications, including automotive, aerospace, marine, rail, energy, construction, and defence sectors. Textile fabric-based fibre reinforcements for composites possess some outstanding features, such as good dimensional stability, subtle conformability, deep draw moldability/processability, lightweightness, high strength and stiffness, and low cost. The greatest advantage of textile fibre-reinforced composites is the freedom to tailor their strength and stiffness properties for specific applications. Therefore, the design of composites involves defining the fabric geometry, stacking sequence, and orientation of fibres to optimise the system. Compared to knitted, stitched, and non-crimp fabrics, woven fabric-based fibre-reinforced composites are widely used in the industry. The properties of woven fabric-reinforced composites depend on several factors, such as types of fibre, compositions, polymeric matrices, and fibre/matrix interfacial strength. Some of the advantages are reduced preforming process steps, good impact and delamination resistance, and thermo-mechanical properties. This review has been written to provide detailed information and discussions, including the fabrication processes, relationship between fabric structure and composite properties, and morphological characteristics encompassing the current state-of-the-art in woven fabrics for composite reinforcement.

Acknowledging the importance of sustainability and implementing measures to achieve the UN’s 17 Sustainable Development Goals (SDGs) by 2030 represent a holistic approach to promoting peace and prosperity for the planet and its inhabitants. LCA is a valuable tool for organisations to enhance sustainability and reduce environmental impact. There has been a notable increase in LCA research subjects, indicating a recognition of its significance in promoting sustainability. The field has experienced a significant expansion in the past decade, with a 30% annual percent growth rate in LCA publications since 2010. In the most recent 4 years alone, 47% of all LCA publications since 1991 were produced. This paper presents a comprehensive review of LCA research from 1991 to 2022, with a specific focus on the period from 2019 to 2022. The study identifies research avenues and trends in LCA research using diverse bibliometric analysis techniques alongside content examination and the SciVal topic clusters prominence indicator. This comprehensive approach reveals evolving trends, such as an increased emphasis on practical applications for global sustainability goals, LCA’s expansion into bio-based materials due to plastic pollution concerns, and quantification of circular economy benefits in solid waste management. Moreover, deeper exploration of energy-related sustainability aspects and the integration of LCA into early product development for eco-conscious design are observed. These trends signify widespread LCA adoption across industries to address energy and design-related sustainability challenges. The study acknowledges interdisciplinary collaboration among researchers, industry, and governments, shaping a robust LCA research landscape. China’s heightened contributions as a leading contributor to the field have reshaped the global LCA landscape mirrored in the evolving prominence of journals, institutes, and funding organisations.

Basalt mineral fibre, made directly from basalt rock, has good mechanical behavior, superior thermal stability, better chemical durability, good moisture resistance and can easily be recycled when compared to E-glass fibres (borosilicate glass is called ‘E-glass’ or ‘electric al-grade glass’ because of its high electrical resistance) which are traditionally used in structural composites for industrial applications. Industrial adoption of basalt fibre reinforced composites (FRC) is still very low mainly due to inadequate data and lower production volumes leading to higher cost. These reasons constrain the composites industry from seriously considering basalt as a potential alternative to conventional (e.g., E-glass) fibre reinforced composites for different applications. This paper provides a critical review of the state-of-the-art concerning basalt FRC highlighting the increasing trend in research and publications related to basalt composites. The paper also provides information regarding physico-chemical, and mechanical properties of basalt fibres, some initial Life cycle assessment inventory data is also included, and reviews common industrial applications of basalt fibre composites.

Awareness of environmental issues has led to increasing interest from composite researchers in using “greener” materials to replace synthetic fiber reinforcements and petrochemical polymer matrices. Natural fiber bio-based thermoplastic composites could be an appropriate choice with advantages including reducing environmental impacts, using renewable resources and being recyclable. The choice of polymer matrix will significantly affect the cost, manufacturing process, mechanical properties and durability of the composite system. The criteria for appropriate monomers are based on the processing temperature and viscosity, polymer mechanical properties, recyclability, etc. This review considers the selection of thermoplastic monomers suitable for in situ polymerization during resin, now monomer, infusion under flexible tooling (RIFT, now MIFT), with a primary focus on marine composite applications. Given the systems currently available, methyl methacrylate (MMA) may be the most suitable monomer, especially for marine composites. MMA has low process temperatures, a long open window for infusion, and low moisture absorption. However, end-of-life recovery may be limited to matrix depolymerization. Bio-based MMA is likely to become commercially available in a few years. Polylactide (PLA) is an alternative infusible monomer, but the relatively high processing temperature may require expensive consumable materials and could compromise natural fiber properties.

Out-of-autoclave (OOA) manufacturing techniques for composites result in lower fibre volume fractions than for fully compressed laminates. The lower fibre volume fraction produces a higher resin volume fraction, which becomes resin-rich volumes (RRV). Textile reinforcements with clustered fibres and consequent RRV generally have low strength but high in-plane process permeability, whereas the opposite is true for uniformly distributed fibres. The inevitable increase in resin volume fraction of OOA composites often compromises composite performance and leads to relatively higher weight and fuel consumption in transport applications. The retention of autoclave processing is recommended for highest performance when compression press moulding is not appropriate (for example, for complex 3D components). The traditional autoclave processing of composites heats not only the component to be cured but also parasitic air and the vessel insulation. Subject to minor modifications of the pressure vessel, electrically heated tooling could be implemented. This approach would need to balance insulation of the heated tool surface (and any heater blanket on the counter-face) against the quenching effect during the introduction of the pressurised cool air. This process optimisation would significantly reduce energy consumption. Additionally, the laminate on the heated tool could be taken to the end of the dwell period before loading the autoclave, leading to significant reductions in cure cycle times. Components could be cured simultaneously at different temperatures provided that there are sufficient power and control circuits in the autoclave. While autoclave processing has usually involved vacuum-bagged pre-impregnated reinforcements, implementation of the cool-clave technique could also provide a scope for using the pressure vessel to cure vacuum-infused composites.

This review considers the influence of resin-rich volumes (RRV) on the static and dynamic mechanical and physical behaviour of fibre-reinforced composites. The formation, shape and size, and measurement of RRV in composites, depending upon different fabric architectures and manufacturing processes, is discussed. The majority of studies show a negative effect of RRV on the mechanical behaviour of composite materials. The main factors that cause RRV are (a) the clustering of fibres as bundles in textiles, (b) the stacking sequence, (c) the consolidation characteristics of the reinforcement, (d) the resin flow characteristics as a function of temperature, and (e) the composite manufacturing process and cure cycle. RRV are stress concentrations that lead to a disproportionate decrease in composite strength. Those who are considering moving from autoclave consolidation to out-of-autoclave (OOA) processes should be cautious of the potential effects of this change.

Lignocellulosic natural fibres are hydrophilic, while many matrix systems for composites are hydrophobic. The achievement of good mechanical properties for natural fibre-reinforced polymer (NFRP) matrix composites relies on good fibre-to-matrix bonding at the interface. The reinforcement is normally coated with an amphiphilic coupling agent to promote a strong interface. A novel alternative approach is to dissolve the coupling agent in the hardener for the resin before creating the stoichiometric mix with the base epoxy resin. During composite manufacture, the hydrophilic (polar) end of the coupling agent migrates to surfaces (internal interfaces) and bonds to the fibres. The hydrophobic (non-polar) end of the coupling agent remains embedded in the mixed resin. Mechanical testing of composite samples showed that silane added directly to the matrix produced a NFRP composite with enhanced longitudinal properties. As pre-process fibre coating is no longer required, there are economic (shorter process times), environmental (elimination of contaminated solvents) and social (reduced worker exposure to chemical vapours) benefits arising from the new technique.