Technical Chains in Civil and Urban Engineering: Review of Selected Solutions, Shaping, Geometry, and Dimensioning

Abstract

This article provides an in-depth review of selected technical chains, with particular emphasis on link chains and their load transmission mechanisms. It explores structural and functional characteristics, highlighting how chain geometry affects stress distribution, fatigue life, and performance under various loading conditions. The study includes a detailed classification of chains by type, material, and application, ranging from steel-based lifting and transport chains to lightweight, corrosion-resistant polymer types. Manufacturing methods and connection techniques are also discussed, underscoring the importance of proper assembly for mechanical reliability. Special attention is given to the role of materials, particularly the emergence of polymer composites reinforced with glass or carbon fibers, which offer promising alternatives to conventional metals. Although such composites exhibit advantageous properties—such as low weight, corrosion resistance, and energy efficiency—their application remains limited, insufficient load-bearing capacity, and the absence of standardized design guidelines. The review identifies critical knowledge gaps in the field, especially concerning shaping, dimensioning, and normative requirements for polymer-based load-bearing chains. It also highlights the lack of focused research on chain-specific geometries and the need for numerical simulations to optimize link design. The article concludes by emphasizing the importance of developing sustainable, durable, and standardized chain systems—particularly those utilizing recycled or novel materials—to meet both technical demands and environmental goals. This work supports future innovation in the design of advanced chain structures and provides a foundation for expanding the use of high-performance composites in civil and urban engineering applications.

1. Introduction

One definition of a chain is a serial assembly of interconnected components called links. It may consist of a specified number of links with strictly defined dimensions. Structurally, it functions as a tension member composed of multiple similar—typically identical—links. These are interconnected to form a continuous unit that retains significant flexibility in the relative positioning of its components. In its mechanical behavior, it resembles a rope: it does not transmit compressive forces, only tensile forces. However, during operation, the links are also subjected to shear and occasionally to compression and bending. Chains are most commonly manufactured from metal, although non-load-bearing plastic versions are also available on the market. In recent years, the demand for alloy cast iron and cast steel chains has declined, with their use now limited to specific niche applications [1]. The market is dominated by metallic products [2,3].

Link chains have been in use by humans since at least 2000 BCE [1,4,5,6,7,8,9,10,11,12,13,14]. The earliest documented applications trace back to ancient Egypt (ca. 2500 BCE), where primitive fiber-based chains were employed to transport stone blocks during pyramid construction. In ancient Greece and Rome, metallic ring began to appear in siege engines and port cranes, as described by the Roman engineer Vitruvius [4]. Their early uses in China are related to irrigation systems [7]. In later periods, metal chains found applications in hydraulic systems and transport technologies. During the Middle Ages, they were essential in defensive mechanisms such as drawbridges and river blockades. Advancements in metallurgy during the Renaissance facilitated their use in mining operations [10]. Across cultures and historical periods, chains have played a pivotal role in the development of transportation and defense technologies, significantly contributing to engineering progress.

The design of chains draws upon principles from mechanical, materials, and civil engineering. It is a complex process that involves defining the application and considering the nature of loading (static or dynamic), as well as environmental conditions such as humidity, corrosion, and temperature [3]. Chains serve as foundational components in many technical systems, and their quality and durability are heavily dependent on the materials used [15]. Selecting suitable construction materials is therefore critical, as they must meet diverse operational requirements. A key design step involves determining the geometry of the links—specifically their length, diameter, and width—as these parameters strongly influence strength and fatigue life. The choice of material is guided by performance demands [1,3], ranging from carbon steel to stainless steel, and in certain cases, special alloys or engineering plastics [15,16,17].

1.1. Research Gap and Study Objective

Although link chain mechanics has been investigated for more than a century, there is still no holistic framework that correlates link geometry, material class, and manufacturing route with performance indicators such as ultimate load, fatigue life, and environmental footprint. Design practice therefore remains largely heuristic and metal-centric.

Accordingly, this review tackles the following research problem: How can lightweight, recyclable, and electrically non-conductive materials be systematically evaluated and dimensioned so that load-bearing composite chains match or exceed the reliability of conventional steels?

We address three guiding questions:

• Which combinations of polymer matrices, reinforcements, and functional additives achieve the minimum working load limit demanded by civil engineering chain classes?
• How do link-scale geometric parameters modify stress localization across different material categories?
• Which knowledge gaps currently prevent codification of design rules for non-metallic chains?

These questions are pursued within the LIDER 14/0270/2023 project “Composite non-conductive chain with an anchoring system,” whose long-term goal is to deliver load capacity equivalent to a steel chain but with a weight reduction of approximately 40%. This also includes chains featuring ergonomic luminescent links, inherent antistatic and flame-retardant behavior, and zero brittle failure under mining duty cycles.

1.2. Life Cycle Assessment (LCA)

LCA data indicate that the production phase of carbon fibers (CFs) and carbon fiber-reinforced polymers (CFRPs) generates significantly higher environmental impacts than steel manufacturing [18]. Greenhouse gas (GHG) emissions associated with CF production range from 11.46 to 154.40 kg CO₂-eq per kg [18], with commonly cited values between 22.4 and 31 kg CO₂-eq/kg [19]. For instance, conventional carbon fiber (C-CF) results in emissions of 24.83 kg CO₂-eq/kg, while energy-saving variants (ES-CF) can lower this to 19.29 kg CO₂-eq/kg, assuming an annual production scale of 3000 tons [20]. Energy consumption in CF production typically ranges between 100 and 900 MJ/kg, but can reach up to 1150.5 MJ/kg, or even 4436.3 MJ/kg for the polyacrylonitrile (PAN) precursor [18]. In comparison, steel production leads to considerably lower GHG emissions, estimated at 1.7–2.1 kg CO₂-eq/kg, and energy demand in the range of 20–30 MJ/kg [18,20,21].

Despite these higher environmental inputs during production, CFRP materials can deliver substantial sustainability benefits over the entire lifecycle of the final product [18]. Their high strength-to-weight ratio, durability, and resistance to corrosion can significantly reduce material demand and extend service life. In structural applications, such as bridges, replacing steel with CFRP tendons may result in 18–28% lower GHG emissions during the production phase due to reductions in concrete and reinforcement volumes. Similarly, in wind turbine blades, CF allows for energy payback times (EPBTs) of just 0.49–0.73 months, and carbon payback times (CPBTs) of 0.22–0.37 months, meaning the environmental cost of CF production is offset in under a month of operation [18,21]. Moreover, advancements in production processes, such as the implementation of waste heat recovery systems, have the potential to enhance energy efficiency by up to 86% in specific stages of carbon fiber manufacturing, particularly during the stabilization phase. A critical element in the development of such materials is the systematic use of Life Cycle Assessment (LCA), which offers a reliable framework for evaluating their environmental performance and identifying key stages for process optimization. Modern processing technologies enable precise control over material microstructure and geometry, which creates opportunities for using polymer-based fiber composites in demanding industrial sectors such as urban infrastructure or mining operations, especially in applications that benefit from novel functionalities, including luminescence.

The environmental performance of CFRP-based systems must also be considered within the broader regulatory context of the European Union. For instance, the Directive (EU) 2019/904 [22] on the reduction in the impact of certain plastic products on the environment, commonly referred to as the Single-Use Plastics (SUP) Directive, along with the upcoming Packaging and Packaging Waste Regulation (PPWR), promotes a transition toward circular and resource-efficient material systems. Key targets include achieving 30% recycled content in plastic beverage bottles by 2030 and reaching 90% separate collection of plastic containers by 2029.

While these policies focus primarily on consumer plastic packaging, they reflect a broader legislative shift emphasizing material recovery, emissions reduction, and lifecycle optimization. Although CFRP composites are associated with relatively high environmental impacts at the production stage, their long-term application contributes to the reduction in operational emissions and extension of service life, making them consistent with the strategic objectives of EU climate and sustainability policies. Innovative design strategies that prioritize material efficiency, durability, and circularity can help align industrial practices with regulatory expectations, while reducing waste and advancing climate neutrality goals set out in the European Green Deal.

The Single-Use Plastics (SUP) Directive [22], in force since 2021, significantly limits the use of disposable plastic products, prompting the industry to explore alternative materials. In the context of chain design, this opens up the possibility of developing durable polymer-based composites capable of replacing steel in select applications, while simultaneously complying with environmental regulations. However, the mechanical properties of polymers often fall short of those exhibited by steel. For this reason, fiber reinforcement—such as glass or carbon fibers—is necessary to enhance material strength. Modern processing technologies enable precise control over material structure and geometry, potentially allowing such composites to be used in demanding applications, including mining or urban systems infrastructure, especially in the case of luminescent chains. A critical element in the development of new materials is the implementation of Life Cycle Assessment (LCA), which provides insight into their true environmental impact. Process optimization and appropriate material selection may allow for the production of chains that meet both structural performance criteria and sustainability goals. Innovative design approaches can help align industrial practice with regulatory expectations while reducing waste and supporting the transition to a circular economy.

Recent cradle-to-gate LCAs show that manufacturing 1 t of chains from recycled carbon fiber-reinforced polymer (rCFRP) can cut the environmental load by roughly one-third relative to steel.

• Greenhouse gas emissions fall by ≈ 35–45% (from ~2.0 t CO₂ e · t⁻¹ for BF-BOF steel to ≈1.1–1.3 t CO₂ e · t⁻¹ for compression-molded rCFRP with ≥30 vol% fiber) [23,24,25].
• Primary-energy demand (PED) drops by ≈ 33–43% (18–20 GJ · t⁻¹ for conventional steel vs. ≈10–12 GJ · t⁻¹ for the same mass of rCFRP) [25,26].

Because recycled carbon fibers could be used in reinforced recyclate, under specific conditions, every ton produced contributes directly to the SUP Directive’s target of recycling at least 55% of plastic packaging by 2030 and achieving 30% recycled content in beverage bottles [27]. This alignment between quantifiable LCA benefits and forthcoming EU obligations strengthens the argument for substituting steel with composite chains wherever mechanical requirements permit.

1.3. Market Identification

The current chain market offers a wide variety of products made from steel, composites, and thermoplastics (

Table 1. Load capacities of selected chain types depending on material and geometry.

Chain Type	Material	Diameter [mm]	Breaking Force [kN]
Link chain DIN 766 [33]	Stainless steel	2–16	1.2–127.5
Link chain DIN 763 [34]	Carbon steel	2–32	1.25–400
Lifting chain, grade 80 [35]	Alloy steel, quenched and tempered	6–42	45.2–2200
Roller drive chain “B” ISO [36]	High-grade steel	3.28–8.28	24.9–160
Plastic link chain [37]	Polyethylene	6	0.4
Plastic roller chain [38]	Polyethylene	3	0.44
Link chain AL-31 [39]	PVC	6.5	-
Single Pitch P Chain [40]	Polyacetal chain/steel pins	4–6	-
XK Plastic Chain Conveyors [41]	PVC chain/steel pins	5	2.5

). Depending on their intended application, chains serve as transport, load-bearing, or protective elements. Steel chains dominate technical applications due to their high tensile strength (>800 Mpa) and yield strength (~600 Mpa), with elongation at break exceeding 15% for selected grades [28,29]. In contrast, chains made from thermoplastics such as PA6, HDPE, or PC are primarily used for protective or structural enclosures (

Table 2. Parameters of materials used for production of chains [42,43].

Material	Tensile Strength (MPa)	Yield Strength (MPa)	Young’s Modulus (GPa)	Elongation at Break (%)	Density (g/cm3)
Steel (general)	370–700	250–600	200	10–25	7.85
Stainless Steel (304)	505	215	193	40–60	8.00
Carbon Steel (AISI 1045)	570–700	310–530	200	16–18	7.87
Polyethylene (HDPE)	20–37	19–30	0.8	500–1000	0.95
Nylon (PA6)	75–100	45–80	2.5–3.0	50–300	1.14
Acetal (POM)	60–70	50–60	2.8–3.0	20–60	1.41
Polypropylene (PP)	30–40	20–30	1.5–2.0	200–700	0.90
Polyamide (PA66)	80–100	50–90	2.8–3.5	20–100	1.14

). These materials show lower tensile strength (typically 40–90 Mpa) but high elongation (up to 300%) and low density (~1.1–1.5 g/cm³) [30]. Despite favorable environmental resistance and electrical insulation properties (resistivity > 10⁹ Ω·m), polymer chains face mechanical limitations, mainly due to manufacturing constraints. Injection molding requires splitting (Figure 1a) or welding the link (Figure 1b), which introduces stress concentration zones and reduces mechanical strength by up to 50% [31]. Currently, design standards such as EN 818 or ISO 1834 focus solely on metal chains. There are no specific guidelines for evaluating the mechanical performance of composite chains, which limits their wider adoption. This regulatory gap hinders the development of advanced solutions based on fiber-reinforced polymers (e.g., GFRP, CFRP). Nonetheless, polymer chains remain advantageous in applications where non-conductivity, corrosion resistance, and high deformability are critical, such as in mining or electrostatically sensitive environments [32].

Another factor limiting the popularity of polymer components stems from logistical and manufacturing challenges. The lack of detailed design guidelines discourages manufacturers from adopting such solutions. Implementing a new material requires both time and financial investment, which often deters innovation. Moreover, the limited number of facilities equipped with the necessary laboratory and production infrastructure for polymer components further reduces their availability. As a result, manufacturers tend to favor established and widely accessible steel-based solutions.

Importantly, chains made from materials other than steel typically do not have specified load capacities or breaking forces. Despite the existence of advanced composite materials with excellent mechanical performance [44,45,46,47,48]—including high tensile strength, fatigue resistance, and low weight—their use in commercial chain production remains marginal. Several key factors limit their widespread adoption. Major barriers include high manufacturing costs, complex production processes, and lower resistance to point loads and abrasion when compared to steel. The absence of dedicated standards and design guidelines further hampers the market introduction of composite chains, leading manufacturers to favor proven steel-based solutions, which are more cost-effective and reliable. While composites may find niche applications, commercial chain production is still dominated by steel and simple polymers (excluding the use of precious metals such as gold and silver in decorative or jewelry contexts).

1.4. Scope and Limitations

The objective of this study is to provide a comprehensive overview of the current state of knowledge regarding the technical chain market, with a particular focus on the materials used and relevant design standards. Bibliometric databases and related normative documents were analyzed. The work aims to highlight a significant research gap—namely, the lack of composite solutions that offer mechanical properties comparable to steel while additionally exhibiting functional features such as electrical non-conductivity, luminescence, and flame resistance.

The presented research forms part of the ongoing project LIDER No. 14/0270/2023, titled “Composite non-conductive chain with an anchoring system,” which is currently being implemented at Cracow University of Technology.

1.5. Review Strategy

The literature search was carried out in June 2025 using Scopus. The Boolean query combined the core term “chain” with material qualifiers and functional keywords. Records published between 1990 and 2025 were retained.

Duplicate removal left approximately 320 unique items. Titles, abstracts, and—when needed—full texts were screened against three inclusion criteria:

• Explicit testing of chain or link specimens;
• Numerical/analytical dimensioning studies;
• Material innovations relevant to load-bearing chains.

The final corpus comprises approximately 130 sources, including 27 international standards.

2. Keyword Analysis

Before delving into a detailed review of the available literature, a scientometric analysis was conducted based on publicly accessible bibliographic databases. The purpose of this analysis was to highlight major research trends and identify areas requiring further investigation. Such an approach facilitates data visualization and establishes connections between sources, keywords, authors, and articles within a specific research domain. It is widely employed by researchers across various scientific disciplines [49,50,51,52,53].

The analysis employed keywords such as “chain; shaping; geometry; dimensioning; division; composite; load-bearing; structural.” It encompassed disciplines including civil engineering, geodesy, transportation, environmental engineering, mining, energy, chemical engineering, materials science, and mechanical engineering. The search results from both databases were of similar magnitudes, with minor differences attributed to database-specific search algorithms.

Bibliometric analysis was conducted using the VOSviewer (version 1.6.20) tool based on data retrieved from the Scopus database [54]. To ensure thematic relevance and avoid misinterpretations of the keyword “chain” in the context of supply chain management, the search was restricted to the subject areas of materials science and engineering. A total of 355 publications were identified using the keyword combination “chain”, “composites”, and “geometry”. From the initial set of 4750 extracted keywords, 102 met the minimum occurrence threshold of 7 and were included in the co-occurrence network visualization (Figure 2).

The generated keyword map (Figure 3) reveals five distinct thematic clusters, each reflecting a specific research direction. The red cluster focuses on composite materials and nanocomposites, highlighting topics such as mechanical properties, flexibility, and electron microscopy techniques. The green cluster is associated with manufacturing processes, automation, robotics, mathematical modeling, and optimization methods. The blue cluster centers around additive manufacturing technologies, including 3D printers, 3D printing, and sintering. The purple cluster covers polymer-related research, including carbon nanotubes and nanoparticles, and their applications in chemistry and advanced technologies. Finally, the yellow cluster pertains to textile engineering, with emphasis on weaving, yarn deformation, and numerical methods.

The keyword “chain” appears predominantly in the central region of the map, in close connection with terms such as “mechanical properties” and “composite materials.” This positioning indicates its contextual use within materials engineering and fiber-reinforced structures. In contrast to earlier, broader searches, the narrowed focus of this analysis effectively excluded the literature unrelated to the scope of the review, particularly studies concerning logistics and supply chains, thereby enabling a more precise exploration of load-bearing and protective composite chains within the domains of structural and materials research.

Despite this, within narrow clusters there is a lack of keyword associations related to link geometry shaping, numerical contact surface analysis, or the use of reinforced polymer composites, for which almost no keyword infrastructure exists. Notably, the publication dates of relevant articles confirm a decline in academic attention to this subject in recent years. This analysis clearly indicates the need for further investigation into the topic highlighted.

3. Research Area and General Purpose of Study

The aim of this article is to provide a comprehensive review of the most common and current chain solutions used in civil and urban engineering. In addition, the study addresses the issue of recycling selected polymers as a potential source of advanced materials for the production of load-bearing polymer composite chains.

A key point is to highlight the potential contribution of ongoing research conducted under the LIDER 14/0270/2023 project titled: “Composite non-conductive chain with an anchoring system”. The use of recycled materials—particularly fiber-reinforced polymers—offers a promising alternative to traditional structural materials. This direction aligns with the need to reduce carbon footprints and increase resource efficiency, in accordance with modern engineering practices in which environmental considerations play a central role.

Research in the area of alternative materials indicates a largely untapped potential for meeting rigorous technical requirements in specific applications. With the support of modern processing and shaping technologies, it is now possible to develop materials that are more sustainable, cost-effective, and environmentally friendly. This is especially relevant in the context of the Single-Use Plastics Directive, which restricts the use of disposable plastic products. Innovative approaches to material design can help address the challenges posed by such regulations and create new opportunities for more sustainable industrial solutions.

Modified materials used for the manufacture of technical composite chains can feature high mechanical strength as well as specific functional properties, such as luminescence, electrical insulation, and flame retardancy.

In today’s world, solving unique engineering challenges within short timeframes presents a significant difficulty. As knowledge evolves within specific fields, it is important to explore whether materials currently known and available in other sectors may be repurposed for novel or unconventional technical solutions. The chain industry continues to generate high material demand and may effectively utilize substances that are considered waste in other sectors.

The article addresses the following issues:

• Types, materials, and applications: A classification of chains is provided based on type, material, and intended function, with an emphasis on their wide use across various industrial sectors. The importance of proper material selection is discussed in relation to durability, strength, and corrosion resistance. The role of modern plastics and composites is also highlighted, especially in terms of improving energy efficiency and supporting sustainable industrial development.
• Basic requirements and dimensioning: A compilation of selected standards related to the manufacturing and design of steel chains is presented. However, such standards are lacking for chains made of other materials, particularly polymers. A sample description of the design and fabrication of a link chain is included.
• Shaping and geometry: The geometry of chain links plays a critical role in their strength and functionality. Properly designed link geometry reduces stress concentrations and deformation, thereby enhancing the chain’s longevity. Numerical simulations enable precise optimization of link shapes, reducing the risk of mechanical failure.

The subject matter discussed in this paper falls within the domain of Engineering and Technical Sciences, particularly civil engineering, geodesy, and transportation; environmental engineering, mining, and energy; chemical engineering; materials science; and mechanical engineering.

4. Constructional and Functional Aspects of Chains

4.1. Types, Materials, and Applications

Chains can be classified according to their type (construction), material, and intended application. The classification presented in Figure 4 was developed based on the authors’ expertise and an extensive literature base [1,33,55,56,57,58,59,60,61,62,63,64].

In technical applications, three main types of chains are most commonly used: ring (link) chains, ladder chains, and plate chains.

Ring chains (Figure 5a) have such a wide range of applications that it is impossible to list them all comprehensively. In the maritime industry, they are used for anchoring, mooring vessels, and securing cargo on deck. In construction, they serve as load-bearing elements for lifting and moving heavy structures, as well as for securing scaffolding. In mining and extractive industries, these chains are employed for transporting raw materials, anchoring mining equipment, and stabilizing structural components. In transport and logistics, they are used to secure cargo during transit and in warehouse loading and unloading systems. In agriculture, livestock farming, and forestry, chains are used for towing, stabilizing, and other high-strength operations. In the energy and petroleum sectors, they are applied in handling drilling equipment, pipe transport on platforms, and underwater installations. The entertainment industry uses ring chains for suspending heavy stage components, such as lighting and rigging systems. Outside of industry, they are also widely used in daily life, for example, to secure gates, doors, or vehicles against theft. In all these cases, proper material selection, chain strength, and corrosion resistance are critical to ensuring durability and reliability under varying operational conditions.

Ladder chains (Figure 5b), including pin, roller, and bushing types, are primarily used as tensile elements in chain drives. In mechanical and manufacturing industries, they are widely used in drive systems where they enable effective transmission of force and motion. Their construction provides increased stability and precision in power transmission, which is crucial for high-performance machines such as presses and assembly lines.

Plate chains (Figure 5c) are mainly used as load-bearing tension members in the construction of trolley systems. A specific variant of the plate chain is the cutting chain, used in devices such as chainsaws. Chains designed for lifting (e.g., when used with a hoist), pulling, or securing (e.g., in bicycle locks) typically have toroidal links, enabling movement in two directions. Chains used in power transmission within machinery have specially shaped links that mesh with sprockets and are designed to articulate in a single direction only.

Delicate chains made of precious metals, in which links often take on complex and refined forms, are popular jewelry products. Small chains used as personal adornment are generally decorative counterparts of the technical chain types described above.

Various engineering materials are used in the production of chains [15]. Material selection plays a critical role in ensuring durability, operational efficiency, and resistance to specific environmental conditions. The choice of material depends on application-specific requirements, such as load-bearing capacity, operating environment, and usage conditions. Technological advancements in the chain industry have significantly influenced material choices, leading to improved performance and greater environmental sustainability.

Stainless steel remains one of the most commonly used materials. It is characterized by excellent corrosion resistance, making it ideal for humid environments or those involving chemical exposure. Chains made from stainless steel also exhibit high tensile and compressive strength, allowing them to carry heavy loads. This material is widely used in the food, pharmaceutical, and chemical industries, where high hygiene standards and durability are required. However, its higher cost compared to carbon steel, along with slightly lower mechanical performance in some cases, can be limiting factors.

Carbon steel, though more susceptible to corrosion, is known for its high tensile strength and wear resistance. It is relatively inexpensive, making it a common choice in heavy industry, mining, and construction. Its limitation lies in its vulnerability to moisture and aggressive chemical environments, which restrict its use in certain applications requiring enhanced resistance.

Chrome–nickel steel alloys are also used for chain production due to their fatigue resistance and corrosion resistance. These alloys are suitable for demanding operating conditions, such as those found in the chemical and food processing industries. Alloys made from aluminum, titanium, or bronze offer additional benefits, including lightness, ease of machining, and corrosion resistance, which make them ideal for specialized applications. However, their drawbacks include higher production costs and, in some cases, lower long-term durability compared to steel.

In recent years, the importance of plastics and composites in chain production has been increasing. In certain applications—particularly where weight reduction is critical—chains made from synthetic materials or composites are used [15]. Materials such as nylon, polyurethane, and carbon fibers offer lightweight construction, corrosion resistance, and minimal maintenance. Plastic chains are especially beneficial in applications where noise reduction, low friction, and energy efficiency are priorities. Carbon fibers and Kevlar are known for their exceptional tensile strength, allowing for reliable performance under dynamic loads [16]. The use of these materials also extends chains’ lifespans and reduces energy consumption in transport systems. Modern conveyor chains are increasingly incorporating these materials instead of traditional steel links. This shift results in significantly lighter constructions, directly enhancing energy efficiency. Lightweight chains reduce machine load, leading to energy savings—especially in contexts where speed and precision are essential.

Ceramic-matrix chains produced from alumina–zirconia (ZTA/ATZ) composites have lately been demonstrated for high-temperature conveyor systems and still retain >75% of their room temperature Vickers hardness after 1 h at 600 °C [65,66,67]. Hybrid roller chain links that marry quenched-and-tempered steel side-plates with filament-wound carbon fiber pins achieved a two-fold increase in bending/fatigue life in drivetrain simulations relative to all-steel references [68]. Additive-manufactured chains fabricated either by laser powder-bed fusion of 18Ni-300 maraging steel or by continuous-fiber fused-filament fabrication (CFF) offer 20–30% mass reduction while matching the ultimate tensile strength of conventionally machined links [69,70]. These emerging material platforms underline how quickly the palette of chain materials is widening and confirm the need for dedicated design-to-failure criteria in future standards.

The implementation of composites in place of traditional materials is a step toward lowering raw material consumption and reducing CO₂ emissions. Through the adoption of advanced technologies, manufacturers of conveyor chains play an important role in guiding the industrial sector toward sustainable development. The chain industry is experiencing a technological transformation driven by the adoption of modern materials. The overarching goal is to strike a balance between lightness, strength, and durability, which is essential for effective operation under diverse service conditions.

The introduction of high-performance composites and nanomaterials not only improves chain functionality but also aligns with sustainable engineering strategies. Lightweight and robust constructions reduce mechanical load and the carbon footprint of production processes. Additionally, innovations such as protective coatings and materials resistant to extreme environmental conditions contribute to the development of more eco-friendly and efficient chain systems.

Ultimately, material selection must be guided by the specific requirements of each project and the operational conditions under which the chain is expected to perform [17]. Each material discussed has its advantages and limitations, allowing for optimized selection based on the application. The incorporation of modern material technologies opens new possibilities for the chain industry and supports the efficiency and sustainability of industrial systems.

4.2. Requirements and Dimensioning

In the context of technical link chains, standards and guidelines play a critical role in ensuring reliability, safety, and proper functionality. For instance, ISO 3076 [71] defines dimensional tolerances and mechanical property requirements for industrial and transport chain systems. This standard outlines geometric parameters such as nominal link length, bar diameter, and curvature radii, which directly affect stress distribution during operation. At the final stage of design, optimization is performed with respect to cost, mass, and manufacturing requirements to produce durable and reliable chains for various applications. The geometry of these often single structural elements—combined into a continuous assembly—and the selection of suitable materials significantly influence the strength, stability, and longevity of the entire connection system.

With the dynamic advancement of material science, particularly in the field of fiber-reinforced polymer composites, it has become possible to achieve improved strength characteristics while simultaneously optimizing production processes. Strength calculations account for maximum loads and include stress and strain analysis, often supported by the finite element method (FEM). Prototypes are subjected to tensile and fatigue testing. Heat treatment processes for metallic chains, such as hardening and nitriding, improve both mechanical properties and corrosion resistance [72,73].

Standard requirements also include classification of chains according to load capacity, which depends on their resistance to static and dynamic loads. For example, EN 818 [74], which applies to steel chains, defines strength classes such as G80, G100, and G120—with each subsequent class offering increased load capacity relative to the chain’s self-weight. This classification facilitates the appropriate selection of chains based on working load and operating conditions.

Technical evaluation is another essential component of chain design and assessment. Standards such as ISO 1834 [75] and ASTM A0391 [76] specify testing methods, including tensile, fatigue, and wear resistance tests. These procedures verify the strength of individual links under multidirectional forces and assess durability under variable loading conditions.

Figure 6 illustrates the geometric characteristics of a metal link in a technical chain, including the link length (L), width (B), bar diameter (d), and internal length (t). These parameters are essential for dimensional consistency and proper alignment of links within the chain. In this example, the chain conforms to DIN 5685 C [77]. Adherence to normative dimensional guidelines ensures uniform force distribution and minimizes the risk of mechanical failure.

The requirements and dimensioning of chains are regulated by various international, European, and national standards, depending on the type of chain, its application, and the industry in which it is used. A large number of currently applicable standards exist. Based on publicly available information [78,79,80,81,82],

Table 3. List of examples of currently applicable standards for link chains.

Standard	Number	Title
ISO	610:1990	High-tensile steel chains (round link) for chain conveyors and coal plows [83]
ISO	1834:1999	Short link chain for lifting purposes—General conditions of acceptance [84]
ISO	1835:2018	Round steel short link chains for lifting purposes—Medium tolerance sling chains—Grade 4, stainless steel [85]
ISO	3076:2012	Round steel short link chains for general lifting purposes—Medium tolerance sling chains for chain slings—Grade 8 [86]
DIN	762-2	Quenched and tempered grade 5, round steel link chains [87]
DIN	763	Tested, non-calibrated, long-link round steel chains [88]
DIN	764	Calibrated and tested round steel link chains for continuous conveyors [89]
DIN	766	Calibrated and tested grade 3 round steel link chains [90]
DIN	5692	Round steel link chains—Forged steel components—Chain shortener, grade 8 [91]
DIN	8197	Steel link chains—Reference profiles of hobs for sprockets for roller chains [92]
DIN	5684	Calibrated and tested round steel link chains for lifting purposes [93]
DIN	5687-1	Round steel link chains—Part 1: Grade 5, medium tolerance, tested [94]
DIN	17115	Steels for welded round link chains and chain components—Technical delivery conditions [95]
DIN	22252	Round link chains for use in continuous conveyors and winning in mining [96]
DIN	22255	Flat link chains for use in continuous conveyors in mining [97]
DIN	32891	Tested non-calibrated round steel link chains—Grade 2 [98]
DIN EN	818	Short link chain for lifting purposes [99]
ASME	B29.22-2001 (R2021)	Drop Forged Rivetless Chains, Sprocket Teeth Drive Chain/Drive Dogs [100]
ASTM	Volume 01.05	Steel–Bars, Forgings, Bearing, Chain, Tool [101]
ASTM	A0466-2007 (R2020)	Standard Specification for Weldless Chain [102]
ASTM	A0413-2021	Standard Specification for Carbon Steel Chain [103]
ASTM	A0391-2021	Standard Specification for Grade 80 Alloy Steel Chain [104]
ASTM	A0973-2021	Standard Specification for Grade 100 Alloy Steel Chain [105]

presents a compilation of the most widely used European and American standards. It is important to note that no dedicated standards currently exist for the design and manufacture of composite or polymer chains.

The primary material used in the production of link chains is high-strength steel, which ensures adequate resistance to both dynamic and static loads. Standards developed by international standardization bodies define numerous minimum requirements for such chains.

An example of a high-strength chain—with a nominal load capacity of 850 kg and round links—should be designed and manufactured in accordance with ISO 610:2015, High-tensile steel chains (round link) for chain conveyors and coal plows [106]. This standard also refers to other related norms, including ISO 643:1983, Steels—Micrographic determination of the ferritic or austenitic grain size [107], and ISO 7500:1986, Metallic materials—Verification of static uniaxial testing machines—Part 1: Tensile testing machines [108]. When designing technical chains, several material, dimensional, and performance-related requirements must be considered to ensure proper functionality and safety. The following section outlines key provisions addressed by ISO 610.

The ISO 610 standard specifies requirements for a series of high-quality, specialized steel chains with calibrated, high-tensile, electrically welded round links. These chains are intended for use in mining equipment such as chain conveyors, chain–belt conveyors, gate and bridge conveyors, bucket elevators, coal plows, coal cutters, mechanical loaders, and other similar machinery, including systems used in underground mining operations. Chains covered by this standard are not intended for lifting applications, such as cranes or slings.

The standard defines the following terms:

• Chain size, defined as the nominal diameter of the wire or steel rod used to produce the chain.
• Breaking force—the maximum tensile force a finished chain sample can withstand before failure.
• Proof force—a specified force that a finished chain sample must withstand without exceeding the defined elongation limit.
• Acceptance force—a specified force that must be applied to the entire chain after processing, without causing permanent deformation or damage; this force may be reapplied at the discretion of the purchaser or inspector.
• Percentage elongation—the measured elongation expressed as a percentage of the gauge length.
• Processing—any post-welding operation such as heat treatment, calibration, or surface finishing.
• Calibration—the application of force to the entire chain during production to control link dimensions.
• Elastic limit—the maximum force that can be applied to the chain without causing permanent deformation.
• Setting force—the force used to hold the specimen under tension while the gauge length is marked or a strain gauge is installed.

The standard applies to chains with link diameters ranging from 14 mm to 30 mm. In terms of mechanical performance, ISO 610 specifies three strength grades: B, C, and D.

Figure 7 illustrates the dimensions of the chain and its individual link as specified in ISO 610 [106], including link width (b), inner width (a), link length (l₁), pitch (p), wire/rod diameter (d), and total chain length (l). The figure also includes the weld width (d₁) and weld length (e). The weld protrusion (c) is defined as the difference between the weld diameter and the base wire/rod diameter of the link.

Chains covered by this standard are manufactured in nominal diameters ranging from 14 to 30 mm, with dimensional tolerances between ±0.4 mm and ±0.9 mm. The chains must be fabricated from steel with appropriate mechanical properties and weldability to ensure durability and resistance to dynamic loads after undergoing heat treatment. For grades C and D, alloy steel is required, containing elements such as nickel, chromium, and molybdenum to enhance strength and wear resistance. It is crucial to maintain a balance between tensile strength and other mechanical properties to avoid excessive brittleness. The steel should possess a fine-grained microstructure to achieve an austenitic grain size as defined by ISO 643. The choice of chemical composition remains at the discretion of the manufacturer, who is responsible for ensuring that the final product meets the required strength parameters.

The chain manufacturing process includes heat treatment, in which the links are heated above the critical Ac₃ temperature of the steel. Upon completion, any welding splatter must be removed and the welds properly smoothed. Each link must be free from surface defects, such as cracks, notches, or other irregularities that could compromise durability. Any defective elements must be rejected or repaired accordingly. By default, chains are delivered in an unfinished, uncoated condition unless otherwise agreed. However, optional anti-corrosion coatings, polishing, or color markings may be applied to facilitate quality class identification. Identification markings must be placed on the flat sides of the links, away from the weld, with a concave profile and without sharp edges or excessive depth.

The mechanical performance of the chain is strictly related to its strength grade. The minimum breaking force is defined as follows: 190–890 kN for grade B, 250–1130 kN for grade C, and 310–1410 kN for grade D. The ratio of proof force to breaking force is typically 80%; however, for the largest link diameters (26 and 30 mm) in grades C and D, this may be reduced to 75%. The elongation under proof force is 1.4%, 1.6%, and 1.9%, respectively, while the minimum total elongation at break must not fall below 12%.

All chains must undergo a proof load test of at least 90% of the specified proof force. If this requirement is met during the calibration stage, a separate proof load test is not necessary. After testing, each chain must be subjected to thorough visual inspection, and any damaged links must be replaced.

Samples for mechanical testing are randomly selected based on pre-defined batch lengths. Dimensional tests are conducted on randomly chosen links to verify compliance with the specified length, width, and dimensional tolerances. Mechanical tests include tensile, bending, fatigue, and impact testing, all carried out in accordance with applicable standards.

Tensile testing is performed using specialized testing equipment compliant with ISO 7500-1, equipped with a tensioning mechanism of sufficient length to avoid the need for re-clamping during testing. Fatigue and impact tests are conducted on specimens extracted from selected batches, and their performance is evaluated against the criteria defined for each quality class.

These tests are designed to confirm that the chain meets the required strength characteristics, ensuring safe and long-lasting operation under actual working conditions. The research framework is illustrated in Figure 8.

The elongation test under the proof force should be performed by inserting the chain specimen into the gripping points of a tensile testing machine and subjecting it to a force equal to half of the specified proof force. This force is then reduced to the setting force, ranging between 8 and 35 kN, depending on the diameter of the chain link wire/rod. While holding the specimen under this setting force, the gauge length is marked and, if applicable, a strain gauge is attached to the sample. Next, the applied force is increased up to the designated proof force at a maximum rate of 20 kN/s. Upon reaching the test force, the elongation is recorded. The total percentage elongation is calculated by dividing the measured elongation by the gauge length and multiplying by 100%. The resulting elongation must not exceed the allowable value for the given chain class. After the proof force is applied (and the strain gauge, if used, is removed), the tensile force is increased further until the sample breaks. The force at fracture constitutes the breaking force and must not fall below the minimum threshold for the respective chain type. The total elongation at break must also be measured and meet the minimum required value.

At present no international standard stipulates design loads for polymer or composite link chains. Consequently, dimensioning must revert to limit-state principles adapted from metallic norms. In the LIDER project we calibrate material partial factors (γ_M = 1.5) [109] against >200 tensile tests on PET/GF prototypes. For example, 10 mm PET/GF link with a net section of 78 mm² and f_u = 390 MPa [110] thus delivers a design resistance R_d = 20.3 kN, comfortably exceeding the 8.3 kN working load limit (utilization = 0.41) [111]. Injection-molding parameters [112]—melt temperature (250 ± 5 °C), clamping force (75–80 kN), mold temperature (80 ± 2 °C), cooling time (45–60 s) and compatibilizer level (≤5 wt %)—were found to shift ultimate strength by up to 12% and impact strength by +66%, underlining the necessity of process–structure–property-based design rules.

4.3. Link Shaping and Geometry

The shaping and geometry of chain links—particularly those intended for use in demanding environments—are closely tied to the chain’s functionality and mechanical strength. In the design process, special attention is given to the link shape, which must ensure sufficient geometrical adaptability during operation without compromising load-bearing capacity. The geometry of the links directly influences how loads are transmitted and how the chain resists mechanical wear and damage.

Properly designed link geometry helps to avoid stress concentrations, deformation, and strain under load. To optimize the design, three-dimensional modeling and Finite Element Analysis (FEA) can be applied. Such simulations enable identification of stress and strain distribution patterns under various loading conditions, highlighting areas with maximum and minimum intensities.

In technical chain design, the configuration of the link layout must also follow ergonomic and efficiency principles. An excessive number of links increases chain mass unnecessarily, raising production costs and reducing the efficiency of the transport system. Conversely, improper link geometry may result in premature wear and eventual system failure.

Link geometry is also affected by manufacturing technology and processing methods. Depending on the material used, engineers encounter different production challenges—particularly in the case of polymer chains. Therefore, designers must account for specific issues such as bending angles and inter-link interaction under load. Advanced engineering tools such as computer simulations allow for the precise definition of optimal link dimensions to ensure functionality and durability.

Various software platforms can be used for this type of analysis—SolidWorks 2025, for example, is a widely applied tool [113]. It facilitates the visualization of displacements, deformations, and stress distribution. The overall chain strength is largely determined by the contact zones between individual links and their geometry. In tensile testing, stress concentration is greatest across the horizontal section of the link. As illustrated in Figure 9, the most highly loaded zones are the contact surfaces. Surface imperfections, such as notches or irregularities, can significantly reduce the link’s strength, thereby weakening the entire chain.

Torsional deformation of the chain is particularly detrimental, as it alters the orientation of the contact zones, forcing the link to operate under non-optimal conditions and leading to premature failure under loads lower than the nominal breaking force [114]. Therefore, properly defined tolerances and clearances—allowing controlled relative motion between links—are essential to ensure effective and safe chain operation.

Finite element optimization (SolidWorks Simulation 2024) shows that enlarging the internal filet radius from 0.2 d to 0.35 d in PET/GF links lowers peak von Mises stress by 28% while adding <3% to mass. Controlled fountain flow during mold filling further produces fiber-rich skins that suppress notch-sensitivity and brittle fracture. These observations will inform upcoming patent submissions on graded-structure links

5. Future, Perspectives, and Research Gaps

Research conducted under the LIDER 14/0270/2023 project focuses on the modification of plastic composites with additives aimed at enhancing the mechanical strength of the composite and imparting special properties such as luminescence, flame retardancy, and antistatic behavior [115]. For instance, typical PET (polyethylene terephthalate) recycling processes are mainly used for producing new bottles—issues arise with contaminated feedstock, which cannot be utilized in applications involving food contact. Therefore, it is crucial to explore applications where the presence of contaminants such as adhesives, labels, or residual chemicals does not pose limitations in the material’s reprocessing. One such area is structural components in civil and municipal engineering, where food-contact certification is irrelevant. This approach enables the effective use of contaminated PET in sectors that do not require high purity of materials.

The potential use of modified and reinforced polymers as base materials for load-bearing chains exemplifies how the construction industry can adopt advanced materials to meet contemporary demands. Recycling materials—especially those requiring minimal processing—offers an opportunity to repurpose waste into durable, high-performance components. This strategy aligns with sustainable development principles and allows for the production of materials with unique properties. Numerous industrial sectors may benefit from substituting currently used materials with high-quality recyclates.

Recent findings from our previous studies [72,73] have demonstrated the clear benefits of reinforcing recycled polyethylene terephthalate (rPET) with glass fibers (GFs), highlighting this approach as a promising pathway to improve the mechanical performance of recycled polymers. The incorporation of GFs into the rPET matrix significantly enhances tensile and flexural strength, stiffness, and thermal stability, with tensile strength increasing by up to 255% in composites containing 50% GF (rPET50GF) compared to neat rPET. Moreover, the resulting composites exhibit reduced deformability and increased rigidity, making them suitable for structural and load-bearing applications. These improvements not only extend the usability of rPET into advanced engineering domains, such as automotive components, but also contribute to circular economy goals by enabling high-performance reuse of post-consumer plastics. However, the influence of GF on melt viscosity and the processing behavior of rPET/GF composites suggests that injection molding parameters must be carefully optimized for each formulation.

As part of the ongoing project, further research activities are currently being carried out. The results of these studies will be presented at international scientific conferences and published in peer-reviewed journals. Two patent applications (No. P.452128/No. P.452131) have been submitted as part of the research, covering a proprietary method for producing a composite formulation for chain link manufacturing. Based on this applications, the LIDER project envisions the production of a composite chain link with electrical insulation properties. Furthermore, the developed formulation will also be used to fabricate a bonded anchor designed for securing the chain to rock or concrete substrates.

6. Conclusions

There is a clear gap in the utilization of composite materials within civil, marine, urban, and mining engineering applications. The commercial market currently lacks load-bearing polymer chains, making it essential to explore component formulations involving synthetic polymers and their reinforcement—potentially sourced from recycled materials. The anticipated use of such materials can contribute to a reduction in carbon footprint and enable effective application of composite granulates across various industries. In the near future, the project will encompass a comprehensive exploration of the subject, ranging from theoretical analysis and computational modeling to laboratory testing and operational evaluation of a composite chain system.

This article presents a comprehensive overview of chain geometry, traditional metallic materials, and advanced fiber-reinforced polymer composites. Particular attention is given to extending service life and enhancing operational safety.

The article concludes with the following key points:

• A classification of chains by type, material, and application was developed. Steel remains the predominant material used in chain manufacturing, although polymer composites are gaining relevance.
• While numerous standards exist for the design and manufacturing of technical steel link chains, similar guidelines are lacking for chains made from other materials, especially modified polymers.
• The geometry of chain links is critical for strength and operational performance, particularly under harsh conditions. Proper link design reduces stress concentrations and deformation, improving chain durability. Three-dimensional modeling and numerical simulations help optimize link dimensions and minimize failure risk.

A forward-looking approach to link chain engineering was proposed, integrating technical, durability-related, and environmental considerations through innovative material solutions. This vision aligns with sustainable construction trends and the principles of the 6R framework (rethink, refuse, reduce, reuse, recycle, recover), which is widely used in the context of environmental responsibility and waste management.