Development and characterisation of novel structural composites from recycled materials

Carpets are composite materials and, like many composite materials, waste carpet is both difficult and expensive to recycle because of the complicated, multi-stage processes involved. In the UK, approximately 400,000 tonnes of carpet waste are sent to landfill annually. However, the landfill option is becoming uneconomic due to increasing landfill charges, the reduction in landfill sites and changes in environmental legislation. This project, in collaboration with ECO2 Enterprises, aimed to avoid the landfill option and develop novel structural composites from carpet waste, which could be used to replace timber and PVC posts and rails in equestrian fencing. The development of these composites is a recycling approach that makes use of carpet waste which would otherwise be sent to landfill thereby increasing environmental pollution. The study encompasses the investigation of relevant material and mechanical properties and processing characteristics of the prototype novel waste carpet composites both as a structural beam and an assembled fencing system. Details of the manufacturing processes of the novel waste carpet structural composites are described. Extensive experimental testing has been carried out to determine and compare the mechanical properties of the novel waste carpet structural composites to timber and PVC materials. In addition, experimental load tests and Finite Element (FE) analysis on typical equestrian timber and PVC post and rail fencing structures (benchmark data) were carried out to evaluate their stiffness characteristics against corresponding characteristics for a similar fencing structure comprised of the novel waste carpet structural composites. Design optimisation via geometric changes and FE analyses showed that a 69 % increase in the depth (from 71 to 120 mm) of the novel waste carpet composite posts resulted in a transverse stiffness similar to that of the timber fence. The results obtained from this study has demonstrated that the mechanical properties of the novel structural composites could potentially serve as an alternative/replacement for some common materials used in structural applications, such as timber and PVC fencing

Experimental investigation and Finite Element (FE) analysis of the load-deformation response of PVC fencing structures

Polyvinyl Chloride (PVC) posts and rails are increasingly being used as components of fencing structures because of their good mechanical properties, which include long service life, good chemical resistance, ability to be processed into complex geometry and good aesthetics. However, there has been no experimental or Finite Element (FE) study on the load-deformation response of PVC fencing structures. In addition, currently, no stiffness or structural load-bearing design standards exist for these types of fencing structures. Therefore, this study describes an investigation of the load-deformation response of a two-bay PVC post and rail fencing structure. The fencing structure was loaded experimentally at the top of the centre post and mid-bay points of the top rail. The load-deflection responses recorded during the tests on the fencing structure are presented and shown to be both linear and repeatable (i.e. three load-unload tests were carried out and showed identical responses). Based on the transverse deflection at the maximum applied load, the transverse stiffness of the two-bay PVC fencing structure was calculated to be 12.7–14 N/mm. A comparison of the transverse stiffness of the PVC fence with a similar timber fence showed the timber fence was approximately 262% stiffer than the PVC fence. Furthermore, FE modelling using a commercial software (ANSYS) was carried out on the PVC fencing structure to supplement the experimental work, and good agreement between the FE analyses and experimental test results was demonstrated. Hence, this paper provides initial knowledge and understanding of the linear elastic load-transverse deflection response of PVC fencing structures, and constitutes useful structural design guidance for what may be regarded as the in-service or practical deformation limit. The results of this study also provide useful benchmarks for future composite materials and components for fencing and other structural applications

Experimental and Finite Element (FE) modelling of timber fencing for benchmarking novel composite fencing

Timber is a widely used composite material in structural load-bearing applications because of its good mechanical properties. However, with global forest loss occurring at a high rate, mainly due to the timber trade, and deforestation accounting for about 12% of global CO2 emissions, there is an increasing demand for alternative structural materials with a lower carbon footprint to mitigate climate change. This has led to an increased interest in the use of recycled materials for the development of novel structural composites. This paper describes an investigation of the structural load-deformation behaviour of a typical post and rail type fence fabricated from timber sections – the target application for replacement with alternative novel and lower carbon footprint composite materials/components. The post and rail fence is a two-bay frame comprised of three posts and two rails. Prior to testing the frame, three-point bending tests were carried out on the ungraded timber posts and rails to determine their longitudinal elastic flexural moduli. Tip-loaded cantilever bending tests were also carried out to determine the semi-rigid rotational stiffness of the bolted joint at the base of the posts. Using the geometry, moduli and stiffness results, Finite Element (FE) analyses were carried out using ANSYS software to investigate the structural behaviour of the timber post and rail fence. The FE results were compared with the experimental results and shown to be in good agreement. As there are no structural load-bearing standards for agricultural fencing, the experimental and FE timber fencing results provide useful benchmarks for assessing the structural stiffness of novel recycled composite materials and components presently under development for fencing applications

Carpet recycling:a review of recycled carpets for structural composites

Carpets are multilayer mixtures of different polymers and inorganic fillers that are difficult and costly to reprocess upon disposal. About 400 000 tonnes of carpets are sent to landfill in the UK annually, however, the landfill option is becoming increasingly impractical due to increasing landfill costs and the physical limitations on the number of landfill sites available in the UK. In addition, carpets are non-biodegradable and reduce the availability of landfill for other uses. Hence, this leads to a major drive to increase carpet recycling, which could potentially have a significant positive impact on the environment. This paper gives an overview of the composition of carpets, and the different classifications of carpet waste. In addition, the paper discusses the different end of use options for carpets in the UK. The paper also reviews the different manufacturing processes that utilise carpet waste as raw material in the fabrication of structural composites. The tensile and flexural properties of these composites are presented and discussed. These mechanical properties appear to support the use of carpet waste as potential composite materials for structural load-bearing applications

Evaluation of the structural behaviour of beam-beam connection systems using compressed wood dowels and plates

To support the transition to a bio-based society, it is preferable to substitute metallic fasteners and adhesives in timber construction with an eco-friendly alternative. Recent studies have identified compressed wood dowels and plates as a possible substitute for metallic fasteners in contemporary and mainstream applications. In this study, a spliced beam-beam connection system using compressed wood dowels and slotted in compressed wood plates was examined under four-point bending. The study has considered specimens with compressed wood dowels of two different diameters, 10 mm and 15 mm. The load carrying capacity of connection using compressed wood dowels and plates were compared to connections utilising steel dowels and plates of equivalent capacity. Typical failure modes, moment resistance and bending stiffness of both connection systems are evaluated on the basis of the experimental results.The study had been conducted within the framework of project “Towards Adhesive Free Timber Buildings - AFTB” at the College of Engineering and Informatics, National University of Ireland Galway, Ireland. The AFTB project is funded by Interreg North West Europe via the European Regional Development Fund (ERDF).peer-reviewe