Semi-structural Applications Research Articles

Manufacturing of Sustainable Composite Materials: The Challenge of Flax Fiber and Polypropylene.

The widespread use of synthetic composite materials has raised environmental concerns due to their non-biodegradability and energy-intensive production. This paper explores the potential of natural composites, specifically flax-polypropylene, as a sustainable alternative to traditional composites for semi-structural applications. In fact, the mechanical properties of flax-polypropylene composites are similar to synthetic ones (such as those made with E-glass fibers). However, processing challenges related to fiber-matrix interaction and material degradation necessitate suited process parameters for this sustainable type of material. For this reason, this review highlights the importance of optimizing existing manufacturing processes, such as hot press molding, to better accommodate the specific characteristics of polypropylene-flax composites. By refining the parameters and techniques involved in hot press molding, researchers should overcome current limitations and fully capitalize on its potential to produce composite materials of optimal quality. Therefore, a comprehensive literature assessment was conducted to analyze the properties and processing challenges of flax-polypropylene composites. Key process parameters affecting the material's performance are identified and discussed. By optimizing process parameters for flax-polypropylene composites, it is possible to develop a sustainable and high-performance material with a reduced environmental footprint. Further research is needed to scale up production and explore different applications for this sustainable composite material.

Fatigue Behaviour of High-Performance Green Epoxy Biocomposite Laminates Reinforced by Optimized Long Sisal Fibers.

In recent decades, in order to replace traditional synthetic polymer composites, engineering research has focused on the development of new alternatives such as green biocomposites constituted by an eco-sustainable matrix reinforced by natural fibers. Such innovative biocomposites are divided into two different typologies: random short fiber biocomposites characterized by low mechanical strength, used for non-structural applications such as covering panels, etc., and high-performance biocomposites reinforced by long fibers that can be used for semi-structural and structural applications by replacing traditional materials such as metal (carbon steel and aluminum) or synthetic composites such as fiberglass. The present research work focuses on the high-performance biocomposites reinforced by optimized sisal fibers. In detail, in order to contribute to the extension of their application under fatigue loading, a systematic experimental fatigue test campaign has been accomplished by considering four different lay-up configurations (unidirectional, cross-ply, angle-ply and quasi-isotropic) with volume fraction Vf = 70%. The results analysis found that such laminates exhibit good fatigue performance, with fatigue ratios close to 0.5 for unidirectional and angle-ply (±7.5°) laminates. However, by passing from isotropic to unidirectional lay-up, the fatigue strength increases significantly by about four times; higher increases are revealed in terms of fatigue life. In terms of damage, it has been observed that, thanks to the high quality of the proposed laminates, in any case, the fatigue failure involves the fiber failure, although secondary debonding and delamination can occur, especially in orthotropic and cross-ply lay-up. The comparison with classical synthetic composites and other similar biocomposite has shown that in terms of fatigue ratio, the examined biocomposites exhibit performance comparable with the biocomposites reinforced by the more expensive flax and with common fiberglass. Finally, appropriate models, that can be advantageously used at the design stage, have also been proposed to predict the fatigue behavior of the laminates analyzed.

The health status and life satisfaction of caregivers of elderly with Alzheimer’s

Introduction: The health status of caregivers is associated with satisfaction with life and so in the way of delivering care to the elderly with Alzheimer’s. Objective: To evaluate the health status and life satisfaction of family caregivers of elderly with Alzheimer’s, users of a Reference Center for Care in Alzheimer’s disease in Curitiba, Paraná, Brazil. Materials and methods: This is a cross-sectional quantitative study. The convenience sample consisted of 208 family caregivers and selected during the period December 2009 to February 2010, through the inclusion and exclusion criteria. The study was conducted in the Reference Center. Data were collected through semi-structured interviews and application of the scales: Zarit caregiver burden interview, Subjective Well-Being and Functional Staging. For statistical analysis, we applied the Chi-square, Mann-Whitney and Kruskal-Wallis test, using Epi-Info 6.04. Results were considered statistically significant if their level was less than 5% (p

Evaluation of the durability of cementicious composites reinforced with natural vegetable fibers from the Amazon

The study of the use of plant fibers as reinforcement for cementitious composites has become increasingly common in recent years, thanks to the advancement of technologies and the demand for innovative and sustainable materials. In the Amazon, this resource is widely found and used for different applications, and the present work is interested in evaluating the use of these fibers as structural reinforcement of cement slabs. The mechanical and durability properties of cementitious composites reinforced with a content of 5% vegetable fibers from jute (Corchorus capsularis) and mallow (Urena lobata L.) were investigated. The objective was to evaluate the quality and performance of these fibers as reinforcement of cementitious plates for a possible use of these composites in Civil Construction. Spreading and thermogravimetry tests were carried out on the matrix and tensile tests in flexion at 4 points on the composites. The results obtained indicated that the fibers provided an increase in the flexural strength and toughness of the composites, as well as the use of metakaolinite as a pozzolanic material, contributed to increasing the durability of these composites, indicating a great possibility of using them in structural and semi-structural applications.

From industrial jute fibre spinning wastes to biofibre-reinforced plastics

A huge amount of jute caddies is generated as a by-product in jute spinning industries solid waste is generally disposed of either in landfilling or burned as boiler fuel triggers environmental pollution. Owing to their higher fibre length and moderate single fibre tensile properties, the waste fibres in jute caddies can be transformed into dry fibre preform which in turn could be used in the production of composites. In this work, jute caddies were cleaned by compressed air before being pressed into dry fibre preform in order to increase the fibre packing capacity in the composites. Thermoplastic composites were manufactured by combining 40 % fibre with 60 % polypropylene (PP) matrix (by weight) using a hot press machine. The effect of chemical treatments (alkali and benzoyl chloride) on jute fibre was characterized by FTIR, TGA, and SEM. Tensile and flexural properties were evaluated to see the performance of composites. The findings of this study demonstrated that this newly developed dry short fibre jute caddies-based thermoplastic composites possess improved flexural properties by ⁓42.75 % if they are chemically modified with binders. Polyvinyl alcohol (PVA) can react with the functional groups of jute fibre to form strong hydrogen bonding that may result in enhanced bending properties of the composites. Therefore, the proposed composite made from jute caddies waste could be ideally used in semi-structural composite applications leading to a sustainable approach to disposing of jute industry solid waste through a circular economy.

Effect of Plant Oil Derived Bio-Resin and Curing Temperature on Static and Dynamic Mechanical Properties of Epoxy Network

The depletion of petrochemical resources and greater worldwide environmental consciousness has led to a growing interest in polymers made from renewable resources during the last two decades. Hence, this work has attempted to reduce the dependence on petroleum-based epoxy by partially replacing it with epoxidized castor oil (ECO). The ECO was blended with epoxy at 10, 20, and 30% and cured with amine hardener. The effect of bio-resin on tensile, flexural, impact strength and dynamic mechanical properties were investigated. Further, the result of post-curing temperature on static and dynamic properties was examined. It was found that the addition of ECO up to 30% increased the impact strength. The 20% ECO sample showed balanced stiffness to toughness property and could be considered for semi-structural composite applications. The post-curing of samples at 150 °C showed better mechanical and dynamic properties except for impact strength.

Social indicators and other factors associated with chronic non-communicable diseases in rural quilombolas in the north of Minas Gerais

The aim of this article is to investigate factors associated with self-reported non-communicable chronic diseases (NCDs) in quilombolas from rural communities in the northern region of Minas Gerais, Brazil. It is a cross-sectional study, conducted in 2019 through semi-structured interviews and questionnaire application on 1110 individuals. A log-linear Poisson model was used. Twenty-seven percent of the sample had at least one of the listed NCDs. The highest prevalence was detected in females (PR: 1.31; 95%CI: 1.17-1.48), aged over 60 years (PR: 2.19; 95%CI: 1.77-2.70). There was an increased prevalence of NCDs in people who reported having suffered prejudice while seeking healthcare (PR: 1.17; 95%CI: 1.04-1.31) and who had their last healthcare service more than 12 months ago (PR: 1.22; 95%CI: 1.05-,1.42). This reality demonstrates that, despite advances in specific public policies aimed at these groups, prejudice, difficulty in accessing healthcare, and affirmative action policies still persist.

Mechanical and thermal properties of recycled polypropylene bamboo fibre-reinforced composites

<span lang="EN-US">In this article, a kind of green composite was prepared from recycled polypropylene (r-PP) which was further reinforced with various loadings of chemically modified bamboo fibres. Effects of bamboo fibre loading on the mechanical and thermal properties of r-PP/bamboo composites were studied. Those properties were characterized by tensile testing, impact testing, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). Standardized test specimens with 0%, 10%, 20%, and 30% mass fractions of bamboo fibre were obtained by an extrusion process which was then finalized on injection molding. The experiment revealed the tensile strength and strain of the composite become greater with the increase of bamboo fraction in the ultimate value of 20% mass fraction. The composite with 10% bamboo fibre loading recorded the highest value of impact strength. Meanwhile, it was evident that the presence of bamboo fibre decreased the thermal stability of recycled polypropylene materials. Therefore, this composite material may find good potential for semi-structural loading applications in relatively low-exposure working.</span>

Characterization of a new natural novel lignocellulose fiber resource from the stem of Cyperus platystylis R.Br.

This study deals with the characterization of a natural fiber which is extracted from the stem of an unexplored plant of Cyperus platystylis R.Br. (CPS) with an aim to establish it as a potent alternative fiber for the plant fiber-based industries. CPS fiber has been investigated for its physical, chemical, thermal, mechanical, and morphological characteristics. The presence of different functional groups in CPS fiber i.e., cellulose, hemicellulose, and lignin which was ensured by Fourier Transformed Infrared (FTIR) Spectrophotometer analysis. X-ray diffraction and chemical constituent analysis revealed high cellulose content and crystallinity i.e., 66.1% and 41.12% respectively, which is comparatively moderate in the case of CPS fiber. Scherrer's equation has been used to determine crystallite size i.e., 2.28 nm. The mean length and diameter of the CPS fiber were 382.0 and 23.36 μm, respectively. The maximum tensile strength was obtained at 657 ± 58.8 MPa for 50 mm fiber and young’s modulus 88.76 ± 30.42 MPa for 50 mm fiber. The required energy to break has been recorded at 346.16 J. Thermal analysis revealed that CPS fibers have thermal stability up to 279 °C. The unique Cyperus platystylis stem fibers could therefore be a suitable reinforcement material for the bio-composites used in semi-structural applications since they have higher functional qualities.

Re-use of jute fiber hybrid nonwoven breather within laminated composite applications: A case study

Jute/polyester hybrid nonwoven mats were developed as an alternative to the conventional nylon or polyester breather to reduce the use of synthetic polymers and associated waste generated during composite manufacturing. However, end-of-life breathers still face the challenge of waste management. In this study, a circular economy strategy for multiple applications of waste hybrid nonwoven breathers was thus proposed to study their recycling possibilities. Hybrid nonwoven breathers were first used to facilitate the autoclave forming of carbon fiber-reinforced plastics, and non-destructive and mechanical tests were performed to determine the quality. The used breathers were then recycled and reused in three ways: directly as reinforcing material and in hybrid combinations with glass fibers and ramie fibers for the production of new composites. Results of quality checks show that the hybrid nonwoven breather is a viable alternative to commercial breathers. The thermal, mechanical, and damping properties of the composites incorporating reused material were investigated. The hybrid nonwoven breather/Glass fiber composites show superior thermal and mechanical properties as well as improved damping properties. The hybrid nonwoven breather/Ramie fiber composites have the advantages of low density and high loss factor reaching up to 0.1572. The product of specific modulus and loss factor was then used as the figure of merit to estimate the structural damping properties of the composites. Both glass fiber and ramie fiber hybrid composites presented a higher figure of merit with 0.86 and 0.83 GPa/(g/cm3), respectively. Therefore, hybrid nonwoven breathers can be adapted to replace synthetic materials in semi-structural applications.

Investigation of the Mechanical Properties of Sandwich Composite Panels Made with Recyclates and Flax Fiber/Bio-Based Epoxy Processed by Liquid Composite Molding

Despite significant advancements in bio-based natural-fiber-reinforced composites, the recyclability/reprocessing of thermoset composites remains a persistent challenge that needs to be addressed. In the present study, an effort is made to provide a justification for the recyclability/reprocessing assessment of sandwich composite panels made with ‘recyclate’ (i.e., recycled flax/bio-based epoxy composite) cores and (flax/bio-based epoxy) skins produced by liquid composite molding. Resin transfer molding and vacuum-assisted resin infusion processes were used to investigate the influence of production processes on mechanical properties. Two different recyclate sizes—4 mm and 10 mm—were used to fabricate sandwich composite panels to study the effect of size on the mechanical properties of the panels. This study aims to compare the qualities of sandwich panels to those of virgin composite panels in terms of their physical (density) and mechanical properties (tensile and flexural). Additionally, the recyclate packing was verified by employing digital microscopy. The results illustrated that the sandwich panels made with the 4 mm recyclates exhibited better mechanical properties compared to those made with the 10 mm recyclates. In comparison with virgin composite panels, the sandwich composite panels made of flax fiber and (flax/epoxy) recyclate exhibited significantly higher flexural moduli, which was attributed to their moments of inertia. This article emphasizes recycling/reprocessing and demonstrates an effective closed-loop approach. Thus, by preserving the structural integrity of recyclates, sandwich panels could be advantageous for semi-structural applications.

The evaluation of the mechanical properties of glass, kenaf, and honeycomb fiber-reinforced composite

Abstract The development of hybrid composite materials using honeycomb structure, typically a lightweight material, is commonly used in aircraft structures. However, the use of honeycomb with natural or synthetic composite remains unexplored in the literature. Therefore, this study aims to partially replace synthetic fiber, woven glass with a natural fiber of woven kenaf and honeycomb core. An experimental analysis investigated the mechanical strength of three different compositions using glass, kenaf, and honeycomb materials for structural application purposes. The properties of the sample were evaluated through the tensile, flexural, and impact strength, and the morphological damage was observed using scanning electron microscopy. The results showed that the composition of GKGKG laminate composite is the highest in tensile strength (147.64 MPa) and modulus (3.9 GPa), while the GKHKG composite was good in flexural strength (219.03 MPa) and modulus (11.47 GPa). In terms of impact properties, there was a slight difference in energy level (20–30 J) by GKGKG and GKHKG, showing the optimal hybrid configuration of composite for the newly developed material. In conclusion, the application of the new hybrid of GKHKG composite is promising in semi-structural and structural light-weight applications.

Assessment of the Potential of Waste Copper Chromium and Arsenic (CCA)-Treated Timber Fibre Reinforced Polypropylene Composites for Construction

This paper investigates the potential of recycling waste copper chromium and arsenic (CCA)-treated timber for use as a reinforcement material in wood–plastic composites (WPCs) produced for use in construction, including an assessment of mechanical properties and the leaching of heavy metals. Wood flour was obtained through mechanical grinding, and fibres were obtained through alkaline digestion followed by bleaching. Composites produced with 40 wt.% bleached fibres showed increased tensile strength from 18.5 MPa for the polypropylene used as the matrix to 27.6 MPa. Likewise, the Young’s modulus was increased from 0.84 to 2.33 GPa. The treatment of fibres was found to reduce arsenic concentration by up to 99.9%. Furthermore, the arsenic in the leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing CCA-treated wood flour composites to bleached fibre composites. The composites’ material properties indicate that the use of end-of-life CCA-treated timber could be used to produce a composite material that could be used in New Zealand’s building sector to meet the requirements of semi-structural applications.

Effect of graphite fillers on woven bamboo fiber-reinforced epoxy hybrid composites for semistructural applications: fabrication and characterization

Effect of graphite fillers on woven bamboo fiber-reinforced epoxy hybrid composites for semistructural applications: fabrication and characterization

Mechanical Performance of Flax Fiber Composites with Waste Glass Fibers as a Core Structure.

This work sheds light on the first steps towards using glass fiber waste for semi-structural applications. This work aims to improve the properties of random flax fiber composites by incorporating waste glass fibers (WGF) obtained from the fiber production line. The waste glass fibers were incorporated as a core structure between the flax layers to form a hybrid composite. Two routes of manufacturing viz. vacuum infusion and autoclave were used to identify the optimum route to incorporate the WGF in flax fiber composites. The quality of composites was investigated in terms of residual void content and thickness uniformity. Residual void content was identified to be directly proportional to the WGF content in the composites. With the increase in WGF content, the flexural and impact properties were increased by 47% and 117%, respectively, indicating a positive hybridization effect. Furthermore, a global warming potential indicator was identified to be small, indicating the eco-friendliness of these composites.

Development of functional gradient multi-material composites using Poly Lactic Acid and walnut shell reinforced Poly Lactic Acid filaments by fused filament fabrication technology

In construction and architectural industries, multi-material additive manufacturing is gaining more interest because of obtaining the combined material properties in a single additive process by multiple materials. The present work concentrates on developing functionally gradient multi-material composite using Poly Lactic Acid (PLA), and novel extruded walnut shell particle reinforced Poly Lactic Acid (WPLA) by Fused Filament Fabrication technology. This work followed single and multi-gradient material deposition approaches, and their mechanical, thermal, and tribological properties were compared with standard 3D printed PLA and walnut shell-reinforced PLA composite. Among the 3D printed functional graded multi-materials, the composites with single-gradient PW configuration exhibits better compressive and D shore hardness value of 63.68 MPa and 76.2 compared with the neat PLA composite. The results show that considering the tensile and flexural samples the single gradient PLA samples shows better values when compared with all other multi gradient prepared composites. The highest heat deflection temperature of 56 °C was observed on the WPLA composite and for gradient materials PW composite which is PLA (50%) and walnut shell reinforced PLA (50%) sample exhibits the maximum heat deflection temperature of 54.4 °C. Furthermore, considering the tribological and thermal properties, the multi-gradient composite of WPW configured with PLA of 40% as inner core exhibits the lowest thermal conductivity of 0.087 W/mK and a specific wear rate of 1.631 × 10−6 mm3/Nm when compared with neat PLA composite. Therefore, among the novel functional graded multi-material, the sample PW with PLA (50%) and walnut shell reinforced PLA (50%) composite will be more suitable for semi-structural applications, and the composite with WPW designation (PLA of 40% as inner core) will suit the high wear-resistant and constructional building panel material for thermal proofing applications.

Natural Fiber Composite with α-Resorcylic Acid Based Bio-Epoxy Matrix

Comprised of biopolymer matrix and/or bio-fiber reinforcement, bio-composites are environmentally friendly, lightweight, sustainable, and normally biodegradable. Their unique characteristics have enabled them an alternative material for replacing conventional metallic materials and other composites such as glass fiber reinforced composites. This work is focused on developing and characterizing a novel bio-composite that combines a natural fiber reinforcement with a unique α-resorcylic acid-based epoxy bio-resin. Kenaf fiber mats are impregnated with the epoxy bio-resin and compression molded into a bio-composite. Thermal properties of the bio-composite are characterized with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Indentation testing in a micro-scale is conducted on the bio-resin matrix and the fiber cross sections. The elastic modulus of the fiber transverse cross section is found to be 7.8 GPa, higher than that of the bio-epoxy resin, 4.3 GPa. Furthermore, the tension performance of the bio-composite is evaluated and compared with that of a conventional epoxy composite with similar kenaf fiber percentage. The bio-epoxy composite has comparable tensile modulus and strength with the conventional epoxy composite. Finally, the fracture surface of the tested samples is characterized using scanning electron microscopy (SEM) and different failure modes, such as fiber fracture, fiber pullout, fiber defibrillation, and matrix fracture, are observed. It is concluded that this novel bio-composite has a great potential to replace conventional epoxy resin based composite for semi-structural applications.

Evaluation of Night Eating Syndrome within the Context of Object Relations through Projective Tests

Psikanalitik kurama göre erken dönem nesne ilişkilerinin niteliği ruhsallığın gelişiminde büyük önem taşımaktadır. Psikanalitik çalışmalarda, çocukluk dönemindeki engellenmelerin, duygusal ihmalin ve ayrılma-bireyleşme süreciyle ilgili sorunların yeme bozukluğunun gelişiminde etkili olduğu görüşü hâkimdir. Bununla birlikte psikanalitik teoriler, yemek yeme, rüya görme ve ruhsal süreçler arasındaki ilişkiyi daima vurgulamıştır. Buradan yola çıkılarak bu çalışmada, erken dönem nesne ilişkilerindeki sorunsalların yeme bozukluğuna etkisi incelenmiştir. Donald W. Winnicott ve Wilfred R. Bion’un kuramları temel alınarak, uyku sorununun da eşlik ettiği gece yeme sendromunun ele alınması çalışmanın asıl odak noktasıdır. Bu bağlamda projektif testler olan Rorschach ve Tematik Algı Testi aracılığıyla gece yeme sendromu olan obez bir kadın danışanın ruhsal süreçleri incelenmiştir. Psikanalitik yönelimli klinik görüşmelerden sonra sırasıyla Rorschach ve Tematik Algı Testi uygulanmıştır. Fransız Okulu'nun içerik analizi yöntemine bağlı kalınarak psikanalitik yönelimli yarı yapılandırılmış klinik görüşmeler ve projektif test bulguları değerlendirilmiştir. Ayrıca danışanın ruhsal süreçleri ile rüya görememe arasındaki ilişki psikanalitik kuram temel alınarak yorumlanmıştır.

Review on natural plant fibres and their hybrid composites for structural applications: Recent trends and future perspectives

Sustainability and environmental protection have given rise to the use of renewable and biobased materials in several application areas. Fibre reinforced composites are currently gaining a high market value in both structural and semi-structural applications. Making these materials environmentally friendly, renewable and lighter will protect the environment and increase resource use efficiency. Opposed to synthetic fibres such as carbon and glass, natural plant fibres are less expensive, lighter, degradable, easy to produce, non-toxic and environmentally friendly. However, natural plant fibres are inferior to their synthetic counterparts in both mechanical performance and tolerance to harsh environmental conditions. One method of compensating for these disadvantages is to combine natural and synthetic fibres in a single matrix forming a hybrid composite where the disadvantages of one are compensated by the other. In this way, sustainability and cost minimisation are achieved with acceptable mechanical and physical responses. However, successful implementation and advancement in the development of natural plant fibre reinforced polymer (FRP) hybrid composites require the development of workable conceptual design, suitable manufacturing techniques and understanding of the strengthening mechanisms. The main objectives of this review are to critically review the current state of knowledge in the development of natural FRP hybrid composites, outlining their properties and enhancing them while reducing environmental impact of the product through the hybridisation approach.

High performance short jute fibre preforms for thermoset composite applications

Jute fibre reinforced composites (JFRCs) are facing challenges to composite manufacturers due to the high cost of dry fibre preforming and inferior fibre performance compared to other commonly used natural plant fibres such as flax, sisal, hemp, and kenaf. Therefore, long fibre architecture jute fibre preforms often cannot fulfil the performance requirement of the composites. Using shorter length of jute fibres and then transform them into dry preforming sheet can ideally be used in manufacturing intricate composite products with low processing cost and high fibre reinforcing effect. On the other hand, short jute fibres suffer with extremely low fibre content and hence, they are difficult to use in making complex shape composite structures. In this work, a highly individualised and chemically treated (alkali) short jute fibre preforms with increased fibre contents were developed with the help of compression moulding. Composites were fabricated by impregnating the dry fibre preforms with epoxy resin by wet layup technique and cured in the hot press. These composites were found to have significantly higher mechanical properties when compared to traditional randomly orientated short jute fibre composites; showing the tensile strength ⁓93 MPa and flexural strength ⁓190 MPa for these composites, are the highest than any other natural short fibre composites reported so far in the literature. It was found that the extent of the improvement of mechanical properties of these composites, is related with the content of fibre in the composites, chemical modification of fibre ensuring higher bonding between the fibre and matrix. This work highlights new insights into high performance short jute fibres. If short jute fibres can be transformed into highly packed dry fibre preform, then it can be used in many semi-structural and structural composite applications.