Tensile Strength Of Composites Research Articles

Strengthening the fiber-cement matrix interface by introducing functional groups on fiber surface

Polypropylene (PP) fiber is widely used for reinforcing cement matrix to improve its cracking resistance, but the poor interaction between two materials caused localized cracks along the fiber thus adverse effect on the fiber reinforced composites. Thus, novel methods for strengthening the fiber-cement matrix interface were proposed in this study. Amidoxime and amine functional groups were successfully grafted onto PP fiber surface through a two-step chelating procedure. XPS, FTIR, iGC-SEA and TG were employed to characterize the modified fibers, and the results verified that the surface treatment significantly improved the surface roughness, specific surface area, hydrophily and thermostability of PP fiber. Moreover, single fiber pullout, uniaxial tensile and three-point bending were conducted to assess the efficiency of surface treatment in enhancing the bonding between fiber and cement matrix, as well as the tensile and flexural strength of composites incorporating PP fibers. The bonding strength was increased by 84.15%–90.08 % and the flexural strength at 28 days was increased by 23.7%–26.4 %. The change in PP fiber surface led to densified fiber-cement matrix ITZ, enhanced chemical bonding and mechanical interlocking thus stronger interaction between fiber and cement matrix. Overall, the proposed surface treatment method is of great potential to be used in producing high performance concrete due to its easy of application and high efficiency.

Effect of Layers on Delamination and Tensile Strength of Woven Fiber Composites with Polyester Matrix

A composite is a combination of 2 or more different materials. The composite joining process can use adhesives or mechanically by making holes. During the process of making holes in the composite, it can cause delamination in the composite. Delamination and layer thickness greatly influence the strength of hollow composite joints. This research aims to determine the effect of delamination factors and the number of layers on the tensile strength value of the composite. The materials used in this research are polyester resin and woven glass fiber. The method used is vacuum bagging with variations in the number of layers, namely 3 layers, 4 layers, 5 layers, and 6 layers. Tensile testing refers to ASTM D638 standards. Specimens that have been cut according to standards will then be perforated in the center with a hole diameter of 4 mm using a milling machine. The highest tensile strength value was obtained in the 6-layer variation of 237.448 MPa and the lowest value was obtained in the 3-layer variation of 186.221 MPa. The delamination value greatly influences the tensile strength of the composite, where the more layers, the delamination value will decrease and increase the tensile strength of the composite.

Mechanical properties and functionalization of Graphene oxide‐Thermoplastic polyurethane polymer composites regulated by internal microstructure: From disorder arrangement to nacre‐like laminated structure

AbstractGraphene oxide (GO) is a two‐dimensional material known for its exceptional mechanical, chemical and electrical characteristics. Here, the mechanical properties and functionalization of GO reinforced thermoplastic polyurethane (TPU) polymer composites with GO content ranging from low to high were investigated. It shows that the GO can mix with TPU in any proportion. The microstructure changed from disorder arrangement to a regular nacre‐like staggered structure, accompanied by different kinds of internal defects as the content increases, resulting in multiple peaks in the tensile properties of composite materials. The tensile strength of composites containing 80 wt% GO is 194% higher than that of pure TPU. This result is closely related to the changes in internal microstructure arrangement, the corresponding stress distribution and the transformation of damage mechanisms. Simultaneously, it shows that the composites exhibited shape memory function at low GO content of 1.5 wt% with about 100% shape recovery at 70°C, and electrical conductivity and deicing function at high GO content of 80 wt% after chemical reduction, which can reach a temperature of 107°C at 10 V AC. These findings will help to comprehensively understand the structural and functional integration design of GO reinforced polymer composites.Highlights Mechanical properties and functionalization of GO/TPU composites were studied. Increased GO causes the arrangement to change from disorder to a nacre‐like structure. Stress distribution and damage mechanisms transformed as the GO content changed. The GO/TPU composites exhibited shape memory and deicing function.

Versatile biochar for wood‐plastic composites: Improving mechanical properties, dimensional and thermal stability

AbstractIn this study, three types of biochar including wood biochar (WB), rice husk biochar (RHB), and bamboo biochar (BB) were used as fillers to mix with wood flour (WF), polypropylene (PP), and maleic anhydride polypropylene (MAPP) to prepare wood polymer biochar composites (WPBC). The influences of biochar types and addition amounts (10 wt%, 20 wt%, 30 wt%, and 40 wt%) on the mechanical properties, dimension stability, and thermal stability of WPBC were investigated. The results showed that the water absorption rate and thickness swelling rate of WPBC were lower than control group due to the hydrophobic nature of the biochar. Additionally, the presence of biochar was beneficial to the interfacial bonding and stress transmission in composites, resulting in better mechanical properties. Composites containing 20 wt% RHB showed the highest flexural modulus among all, which increased by 11.27% compared to control group. Adding WB also enhanced the tensile and impact strength of composites at a loading level of 10 wt%, with the value of 39.10 MPa and 15.55 KJ/m2, respectively. The thermal stability and flame retardancy of WPBC was improved due to the presence of SiO2 in biochar, which could hinder heat transmission and thermal degradation during combustion process. Concurrently, the rate of heat release and smoke generation in WPBC also decreased significantly. The oxygen limiting index (LOI) of composites with 20 wt% RHB was as high as 26.64%, increasing by 30.14% compared to control group. The results suggested that biochar was a promising alternative to commercial additives for the cost‐effective production of composites.Highlights Effects of biochar loading level and type were compared. Enhanced the mechanical properties by optimizing interfacial bonding. Biochar improved the dimensional and thermal stability. Biochar is a versatile and cost‐effective additive.

Joint shear strength prediction for fiber reinforced concrete beam-to-column connections

Beam-to-column joints experience substantial shear forces and deformations, playing a pivotal role in maintaining the overall stability and integrity of moment-resisting frames under earthquake loading. If fiber reinforced concrete is used instead of reinforced concrete, beam flexural failure can be achieved, which leads to a ductile behavior and increased energy dissipation capacity, when compared to joint shear failure. To ensure a ductile failure mode, accurate prediction of the joint shear strength is essential. However, there are only a limited number of analytical studies on predicting the shear strength of fiber reinforced concrete joints, most of which are only applicable to steel fibers. In this study, a comprehensive database of prior experiments conducted on fiber reinforced concrete beam-to-column connection subassemblies is compiled. Based on Pearson Correlation Analyses, the factors influencing the seismic response are determined to be the composite tensile cracking strength, axial load on the column, aspect ratios of member dimensions, and specific fiber properties such as aspect ratio and volume fraction. A joint shear strength prediction equation is then developed utilizing statistical nonlinear regression method. Validation against experimental data confirms that the proposed equation provides conservative estimates of joint shear strength and can be utilized for composites with any fiber type, even hybrid fibers; in contrast to existing equations which often lead to overestimation of strength and restricted to a specific fiber type. Moreover, the proposed equation provides engineers a practical tool to assess the seismic behavior of such connections, which has not been addressed by current structural design codes yet. The improved accuracy of the proposed equation, demonstrated by the lowest mean absolute error and coefficient of variation and the highest coefficient of correlation, positions it as a promising candidate for integration into structural design codes.

Fabrication of nano filler doped PVA/starch biodegradable composites with enhanced thermal conduction, water barrier and antimicrobial performance for food industry

In this work there was investigated the synergistic effect of the nanomaterials-the Montmorillonite (MMT) and the vanadium pentoxide (V2O5) on the polyvinyl alcohol (PVA)/starch composite. The composite films were prepared by the solvent casting method. The characterization of the composites showed that the addition of the MMT and the V2O5 to PVA/starch composite decreased the water solubility and water absorption capacity of the film. Both of the reinforcement materials enriched values of thermal conductivity and thermal stability of the composite. The TG/DTA and universal testing machine (UTM) analysis exhibited that MMT and V2O5 augmented the thermal robustness and tensile strength of composites and decreased the strain to break. It was also observed that greater MMT concentration accelerates mechanical strength deterioration of the film owing to agglomeration. The scanning electron microscopy (SEM) analysis reflected great change in the surface morphology of the films in the presence and absence of MMT and V2O5. This was due to the interaction amid constituents of the composite. The chemical interaction between the PVA, Starch, MMT and the V2O5 was also established via Fourier-transform infrared spectroscopy (FTIR) analysis, which revealed fluctuations in the absorbance position and intensity of the PVA/Starch. Antimicrobial activities against seven different cultures of bacteria (both-gram positive and -negative) and one fungus (Candida albicans), exposed that antimicrobial performance of the PVA amplified upon addition of the starch, MMT and V2O5, making these composites prospective candidates for the biodegradable packaging materials.

Finite Element Analysis of Polymeric Matrix Composites with Sisal Fiber Reinforcement

Recently, there has been a growing interest in investigating the mechanical properties of plant fibers, particularly in developing nations. This surge is primarily fueled by the escalating environmental concerns, which are becoming more evident and alarming. Against this backdrop, various sectors of materials engineering are actively seeking alternatives to mitigate the environmental impact across the entire lifecycle of products - from production to use and disposal. This study aims to conduct a computational analysis to examine the influence of fiber quantity on the tensile strength of composites containing sisal fibers. It compares the findings with existing experimental test results and demonstrates the outcomes using the finite element method. The research reveals that greater tensile strength in the composites is achieved with higher volumetric fractions of sisal fiber, as observed in both experimental and computational analyses. These results underscore a strong correlation between finite element analysis and experimental tests documented in the literature.

Valorization of purified agricultural brown eggshell by-product as filler in bio-epoxy composites

This study presents tensile, flexural and water absorption properties of composites made from bio-epoxy resin containing brown eggshell (with membrane), purified brown eggshell (without membrane) and mineral limestone at three filler levels of 5, 10 and 20 wt%. Composites were made by an open silicone mold casting method. Fourier transform infrared (FTIR) spectroscopy was used to demonstrate removal of the membrane. Inductively coupled plasma mass spectrometry (ICP-MS) indicated brown eggshells without membrane had a higher calcium carbonate content suggesting the purification technique worked well. Although composite tensile strengths and flexural strengths were lower than the pure bio-epoxy, the composites containing brown eggshells (with membrane) had slightly better strengths than composites containing purified brown eggshells (without membrane) and mineral limestone for the same particle size of 32 µm. The organic membrane contains proteins on the surface of the eggshells which may be beneficial for chemical bonding to occur with the bio-epoxy resin. Filler contents of 5–10 wt% were acceptable for tensile and flexural strengths. Scanning electron microscopy (SEM) provided visual observations of the fractured surfaces where an increase in surface roughness was related to an increase in filler loading, implying changes occurred within the composite materials. Brown eggshells can be exploited as a waste management opportunity for use as a filler in bio-epoxy composites.

Preparation and mechanical properties of biomimetic mineralization collagen for dopamine-polyacrylamide-induced small intestinal submucosa

Bone-like lamellar hydroxyapatite(HAP) was successfully synthesized by biomimetic mineralization on small intestinal submucosa(SIS) induced by dopamine(DA)-polyacrylamide (PAM).HAP was uniformly grown by the method of “collagen fiber active site-regulated ion nucleation growth” on SIS film by a lab-built ion diffusion experimental system. The hydrophilic angles before and after SIS modification were 85.3 ± 1.3° and 35.7 ± 1.2°, respectively. The morphology of grow HAP crystals was similar to that of nature bone. Then, DA-PAM@SIS/HAP material was prepared to mimic bone components and basic unit microstructure of natural bones. The tensile strength of composites was about 12 MPa, which was 2.4 times higher than that of the unmineralized films. The mineralized film should be expectedto be applied in the field of bone remodeling and bone tissue engineering.

Recyclable flexible materials with MOF-derived nanospheres for electromagnetic wave absorption

Self−healing and recyclable characteristics were beneficial for wave−absorbing materials to extend the service life, reduce the cost, stability and electromagnetic pollution in the practical application. The flexible composites with recyclable and electromagnetic wave (EMW) absorption were fabricated by employing MOF derived carbon nanoparticles (ZnCoNC) and polymers with dynamic boron ester bonds. The benzene structure of eugenol derived polybenzoxazine structure can stick on the surface of the MOF−derived nanoparticles by π−π interaction, which benefits the recyclable and mechanical properties. With the synergistic effect of dynamic boron ester bond and π−π interaction, the tensile strength of composites with 15 wt% ZnCoNC reached 7.88 MPa after 3 times recycling, it remained 88 % compared to origin composites. The minimum RL obtained is −36.6 dB at a thickness of 2 mm, it can approximately maintain the same effect in EMW absorption performance after recycling. This work was expected to broaden the EMW absorption application field and extend the service life of materials.

Reducing stress concentrations in static and fatigue tensile tests on unidirectional composite materials: A review

The longitudinal tensile strength is an important basic property of unidirectional (UD) composites or plies that often governs failure in multidirectional laminates. The standard tensile testing methods almost always result in sample failure near the grip. Finite element analyses revealed the presence of multiaxial stress concentrations, including longitudinal, transverse, and shear stresses in the tabbed section of the standards’ recommended design. There are still unknowns and uncertainties about the causes of these stress concentrations and ways to eliminate them. A major challenge is obtaining acceptable failure within the gauge section and yielding the highest tensile strength of UD composites. This paper reviews the different methods for performing quasi-static and fatigue tensile tests on UD composites. The primary sources of stress concentrations and the parameters that affect them are reviewed using the available experimental and modeling investigations. We survey the effects of the different specimen and end tab designs as well as test setups on quasi-static and fatigue loading. Specific proposals are made for each of the discussed parameters for more reliable results.

The mechanical and heat aging properties of natural rubber latex modified by carbon nanodots

AbstractDue to their unique structure and tuneable physical, optical, and electronic properties, carbon nanodots (CDs) become one of the perfect nano‐materials in many fields such as biomarkers, optical sensing, and catalysis. The application of CDs in modifying polymers has also attracted much interest. In this work, a simple process was employed for introducing CDs to modify natural rubber (NR) latex. Glucose was applied as the precursor to prepare CDs by hydrothermal method, subsequently, the crude CDs were directly added to NR latex at a very lower concentration to prepare NR/CDs films. The results of mechanical properties demonstrate that the 500% modulus, tensile and tear strength of NR composites are significantly improved by the introduction of CDs. When the theoretical loading of CDs is 2 phr, the tensile strength and tear strength of NR/CDs film reach to 33.1 MPa and 56.4 N/mm, and improve 17.8% and 29.4% than NR without CDs respectively. It is particularly noteworthy that when the amount of CDs is higher than 1.5 phr, the heat‐aging resistance of NR has been enhanced. It has been confirmed by crosslink density, dynamic mechanical analysis, and Fourier Transform Infrared Spectrometer analysis that CDs have a certain confinement effect on the mobility of rubber molecular segments through physical adsorption and chemical crosslinking. The Tube model theory was employed to calculate parameters of the network structure of NR/CDs films (based on the stress–strain curves), the results indicate that CDs give NR film more chemical crosslinking points and less entanglement network.Highlights The crude carbon nanodots are used to modify NR latex at a lower concentration The mechanical properties of NR films are obliviously improved The heat‐aging resistance of NR has been enhanced by adding carbon nanodots higher than 1.5 phr The Tube model theory are employed to analysis the crosslink network CDs give NR film more chemical crosslinking points and less entanglement network

Effect of thermal cycling on open‐hole tensile strength of sustainable composites: An experimental investigation

AbstractSustainable composites are presently employed in applications where structural demands are minimal. Basalt fiber reinforced PLA (BFPLA) and polybutylene succinate (BFPBS) composites, incorporates bio‐based materials, offer the potential to reduce non‐renewable resource consumption and improve end‐of‐life disposal practices. Given the significance of thermal aging in semi‐structural applications and the necessity for open holes (notches) for installation and assembly, little is known about how thermal cycling (TC) affects the open‐hole strength of sustainable composites. This experimental work establishes a quantitative relationship between open‐hole strength and TC, taking into account varying abrasive waterjet pressures, and explores the impacts of thermal aging on the notch sensitivity, thermal, mechanical, and physical properties. BFPBS displayed better unnotched tensile strength and notched strength than pre‐thermal BFPLA specimens after they have been subjected to 100 TC ranging from −20 to 55°C. Thermal aging significantly influenced notch sensitivity, emphasizing its consideration in evaluating notch performance. This research provides a significant contribution to our current understanding of the effects of thermal aging on sustainable composites, enabling their informed application in a variety of industries and the results highlight their promising potential, in particular BFPBS, as strong alternative for medium load applications.Highlights Evaluated thermal aging effects on basalt fiber (BF) composites, revealing improved properties in BF/PBS composites after thermal cycles. Established quantitative link between mechanical behavior and thermal cycling using varying waterjet pressure values. Basalt fibers enhanced crystallinity and thermal stability of PLA and PBS polymers, showing promise for sustainable composites. Notch sensitivity impacted by thermal aging, underlining the importance of considering these effects in notch performance evaluation. BF/PBS composites demonstrated potential as robust alternatives for indoor products and sports equipment.

Influence of single and multi-walled CNT on the mechanical performance of glass fiber hybrid polymer composites

The structural materials of the twenty-first century have evolved with the inclusion of nano scale materials which can be utilized to improve the performances of the materials significantly. One of such widely adopted nano material is carbon nano tubes (CNTs) which can further be categorized as single walled and multi walled CNTs (SWCNT and MWCNT). Similarly, glass fiber reinforced polymer composites (GFRP) are a promising material for a wide range of applications, including automotive parts, aircraft components, boat hulls, wind turbine blades, and construction materials. Research by material designers continues to explore new avenues for further improving properties of GFRP composites by using nanomaterials and other advanced materials. In the present work, a new class of polymeric composite material is developed with different filler loading (i.e., 1% to 5% with a step of 1%) of single and multi-walled CNT with glass fiber as reinforcement phase. The tensile and flexural strengths of the hybrid nano composites were determined. The incorporation of CNT with glass fiber epoxy composites strengthened the matrix phase thereby enhancing the tensile and flexural strengths of the developed composites. Further, the obtained experimental findings outlined that the multi walled carbon nano tube filler provided optimum tensile and flexural strength among developed composites due to the better interphase bonding with multi walled structure of MWCNT filler structure. Further, the microscopic analysis of the fractured surfaces was conducted to analyze different mechanisms leading to failure of composite materials during loading.

A Review on Mechanical Properties of Natural Fibre Reinforced PLA Composites

Abstract: Presently, scientists and researchers are in an endless quest to develop green, recyclable, and eco-friendly materials. Natural fibre reinforced polymer composites became popular among materialists due to their lightweight, high strength-to-weight ratio, and biodegradability. However, all-natural fibre reinforced polymer composites are not biodegradable. Polymer matrices like poly-lactic acid (PLA) and poly-butylene succinate (PBS) are biodegradable, whereas epoxy, polypropylene, and polystyrene are non-biodegradable polymer matrices. Besides biodegradability, PLA has been known for its excellent physical and mechanical properties. This review emphasises the mechanical properties (tensile, flexural, and impact strengths) of natural fibrereinforced PLA composites. Factors affecting the mechanical properties of PLA composites are also discussed. It also unveils research gaps from the previous literature, which shows that limited studies are reported based on modeling and prediction of mechanical properties of hybrid PLA composites reinforcing natural fibres like abaca, aloe vera, and bamboo fibres.

Effects of alkaline treatment and manufacturing process on mechanical and absorption properties of Wild Abyssinia Banana fiber reinforced epoxy composite

To enhance the properties of natural fiber composite, proper selection of an optimum alkaline concentration for fiber surface modifications and composite manufacturing techniques are the main criteria to be considered. This study examined how NaOH and manufacturing methodsaffect the mechanical and absorbency characteristics of a Wild Abyssinia Banana (WAB) epoxy composite. 2 %, 5 %, and 7 % (w/v) NaOH concentrations; hand-layup and hydraulic press manufacturing techniques have been considered. Petroleum, diesel, distilled, and artificial lake water (wastewater) were used for the absorption test. A 5 % NaOH treatment improves composite tensile, flexural, and impact strengths by 14.78 %, 8.59 %, and 29.63 %, respectively. Moreover, the 5 % NaOH treatment reduced the absorption rate of the WAB fiber composite. Hydraulic press manufactured untreated WAB fiber composite was observed to have 26.27 % and 13.45 % higher tensile and flexural strengths than hand layup. The treated WAB fiber-reinforced composite can be utilized in gas stations, home appliances, and finishing materials for construction applications.

Investigation of Tensile Strength of Long-Fiber Thermoplastic Composites Based on Evaluation of Fiber-Reinforced Structure

Investigation of Tensile Strength of Long-Fiber Thermoplastic Composites Based on Evaluation of Fiber-Reinforced Structure

A Novel Banana Fiber Reinforced Green Composite from Maleated Castor Oil and Linseed Oil

In recent decades, the consumerist society has recognized the consequences of petrochemicals, hence the interest of scientists has been drawn toward renewable products obtained from biological sources. In this study a novel biocomposite with the use of the least chemicals was fabricated by crosslinking maleated castor oil (MACO) and linseed oil (LO) by free radical polymerization, using benzoyl peroxide (BPO) as the free radical initiator. The significance of this study is that the polymer matrix is derived entirely from vegetable oils with slight modifications. Banana fibers are one of the strongest natural fibers that may be taken from the banana pseudo-stem that is discarded after the fruit is harvested. To convert this post-harvest waste into a value-added product, NaOH-treated banana fibers were used as the reinforcement for the developed composite. The characterization of the fibers and the composites was carried out by performing Fourier-transform infrared spectroscopy (FT-IR), X-Ray diffraction analysis (XRD), Dynamic mechanical analysis, tensile and compressive stress analysis, Scanning electron microscopy (SEM), Thermogravimetric (TG)/derivative thermogravimetric (DTG) and thermal conductivity analysis. Composites were also analyzed for their water absorptivity and chemical resistivity. The influence of varying banana fiber weights on the composite’s mechanical strength was investigated using a dual cantilever flexural test. It revealed that the composite’s strength increased with increasing fiber content until 50% (w/w) and then dropped as the fiber content increased further. The maximum tensile strength of the optimum composite was 16.92 ± 4.70 Megapascal (MPa) and the composite was resistant against a compressive force of 4,500 kN without any fractures. The composites’ water absorptivity and chemical resistivity tests revealed that increasing the fiber content enhanced the composites'swelling. The composite was acidic and saline water resistant, but not alkaline solution resistant. Additionally, the thermal conductivity measurements of the composite showed that the composite is a thermal insulator. The composite with 50% (w/w) fiber load, 20% (w/w) BPO, 10% (w/w), LO and 20% (w/w) MACO exhibited the best overall performances.

Effects of Physical and Mechanical Properties of Coir Fiber and Reinforced Epoxy Composites Treated with Acetic Anhydride and Alkali

ABSTRACT Modified coir fiber improves compatibility between fiber and matrix. To explore a better fiber treatment approach and enhance the mechanical properties of composites, this study conducted alkali treatment and acetic anhydride treatment on long and short coir fibers. The effects of different treatments on the properties of coir fibers were characterized using TGA, FTIR, SEM, and stereomicroscopy, and the mechanical properties of the composites were tested. Results showed that the tensile strength of alkali-treated coir fibers (ACF) and acetic anhydride-treated coir fibers (AACF) were remarkably improved. Notably, ACF exhibited a significant 69% increase in tensile strength. The tensile strength of composites with alkali-treated long coir fibers (ALC) and composites with alkali-treated short coir fibers (ASC) reached 34.51 and 21.14 MPa, respectively. The highest flexural strength was found for the acetic anhydride-treated coir fibers, and the flexural strength of composites with acetic anhydride-treated long coir fibers (AALC) and composites with acetic anhydride-treated short coir fibers (AASC) reached 54.38 and 53.46 MPa, respectively. This study presents an improved methodology for enhancing the interfacial bonding ability between coir fibers and the matrix, consequently improving the properties of composites. It offers reference for the investigation of natural fiber composites.

Research on the formulation and performance of high-strength resin matrix T1 for wet winding

Aiming at the higher requirements on the performance of composite materials put forward by new specialized equipment, the development of new high-performance winding resin is carried out. First, basing on the epoxy curing system, the selection of the main resin has been completed, we select the appropriate curing agent according to the characteristics of the screened trifunctional glycidylamine epoxy resin and trifunctional alicyclic epoxy resin, the ratio is calculated and optimised, the curing system is established, and the design of the resin formulation system is completed. Second, according to the nature of the resin curing system, the toughening method is screened, and the synergistic enhancement of heat resistance and toughness of the resin is accomplished through the core-shell nano-toughening method. Finally, the glass transition temperature of the new high-performance winding resin T1 is 165.12°C, and the fracture toughness of the resin KIC can reach 1.74MPa-m1/2, and the annular tensile strength of the T1 resin-based T700 carbon fibre composites can reach 3500MPa, which meets the requirements of the design indexes of specialized equipment.