Mechanisms for Introduction of Pseudo Ductility in Fiber Reinforced Polymer Composites- A Review

Advanced polymer matrix composites are gaining the market in their way due to their exceptional specific stiffness, specific strength, fatigue, and corrosion resistance in the field of Auto-Tech, Aero-Tech, Biotech, etc. However, the lack of ductility and catastrophic failure has limited their application in these areas. Hence there is a need to explore means and protocols for designing the reduced factor of safety with high-performance toughened composites. To address this problem, a new generation of high-performance composites with pseudo-ductile or ductile behavior is needed. The ongoing High-Performance Ductile Composite Technology (HiPerDuCT) program jointly between the University of Bristol U.K and Imperial College London to address this challenge by developing newer materials. The fiber architectures made under this project gave a more gradual failure rather than catastrophic failure which improves the mechanical properties. This paper mainly focuses on addressing this evolution of pseudo ductility in fiber-reinforced composites. In addition to this, an attempt has been made to newer possible fiber positions in matrix materials for inducing reasonable ductility in composites

Mechanisms for Introduction of Pseudo Ductility in Fiber Reinforced Polymer Composites- A Review

Advanced polymer matrix composites are gaining the market in their way due to their exceptional specific stiffness, specific strength, fatigue, and corrosion resistance in the field of Auto-Tech, Aero-Tech, Biotech, etc. However, the lack of ductility and catastrophic failure has limited their application in these areas. Hence there is a need to explore means and protocols for designing the reduced factor of safety with high-performance toughened composites. To address this problem, a new generation of high-performance composites with pseudo-ductile or ductile behavior is needed. The ongoing High-Performance Ductile Composite Technology (HiPerDuCT) program jointly between the University of Bristol U.K and Imperial College London to address this challenge by developing newer materials. The fiber architectures made under this project gave a more gradual failure rather than catastrophic failure which improves the mechanical properties. This paper mainly focuses on addressing this evolution of pseudo ductility in fiber-reinforced composites. In addition to this, an attempt has been made to newer possible fiber positions in matrix materials for inducing reasonable ductility in composites

Experimental and Numerical Study on Vibration-Based Damage Detection and Localization in Laminated Composite Plates

Damage detection in composite materials is crucial for ensuring the safety and reliability of engineering structures. Conventional methods often face challenges in accurately identifying damage in plate-like structures, particularly in scenarios involving multiple damages or small-scale delamination. This study focuses on investigating the detection and localization of delamination in composite plates by employing both experimental and numerical modal analysis. An eight-ply woven Glass-Epoxy composite laminate with and without damage was prepared with the aid of hand lamination technique. Laminate was fixed to a Clamped-Free-Free-Free (CFFF) boundary condition for experimental modal analysis by introducing controlled damage to examine its impact on modal properties. To validate the natural frequencies (NFs) of damaged and undamaged composite laminates, a numerical analysis was conducted using ANSYS Parametric Design Language (APDL). Further, to advance the understanding of using modal shapes and their spatial derivatives for damage localization in composite plates under various damage situations, post-processing of simulation results was conducted using MATLAB. Finite Difference Method has been employed to calculate the derivatives, and a novel damage index (DI) is proposed to enhance damage localization capabilities. The results affirm that the proposed DI is effective and precise in identifying damage in plate-like structures, both for individual and multiple damage scenarios. This research study presents a novel approach for identifying and pinpointing damage in composite plates, thereby making a valuable contribution to the field of structural health monitoring (SHM) application

An assessment of HDPE fillers and fiber wrapping on the strength of reinforced concrete

Fiber-reinforced polymer (FRP) is the most promising technique in the present era to bring sustainability, reliability, and pseudo ductility to concrete structures due to its superior properties. Thermoplastic and thermoset polymers are the most thrown-out synthetic waste that contributes to environmental pollution for a long time. To address this issue an attempt was made to utilize High-Density Polyethylene Fiber (HDPE) fillers of size 40x2 mm has been incorporated in concrete. This investigation aims to estimate the integrity effect of HDPE fillers incorporation and wrapping of concrete with Basalt fiber mats (BFM) and Geo-textile fiber mats (GFM) on split tensile strength, shear strength, and impact resistance as per standards. Results indicate that the addition of an optimum quantity of HDPE has a significant effect on improving the tensile, shear, and impact strengths. Adding HDPE fillers in the range of 0.5 - 1.5% in concrete samples wrapped with Basalt and Geo-textile fiber mats showed an increased tensile strength of up to 14.06% and 7.40% respectively with that conventional concrete. Further, wrapping of concrete using Basalt fiber and geotextile fiber mats showed a 4.16% and 20% increase in shear strength for 0.5% HDPE-incorporated concrete samples. Higher impact resistance was also observed for HDPE-added and fiber-wrapped concrete sample

Effects of residual stresses on interlaminar radial strength of Glass-Epoxy L-bend composite laminates

The built-in heterogeneity of the composite laminates has been exploited to tailor the stiffness and strength requirements of modern structures to meet the specific functional demands. However, the non-homogeneity in these composites is the root cause for most of their failures. One of the undesirable consequences of the inherited heterogeneity is the development of cure-induced stresses during composite manufacturing. This work aims to investigate the influence of process-induced stresses on interlaminar radial strength in curved composite laminates. Glass-Epoxy (GE) laminates of two different thicknesses were prepared by hand lamination technique using V-shaped tooling and cured under room temperature. The state of residual stresses in GE laminates is varied by post-curing these laminates at different temperatures. Curved bending strength (CBS) and corresponding interlaminar radial stress for delamination of L-bend laminates were evaluated experimentally using four points bending test. The residual stress profile in each GE laminate is experimentally characterized by employing the Slitting method. The results indicate that the residual stresses have a negligible effect on the critical stress for initial delamination in GE laminates. But, the critical stress for delamination was found to be independent of the laminate thickness and increased with higher curing temperatures. The delaminated surfaces of L-bend laminates were studied using a scanning electronic microscope (SEM). The enhancement in the critical stress due to post-curing can be attributed to the improved fiber-matrix interfacial bonding with higher curing temperature

Fabrication, Mechanical and Wear Properties of Aluminum (Al6061)-Silicon Carbide-Graphite Hybrid Metal Matrix Composites

In recent times, the use of aluminum alloy-based Hybrid Metal Matrix Composites (HMMCs) is being increased in aerospace and automotive applications. HMMCs compensate for the low desirable properties of each filler used. However, the mechanical properties of HMMCs are not well understood. In particular, microstructural investigations and wear optimization studies of HMMCs are not clear. Therefore, further studies are required. The present study is aimed at fabricating and mechanical and wear characterizing and microstructure investigating of Silicon Carbide (SiC) and Graphite (Gr) added in Aluminum (Al) alloy Al6061 HMMCs. The addition of SiC particles was in the range from 0 to 9 weight percentage (wt.%) in steps of 3, along with the addition of 1 wt.% Gr in powder form. The presence of alloying elements in the Al6061 alloy was identified using the Energy Dispersive X-Ray Analysis (EDX). The dispersion of SiC and Gr particles in the alloy was investigated using metallurgical microscope and Scanning Electron Microscopy (SEM). The gain in strength can be attributed to the growth in dislocation density. The nature of fracture was quasi-cleavage. The microstructure examination reveals the uniform dispersion of the reinforcement. Density, hardness, and Ultimate Tensile Strength values observed to be increased with increased contents of SiC reinforcement. Besides, wear studies were performed in dry sliding conditions. Optimization studies were performed to investigate the effect of parameters that affecting the wear. The sliding wear resistance was noticed to be improved concerning higher amounts of reinforcement leading to a decrease in delamination and adhesive wear. The predicted values for the wear rate have also been compared with the experimental results and good correlation is obtained

Crack suppression by natural fiber integration for improved interlaminar fracture toughness in fiber hybrid composites

In this paper, the effect of integration of natural fibers in UD carbon fiber is studied. The integration of natural fibers in carbon fiber is made via intra fiber hybridization. Natural fiber hybrid composite samples were prepared for Mode I and Mode II fracture tests. XRD analysis was done for the chosen natural fibres to know the crystallinity index and then compared with Carbon and Glass fibres. The fracture test experimental results, revealed that the effect of Jute fiber integration in UD Carbon epoxy composite was found significant in getting relatively good Mode I and II fracture toughness at the crack initiation without losing its stiffness. In addition to this Kenaf Carbon epoxy composite indicated better crack suppression with 30% higher propagation toughness values as compared other hybrid combinations and pristine composites. It is observed that integration of jute fibers in UD carbon epoxy composites was significant in achieving good mode I and mode II fracture toughness at the crack initiation without losing its stiffness and also kenaf carbon epoxy composites indicated better crack suppression with 30% higher propagation toughness as compared to other hybrid combinations used

Drawdown prepreg coating method using epoxy terminated butadiene nitrile rubber to improve fracture toughness of glass epoxy composites

Laminates of fibre-reinforced prepreg have excellent in-plane mechanical properties, but have inadequate performance in the through thickness direction. Here, we address this issue by application of epoxy-terminated butadiene nitrile (ETBN) liquid rubber between the prepreg laminae using an automatic draw bar coating technique. Test results reveal that by adding ETBN in small quantities in the range of 9.33–61.33 g/m2, the interlaminar critical energy release rates (GIc and GIIc) are improved by up to 122% in mode-I and 49% in mode-II. Moreover, this finding is further supported by the dynamic mechanical analysis thermograms that clearly indicate that coating has not altered the Tg of ETBN-coated samples. Scanning electron microscopic analysis of fracture surfaces showed that rubber particles formed micro cavitations in the epoxy, causing localised rubber rich regions. These resin-rich regions require more energy to fracture, resulting in increased toughness of the glass epoxy prepreg systems. </jats:p

Interleaving Carbon-Glass Veil in Glass Epoxy Composite for Improved Mode-I Fracture Toughness – A Hybrid Approach

The present study investigates the influence of hybrid interleaving technique using Glass and Carbon veils to improve the mode-I fracture toughness in Glass epoxy laminates. Commercially available non-woven Carbon and Glass veils with different areal densities were used to develop hybrid interleaved composites. Two approaches of interleaving, namely inter-ply and inter-weaved veils, were followed to manufacture the interleaved composite laminates using the hand layup technique. Double Cantilever Beam (DCB) samples were tested to estimate the interlaminar fracture toughness (IFT). Test results indicate that the inter-ply interleaved composite (I-C30G30) exhibited an improved initial and propagation fracture toughness of about 16.98% and 3.08%, respectively. A decreased IFT during initiation and propagation was observed for I-C15G30 and I-C20G30 when compared to plain samples. In case of inter-weaved veil interleaving approach, an improved fracture toughness (GIC and GIP) of about 7.96% and 12.94%, respectively, was observed for W-C15G30 sample, nevertheless W-C20G30 and W-C30G30 showed a drop in fracture toughness (GIC) of an about 12.15% and 9.22%, respectively, and an improvement in fracture toughness (GIP) of about 12.37% and 13.82%, respectively, when compared to plain sample. Scanning electron photo images (SEPI) of cracked laminates witnessed the fracture mechanisms involved in hybrid ply interleaved and non-interleaved composite laminates