Rizwan Saeed Choudhry - Academia.edu (original) (raw)

Papers by Rizwan Saeed Choudhry

Composites Part B: Engineering

The quest for environmentally friendly and sustainable materials in the production of fibre reinf... more The quest for environmentally friendly and sustainable materials in the production of fibre reinforced composite materials has led to the use of biobased materials, which are easily accessible and renewable. Biomass-derived chemicals, their derivatives, and their applications have become increasingly prevalent in various industries and processes, greatly contributing to the goal of ecological sustainability. The biobased Polyfurfuryl Alcohol (PFA) resin is one of such polymeric materials that is gaining attention for composite applications due to its endearing Fire Smoke and Toxicity properties. Derived from agricultural by products such as sugar cane bagasse, it has been known for applications within the foundry, coating, and wood industries. However, there has been a growing interest in its use for fibre reinforced composite applications. For this reason, this work intends to provide a comprehensive review of the PFA resin in relationship to fibre reinforced composites applications. The work provides an in-depth discussion on the synthesis, curing process, manufacturing, and properties of the PFA resin as well as its composites.

Polymer Composites

This paper presents a comprehensive study on the single‐bolt single‐shear (SBSS) and double‐bolt ... more This paper presents a comprehensive study on the single‐bolt single‐shear (SBSS) and double‐bolt single‐shear (DBSS) lap joint performance of resin‐infused thermoplastic 3D fiber‐reinforced composite (FRC) in on‐axis ( and ) and off‐axis () configurations. The bearing performance and failure mechanisms are compared with thermoset 3D‐FRC. The resin‐infused thermoplastic 3D‐FRC bolted joint shows improved bearing performance in terms of higher ultimate bearing strength, stiffness loss strength, and reduced damage severity than its thermoset counterpart. Additionally, this paper presents a detailed study on the intermediate and final failure mechanisms, obtained from scanning electron microscopy of the interrupted and ultimate bearing tests, to understand damage progression in SBSS and BDSS lap joints at the submicron level. The major damage characteristics of a thermoplastic 3D‐FRC bolted joint include plastic deformation and plastic kinking at the hole front tip, which improve the be...

Mechanics of Materials, Dec 1, 2022

Composite Structures, Aug 1, 2023

Applied Composite Materials, Oct 16, 2021

This paper presents an extensive comparison of the mechanical properties and failure mechanisms o... more This paper presents an extensive comparison of the mechanical properties and failure mechanisms of a recently developed thermoplastic (Elium ®) 3D fabric-reinforced composite (3D-FRC) with the conventional thermoset (epoxy) 3D-FRC. Experiments involved tensile tests, compression tests, V-notch shear tests, and short beam shear tests for specimens produced through the vacuum-assisted resin infusion process in each case. These tests were used for the determination of in-plane elastic constants, failure strengths and for investigating the failure mechanisms. A micro-mechanical model validated against these experiments was used to predict the remaining orthotropic elastic constants. This work enhances our understanding of the mechanics of infusible thermoplastic 3D-FRC as a new class of emerging materials and provides useful data which substantiates that this unconventional thermoplastic resin is also easier to recycle, uses similar manufacturing processes and can be a suitable replacement for conventional thermoset resins.

Composites Part A-applied Science and Manufacturing, Dec 1, 2021

A multiscale progressive damage modelling methodology for 3-dimensional composites is presented. ... more A multiscale progressive damage modelling methodology for 3-dimensional composites is presented. The proposed methodology is generic and can be implemented in most finite element software to create a digital twin for simulation of damage response. It uses 3D solid element (reduced integration) representation of the part for global analysis, while the local damage response, as well as matrix nonlinearity is modelled using a mesoscale constitutive unit-cell model of 3D woven composite consisting of idealised regions of polymer matrix and impregnated yarns. The idealised unit-cell model is defined based on realistic input from X-ray tomography of the 3D-composite part and the micro-level constituent properties of the matrix and fibres. The damage model has been validated using quasi-static tensile/compression tests as well as dynamic drop-weight impact tests for both thermoset (epoxy) and thermoplastic (Elium) 3D composites. These simulations successfully demonstrate the accuracy and efficiency of the model for both 3D-textile composites.

Bonded joints are key structural elements and for parts made from fibre reinforced polymeric matr... more Bonded joints are key structural elements and for parts made from fibre reinforced polymeric matrix composites (FRC), these are preferred over mechanical fasteners such as rivets and bolts. Low velocity impact loading of structures is frequently encountered both in-service and during maintenance and when an object made from FRC is subjected to impact loading, the resulting damage is often quite complex in terms of both multiplicity and unpredictability of damage modes. If the structure involves bonded joints the complexity is increased further. Since the use of composite materials is continuously increasing in all type of structural components the impact threat can no longer be dealt with simplified design approaches and unrealistic in-service operating requirements. All the major commercial Aircraft manufacturers are looking at fibre polymeric composites as the material of choice for the future aircrafts, however, the poor understanding of impact Induced damage mechanisms necessita...

Polymers

The flexure response of novel thermoplastic (Elium®) 3D fibre-reinforced composites (FRC) was eva... more The flexure response of novel thermoplastic (Elium®) 3D fibre-reinforced composites (FRC) was evaluated and compared with a conventional thermoset (Epolam®)-based 3D-FRC. Ten different types of sample 3D-FRC were prepared by varying fibre orientations, i.e., 0°, 30°, 45°, 60° and 90°, and resin system, i.e., thermoplastic and thermoset. The bending characteristics and failure mechanisms were determined by conducting a three-point bend test. Results elucidate that the on-axis specimens show linear response and brittle failure; in contrast, the off-axis specimens depicted highly nonlinear response and ductile failure. The thermoplastic on-axis specimen exhibited almost similar flexure strength; in comparison, the off-axis specimens show ~17% lower flexure strength compared to thermoset 3D-FRC. Thermoplastic 3D-FRC shows ~40% higher energy absorption, ~23% lower flexure modulus and ~27% higher flexure strains as compared to its thermoset counterpart.

Thermochimica Acta, 2021

This paper explains the cure reaction mechanisms of a novel bio-based glass/Polyfurfuryl prepreg ... more This paper explains the cure reaction mechanisms of a novel bio-based glass/Polyfurfuryl prepreg using an experimental and numerical approach. It suggests optimized parameters of rapid curing for isothermal curing conditions. Dynamic scanning calorimetry (DSC) under non-isothermal conditions was used to determine parameters for the two model-free kinetic methods Friedman and Ozawa Flynn Wall. The average activation energy (88.9 ± 4.9 kJ/mol) was found to be higher than that reported for neat resin in literature. The validated models were used to gain insight into reaction mechanisms and were used to predict the evolution of reaction time under isothermal conditions for the PFA prepreg. This suggested that the curing time can be reduced to half by rapidly heating and maintaining isothermal conditions at 160 • C, which provides faster curing using hot-press. In addition, dynamic mechanical analysis (DMA) was carried out to compare the manufacturer recommended cure cycle with the rapid cycle suggested.

Carbon Fibre Reinforced Polymer (CFRP) composites are widely used in several high performance str... more Carbon Fibre Reinforced Polymer (CFRP) composites are widely used in several high performance structures such as aeroplanes, automobiles and wind turbines. In these applications holes are made for access to view, cut-outs for weight reduction as well as joining of composite members. However, these hole possess a threat to the strength and damage tolerance of composites in service. The strength of composites varies with hole diameter known as hole size effect. The hole size effect, becomes more complex once associated with specimen size effect (strength variation with specimen size) as well as anisotropy and heterogeneity of composite material. The leading influencing factors linked with the hole size effect are in-plane and transverse plane thickness, stacking sequence and hole diameter of the specimen. Extensive experimental, analytical and Finite Element (FE) based studies have been done by the researchers in past on this account. Despite these studies, differences still persist a...

2017 Fifth International Conference on Aerospace Science & Engineering (ICASE), 2017

Numerical model for prediction of progressive delamination in woven fabric reinforced composite i... more Numerical model for prediction of progressive delamination in woven fabric reinforced composite is proposed in this paper. An orthotropic model is used in which the interface is modeled as bilinear cohesive zone elements subjected to mixed mode loadings. The mixed mode loading is applied through displacements. Mesh insensitive model is obtained at a converged mesh. Mass scaling is used to run the model at high mesh density and the results are accurately found. Effect of displacement rate is studied. Load displacements graphs are obtained, and they agreed with the experimental load displacements graphs.

Single lap joints of woven GFRP composites have been investigated for impact induced damage modes... more Single lap joints of woven GFRP composites have been investigated for impact induced damage modes using C-scan, X-ray micro tomography, imaging and finite element (FE) modelling. This has allowed for damage modes to be observed in 3D from macro to micro level-resulting in much better understanding of damage mechanisms and realistic FE modelling.

Non-linear dynamic FE simulations of impact event and ensuing progressive delamination and disbon... more Non-linear dynamic FE simulations of impact event and ensuing progressive delamination and disbond failure, were performed for lap joints of composites (woven fabric reinforced phenolic) having four different overlap widths. The joints were impacted transversely using a hemispherical impactor with different velocities in the low velocity impact range. These simulations were used to explain the experimentally observed dependence of damage on overlap width and impact velocity using the concept of characteristic overlap width. The experimental observations of damage mechanisms were carried out using a combination of techniques including, through transmission photography, ultrasonic c-scan and x-ray micro tomography (XMT). Progressive damage simulations like the one described in this study require significant input material properties to run and generally little details are provided in literature about the experimental procedure to determine these values. Thus in this paper, determinati...

Continuously varying fibre angle across flat plates has analytically been shown to improve buckli... more Continuously varying fibre angle across flat plates has analytically been shown to improve buckling performance by up to 60%. However, manufacture of such panels has so far used methods which have either high radius of curvature and low deposition rate (Continuous Tow Shearing) or low radius of curvature and medium deposition rate (Advanced Fibre Placement). Discrete Stiffness Tailoring (DST) is an alternative way of varying fibre angle to increase buckling performance that is compatible with current high rate deposition methods such as Advanced Tape Laying (ATL). DST uses discrete changes of angle within individual layers to effect variation in stiffness across a composite component at the cost of in-plane butt joints within layers. Two schemes of distribution are considered for tailoring stiffness across the width of a panel; (i) Half Seam; where half the layers in a laminate are subject to tailoring and (ii) Full Seam; where all layers are tailored. Compression testing of flat pa...

Handbook of Composites from Renewable Materials, 2017

Composites Part B: Engineering, 2021

Abstract Damage tolerance of a unique resin-infused thermoplastic (Elium) 3D fibre-reinforced com... more Abstract Damage tolerance of a unique resin-infused thermoplastic (Elium) 3D fibre-reinforced composite (3D-FRC) is compared with the conventional resin-infused thermoset (Epoxy) 3D-FRC using compression after impact (CAI) tests and finite element simulations. Higher damage tolerance is demonstrated for the thermoplastic 3D-FRC as its CAI failure strength and CAI stiffness is nearly insensitive to the impact energy levels and subsequent damage, while in contrast, both these properties for the thermoset 3D-FRC get compromised significantly. The buckling performance shows a gradual, almost linear, reduction in critical buckling (44.5% reduction in 0–100 J) for the thermoplastic 3D-FRC. In comparison, the thermoset 3D-FRC shows a much steeper drop in critical buckling, which becomes more pronounced for the higher impact energy cases (84.5% reduction in 0–100 J). It is postulated that the local plastic deformation of the thermoplastic matrix at the impact site as well as better interfacial adhesion is responsible for its better damage tolerance.

Composites Communications, 2021

Abstract This paper presents the quasi-static crush performance of newer resin-infused thermoplas... more Abstract This paper presents the quasi-static crush performance of newer resin-infused thermoplastic 3D fibre reinforced composites (FRC) under axial load. The main objective is to make an assessment of the energy absorption capability of novel 3D composites for improved energy absorbing applications. Flat specimens of resin-infused thermoplastic (TP) and thermoset (TS) 3D composites with three trigger angles, i.e., 15°, 30° and 45° were tested under quasi-static crush loads. The thermoplastic 3D-FRC at 45° trigger angle demonstrated 31% higher specific energy absorption (SEA), and 17% higher average crushing stress. This improved performance is attributed to higher fragmentation failure mechanisms, which absorbed more energy. These results elucidate that the resin-infused thermoplastic composites are suitable for higher energy absorption and lightweight design for automotive and sports applications.

International Journal of Mechanical Sciences, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

IOP Conference Series: Materials Science and Engineering, 2018

An accurate yet easy to use methodology for determining the effective mechanical properties of wo... more An accurate yet easy to use methodology for determining the effective mechanical properties of woven fabric reinforced composites is presented. The approach involves generating a representative unit cell geometry based on randomly selected 2D orthogonal slices from a 3D X-ray micro-tomographic scan. Thereafter, the finite element mesh is generated from this geometry. Analytical and statistical micromechanics equations are then used to calculate effective input material properties for the yarn and resin regions within the FE mesh. These analytical expressions account for the effect of resin volume fraction within the yarn (due to infiltration during curing) as well as the presence of voids within the composite. The unit cell model is then used to evaluate the effective properties of the composite.