A new approach for strength and stiffness prediction of discontinuous fibre reinforced composites (DFC)

A new modelling methodology for strength and stiffness prediction of discontinuous fibre-reinforced composites (DFC) is proposed. This has been validated for both thermoplastic and thermoset, prepreg based, carbon fibre reinforced, random DFC laminates having high volume fraction, by implementing it in a commercial FE solver. The methodology involves explicit generation of internal architecture of DFC through an algorithm which is efficient (faster model generation and solution), easily customizable and scalable. It captures many of the realistic features of the DFC such as variation in volume fraction, interlacing of strands, random orientation and thickness variation of strands. Thus, the model accounts for the natural mechanical property variation, which is characteristic of random DFCs and was found to be conservative in terms of prediction of tensile strength and stiffness for all the validation cases considered. It is generic in the sense that it can be easily extended to generate preferentially aligned and hybrid DFC laminates.Universiti Teknologi PETRONA

Off-axis tensile performance of notched resin-infused thermoplastic 3D fibre-reinforced composites

This study presents a comparison of off-axis tensile performance for notched (open-hole) and unnotched (no-hole) 3D fibre reinforced composites (FRC) specimens having two different types of matrices. The two matrix systems compared are, a novel infusible thermoplastic (Elium) resin and conventional thermoset (epoxy). Three different configurations, (one unnotched and two notched) were tested for each 3D-FRC. The resulting notched net strength, gross strength, failure strains, notch sensitivity and energy absorbed by each configuration were evaluated and compared. Additionally, 2D digital image correlation (DIC) was used to evaluate full-field strain distribution in each case. The results elucidate that thermoplastic 3D-FRCs are notch insensitive irrespective of the notch size and possess higher failure strains (around 30 percent in the cases investigated) and energy absorption (around 33 percent in the cases investigated). In contrast, thermoset 3D-FRC appeared to be notch sensitive, as the notched size increased, and they failed at lower axial strains (up to 60 percent reduction compared to unnotched specimens for the size investigated). Thus, resin-infused thermoplastic off-axis configurations are effective for composite joint applications, particularly in notch-insensitive designs, requiring higher energy absorption and failure strains

A review of advancements in synthesis, manufacturing and properties of environment friendly biobased Polyfurfuryl Alcohol Resin and its Composites

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

Off-Axis and On-Axis Performance of Novel Acrylic Thermoplastic (Elium®) 3D Fibre-Reinforced Composites under Flexure Load

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 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 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

Multiscale Damage Modelling of Notched and Un-Notched 3D Woven Composites With Randomly Distributed Manufacturing Defects

This work proposes a stochastic multiscale computational framework for damage modelling in 3D woven composite laminates, by considering the random distribution of manufacturing-induced imperfections. The proposed method is demonstrated to be accurate, while being simple to implement and requiring modest computational resources. In this approach, a limited number of cross-sectional views obtained from micro-computed tomography (µCT) are used to obtain the stochastic distribution of two key manufacturing-induced defects, namely waviness and voids. This distribution is fed into a multiscale progressive damage model to predict the damage response of three-dimensional (3D) orthogonal woven composites. The accuracy of the proposed model was demonstrated by performing a series of finite element simulations of the un-notched and notched tensile tests (having two different hole sizes) for resin-infused thermoplastic (Elium®) 3D woven composites. Excellent correlation was achieved between experiments and the stochastic finite element simulations. This demonstrates the effectiveness of the proposed stochastic multiscale model. The model successfully captured the stochastic nature of tensile responses (ultimate tensile strength and stiffness), damage modes (matrix damage and fibre failure), and initiation and propagation of transverse cracks in thermoplastic 3D woven composites, consistent with experimental observation. The stochastic computational framework presented in this paper can be used to guide the design and optimization of 3D textile composite structures

Compression and buckling after impact response of resin-infused thermoplastic and thermoset 3D woven composites

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.The authors would like to acknowledge the financial support provided by Universiti Teknologi PETRONAS (grant number 015LC0-197). The authors would also like to acknowledge the support of Dr. Robert J. Barsotti from Arkema in acquiring Elium® resin, Dr. Faiz Ahmad and the Center of Advanced Functional Materials (AFM) in providing the facility for the fabrication of 3D composites

Stochastic Lightning Damage Prediction of Carbon/Epoxy Composites with Material Uncertainties

This study presents a novel stochastic modeling framework predicting lightning thermal damage in carbon/epoxy composites. The stochastic lightning damage model (SLDM) was developed with random distributions of composite’s electrical conductivity and void. The Box-Muller transformation was applied to generate random in-plane and through-thickness electrical conductivities with Gaussian distributions. The SLDM suggested that the predicted lightning thermal damage to carbon/epoxy composites increased slightly with the use of stochastic electrical conductivity, but the presence of voids did not significantly affect the damage development. The predicted size and shape of lightning thermal damage agreed fairly well with experimental results. In addition, the proposed SLDM was first capable of predicting asymmetric lightning damage to carbon/epoxy composites, which was not demonstrated by conventional (deterministic) lightning damage models

Challenges in compression testing of 3D angle-interlocked woven-glass fabric-reinforced polymeric composites

In this paper, the challenges are described in determination of compressive strength for three-dimensional (3D) angle-interlocked glass fabric-reinforced polymeric composites (3D-FRPCs). It makes use of both experimental investigation and finite-element analysis. The experimental investigation involved testing both two dimensional (2D) and 3D-FRPC using ASTM D6641/D6641M-14 and subsequent scanning electron microscopic (SEM) imaging of failed specimens to reveal the stress state at failure. This was further evaluated using laminate level finite-element (FE) analysis. The FE analysis required input of effective orthotropic elastic material properties of 3D-FRPC, which were determined by customizing a recently developed micro-mechanical model. The paper sheds new light on compressive failure of 3D angle-interlocked glass fabric composites, as only scarce data is available in literature about this class of materials. It showed that although the tests produce acceptable strength values the internal failure mechanisms change significantly and the standard deviation (SD) and coefficient of variance (COV) of 3D-FRPC ends up being much higher than that of 2D-FRPC. Moreover, while reporting and using the test data, some additional information about the 3D-fabric architecture, such as the direction of angle interlocking fabric, needs to be specified. This was because, for 3D angle interlocking of fabric along the warp direction, the strength values obtained in the warp and weft direction were significantly different from each other. The study also highlights that, because of complex weave architecture, it is not possible to achieve comparable volume fractions with 2D and 3D fabric-reinforced composites using similar manufacturing parameters for the vacuum-assisted resin-infusion process. Thus, the normalized compressive strength values (normalized with respect to volume fraction) are the highest for 3D-FRPC when measured along the warp direction, they are at an intermediate level for 2D-FRPC and the lowest for 3D-FRPC, when measured in the weft direction

Challenges in compression testing of 3D angle-interlocked woven-glass fabric-reinforced polymeric composites

In this paper, the challenges are described in determination of compressive strength for three-dimensional (3D) angle-interlocked glass fabric-reinforced polymeric composites (3D-FRPCs). It makes use of both experimental investigation and finite-element analysis. The experimental investigation involved testing both two dimensional (2D) and 3D-FRPC using ASTM D6641/D6641M-14 and subsequent scanning electron microscopic (SEM) imaging of failed specimens to reveal the stress state at failure. This was further evaluated using laminate level finite-element (FE) analysis. The FE analysis required input of effective orthotropic elastic material properties of 3D-FRPC, which were determined by customizing a recently developed micro-mechanical model. The paper sheds new light on compressive failure of 3D angle-interlocked glass fabric composites, as only scarce data is available in literature about this class of materials. It showed that although the tests produce acceptable strength values the internal failure mechanisms change significantly and the standard deviation (SD) and coefficient of variance (COV) of 3D-FRPC ends up being much higher than that of 2D-FRPC. Moreover, while reporting and using the test data, some additional information about the 3D-fabric architecture, such as the direction of angle interlocking fabric, needs to be specified. This was because, for 3D angle interlocking of fabric along the warp direction, the strength values obtained in the warp and weft direction were significantly different from each other. The study also highlights that, because of complex weave architecture, it is not possible to achieve comparable volume fractions with 2D and 3D fabric-reinforced composites using similar manufacturing parameters for the vacuum-assisted resin-infusion process. Thus, the normalized compressive strength values (normalized with respect to volume fraction) are the highest for 3D-FRPC when measured along the warp direction, they are at an intermediate level for 2D-FRPC and the lowest for 3D-FRPC, when measured in the weft direction

Bending performance and failure mechanisms of hybrid and regular sandwich composite structures with 3D printed corrugated cores

The effect of core geometry and hybridization on the bending performance and failure mechanisms of carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) corrugated sandwich composite structures (SCS) were experimentally investigated using a three-point bend test. The CFRP and GFRP corrugated cores and facesheets were produced using Fused Filament Fabrication (FFF) and vacuum-assisted infusion processes, respectively. Three types of corrugated SCSs were built: SCSs with different core geometries (circular, square, trapezoidal, sinusoidal, and triangular), hybrid SCSs with different CFRP and GFRP cores and facesheets, and fully 3D-printed CFRP and GFRP SCSs. The corrugated SCS with square core geometry outperformed due to the presence of vertical walls and a large bonding area. The hybrid SCSs with a CFRP core showed a significant load drop due to shear failure in the 3D-printed core caused by weak inter-layer bonding. In contrast, the hybrid SCS with a GFRP core deformed plastically and absorbed more energy without failure due to strong inter-layer bonding. In fully 3D printed SCSs, the GFRP specimen failed catastrophically due to higher bending stress at the bottom facesheet, while the CFRP undergoes plastic deformation without failure. Results elucidate that the hybrid corrugated SCS with a GFRP top facesheet and 3D-printed core is an appropriate configuration for superior bending performance. The proposed 3D-printed SCS enables optimising complex shapes and material distribution in the core, resulting in improved strength-weight ratios. These findings will make an important contribution to the design and development of fibre-reinforced 3D-printed SCS for lightweight and high-performance applications