Fiber Reinforced Plastic Composites Research Articles

Adhesion of 3D printed material on textile substrates

PurposeComposites combining two or more different materials with different physical and chemical properties allow for tailoring mechanical and other characteristics of the resulting multi-material system. In relation to fiber-reinforced plastic composites, combinations of textile materials with 3D printed polymers result in different mechanical properties. While the tensile strength of the multi-material system is increased compared to the pure 3D printed material, the elasticity of the polymer layer can be retained to a certain degree, as the textile material is not completely immersed in the polymer. Instead, an interface layer is built in which both materials interpenetrate to a certain degree. The purpose of this study is to investigate the adhesion between both materials at this interface.Design/methodology/approachThis paper gives an overview of the parameters affecting the interface layer. It shows that both the printing material and the textile substrate influence the adhesion between both materials due to viscosity during printing, thickness and pore sizes, respectively. While some material combinations build strong form-locking connections, others can easily be delaminated.FindingsDepending on both materials, significantly different adhesion values can be found in such 3D printed composites.Practical implicationsThis makes some combinations very well suitable for building composites with novel mechanical properties, while other suffer of insufficient connections.Originality/valueFor the first time, the dependence of the polymer-textile adhesion force was evaluated according to the distance between both compound partners. It was shown that this value is of crucial interest and must thus be taken into account when producing printed polymer-textile composites.

Analysis of thrust force and delamination in drilling GFRP composites with candle stick drills

Drilling is an indispensable process for assembling the composites components. The drilling-induced delamination damage generally refers to the peel up delamination on the entrance surface and the push down delamination on the exit surface. Many researchers have carried out studies on drilling force and delamination damage in composites using special drills. Candle stick drills have been recognized as advantageous tools for the reduction of thrust force and delamination damage in drilling composites. Drilling experiments of glass fiber-reinforced plastic (GFRP) composites and finite element simulations were carried out in this paper. Three candle stick drills with different drill tip geometries and one twist drill were compared in terms of thrust force, peel up delamination, and push down delamination. The results revealed that, compared to twist drill, not all candle stick drills could get relatively good drilling results. What is more, drilling results of candle stick drills had a great relationship with the drill tips geometry angles. Finally, an optimized candle stick drill with appropriate drill tip geometry achieved relatively excellent drilling results.

Experimental study on micromachining of CFRP/Ti stacks using micro ultrasonic machining process

Carbon fiber-reinforced plastic (CFRP) composite is one of the most sought after material owing to its superior physical and mechanical properties such as high durability and high strength-to-weight ratio. CFRP composites are often used by stacking up with titanium (Ti) to form multi-layered material stacks for applications involving extreme mechanical loads such as in aerospace and automotive industries. However, the machining of CFRP/Ti multi stacks is quite complex and challenging task since both materials are difficult-to-machine materials and show completely different machinability properties. The challenge is further escalated when there is a need to machine the CFRP/Ti stacks at micron level. Several problems arise during the machining process due to the non-homogeneous structure and anisotropic and abrasive properties of composites. Traditional methods of micromachining the CFRP/Ti stacks result in several issues including high cutting force and high tool wear, composite delamination, large groove depth in composites, and poor surface quality. Ultrasonic machining (USM) process has been successfully used to machine titanium, CFRP, and CFRP/Ti stacks at macro scale. Micro ultrasonic machining is a downsized version of macro USM process that is developed to machine hard and brittle materials such as quartz, glass, and ceramics at micron scale. This research explores the possibility of using the micro USM process to conduct micromachining of CFRP/Ti multi stacks. The effects of various process parameters including abrasive grit size, tool material and type on the material removal rate and surface quality are studied. The study found that micro ultrasonic machining process is capable of successfully micromachining CFRP/Ti stacks. In comparison with conventional processes, micromachining of CFRP/Ti stacks using micro ultrasonic machining process resulted almost zero CFRP delamination, minimal variation in CFRP and Ti hole sizes, and longer tool life.

Designing a phthalonitrile/benzoxazine blend for the advanced GFRP composite materials

High performance resin must be used in the high performance glass fiber-reinforced plastic (GFRP) composites, but it is sometimes difficult to balance the processabilities and the final properties in the design of advanced thermoset GFRP composites. In this study, a phthalonitrile/benzoxazine (PPN/BZ) blend with excellent processability has been designed and applied in the GFRP composite materials. PPN/BZ blend with good solubility, low melt viscosity, appropriate gel condition and low-temperature curing behavior could enable their GFRP composite preparation with the prepreg-laminate method under a relatively mild condition. The resulted PPN/BZ GFRP composites exhibit excellent mechanical properties with flexural strength over 700 MPa and flexural modulus more than 19 GPa. Fracture surface morphologies of the PPN/BZ GFRP composites show that the interfacial adhesion between resin and GF is improved. The temperatures at weight loss 5% (T 5%) and char residue at 800 °C of all PPN/BZ GFRP composites are over 435 °C and 65% respectively. PPN/BZ GFRP composites with high performance characteristics may find applications under some critical circumstances with requirements of high mechanical properties and high service temperatures.

Mechanical characterization of pseudoelastic shape memory alloy hybrid composites

Shape memory alloys (SMAs) are embedded in fiber reinforced plastic (FRP) composites material to achieve properties like higher toughness, shape morphing, variable stiffness etc. Pseudoelastic SMAs are mostly used in improving the energy absorbing capability of composites subjected to impact loading. Pseudoelastic SMA material has the property of absorbing higher strain energy without failure as compared to other engineering materials. Embedding SMA in FRP composites may affect its in-plane properties. This paper deals with study on SMA hybrid GFRP (Glass Fiber Reinforced Plastic) composites to find out the effect of embedding SMA in composites on the mechanical properties such as longitudinal tensile and compressive strength, transverse tensile strength and compressive strength and in-plane shear strength. Experimental results show that longitudinal compressive strength of shape memory alloy hybrid composites (SMAHCs) increases by approximately 30% over pristine composites. There is a marginal change in values of longitudinal tensile strength and in-plane shear strength in SMAHCs as compared to pristine composites whereas there is reduction observed in transverse tensile and compressive strength in SMA hybrid GFRP composites as compared to pristine GFRP composites.

A simple repair method for GFRP delamination using ultraviolet-curable resin

Fiber-reinforced plastic (FRP) composites are widely used in engineering because of their high strength and light weight in comparison to monolithic metal alloys. They are mostly used in laminate form and are stronger within layers than between layers, making them prone to cracking and peeling. This type of structural degradation can be dangerous during operation. For this reason, research on FRP composites with the ability to self-repair has attracted much attention. In this study, we developed a new method to repair glass fiber-reinforced plastic (GFRP) composites by using ultraviolet-(UV) cured resin. As GFRP composites are UV transmissive, the repair process can be carried out externally by exposing the damaged part to UV light. The transmittance of EP GFRP is about 40%. Holes were pre-drilled with wires in order to facilitate the injection of UV resin between the layers of the composite, and this process was accomplished without degrading the mechanical properties of the material. A double cantilever beam (DCB) test was performed on the GFRP composite to induce interlaminar fracturing. UV-curable resin was then injected between the layers of the composite through a series of pre-drilled holes. Following this repair, the DCB test was performed again to evaluate the repair rate. A compressive after impact (CAI) test was also performed on the GFRP composite to induce delamination. Compressive strength before and after the repair was also evaluated.

Ultrasonic inspection for the detection of debonding in CFRP-reinforced concrete

Fibre-reinforced plastic (FRP) composites are extensively used to retrofit civil structures. However, the quality and the characteristics of the bond between the FRP and the structure are critical to ensure the efficacy of the retrofit. For this reason, effective non-destructive evaluation (NDE) methods are often necessary to assess the bonding conditions. This article presents an ultrasonic technique for detecting defects at the FRP-substrate interface. The technique uses the Akaike Information Criterion, to detect automatically the onset of the ultrasonic signals, and the novel Equivalent Time Lenght (ETL) parameter, to quantify the energy of the propagating ultrasonic signals along the interface between FRP and concrete. The uniqueness of the ETL is that it is not affected by the coupling conditions between the ultrasonic probes and the structure. The proposed NDE technique has been tested numerically by performing 2D Finite-Element analysis and experimentally on reinforced concrete samples. The results show that the method is robust and cost-effective.

One-step manufacturing of innovative flat-knitted 3D net-shape preforms for composite applications

Mostly due to the cost-intensive manually performed processing operations, the production of complex-shaped fibre reinforced plastic composites (FRPC) is currently very expensive and therefore either restricted to sectors with high added value or for small batch applications (e.g. in the aerospace or automotive industry). Previous works suggest that the successful integration of conventional textile manufacturing processes in the FRPC-process chain is the key to a cost-efficient manufacturing of complex three-dimensional (3D) FRPC-components with stress-oriented fibre arrangement. Therefore, this work focuses on the development of the multilayer weft knitting technology for the one-step manufacturing of complex 3D net-shaped preforms for high performance FRPC applications. In order to highlight the advantages of net-shaped multilayer weft knitted fabrics for the production of complex FRPC parts, seamless preforms such as 3D skin-stringer structures and tubular fabrics with load oriented fibre arrangement are realised. In this paper, the development of the textile bindings and performed technical modifications on flat knitting machines are presented. The results show that the multilayer weft knitting technology meets perfectly the requirements for a fully automated and reproducible manufacturing of complex 3D textile preforms with stress-oriented fibre arrangement.

Investigations on micro-cutting mechanism and surface quality of carbon fiber-reinforced plastic composites

To study micro-cutting mechanism of carbon fiber-reinforced plastic (CFRP) composites, a constitutive model of CFRP composites considering random distribution of carbon fiber in the plastic composites is proposed in this paper. Brittle material model is utilized to simulate carbon fiber, interpolation method is used to approach the stress-strain relationship of resin matrix, and traction separation cohesive model is applied to model the interfacial phase between fiber and matrix, all of which make the model close to actual mechanical performance of CFRP composites. Further, a three-dimensional FEM simulation model for the micro-cutting process of CFRP composites is built, and micro-cutting experiments are conducted to verify the FEM simulation results. On the basis of FEM simulation and micro-cutting experiments, the mechanism of deformation and damage of fiber reinforcement, matrix, and interfacial phase in the micro-cutting process are studied, and the influences of cutting speed, cutting depth, and fiber orientation are analyzed.

Effects of Molding Conditions on the Deflection of Rib Moldings of Fiber-reinforced Plastic Composites in Compression Molding

Effects of Molding Conditions on the Deflection of Rib Moldings of Fiber-reinforced Plastic Composites in Compression Molding

Assessing the fatigue of fibre-reinforced plastic composites using the example of rotor blades

Assessing the fatigue of fibre-reinforced plastic composites using the example of rotor blades

A novel microbond bundle pullout technique to evaluate the interfacial properties of fibre-reinforced plastic composites

The interfacial properties of the fibre composite systems decide the overall usability of a composite in simple and complex shapes, as they are the deciding factors in determination of the mechanical properties, structural properties and above all a complete understanding of the reliability of composite systems. In the present investigation, the interfacial properties of carbon fibre/epoxy composites viz., matrix shrinkage pressure, interfacial frictional stress, interfacial shear stress and coefficient of friction were evaluated through a novel microbond bundle pullout test. This test is different from the single fibre pull out, fibre fragmentation or the fibre push in test. Based on some of the physical principles involving the single fibre microbond pullout test, like the contact angle of the microbond matrix drop with the fibre surface, the surface tension/energy of the two surfaces before and after adhesion and the interfacial fibre/matrix chemistry, this is simple to perform and statistically averaged mesomechanical test is also easy to evaluate and is shown to be a test method that enables a conservative prediction of the laminate level or macromechanical shear properties of fibre composite systems. This test demonstrates the validity of the mesomechanical tests that are more relevant to the macromechanical tests than the micromechanical tests. Fractography carried out to corroborate the observed mechanical properties with the fracture features is also reported. The general advantages of the mesomechanical interfacial tests over those based on micromechanical assumptions is also discussed along with some common limitations.

Mechanical properties and piezoresistive sensing capabilities of FRP composites incorporating CNT fibers

The present study investigates the mechanical properties and piezoresistive sensing capabilities of glass and carbon fiber-reinforced plastic (GFRP and CFRP) composites incorporating solid state spun-carbon nanotube (CNT) fibers. The FRP composite specimens were fabricated by stacking in layer-by-layer sequence in a resin matrix via vacuum infusion process. The mechanical properties were examined by tensile strength tests, while piezoresistive sensing characteristics were explored by measuring the electrical resistance change during loading. The maximum electrical resistance change rate of CNT fiber-incorporated GFRP composites was 3.15%, corresponding to a value 10 times higher than those obtained in previous studies using wet spinning method for the fabrication of CNT fibers. Moreover, continuous sensing characteristics of the CNT fiber-incorporated GFRP composite subjected to cyclic tensile loadings were verified, thereby assessing the feasibility of CNT fibers in practical applications as a piezoresistive sensor.

Failure mode–driven quality analysis of operational risks for composite fiber-reinforced plastic assembly

Composite fiber-reinforced plastic products have many failure modes in the manufacturing stage. The cost of rework is high. To ensure a reliable manufacturing process and outcome, this article presents a new method to prioritize assembly process errors according to a risk-based cost of poor quality. The method combines a range of reliability techniques including cause–effect diagram, fault tree, and analytic hierarchy process to achieve multiple failure mode assessment. The outcome of this research provides direct links to develop risk mitigation plans to treat the prioritized risks of production errors in the composite fiber-reinforced plastic assembly process.

Influence of cutting temperature on carbon fiber-reinforced plastic composites in high-speed machining

Carbon fiber-reinforced plastic (CFRP) composites have been widely used in many industries, including aerospace, automobiles, medical devices, and building materials, because of their good material properties, such as weight, rigidity, strength, and wear resistance. We experimentally evaluated the high-speed machining characteristics of CFRP composites. First, dry-cutting experiments were performed to test prepared CFRP specimens. Above a certain cutting speed, the epoxy matrix melted owing to the heat caused by the friction between the tool and specimen. Next, high-speed cutting experiments were performed at a low temperature (approximately -20 °C). Many sensors were used to investigate the characteristics of the high-speed cutting process, and the results were analyzed.

Low-velocity impact performance of carbon fiber-reinforced plastics modified with carbon nanotube, nanoclay and hybrid nanoparticles

Addition of nanoparticles in polymeric composites for use in fabrication and characterization of fiber-reinforced plastic composites has recently shown a lot of promise. Nanoparticles typically used in most studies include multi-walled carbon nanotubes (MWCNTs) and nanoclay. In the current research, in addition to including nanoclay and MWCNTs individually, we have also studied the effect of hybrid of the two in enhancing the impact performance of carbon fiber-reinforced plastic (CFRP) composites. We have fabricated CFRP composites with 0.3 wt.% of MWCNTs, 2 wt.% of nanoclay and hybrid of MWCNTs and nanoclay at 0.1 wt.% and 2 wt.%, respectively. Control samples were also fabricated with no nanoparticles. Composite laminates were subjected to impact loading at 30, 40 and 50 J energy levels. Energy, load, displacement and velocity responses of samples were obtained. Damage area of control and all modified samples were investigated using digital thermography technique and compared. MWCNT and nanoclay enhanced the impact properties and reduced the damaged area of composite samples slightly. However, significant improvement was noticed for the hybrid nanoparticle-reinforced composite samples.

Composite Fiber Reinforced Plastic one-shoot drilling: Quality inspection assessment and tool wear evaluation

This work focuses on the analysis of Composite Fiber Reinforced Plastics (CFRP) drilling performed during the assembly of aeronautical components. One-shoot operations are desired to minimize positional errors, enhance tight tolerances and reduce process time. Also, it is usually included the countersinking cycle to maintain the aerodynamic shape of the component.Wear testing was carried out on test specimens representative of aeronautical materials and with cutting parameters similar to real production in order to increase composites drilling know-how and improve efficiency of the operations by extending the useful life of the tools.

Comparison of the Stress Concentration Factors for GFRP Plate having Centered Circular Hole by Three Resource-Conserving Methods

Fiber reinforced plastic (FRP) composites have drawn increasing attentions worldwide for decades due to its outstanding properties. Stress concentration factor (SCF) as an essential parameter in materials science are critically considered in structure design and application, strength assessment and failure prediction. However, investigation of stress concentration in FRP composites has been rarely reported so far. In this study, three resource-conserving analyses (Isotropic analysis, Orthotropic analysis and Finite element analysis) were introduced to plot the <TEX>$K_T^A-d/W$</TEX> curve for E-glass/epoxy composite plate with the geometrical defect of circular hole placed centrally. The plates were loaded to uniaxial direction for simplification. Finite element analysis (FEA) was carried out via ACP (ANSYS composite prepost module). Based on the least squares method, a simple expression of fitting equation could be given based on the simulated results of a set of discrete points. Finally, all three achievable solutions were presented graphically for explicit comparison. In addition, the investigation into customized efficient SCFs has also been carried out for further reference.

Research on the carbon fibre-reinforced plastic (CFRP) cutting mechanism using macroscopic and microscopic numerical simulations

The essence of cutting carbon fibre-reinforced plastic (CFRP) composites is a process of material failure and chip formation. The mechanism of cutting CFRPs can be explained from the perspective of local removal of material on the microscopic level. The morphology of the chips resulting from the cutting process can be determined from the perspective of the overall failure of the material on the macroscopic level. To reveal the mechanism of cutting CFRPs at both levels, a macroscopic model and a microscopic model are established in this study. Orthogonal cutting is applied in both of the models to illuminate the removal process. Combined with experimental observations, the results that obtained from both the macroscopic and microscopic level revealed the different mechanics of cutting CFRPs for different fibre orientations. For example, the forms of fracture that occur at 0° fibre orientation are primary interface cracking and fibre bending; the resulting chips have long shapes.

Characterization and Effects of Fiber Pull-Outs in Hole Quality of Carbon Fiber Reinforced Plastics Composite.

Hole quality plays a crucial role in the production of close-tolerance holes utilized in aircraft assembly. Through drilling experiments of carbon fiber-reinforced plastic composites (CFRP), this study investigates the impact of varying drilling feed and speed conditions on fiber pull-out geometries and resulting hole quality parameters. For this study, hole quality parameters include hole size variance, hole roundness, and surface roughness. Fiber pull-out geometries are quantified by using scanning electron microscope (SEM) images of the mechanically-sectioned CFRP-machined holes, to measure pull-out length and depth. Fiber pull-out geometries and the hole quality parameter results are dependent on the drilling feed and spindle speed condition, which determines the forces and undeformed chip thickness during the process. Fiber pull-out geometries influence surface roughness parameters from a surface profilometer, while their effect on other hole quality parameters obtained from a coordinate measuring machine is minimal.