Investigation on mechanical properties of hybrid aluminum/composite tubes manufactured by filament winding and hand lay-up

Nowadays, composite tubes have a wide range of applications in industries. Composite tubes are appropriate alternatives for metal energy absorbers. In this investigation, aluminum-composite tubes are made using Filament Winding (FW) and hand lay-up methods. Carbon Fiber (CF) and Glass Fiber (GF) are used in the FW method, and for the hand lay-up method, glass cloth is used. Five samples were fabricated with different stacking sequences, specimens with one, two, and three glass layers, one carbon layer, and hybrid carbon/glass layers. Characterization is performed by Scanning Electron Microscopy (SEM) analysis and mechanical tests (bending, compressive, and fatigue). The maximum bending force in the triple-layer GF tube is higher than other samples, while the maximum compressive force is observed in the hybrid carbon and GF tube. On the other hand, the fatigue strength of single-layer CF tubes is higher than single-layer GF tubes, so that the fracture cycles of single-layer CF tubes (600597) is significantly more than that of single-layer GF tubes (470068) at the force of 35 N. In addition, the compressive and bending energies absorption of samples were calculated. The hybrid carbon and GF tube absorbed higher energy than other samples. In GF and CF hybrid tubes, failure did not occur suddenly but gradually. This appropriate failure mechanism in the hybrid tube resulted in higher energy absorption and made it a suitable choice for industrial applications.

Generation of filament winding patterns for elbows with various cross-sections

As a connecting component of tubes, the elbow is indispensable to pipe-fitting in composite products. Previous studies have addressed methods for generating winding paths based on parametric equations on the elbow. However, these methods are unsuitable for elbows whose surfaces are difficult to describe using mathematical expressions. In this study, a geometric method was proposed for generating winding patterns for various elbow types. With this method, the mandrel surface is first converted into uniform and high-quality quadrilateral elements; an algorithm is then provided for calculating the minimum winding angle for bridging-free. Next, an angle for non-bridging was defined as the design-winding angle to generate the uniform and slippage-free basic winding paths on the quadrilateral elements in non-geodesic directions. Finally, after a series of uniform points were calculated on the selected vertical edge according to the elbow type, the pattern paths were generated with the uniform points and basic paths. The proposed method is advantageously not limited to the elbow’s shape.

Application of the Proposed Fiber Optic Time Differential BOCDA Sensor System for Impact Damage Detection of a Composite Cylinder

An optical-fiber-embedded composite cylinder was fabricated using the filament winding process with an interval of 12 mm in the longitudinal direction of the cylinder. The optical fiber was wound 160 turns around the cylinder, and the straight length was about 125 m. After a total of twelve impact events of 5, 10, 15, and 20 J, the residual strain in the cylinder was measured using the proposed time differential BOCDA sensor system. This method makes the traditionally used optical delay unnecessary while increasing the degrees of freedom of using the modulation rate, which determines the spatial resolution of this measurement system. The modulation rates of optical light in the system were applied up to 16 Gbps, which is an eight-fold increase compared to our previous experiments. Damage maps were obtained by mapping the measured residual strain onto the structure of the cylinder, and compared using three spatial resolutions of 20, 10, and 6.25 mm. In the measured damage map, expansion deformation due to impact was measured at all impact points, and the impact location on the map and the actual location on the cylinder were exactly the same. The map measured from the composite showed a clear point-symmetrical shape with an increase in sharpness as the measurement resolution increased. At the highest resolution, material expansion and compression were observed to alternate with respect to the center of impact, like the surface deformation of a liquid caused by a thrown object. Furthermore, considered together with our previous experiments, we confirmed that this phenomenon propagated from the surface of the composite material to the interior, where the optical fiber was embedded. The total amount of residual strain formed around each impact point was linearly proportional to the applied external impact energy.

Using potential of filament-wound carbon/glass polymeric composites as rocket motor thermal insulation

The study aim is to develop hybrid filament-wound polymeric composites based on flame retardant polyester resin (UPe) and multi-layer structured glass or combined carbon and glass fibers for use as ablative thermal insulation of rocket motor by wet filament winding technique. The composites have a multi-layered structure consisting of two layers of carbon (CF) or glass woven fabric (GF) and one layer of carbon or glass direct roving (CR or GR, respectively), repeated in three cycles. Structural analysis, performed using FTIR spectroscopy and dynamical-mechanical analysis, confirm highly polymerized network. Lower values of the tanδ peak height indicate improved interfacial adhesion between carbon/glass fibers and UPe. The improvements of thermal insulation index of 37% and erosion rate of 38.6% at 180°C are achieved for combined carbon/glass fiber–based composite compared to the neat UPe. Tensile and interlaminar shear properties are investigated according to the fiber orientation and the highest values of tensile and interlaminar shear strengths are obtained for composites with longitudinal orientation, 417.48 MPa and 22.30 MPa, respectively. Compared to the neat UPe, which degrades after 50 s at 3000°C, the composites are stable up to 192 s.

Burst strength analysis of composite overwrapped pressure vessel using finite element method

The purpose of this numerical study was to investigate the burst performance of a type III composite overwrapped pressure vessel (COPV) using finite element methods. An Aluminum overwrapped composites pressure vessel was modeled from four layers of carbon fiber/epoxy ply with 0.762 mm and arranged in two different sequences and orientations. The overwrap composite pressure vessel burst performance was examined by applying an internal pressure of 55 MPa on a ply arrangement of [-15°/0°/+15°/90°] and other research findings on [+55°/-55°] as an optimum filament winding angle were used for comparison purpose. Moreover a ply level orientation effect analysis, which is a superior feature of ABAQUS, was used for the composite modelling. The designed ply sequence and orientation exhibit a higher burst pressure at [0°] ply and minimum at [90°] ply orientation. The vertical COPV design displays a maximum stress along the axial direction that leads to the consideration of maximum vessel thickness to be along axial direction for burst resistant design of COPV.

Flexural Pseudo-Ductility Effect in Hybrid GFRP/CFRP Bars under Static Loading Conditions

The problem with composite rebars in the civil engineering industry is often described as the material’s brittleness while overloaded. To overcome this drawback, researchers pay attention to the pseudo-ductility effect. The paper presents four-point bending tests of pure unidirectional (UD) rods with additional composite layers obtained by filament winding and hand braiding techniques. Two types of core materials, glass FRP (fibre reinforced polymer) and carbon FRP, were used. Regarding the overwrapping material, the filament winding technique utilized carbon and glass roving reinforcement in the epoxy matrix, while in the case of hand braiding, the carbon fibre sleeve was applied with the epoxy matrix. Microstructural analysis using scanning electron microscopy (SEM) and computed tomography (CT) was performed to reveal the structural differences between the two proposed methods. Mechanical test results showed good material behaviour exhibiting the pseudo-ductility effect after the point of maximum force. The two applied overwrapping techniques had different influences on the pseudo-ductility effect. Microstructural investigation revealed differences between the groups of specimens that partially explain their different characters during mechanical testing.

Material Monitoring of a Composite Dome Pavilion Made by Robotic Coreless Filament Winding

A hemispherical research demonstration pavilion was presented to the public from April to October 2019. It was the first large-scale lightweight dome with a supporting roof structure primarily made of carbon- and glass-fiber-reinforced composites, fabricated by robotic coreless filament winding. We conducted monitoring to ascertain the sturdiness of the fiber composite material of the supporting structure over the course of 130 days. This paper presents the methods and results of on-site monitoring as well as laboratory inspections. The thermal behavior of the pavilion was characterized, the color change of the matrix was quantified, and the inner composition of the coreless wound structures was investigated. This validated the structural design and revealed that the surface temperatures of the carbon fibers do not exceed the guideline values of flat, black façades and that UV absorbers need to be improved for such applications.