Mechanical Behavior Of Hybrid Research Articles

Effect of machining processes on the damage response and surface quality of open hole hybrid carbon/flax composites: An experimental study

The influence of conventional drilling (CD) and abrasive water jet (AWJ) machining on the mechanical behavior of hybrid carbon/flax composites was investigated. The specimens were manufactured using woven carbon fiber (C) and unidirectional flax fiber (F) in three configurations: unidirectional [0-90C2/0F6]S, cross-ply [0-90C2/(0/90)F6]S, and angle-ply [0-90C2/(±45)F6]S laminates. The examination of the hole surface revealed severe damage in the form of peel-up, push-out, and secondary delamination of AWJ machined holes, and only push-out delamination at the exit side of the CD drilled hole. A delamination factor was developed to quantify the delamination at the hole surface. The specimens were subjected to quasi-static load-unload tensile tests to assess their damage response and surface fracture. Unidirectional and angle-ply specimens drilled with AWJ accumulated a higher damage compared to CD specimens. This correlates with the delamination factor, indicating that the delamination at the entry and exit of the hole and secondary delamination greatly affect the damage evolution of the laminates.

Microscopic appraisal and mechanical behavior of hybrid Cu/Al joints fabricated via friction stir spot welding-brazing and modified friction stir clinching-brazing

This paper focuses on the improvement of hybrid Cu/Al weld performance via a combination of self-reacting brazing mechanism (for stable metallurgical transformation) and process modification approach (for the elimination of tool profile-induced stress-raiser). The modified friction stir clinching-brazing (MFSC-B) and friction stir spot welding-brazing (FSSW-B) of dissimilar AA5083-H321 aluminum and commercially pure Cu alloys are investigated with the use of a thin Zn intermediate layer. The load-bearing capacity, fracture behavior, and microstructure of the respective joints are investigated and compared. The results show that plausible intermetallic phases of Al–Cu (Al2Cu and Al4Cu9) and Cu–Zn are present at the stir zones of all the joints while the brazed zone of the MFSC-B joint is predominated by uniform lamellar eutectic structure due to higher heat input, localized two-fold Zn melting, and frictional-stirring activated eutectic transformation. The increase in the load-bearing area (brazed + stir zones) of the MFSC-B joint improved the fracture resistance of the joint by 59% as the average tensile-shear loads of about 7.0 and 4.4 kN were obtained in the MFSC-B and FSSW-B joints respectively. The use of MFSC-B is thus recommended as a reasonable alternative for improving the weld performance of dissimilar reactive metals.

Experimental investigation on the mechanical behavior of hybrid bonded (rivet/adhesive) tubular lap joint (composite to metal) under pure torsion

The hybrid joints being used in the design of mechanical structures because of their significant advantages. The tubular lap joints are used widely in aerospace, naval, and transport industries such as rudder and elevator rods, driving shafts, pull push rods, anti-roll bar and stabilizer bar in cars, trucks and trains. The torsional behavior of mechanical, adhesively bonded, and hybrid tubular lap joints for aluminum to aluminum, and composite to aluminum subjected to pure torsion have been investigated experimentally. The effect of outer tube material and thickness, the joint’s type, and cured and post-cured temperature (room temperature and 40 °C), have been investigated experimentally. A fixture and a torsional set-up device have been designed and manufactured to apply the required torque to the joint. The outcomes from composite to aluminum joints confirm that the hybrid joint has 39.5% and 276.6% higher torque capacity than the mechanical joint and adhesively bonded joint, respectively. Furthermore, the cured and post-cured process at 40 °C, increased the maximum torque to failure, 37.6% and 57.1% for adhesively bonded and hybrid (rivet/bonded) joint, respectively. It has been observed that by upgrading the mechanical joint and adhesively bonded joint to the hybrid (rivet/bonded) joint, increasing the amount of joint’s strength and torque capacity in comparison with the increase in the weight of the structure is affordable.

Investigation on Mechanical Behavior of Hybrid Jute/Banana Natural Fiber Reinforced Polyester Composites

Investigation on Mechanical Behavior of Hybrid Jute/Banana Natural Fiber Reinforced Polyester Composites

Mechanical Behavior of Hybrid Glass/Steel Fiber Reinforced Epoxy Composites.

While conventional fiber-reinforced polymer composites offer high strength and stiffness, they lack ductility and the ability to absorb energy before failure. This work investigates hybrid fiber composites for structural applications comprised of polymer, steel fiber, and glass fibers to address this shortcoming. Varying volume fractions of thin, ductile steel fibers were introduced into glass fiber reinforced epoxy composites. Non-hybrid and hybrid composite specimens were prepared and subjected to monolithic and half-cyclic tensile testing to obtain stress-strain relationships, hysteresis behavior, and insight into failure mechanisms. Open-hole testing was used to assess the vulnerability of the composites to stress concentration. Incorporating steel fibers into glass/epoxy composites offered a significant improvement in energy absorption prior to failure and material re-centering capabilities. It was found that a lower percentage of steel fibers (8.2%) in the hybrid composite outperformed those with higher percentages (15.7% and 22.8%) in terms of energy absorption and re-centering, as the glass reinforcement distributed the plasticity over a larger area. A bilinear hysteresis model was developed to predict cyclic behavior of the hybrid composite.

Mechanical behavior of hybrid fiber‐reinforced composites manufactured by pulse infusion

Epoxy/carbon fiber composites have been manufactured by Pulse Infusion. Pulse Infusion allows to control the pressure of the vacuum bag on the dry fiber reinforcement by using a proper designed pressure distributor that induces a pulsed transverse action and promotes the through thickness resin flow. The adopted one‐component commercial epoxy resin has been preliminary modified by adding 0.05% (w/w) of multiwalled carbon nanotubes, in order to take advantage of carbon nanotubes at low concentration. Both neat and hybrid realized composite panels have been mechanically characterized by performing experimental tests to evaluate tensile, interlaminar, and fracture properties in order to investigate the effect of Pulse Infusion and carbon nanotubes on the mechanical and fracture behavior of composites. Results demonstrated an improvement of 36.2% for the interlaminar shear strength, of 35% for the fracture energy at the crack initiation and of 14% for the fracture toughness in mode II. POLYM. COMPOS., 38:2254–2260, 2017. © 2015 Society of Plastics Engineers

An experimental investigation into mechanical behavior of hybrid and nonhybrid composite semi-elliptical springs

This study introduces a new composite semi-elliptical suspension spring by utilizing fiber reinforced composite strength in principal direction instead of shear direction. Three types of composites were tested, namely, carbon/epoxy, glass/epoxy and glass/carbon/epoxy. A comprehensive experimental investigation of composite semi-elliptical suspension springs has been carried out. Typical behaviors of their compression, tension, torsion and cyclic tests are presented and discussed. The results showed that the fiber type and ellipticity ratio significantly influenced the spring stiffness. After 1.15 million fatigue cycles, composite semi-elliptical suspension spring’s useful stroke is reduced by only 2%. The relaxation of the composite elliptic spring found to be very sensitive to the compression rate.

Mechanical Behaviour of Hybrid Polymer/Semiconductor Microtubes

This work focuses on the fabrication and analysis of hybrid polymer/semiconductor microtubes realized by self-rolling technique. They consist of alternated PEI/PAA polymer multilayers deposited on strained semiconductor In 0.2 Ga 0.8 As/GaAs bilayer. To investigate their mechanical and elastic properties, force-distance measurements were carried out on both semiconductor and hybrid channels with different polymer thickness, revealing reinforced tubes due to the polymer multilayer presence and an increase of the stiffness by increasing either the number of multilayers or the number of wrappings. Additionally hybrid microtubes were post-processed thus exposing the inner polymer surface and demonstrating the possibility of engineer more complex architectures.

Hybrid jute/cotton fabric–polyester composites: effect of fabric architecture, lamina stacking sequence and weight fraction of jute fibres on tensile strength

The tensile mechanical behaviour of hybrid jute/cotton fabric reinforced polyester composites was evaluated. Three fabric configurations, with varying jute weight fractions, were used and five stacking sequences were analysed, namely: [0]; [0/90]; [0/90/0]; [90/0/90] and [0/90/0/90]. The data suggest that differences on the areal density of the fabrics were of minor importance to the tensile behaviour of the composites with jute fibres aligned to the loading direction, [0]. The results obtained for the other configurations – with [90] layers – were strongly influenced by the lack of resin impregnation inside the tow of the fibre, by the weak jute/polyester matrix interface and by the presence of jute fibres aligned perpendicularly to the loading direction. For these stacking sequences, the results obtained were dominated by the maximum strain sustained at the jute/polyester interface. Cotton fibres were shown to be non-reinforcing, and to act only as a convenient ancillary fibre aiding at the fabric manufacture.

Analytical Two-Dimensional Model of a Hybrid (Bolted/Bonded) Single-Lap Joint

The mechanical behavior of hybrid (bolted/bonded) joints applied to aeronautic structures is investigated. The joints under study are balanced single-lap joints, and an elastic behavior of the materials is assumed. A fully parametric analytical two-dimensional model, based on the finite element method, is presented. A special finite element, named beams element, is computed to simulate the bonded adherends. The method and the equations to obtain the stiffness matrix of this new element are presented in this paper. The simulation of fasteners is examined through experimental and numerical approaches. The bolt load transfer is measured by the use of specially instrumented bolts, whereas a finite element 3-D model is developed to calibrate the analytical model. Good agreement is found between the analytical, experimental, and numerical results.