Hybrid Composite Beams Research Articles

Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

An experimental and numerical investigation into the static and dynamic responses of shape memory alloy hybrid composite (SMAHC) beams is performed to provide quantitative validation of a recently commercialized numerical analysis/design tool for SMAHC structures. The SMAHC beam specimens consist of a composite matrix with embedded pre-strained SMA actuators, which act against the mechanical boundaries of the structure when thermally activated to adaptively stiffen the structure. Numerical results are produced from the numerical model as implemented into the commercial finite element code ABAQUS. A rigorous experimental investigation is undertaken to acquire high fidelity measurements including infrared thermography and projection moiré interferometry for full-field temperature and displacement measurements, respectively. High fidelity numerical results are also obtained from the numerical model and include measured parameters, such as geometric imperfection and thermal load. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

Failure analysis of a hybrid composite structural beam

The purpose of this study was to identify the failure mode of a particular composite structural beam developed for the civil infrastructure market and to develop a strength prediction that could be utilized in fatigue life predictions. First, a global–local finite element stress analysis is utilized to examine the possibility of compression failure. We then investigate the possibility of a delamination failure using a successive sub-modeling approach that allows detailed analysis of the inter-laminar stresses in regions of high stress gradients, including free edges and tapered laminates. The results of the analyses are compared with experimental test data from full-scale bending tests. The results indicate a compression dominated failure in the top flange in the vicinity of the load patch. This study highlights the difficulty in applying a stress-based approach to predicting delamination failure, particularly in complex laminated structures.

Coupled Efficient Zigzag Finite Element Analysis of Piezoelectric Hybrid Beams under Thermal Loads

A new one-dimensional beam finite element is developed for hybrid piezoelectric beams under thermal load, using a coupled efficient layerwise (zigzag) theory developed recently by the authors. The theory accounts for the layerwise variations of the axial and the transverse displacements while keeping the number of displacement variables independent of the number layers. The beam element has two nodes with four mechanical and a variable number of electric potential degrees of freedom at each node. In the thickness direction, the thermal and the electric fields are approximated as piecewise linear across an arbitrary number of sublayers in a layer. Cubic Hermite interpolation is used for the deflection and electric potentials at the sublayers and linear interpolation is used for the axial displacement and the shear rotation. The thermal field is computed using a consistent six-noded thermal finite element with a quadratic interpolation along longitudinal direction and a linear interpolation along thickness direction. The formulation is validated by comparing the results with the Navier-type solution of the zigzag theory for simply-supported hybrid beams. The element is free from shear locking. The accuracy of the zigzag theory is established by comparing the results of hybrid composite and sandwich beams with the two-dimensional finite element results using ABAQUS for cantilever and clamped-clamped end conditions under different thermal loads. The control of thermal deflection by the application of actuation potential is illustrated. The effects of electric boundary conditions and the pyroelectric effect on the response are discussed.

Experimental study of hybrid composite beams

In this study, a new type of hybrid confining device, a perforated steel tube that is externally protected by a thin fiber reinforced polymer skin is proposed and experimentally investigated. Hybrid composite beams were fabricated by filling fresh concrete into the hybrid composite tube. Fifteen scaled-down square beams, which had varying numbers of perforated steel faces or ‘steel grids’ and a dimension of length 55.9 cm, height 10.1 cm, and width 10.1 cm, were prepared. Four-point bending tests were conducted on all the specimens. In addition to the load–displacement curves obtained from the tests, strain gages were installed to monitor the local strain distributions. Test results show that the grid tube encased specimens lead to higher specific strength and ductility than the solid steel tube encased counterparts. Compared to other configurations, the specific strength and ductility are the highest when all the four faces are made of steel grids.

Efficient layerwise finite element model for dynamic analysis of laminated piezoelectric beams

An one-dimensional beam finite element with electric degrees of freedom is presented for the dynamic analysis of hybrid piezoelectric beams, using the coupled efficient layerwise (zigzag) theory developed recently by the authors. The beam element has two nodes with four mechanical and a variable number of electric potential degrees of freedom at each node. In the thickness direction, the electric field is approximated as piecewise linear across an arbitrary number of sub-layers in the piezoelectric layers. Cubic Hermite interpolation is used for the deflection and electric potentials at the sub-layers and linear interpolation is used for the axial displacement and the shear rotation. The formulation is validated by comparing the results with the available analytical solution of the zigzag theory for hybrid composite and sandwich beams with simply-supported ends. The finite element model is free of shear locking. The present zigzag finite element results for natural frequencies, mode shapes and forced vibration response of cantilever and clamped–clamped beams are compared with the two-dimensional finite element results using ABAQUS to establish the accuracy of the zigzag theory for dynamic response under these boundary conditions.

Efficient Coupled Zigzag Theory for Hybrid Piezoelectric Beams for Thermoelectric Load

An efficient coupled zigzag theory is developed for electrothermal stress analysis of hybrid piezoelectric beams. The thermal and potential fields are approximated as piecewise linear for the sublayers. The deflection is modeled to account for the transverse normal strain due to piezoelectricity and temperature. The longitudinal displacement is approximated as a combination of third-order global variation and a layerwise linear variation. The shear continuity conditions at the layer interfaces and the shear traction-free conditions at the top and bottom are used to formulate the theory in terms of three primary displacement variables. The theory is assessed by comparing the analytical solution for simply supported beam with the exact piezothermoelasticity solution. Comparisons for two thermal loads on a hybrid test beam devised for this study and hybrid composite beams establish that the present theory yields quite accurate results.

Analysis of hybrid beams composed of GFRP profiles and polymer concrete

In this paper, a numerical approach for the analysis of a new type of hybrid composite beams is presented. Such beams are composed of composite materials that resist shear and tensile stresses, and polymer concrete acommodating compression stresses.The beams offer an optimized configuration in terms of stiffness and strength, with much potential for mechanical and civil engineering structures.The current numerical model is based on a finite element formulation for layered shell-like structures. The model accounts for a polymer concrete material model, orthotropic material model, and considers the analysis of geometric and material nonlinearities. The first-order shear deformation theory is used in order to describe the shell deformation under a total Lagrangian formulation. The model is validated experimentally and a close agreement with experimental results makes this model an attractive solution method for this type of composite hybrid beams.

Optimal lay-up of hybrid composite beams, plates and shells using cellular genetic algorithm

Laminated composite structures find wide range of applications in many branches of technology. They are much suited for weight sensitive structures (like aircraft) where thinner and lighter members made of advanced fiber reinforced composite materials are used. The orientations of fiber direction in layers and number of layers and the thickness of the layers as well as material of composites play a major role in determining the strength and stiffness. Thus the basic design problem is to determine the optimum stacking sequence in terms of laminate thickness, material and fiber orientation. In this paper, a new optimization technique called Cellular Automata (CA) has been combined with Genetic Algorithm (GA) to develop a different search and optimization algorithm, known as Cellular Genetic Algorithm (CGA), which considers the laminate thickness, angle of fiber orientation and the fiber material as discrete variables. This CGA has been successfully applied to obtain the optimal fiber orientation, thickness and material lay-up for multi-layered composite hybrid beams plates and shells subjected to static buckling and dynamic constraints.

Testing of hybrid FRP composite beams in bending

This paper presents tests where hybrid composite beams have been investigated. The hybrid beam consists of a glass fibre I-beam with carbon fibre strengthened bottom flange and a rectangular concrete block in the compressive zone. The interaction between the concrete and composite beam were obtained in two ways; casting in shear connectors of steel and bonding by epoxy adhesive. As a reference, a beam without concrete in the compressive zone was also tested. The idea of combining carbon, glass and concrete was to utilize the stiffness contribution from the carbon and the compressive strength from the concrete. The glass fibre I-beam would then take up the main part of the shear force. The results from the test showed that a good composite action could be achieved between carbon, glass and concrete. However, it could also be noticed, as expected, that an I-beam is not the ultimate form due to stability problems. In the tests, problems arose due to lateral instability, but this was solved by placing stiffeners manufactured from wood between the flanges of the Fibre Reinforced Polymer beam over the supports. With a few modifications of the hybrid beam it is believed, that it would be possible to create both a technical and economical hybrid profile that benefits from carbon, glass and concrete.

Optimal lay-up of hybrid composite beams, plates and shells using cellular genetic algorithm

Laminated composite structures find wide range of applications in many branches of technology. They are much suited for weight sensitive structures (like aircraft) where thinner and lighter members made of advanced fiber reinforced composite materials are used. The orientations of fiber direction in layers and number of layers and the thickness of the layers as well as material of composites play a major role in determining the strength and stiffness. Thus the basic design problem is to determine the optimum stacking sequence in terms of laminate thickness, material and fiber orientation. In this paper, a new optimization technique called Cellular Automata (CA) has been combined with Genetic Algorithm (GA) to develop a different search and optimization algorithm, known as Cellular Genetic Algorithm (CGA), which considers the laminate thickness, angle of fiber orientation and the fiber material as discrete variables. This CGA has been successfully applied to obtain the optimal fiber orientation, thickness and material lay-up for multi-layered composite hybrid beams plates and shells subjected to static buckling and dynamic constraints.

Energy Absorption and Dissipation Characteristics of Pultruded Glass-Graphite/Epoxy Hybrid Composite Beams

The response of pultruded glass-graphite/epoxy hybrid composites has been evaluated under two different incident impact energy conditions. A high incident energy (HIE) and a low incident energy (LIE) of impact are chosen to cause either complete fracture or induce delamination, respectively, for assessing the energy absorption characteristics and delamination fracture toughness of these hybrid composites. From the HIE instrumented drop-weight impact tests, the energies required for damage initiation, propagation, as well as total absorbed energies and other parameters necessary for evaluating the impact performance of composites were derived from the load-deformation behavior of each sample. The influence of hybridization on the energy absorption characteristics of pultruded composites was investigated. A parametric study also was performed to correlate the energy absorption characteristics with the energy dissipative mechanisms attributed to the inherent material damping capacity of these composites. The qualitative assessment of the impact performance using inherent damping capacity as a non-destructive testing parameter is highlighted. The samples that were subjected to LIE impact testing were examined using ultrasonic C-scan tests to ascertain changes in the extent of delamination crack propagation as a result of hybridization. Finite element modeling was performed to simulate delamination crack propagation at various levels through the thickness. The strain energy release rate computed using the virtual crack closure technique was monitored to determine the likelihood of delamination crack propagation with increment in crack growth. The results obtained from LIE impact tests and ultrasonic C-scan tests were used to corroborate the predicted delamination fracture toughness of pultruded hybrids. Graphite-outside hybrids exhibited high flexural stiffness, propagation energy, ductility and failure index, but had lower initiation energy along with a greater tendency to delaminate.

Modeling of shape memory alloy hybrid composites for structural acoustic control

Experimental demonstration of active vibration and structural acoustic control using shape memory alloy (SMA) hybrid composites [C. A. Rogers, in Proceedings of the International Congress on Recent Developments in Air and Structure Borne Sound and Vibration (to be published)] has provided the motivation for investigating new control schemes and developing more accurate models. This paper will briefly describe newly developed constitutive models for shape memory alloy actuators and the hybrid material system. A general dynamical model for laminated SMA hybrid composite beams and plates will be presented with several theoretical results. A new structural acoustic model for laminated composite plates [Liang et al., J. Sound Vib. (to be published)] will be briefly described and the potential for active structural acoustic control using SMA hybrid composites demonstrated by numerical simulation.

Shear stress correction factors in hybrid composite material beams : Miller, A.K., Adams, D.F. and Mentock, W.A. Materials Science and Engineering Vol 33 No 1 (April 1978) pp 81–90

Shear stress correction factors in hybrid composite material beams : Miller, A.K., Adams, D.F. and Mentock, W.A. Materials Science and Engineering Vol 33 No 1 (April 1978) pp 81–90

Shear stress correction factors in hybrid composite material beams

Values of the static shear stress correction factors, k1, for hybrid, fiber-reinforced composite beams are calculated using a mechanics of materials approach developed by Bert [1]. These values of k1 are input into the deflection relationships resulting from classical laminated plate theory, which has been extended by Whitney [2] to account for transverse shear deformation effects, and modified to model the deflection of beams under three-point bending [3]. The resulting calculated deflections and strain energies are found not to agree with experimental values reported in ref. 3. It is hypothesized that the discrepancy between the theoretical and experimental values of the shear stress correction factors, the deformations, and the strain energies, may be the result of stress concentrations at the loading and support points of the beam.