Numerical and Experimental Studies on Cured Shape of Thin Unsymmetric Carbon/Epoxy Laminates

2007 ◽  
Vol 334-335 ◽  
pp. 137-140 ◽  
Author(s):  
Fu Hong Dai ◽  
Bo Ming Zhang ◽  
Xiao Dong He ◽  
Shan Yi Du
Keyword(s):  
Analytical Model ◽  
Composite Laminates ◽  
Value Function ◽  
Ritz Method ◽  
Experimental Studies ◽  
Experimental Result ◽  
Multiple Value

An analytical model was established by means of Ritz method to calculate the cured shape of cross-ply unsymmetric composite laminates. A number of experiments of Carbon/Epoxy laminates were conducted. It was found in the experiment that the warped surface could be a multiple-value function, which should be studied further. The result of calculation correlates well with the experimental result except the regions very near the laminate edge. The conclusion is instructive to manufacture of composite laminates.

scholarly journals Parametric structural modelling of fish bone active camber morphing aerofoils

2018 ◽  
Vol 29 (9) ◽  
pp. 2008-2026 ◽  
Author(s):  
Andres E Rivero ◽  
Paul M Weaver ◽  
Jonathan E Cooper ◽  
Benjamin KS Woods
Keyword(s):  
Analytical Model ◽  
Composite Laminates ◽  
Plate Theory ◽  
Ritz Method ◽  
Linear Equations ◽  
Variable Stiffness ◽  
Automated Analysis ◽  
Fish Bone ◽  
Two Dimensional ◽  
Wide Range

Camber morphing aerofoils have the potential to significantly improve the efficiency of fixed and rotary wing aircraft by providing significant lift control authority to a wing, at a lower drag penalty than traditional plain flaps. A rapid, mesh-independent and two-dimensional analytical model of the fish bone active camber concept is presented. Existing structural models of this concept are one-dimensional and isotropic and therefore unable to capture either material anisotropy or spanwise variations in loading/deformation. The proposed model addresses these shortcomings by being able to analyse composite laminates and solve for static two-dimensional displacement fields. Kirchhoff–Love plate theory, along with the Rayleigh–Ritz method, are used to capture the complex and variable stiffness nature of the fish bone active camber concept in a single system of linear equations. Results show errors between 0.5% and 8% for static deflections under representative uniform pressure loadings and applied actuation moments (except when transverse shear exists), compared to finite element method. The robustness, mesh-independence and analytical nature of this model, combined with a modular, parameter-driven geometry definition, facilitate a fast and automated analysis of a wide range of fish bone active camber concept configurations. This analytical model is therefore a powerful tool for use in trade studies, fluid–structure interaction and design optimisation.

An analytical model for predicting the shear strength of unsaturated soils

2022 ◽  
pp. 1-57
Author(s):  
Tuan A. Pham ◽  
Melis Sutman
Keyword(s):  
Shear Strength ◽  
Analytical Model ◽  
Unsaturated Soils ◽  
High Performance ◽  
Micromechanical Model ◽  
Experimental Studies ◽  
Stress Equilibrium ◽  
Proposed Model ◽  
New Equation ◽  
Multi Phase

The prediction of shear strength for unsaturated soils remains to be a significant challenge due to their complex multi-phase nature. In this paper, a review of prior experimental studies is firstly carried out to present important pieces of evidence, limitations, and some design considerations. Next, an overview of the existing shear strength equations is summarized with a brief discussion. Then, a micromechanical model with stress equilibrium conditions and multi-phase interaction considerations is presented to provide a new equation for predicting the shear strength of unsaturated soils. The validity of the proposed model is examined for several published shear strength data of different soil types. It is observed that the shear strength predicted by the analytical model is in good agreement with the experimental data, and get high performance compared to the existing models. The evaluation of the outcomes with two criteria, using average relative error and the normalized sum of squared error, proved the effectiveness and validity of the proposed equation. Using the proposed equation, the nonlinear relationship between shear strength, saturation degree, volumetric water content, and matric suction are observed.

Experimental investigation and modeling of dynamic thermomechanical behavior of 4-harness satin weave carbon/epoxy composites

2017 ◽  
Vol 31 (9) ◽  
pp. 1181-1203 ◽  
Author(s):  
Xueyao Hu ◽  
Hui Guo ◽  
Weiguo Guo ◽  
Feng Xu ◽  
Longyang Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Composite Laminates ◽  
Failure Modes ◽  
Shear Failure ◽  
Experimental Studies ◽  
Temperature Shift ◽  
Thermomechanical Coupling ◽  
Longitudinal Splitting ◽  
Wide Range

Theoretical and experimental studies on the compressive mechanical behavior of 4-harness satin weave carbon/epoxy composite laminates under in-plane loading are conducted over the temperature range of 298–473 K and the strain rate range of 0.001–1700/s in this article. The stress–strain curves of 4-harness satin weave composites are obtained at different strain rates and temperatures, and key mechanical properties of the material are determined. The deformation mechanism and failure morphology of the samples are observed and analyzed by scanning electron microscope (SEM) micrographs. The results show that the uniaxial compressive mechanical properties of 4-harness satin weave composites are strongly dependent on the temperature but are weakly sensitive to strain rate. The peak stress and elastic modulus of the material have the trend of decrease with the increasing of temperature, and the decreasing trend can be expressed as the functional relationship of temperature shift factor. In addition, SEM observations show that the quasi-static failure mode of 4-harness satin weave composites is shear failure along the diagonal lines of the specimens, while the dynamic failure modes of the material are multiple delaminations and longitudinal splitting, and with the increasing of temperature, its longitudinal splitting is more serious, but the delamination is relatively reduced. A constitutive model with thermomechanical coupling effects is proposed based on the experimental results and the increment theory of elastic–plastic mechanics. The experimental verification and numerical analysis show that the model is shown to be able to predict the finite deformation behavior of 4-harness satin weave composites over a wide range of temperatures.

Effect of fixation stitches on out-of-plane response of textile non-crimp fabric composites

2018 ◽  
Vol 48 (7) ◽  
pp. 1151-1166 ◽  
Author(s):  
Somen K Bhudolia ◽  
Kenneth KC Kam ◽  
Pavel Perrotey ◽  
Sunil C Joshi
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Peak Load ◽  
Experimental Studies ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Mode I Fracture Toughness ◽  
Out Of Plane ◽  
Static Indentation ◽  
Sem Investigation

Non-crimp fabrics are fabric tapes stitched to an adjacent orthogonal fabric with no associated crimp. In the current research, the effect of fixation polyester stitches in improving through-the-thickness properties of non-crimp fabric composite laminates is investigated. Detailed experimental studies on interlaminar fracture toughness and static indentation properties of stitched and unstitched thin ply carbon fibre epoxy composites have been conducted. About 23% higher peak load and 37% higher energy absorption were noticed during static indentation tests for the stitched ply composites. A detailed SEM investigation has shown that the stitch-stitch interaction ‘within a bi-angle ply’ and ‘between the bi-angle ply’ plays a significant role in reducing the delamination extent. The critical energy release rate during Mode I fracture toughness of stitched composites was found to be 26.5% higher and SEM investigation depicted that the stitches promote the intra-laminar delamination and enhance the toughness of the composite.

3D Thermal Stresses in Composite Laminates Under Steady-State Through-Thickness Thermal Conduction

2020 ◽  
Vol 12 (06) ◽  
pp. 2050065
Author(s):  
Yan Guo ◽  
Yanan Jiang ◽  
Ji Wang ◽  
Bin Huang
Keyword(s):  
Steady State ◽  
Plane Stress ◽  
Composite Laminates ◽  
Stress Function ◽  
Thermal Conduction ◽  
Thermal Stresses ◽  
Virtual Work ◽  
Ritz Method ◽  
Stress Fields ◽  
Stress Functions

In this study, 3D thermal stresses in composite laminates under steady-state through thickness thermal conduction are investigated by means of a stress function-based approach. One-dimensional thermal conduction is solved for composite laminate and the layerwise temperature distribution is calculated first. The principle of complementary virtual work is employed to develop the governing equations. Their solutions are obtained by using the stress function-based approach, where the stress functions are taken from the Lekhnitskii stress functions in terms of in-plane stress functions and out-of-plane stress functions. With the Rayleigh–Ritz method, the stress fields can be solved by first solving a standard eigenvalue problem. The proposed method is not merely computationally efficient and accurate. The stress fields also strictly satisfy the prescribed boundary conditions validated by the results of finite element method (FEM) results. Finally, some of the results will be given for discussion considering different layup stacking sequences, thermal conductivities and overall temperature differences. From the results, we find that the thermal conductivity greatly affects the stress distributions and peak values of stresses increase linearly for the present model. The proposed method can be used for predicting 3D thermal stresses in composite laminates when subjected to thermal loading.

Analysis of Buckling of Sandwich Plates with Viscoelastic Core Using Layerwise Theory

2015 ◽  
Vol 798 ◽  
pp. 462-469 ◽  
Author(s):  
Arash Ranjbaran ◽  
Mohammad Reza Khoshravan ◽  
Mahsa Kharazi
Keyword(s):  
Composite Laminates ◽  
Ritz Method ◽  
Computational Cost ◽  
Shear Deformation Theory ◽  
Element Model ◽  
Sandwich Plates ◽  
Layerwise Theory ◽  
Buckling Behavior ◽  
Viscoelastic Core ◽  
Good Agreement

Sandwich plates are one of the important components in construction of engineering and especially aerospace structures. In this paper, buckling analysis of sandwich plates was investigated experimentally and analytically using layerwise theory. The sandwich plate was rectangular and made of two composite laminates as skins and a viscoelastic core. The formulation was based on the first order shear deformation theory and the Rayleigh-Ritz method was used for approximating and determining the displacement field. The behavior of viscoelastic material modeled using Zener three-element model. The results obtained from layerwise theory compared with experimental results and showed good agreement. This study demonstrated that, layerwise theory could describe buckling behavior of sandwich plates with high accuracy and represents more realistic and acceptable description of behavior of the plates with much less computational cost.

An analytical model for the response of carbon/epoxy-aluminum honeycomb core sandwich structures under quasi-static indentation loading

2017 ◽  
Vol 21 (6) ◽  
pp. 1930-1952 ◽  
Author(s):  
Abhendra K Singh ◽  
Barry D Davidson ◽  
Alan T Zehnder ◽  
Benjamin PJ Hasseldine
Keyword(s):  
Analytical Model ◽  
Sandwich Structures ◽  
Plate Theory ◽  
Ritz Method ◽  
Design Tool ◽  
Face Sheet ◽  
Total System ◽  
Honeycomb Core ◽  
Static Indentation ◽  
Aluminum Honeycomb

An analytical model is developed to predict the loading and unloading response, as well as the residual dent diameter and dent depth, of carbon/epoxy-aluminum honeycomb core composite sandwich structures undergoing quasi-static indentation loading. The model considers damage created using spherical indenters and is valid up to the barely visible external damage threshold. The initial low load regime (until the onset of core crushing) is modeled using a combination of local Hertzian indentation of an elastic half-space and small deflection plate theory of a circular plate on an elastic foundation. For loads above those required to cause core crushing, the model uses the Rayleigh-Ritz method of energy minimization with the total system energy determined using a combination of face sheet bending energy, face sheet membrane energy and work done to the core during both elastic deformation and crushing. Degraded face sheet properties are used in the model beyond the onset of face sheet delamination, which is predicted using Griffith’s energy criterion. The model is validated using experimental results for sandwich structures consisting of quasi-isotropic 8- (thin) and 16- (thick) ply carbon/epoxy face sheets and aluminum honeycomb cores. The results show that the overall mechanics of the model are fundamentally correct and reflective of physical behavior. Thus, in its present form the model shows promise as a preliminary design tool.

The Experimental Studies of Improving the Aerodynamic Performance of a Turbine Exhaust System

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Stephen Guillot ◽  
Wing F. Ng ◽  
Hans D. Hamm ◽  
Ulrich E. Stang ◽  
Kevin T. Lowe
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Experimental Studies ◽  
Experimental Result ◽  
Test Facility ◽  
Test Rig ◽  
Blow Down ◽  
Recovery Coefficient ◽  
Scale Test ◽  
Turbine Exhaust

Analysis and testing were conducted to optimize an axial diffuser–collector gas turbine exhaust. Two subsonic wind tunnel facilities were designed and built to support this program. A 1/12th scale test rig enabled rapid and efficient evaluation of multiple geometries. This test facility was designed to run continuously at an inlet Mach number of 0.41 and an inlet hydraulic diameter-based Reynolds number of 3.4 × 105. A 1/4th geometric scale test rig was designed and built to validate the data in the 1/12th scale rig. This blow-down rig facilitated testing at a nominally equivalent inlet Mach number, while the Reynolds number was matched to realistic engine conditions via back pressure. Multihole pneumatic pressure probes, particle image velocimetry (PIV), and surface oil flow visualization were deployed in conjunction with computational tools to explore physics-based alterations to the exhaust geometry. The design modifications resulted in a substantial increase in the overall pressure recovery coefficient of +0.07 (experimental result) above the baseline geometry. The optimized performance, first measured at 1/12th scale and obtained using computational fluid dynamics (CFD) was validated at the full scale Reynolds number.

An analytical model on through-thickness stresses and warpage of composite laminates due to tool–part interaction

2016 ◽  
Vol 91 ◽  
pp. 408-413 ◽  
Author(s):  
Zhenyi Yuan ◽  
Yongjun Wang ◽  
Xiongqi Peng ◽  
Junbiao Wang ◽  
Shengmin Wei
Keyword(s):  
Analytical Model ◽  
Composite Laminates
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