Effect of Crack Orientation on Laminated CFRP Composites Using Vibration and Numerical Analysis

2021 ◽  
Vol 79 (11) ◽  
pp. 1081-1093
Author(s):  
Essam Moustafa ◽  
Khalid Almitani ◽  
Hossameldin Hussein
Keyword(s):  
Composite Structures ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Composite Plates ◽  
Mode Shapes ◽  
Crack Orientation ◽  
Test Plate ◽  
Cfrp Composites ◽  
Cfrp Composite ◽  
Vibration Tests

Crack orientation, a critical parameter, significantly affects the dynamic properties of composite structures. Experimental free vibration tests were conducted on carbon fiber–reinforced polymer (CFRP) composite plates at room temperature with different crack orientations. Dynamic properties such as damping ratio, natural frequency, and storage modulus were measured using a four-channel dynamic pulse analyzer. Multi-sensors were mounted on the test plate to pick up the vibration signals. Experimental modal analysis was performed to identify the first three mode shapes of the defective plates. A numerical model using ANSYS software was developed via parametric investigation to predict the correlation between crack orientation and resonant frequencies with corresponding mode shapes. The orientation of the introduced cracks had a significant effect on the dynamic properties of CFRP composites. Vertical cracks had the most significant influence on the eigenvalues of the mode shape frequencies. Furthermore, the damping ratio was an effective method to detect the cracks in CFRP composites.

scholarly journals Effect of architectural components on the dynamic properties of a long-span floor system

1987 ◽  
Vol 14 (4) ◽  
pp. 461-467 ◽  
Author(s):  
G. Pernica
Keyword(s):  
Fundamental Mode ◽  
Composite Structures ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Long Span ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Vibration Tests ◽  
Comparison Of The Results ◽  
Floor System

Vibration measurements were taken to determine the effects of architectural components on the dynamic properties (modal frequency, modal damping ratio, and mode shape) of a long-span floor system. The floor was located above a two-storey gymnasium in a recently constructed three-storey elementary school. The dynamic properties of the bare floor system were measured during the construction phase, immediately after the main structural components and the exterior masonry walls were in place. Six months later, with construction completed and the school ready for occupancy, the properties of the finished floor system, complete with internal partitions, mechanical ducts, furnishings, and carpeting, were again obtained.A comparison of the results of the two test series indicated that the dynamic properties of the floor system were altered by the addition of the architectural components. The fundamental frequency rose by 3% and the frequencies of the higher modes by 23%, even though the static load on the floor increased by about 26%. The substantial stiffening of the floor system necessary to precipitate these increases in frequency was linked to the presence of the internal partitions. A full-span partition was also found to behave as a floor support, creating an additional set of modes which were not previously present. Except for the fundamental mode, damping ratios increased by about 2% of critical, from 1.5% to 3.5% of critical. For the fundamental mode, the negligible increase in damping from 4.1 to 4.2% of critical could not be explained. Key words: floors, composite structures, vibration tests, spectrum analysis, resonant frequency, vibration damping.

Maximizing the Fundamental Natural Frequency of Triangular Composite Plates

1996 ◽  
Vol 118 (2) ◽  
pp. 141-146 ◽  
Author(s):  
S. Abrate
Keyword(s):  
Natural Frequency ◽  
Material Properties ◽  
Composite Structures ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Laminated Composite ◽  
Composite Plates ◽  
Mode Shapes ◽  
Fundamental Natural Frequency ◽  
Wide Range

While many advances were made in the analysis of composite structures, it is generally recognized that the design of composite structures must be studied further in order to take full advantage of the mechanical properties of these materials. This study is concerned with maximizing the fundamental natural frequency of triangular, symmetrically laminated composite plates. The natural frequencies and mode shapes of composite plates of general triangular planform are determined using the Rayleigh-Ritz method. The plate constitutive equations are written in terms of stiffness invariants and nondimensional lamination parameters. Point supports are introduced in the formulation using the method of Lagrange multipliers. This formulation allows studying the free vibration of a wide range of triangular composite plates with any support condition along the edges and point supports. The boundary conditions are enforced at a number of points along the boundary. The effects of geometry, material properties and lamination on the natural frequencies of the plate are investigated. With this stiffness invariant formulation, the effects of lamination are described by a finite number of parameters regardless of the number of plies in the laminate. We then determine the lay-up that will maximize the fundamental natural frequency of the plate. It is shown that the optimum design is relatively insensitive to the material properties for the commonly used material systems. Results are presented for several cases.

Manufacturing Error Detection in Plate and Cylindrical Composite Structures

2020 ◽  
Author(s):  
Cihan Talebi ◽  
Bülent Acar ◽  
Gökhan O. Özgen
Keyword(s):  
Error Detection ◽  
Composite Structure ◽  
Composite Structures ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Element Model ◽  
Mode Shapes ◽  
Fiber System ◽  
Error Identification ◽  
Manufacturing Error

Abstract Due to their superior weight to strength ratio of composites to common metallic structures, composite technology is widely used in aerospace industry. Assessment of damage in composites has gained interest after a large number of accidents caused by unanticipated damages in the composite structures. Many different structural health monitoring applications were developed over the years due to the fact that composite materials may inherit damage from within, not always visible from surface. The most common types of errors encountered in the industry are due to misaligned fibers, a mix-up in ply order, and delaminations: all presenting changes in the vibro-acoustical performance of the composite structure. This paper discusses the change in the dynamic properties of a composite structure contains a manufacturing error such as a ply lay-up error, and a ply angle error. Both plate and cylindrical structure types were considered for the stated error types. Effect of symmetric errors, unsymmetrical and unbalanced errors, and mid-plane errors were considered in the case of ply orientations, and dynamic stiffness matrix was used to identify the error. Identification of the structure’s layup properties and manufacturing error identification is employed. From the measured modal properties of the structure, a back-tracking strategy was used to generate the ply lay-up of the composite structure. Prepreg plates of a single carbon fiber system and filament wound hybrid cylinders consisting of glass and carbon fibers were manufactured for testing. Modal tests on plates and cylindrical composite structures were performed and compared with the analysis. A good match between the finite element model and experiment was shown in natural frequencies and mode shapes.

Dynamic Characteristics of a Wood Frame Structure: (II) the Effect of Artificial Damage

2013 ◽  
Vol 671-674 ◽  
pp. 921-926
Author(s):  
Hai Ling Xing ◽  
Dong Sheng Yao ◽  
Song Tao Xue
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Frame Structure ◽  
Modal Parameter ◽  
Hilbert Huang Transform ◽  
Artificial Damage ◽  
Identification Technique ◽  
Wood Frame ◽  
Frequency Changes ◽  
Vibration Tests

A full-scale, three-storey wood frame structure had been tested in-situ to investigate the changes of dynamic properties due to artificial damage. Beams and braces of the test structure were removed, to simulate damage, and then reassembled, to simulate rehabilitation. Free vibration tests were performed during every stage of the tests. The natural frequencies and damping ratios were obtained using modal parameter identification technique based on the Hilbert-Huang Transform. It is shown that, when the structure is damaged or rehabilitated, the natural frequency changes in accord with the structural stiffness in general while the damping ratio varies irregularly.

Dynamic and Vibration Analysis of a SAR Membrane Antenna

2007 ◽  
Author(s):  
Yu Shen ◽  
Wanping Zheng ◽  
Xiaoyun Wang
Keyword(s):  
Attitude Control ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Base Excitation ◽  
Control Torque ◽  
Satellite Attitude ◽  
Satellite Attitude Control ◽  
Low Mass

Synthetic Aperture Radar (SAR) membrane antennas have attracted much attention for their low mass, small stowed volume, large gain and high resolution. To deploy a membrane antenna requires a deployable support structure providing deployment and rigid support after it is fully deployed. A membrane antenna’s vibration may be caused by the disturbance of the satellite attitude-control torque in spacecraft, and it is determined by the mechanical properties of the membrane and its in-plane tension loads. In this paper, the dynamic properties of the deployable structure are studied with ADAMS when the flexibility of the frames is considered. The mode shapes and the natural frequencies of the membrane are analyzed with ABAQUS when the pre-tension loads provided by the tension cable are changed. The random response of the membrane subjected to the base excitation is studied for different tension forces and damping ratios. This work provides a guideline for the vibration control of the membrane by controlling its tension force or damping ratio.

scholarly journals Dynamic behaviour of a gymnasium floor

1986 ◽  
Vol 13 (3) ◽  
pp. 270-277 ◽  
Author(s):  
J. H. Rainer ◽  
J. C. Swallow
Keyword(s):  
Concrete Slab ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Load Factors ◽  
Resonance Frequencies ◽  
Floor Vibrations ◽  
Vibration Tests

Ten mode shapes, natural frequencies, and modal damping values have been measured for a steel-joist concrete-slab floor spanning 32.1 m. From ambient vibrations and steady-state shaker tests the frequency of the fundamental mode was determined to be 3.5 Hz, and the modal damping ratio to be approximately 1% of critical. A comparison of vibration criteria in Appendix G of CAN3-S16.1-M84 confirms satisfactory performance for walking, but for other rhythmic exercises disturbing vibrations developed. These occurred primarily at the forcing frequency of the exercises and not at floor resonance frequencies. Values of dynamic load factors, α, for rhythmic loadings of this floor were evaluated in accordance with the guidelines on floor vibrations in the Commentary to the National Building Code of Canada 1985. Key words: floors, gymnasiums, vibration tests, resonant frequencies, mode shapes, dynamic loads, dynamic response.

Experimental Study on Lateral Stiffness and Dynamic Properties of Steel Drive-in Storage Racks

2013 ◽  
Vol 351-352 ◽  
pp. 730-733
Author(s):  
Bo Cheng ◽  
Zhen Yu Wu
Keyword(s):  
Load Transfer ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Single Point ◽  
Lateral Stiffness ◽  
Test Results ◽  
Static Test ◽  
Vibration Tests ◽  
Storage Racks ◽  
Deformation Modes

The static and free vibration tests were carried out to investigate the initial lateral stiffness and dynamic properties of steel drive-in storage racks. The bracing configuration and friction between pallets and rail beams were taken into consideration. The static test results indicate that the tested storage racks show sideways and torsional deformation modes under the single-point horizontal force. Both top plan bracings and back spine bracings can change the load transfer through the rack framework, strengthen the initial lateral stiffness of racks, but only back spine bracings can affect the natural frequency and damping ratio of racks. The friction force between pallets and rail beams makes pallets act as links to connect adjacent rack columns, so the pallets are beneficial factors to increase the lateral stiffness of storage racks. Compared with unload racks, the natural frequencies of loaded racks are smaller.

Ambient and forced-vibration tests of the Beauharnois suspension bridge

2000 ◽  
Vol 27 (6) ◽  
pp. 1162-1172 ◽  
Author(s):  
P Paultre ◽  
J Proulx ◽  
T Bégin
Keyword(s):  
Forced Vibration ◽  
Dynamic Properties ◽  
Suspension Bridge ◽  
Rehabilitation Program ◽  
Mode Shapes ◽  
Experimental Program ◽  
Dynamic Amplification Factor ◽  
Dynamic Amplification ◽  
Vibration Tests ◽  
Steel Trusses

Ambient and forced vibration tests were carried out on the Beauharnois Bridge, a unique, 177-m combined suspension and cable-stayed structure near Montreal. A rehabilitation program was completed on the bridge during which the deck was completely rebuilt with an orthotropic slab on two steel trusses. The rehabilitation program also included the addition of two pairs of stay cables on both towers, creating a hybrid suspension system. The paper presents a series of dynamic tests performed to evaluate the dynamic properties and the dynamic amplification factor (DAF) for the rehabilitated bridge. The experimental program involved the measurement of vertical, transverse, and longitudinal acceleration responses of the deck and tower under ambient and controlled traffic loads. Displacement, strain, and integrated acceleration DAFs were computed under different loading conditions. Modal properties were evaluated and used to correlate a three-dimensional finite element model for the bridge, including nonlinear cable behaviour. The paper discusses the experimental setup and the techniques used to evaluate vibration frequencies, mode shapes, and the DAF. Correlation of numerical dynamic properties and experimental results is also presented. Key words: cable-stayed bridge, dynamic amplification, dynamic testing, numerical correlation, modal analysis, suspension bridge.

EFFECTS OF HUMAN-STRUCTURE INTERACTIONS ON THE DYNAMIC PROPERTIES OF BUILDING FLOORS SUSCEPTIBLE TO VIBRATIONS

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mehdi Setareh ◽  
Stephanie Renard
Keyword(s):  
Dynamic System ◽  
Dynamic Models ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Human Movements ◽  
Vibration Serviceability ◽  
Dimensional Parameters ◽  
Vibration Tests ◽  
Floor System ◽  
Two Degree Of Freedom

Excessive vibrations of building floors due to human movements have become an important vibration serviceability problem for building designers and owners. A series of vibration tests on a full-scale laboratory floor with different numbers of humans in various postures were conducted. Using this data, the dynamic properties of a two-degree-of-freedom (2-DOF) dynamic system representing groups of people in different postures were computed. A 3-DOF model representing the floor and humans was developed and its dynamic properties were defined in terms of non-dimensional parameters. The dynamic properties of the floor were measured when occupied by groups of people in different postures and compared to those predicted using the 3-DOF dynamic model considering the identified human models. The results showed that the predicted properties were within the range of those found from the measurements, which validated the identified human dynamic models. This study also showed how the presence of humans can affect the natural frequency and damping ratio of a floor system.

scholarly journals Flame Retardancy Effects of Graphene Nanoplatelet/Carbon Nanotube Hybrid Membranes on Carbon Fiber Reinforced Epoxy Composites

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Dongxian Zhuo ◽  
Rui Wang ◽  
Lixin Wu ◽  
Yanhua Guo ◽  
Lin Ma ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Carbon Fiber ◽  
Flame Retardancy ◽  
Composite Plates ◽  
Hybrid Membranes ◽  
Fiber Reinforced ◽  
Graphene Nanoplatelet ◽  
Cfrp Composites ◽  
Cfrp Composite ◽  
Carbon Fiber Reinforced

Carbon nanotube/graphene nanoplatelet (MWCNT/GNP) hybrid membranes with lower liquid permeability and better barrier effect compared to MWCNT membranes were successfully synthesized by vacuum filtering. Their morphologies, water permeability, and pore structures were characterized by a scanning electron microscope (SEM) and nitrogen adsorption isotherms. Furthermore, MWCNT/GNP membranes were used to improve the flame retardancy of carbon fiber reinforced polymer (CFRP) composites, and the influence of weight percentage of GNPs on the permeability and flame retardancy of MWCNT/GNP membranes was systematically investigated. Results show that incorporation of MWCNT/GNP membranes on CFRP composite plates can remarkably improve the flame retardancy of CFRP composites. Specifically, the incorporation of hierarchical MWCNT/GNP membrane with 7.5 wt% of GNP displays a 35% reduction in the peak heat release rate (PHRR) for a CFRP composite plate with the epoxy as matrix and a 11% reduction in PHRR compared with the incorporation of MWCNT membrane only. A synergistic flame retarding mechanism is suggested to be attributed to these results, which includes controlling the pore size and penetrative network structure.

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