Delaminations in Composite Plates under Transverse Static Loads — Experimental Results

1992 ◽  
Vol 11 (11) ◽  
pp. 1196-1238 ◽  
Author(s):  
Scott R. Finn ◽  
Yi-Fei He ◽  
George S. Springer
Keyword(s):  
Composite Plates ◽  
Experimental Results ◽  
Static Loads

The Improvement of the Micro Torsional Mirror by a Reinforced Folded Frame

2000 ◽  
Author(s):  
Hung-Yi Lin ◽  
Weileun Fang
Keyword(s):  
Thin Film ◽  
Residual Stresses ◽  
Film Thickness ◽  
Experimental Results ◽  
Dynamic Loads ◽  
Inertia Force ◽  
Optical Performance ◽  
Thin Film Thickness ◽  
Static Loads ◽  
Dynamic Inertia

Abstract Stiffness of micromachined structures is limited by thin film thickness. Hence, static loads such as thin film residual stresses, or dynamic loads such as the inertia force could significantly deform the thinness micromachined torsional mirror. This work aims to stiffen the thin film micromachinined torsional mirror. The proposed torsional mirror exploits a reinforced frame to improve the stiffness of the mirror plate. Consequently, the mirror plate has less deformation no matter subject to the residual stresses or to the dynamic inertia force. In addition the reinforced frame stiffen the mirror without increasing the mass significantly. In application of this technique, the micro torsional mirror was fabricated through the integration of DRIE, conventional bulk and surface micromachining processes. The experimental results demonstrated that the proposed design significantly improves the flatness of the mirror plate in both static and dynamic conditions. Consequently, the optical performance of the micro torsional mirror was improved.

Structural Optimization of Laminated Composite Plates for Maximum Buckling Load Capacity Using Genetic Algorithm

2007 ◽  
Vol 348-349 ◽  
pp. 725-728 ◽  
Author(s):  
Omer Soykasap ◽  
Şükrü Karakaya
Keyword(s):  
Genetic Algorithm ◽  
Structural Optimization ◽  
Load Capacity ◽  
Laminated Composite ◽  
Global Solutions ◽  
Composite Plates ◽  
Buckling Load ◽  
Laminated Composite Plates ◽  
Static Loads ◽  
Aspect Ratios

In this study, the structural optimization of laminated composite plates for maximum buckling load capacity is performed by using genetic algorithm. The composite plate under consideration is a 64-ply laminate made of graphite/epoxy, is simply supported on four sides, and subject to in-plane compressive static loads. The critical buckling loads are determined for several load cases and different plate aspect ratios using 2-ply stacks of 02, ±45, 902. The problem has multiple global solutions, the results of which are compared with previously published results.

Progressive Damage Approach to Simulating Low Velocity Impact Response of Plain Weave C/SiC Composites

2010 ◽  
Vol 118-120 ◽  
pp. 241-245 ◽  
Author(s):  
Liu Ding Chen ◽  
Xiao Yan Tong ◽  
Xiang Zheng ◽  
Lei Jiang Yao
Keyword(s):  
Constitutive Model ◽  
Time History ◽  
Composite Plates ◽  
Experimental Results ◽  
Low Velocity Impact ◽  
Progressive Damage ◽  
Low Velocity ◽  
Velocity Impact ◽  
Plain Weave ◽  
User Subroutine

Based on progressive damage theory, a 3D laminated model with an orthotropic property in plane was established to simulate the response of plain weave carbon fiber reinforced silicon carbide(C/SiC) ceramic matrix composites(CMC) under low velocity impact(LVI). Intra-layer damage and inter-layer damage were taken into account, respectively. Three scalar damage variables, associated with the degradation of warp modulus, weft modulus and shear modulus, respectively, were proposed to characterize intra-layer damage evolutions. The intra-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXFAIL1. The potential delamination region was considered as a discrete cohesive zone. Three vector spring elements were placed into every two adjacent nodes to simulate the inter-layer joints. A scalar damage variables, associated with the degradation of the three vector spring elements, were brought forward to characterize the inter-layer damage evolutions. The inter-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXELAS. Damage area, indentation depth of C/SiC composite plates and time history of impact force were obtained to compare with experimental results. The numerical results show overall good agreement with experimental results.

Experimental Study on Seismic Failure Modes of Confined Masonry Structures with Different Enhancements

2017 ◽  
Vol 747 ◽  
pp. 594-603 ◽  
Author(s):  
Hu Xu ◽  
Hao Wu ◽  
Cristina Gentilini ◽  
Qi Wang Su ◽  
Shi Chun Zhao
Keyword(s):  
Experimental Study ◽  
Failure Mode ◽  
Seismic Behavior ◽  
Failure Modes ◽  
Experimental Results ◽  
Masonry Walls ◽  
Masonry Structures ◽  
Structural Collapse ◽  
Static Loads ◽  
Confined Masonry

In this study, confined masonry specimens with regular arranged openings are tested in order to study the influence of different enhancements of the columns on seismic failure modes. In particular, five brick masonry walls and three half-scale two-storey masonry structures are tested under quasi-static loads. The experimental results show that increasing column ratio improves the seismic behavior of the wall specimens to some extent, but an excessive reinforcement ratio of the columns decreases the ductility. The global failure mode of the two-storey masonry structures is modified by inserting iron wires in the mortar bed joints, improving the structural collapse resistant capacity effectively.

Multilayered Composite Plates with Shape Memory Properties

2016 ◽  
Vol 699 ◽  
pp. 1-7 ◽  
Author(s):  
Loredana Santo ◽  
Fabrizio Quadrini ◽  
Denise Bellisario
Keyword(s):  
Shape Memory ◽  
Carbon Fibers ◽  
Shape Recovery ◽  
Composite Plates ◽  
Experimental Results ◽  
Multilayered Composite ◽  
Number Of Layers ◽  
Original Shape ◽  
Shape Memory Properties ◽  
Recovery Percentage

In this study, multilayered composite plates with shape memory properties were produced: carbon fibers prepreg are alternated with layers of shape memory epoxy powder obtaining composite with different number of layers. The differences in the load exerted during shape recovery, and percentage and time of recovery of the composites as a function of layers number have been evaluated. In particular, the actuation load and the shape recovery percentage were measured after a V-shape memorizing step of the composites. The experimental results are very promising, showing that such multilayers can successfully recover the original shape without noticeable damages and an increasing of actuation load per layer has been found at the increase of the layers number.

scholarly journals A New Structural Bump Foil Model With Application From Start-Up to Full Operating Conditions

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Mihai Arghir ◽  
Omar Benchekroun
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Operating Conditions ◽  
Experimental Results ◽  
Static Loads ◽  
Contact Algorithm ◽  
Start Up ◽  
Theoretical Predictions ◽  
Full Speed ◽  
Contact Pressures

Abstract This paper presents a new structural bump foil model that can handle all operating conditions from start-up to full speed. The model is based on a nonlinear contact algorithm with friction and gaps. The top foil is modeled as a curved beam while bump foil uses a coupled truss model. The model considers the gaps between the bump foil and the bearing casing, between the bump foil and the top foil and between the rotor and the top foil. Thus, any numerical interference between the rotor and the top foil is avoided. A mixed lubrication model is used for the thin film pressures. Following this algorithm, contact pressures appear if the film thickness is less than three times the equivalent roughness of the rotor and of the top foil. Fluid pressures are calculated from numerical solutions of Reynolds equation while contact pressures, if present, are calculated with the model of Greenwood and Williamson. The model is validated by comparisons with the experimental results obtained for start-up operating conditions of a first-generation foil bearing of 38.1 mm diameter with static loads of 10–50 N. Theoretical predictions of the start-up torque and takeoff speed compare well with experimental results. It is also shown how manufacturing bump height errors can explain the differences between theoretical and experimental predictions. Further validations are presented for the same bearing operating at high speeds (30, 45, and 55 krpm) and heavy static loads (up to 200 N). The calculated minimum film thickness and attitude angle are compared with experimental data from the literature.

Damage Detection of Composite Structures Using Dynamic Analysis

2005 ◽  
Vol 295-296 ◽  
pp. 33-38 ◽  
Author(s):  
L.H. Yam ◽  
Li Cheng ◽  
Z. Wei ◽  
Y.J. Yan
Keyword(s):  
Damage Detection ◽  
Composite Structures ◽  
Composite Plates ◽  
Experimental Results ◽  
Parameter Analysis ◽  
Dynamic Responses ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Structural Dynamic ◽  
Modal Strain Energy

A study on the use of modal parameter analysis for damage detection of structures made of composites is conducted. The damage-induced variations of modal parameters are investigated both numerically and experimentally. An appropriate finite element model is proposed to analyze the dynamic characteristics of different types of structures made of composites, such as honeycomb sandwich plates and multi-layer composite plates, with internal cracks and delamination. The numerical results are in good agreement with experimental results available in the literature. Natural frequencies, modal displacements, strains and energy are analyzed for the determination of damage severity and location. Vibration measurements are carried out using piezoelectric patch actuators and sensors for comparison and verification of the FEM model proposed in this study. Energy spectrum for wavelet packets decomposition of structural dynamic responses is used to highlight the features of damaged samples. The mechanism of mode-dependent energy dissipation of composite plates due to delamination is revealed for the first time. Experimental results clearly show the dependence of changes of modal parameters on damage size and location. The results obtained in this study show that the measured modal damping change combined with the computed modal strain energy distribution can be used to determine the location of delamination in composite structures. Both numerical and experimental findings in this study are significant to the establishment of guideline for size and location identification of damage in composite structures.

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