On the Prediction of Damping in Composite and Sandwich Structures

Mapping Intimacies ◽

10.1115/imece2001/amd-25409 ◽

2001 ◽

Author(s):

Victor Birman ◽

Larry W. Byrd

Keyword(s):

Composite Laminates ◽

Loss Factor ◽

Polymer Matrix Composites ◽

Sandwich Structures ◽

Free Vibrations ◽

Matrix Composites ◽

Analytical Evaluation ◽

Numerical Examples ◽

Mechanics Of Materials ◽

Good Agreement

Abstract The paper outlines two methodologies for the analytical evaluation of the loss factor in composite laminates and in sandwich structures. One of these methods is based on the analysis of free vibrations, while the second approach utilizes mechanics of materials. The loss factor can be predicted both for specially orthotropic as well as for generally orthotropic laminae, subjected to axial stresses and/or transverse shear. The results for the loss factor of the laminae are in good agreement with available experimental data. As follows from numerical examples, the loss factor of polymer-matrix composites increases with the lamination angle and experiences relatively small variations at large values of these angles.

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Modeling of Depth of Cut in Abrasive Waterjet Cutting of Thick Kevlar-Epoxy Composites

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.443.423 ◽

2010 ◽

Vol 443 ◽

pp. 423-427 ◽

Cited By ~ 3

Author(s):

Tauseef Uddin Siddiqui ◽

Mukul Shukla

Keyword(s):

Polymer Matrix Composites ◽

Linear Regression Analysis ◽

Epoxy Composites ◽

Abrasive Waterjet ◽

Depth Of Cut ◽

Matrix Composites ◽

Water Jet Cutting ◽

Abrasive Water Jet Cutting ◽

Semi Empirical ◽

Good Agreement

Abrasive water jet cutting (AWJC) is one of the widely used non-conventional techniques for cutting difficult-to-cut materials like composites, super alloys and ceramics. However, while conducting initial trials the inability of the jet to cut through the workpiece is a major problem particularly in thicker materials. Therefore an accurate prediction of depth of cut (DOC) is absolutely necessary to achieve through cuts and more so to minimize delamination in polymer matrix composites. In this paper, a semi-empirical model is developed using non-linear regression analysis for prediction of DOC in AWJC of thick Kevlar-epoxy composites. Further, the model is verified by conducting experiments within the investigated range of process parameters and a good agreement is obtained between the two.

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Analysis of Fatigue Damage Mechanisms and Residual Properties of Polymer Matrix Composites

10.1115/imece2000-2161 ◽

2000 ◽

Author(s):

Costas Soutis ◽

Maria Kashtalyan

Keyword(s):

Composite Laminates ◽

Polymer Matrix Composites ◽

Matrix Cracking ◽

Matrix Composites ◽

Residual Properties ◽

Stiffness Properties ◽

Observed Damage ◽

Equivalent Constraint Model ◽

Constraint Model ◽

Longitudinal Cracks

Abstract Resin dominated damage modes such as matrix cracking in the off-axis plies and matrix crack-induced local and edge delaminations are common failure mechanisms in composite laminates under tensile or thermal fatigue. Accurate prediction of the laminate stiffness and strength must consider all the above-mentioned damage modes. In the present paper, an approach is developed for the analysis of cross-ply laminates damaged by transverse and longitudinal cracks and transverse and longitudinal delaminations that initiate and grow along these cracks. It is based on the Equivalent Constraint Model (ECM) of the damaged ply and employs an improved 2-D shear lag method to determine the stress field in the cracked and locally delaminated ply. The method is applied to predict residual stiffness properties of cross-ply graphite/epoxy laminates using experimentally observed damage patterns.

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Influence of cure parameters in polymer matrix composites using embedded optical fibers

Journal of Composite Materials ◽

10.1177/0021998319899153 ◽

2020 ◽

Vol 54 (19) ◽

pp. 2611-2621

Author(s):

Daniel A Drake ◽

Rani W Sullivan ◽

Jonathan E Spowart ◽

Katie Thorp

Keyword(s):

Optical Fibers ◽

Composite Laminates ◽

Composite Structures ◽

Polymer Matrix Composites ◽

Processing Parameters ◽

Internal Strain ◽

Matrix Composites ◽

Molding Process

The influence of cure processing parameters was investigated using strain distributions from embedded optical fibers. The determination of optimized cure parameters is often needed to achieve material properties which meet aerospace industry design requirements. Optical fibers were embedded near the midplane of thin (5 mm; [0/90/90/0]3s) composite laminates to monitor the internal strain during cure for two different cure cycles (manufacturer-recommended and an alternative two-step cure). Each laminate was fabricated using a vacuum-assisted resin transfer molding process. The internal strain with respect to the spatial position and time were monitored. During cure, greater variations in the strain near the vicinity of the laminate edges were observed. However, a two-step cure cycle revealed that the variation of strain near the laminate edges is reduced. The results demonstrate the capability of high-spatial resolution optical fibers to measure the in-situ cure and residual strain during the processing of composite structures.

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Low Cycle Fatigue of Unidirectional Laminates: Stress Ratio Effects1

Journal of Engineering Materials and Technology ◽

10.1115/1.1289024 ◽

2000 ◽

Vol 122 (4) ◽

pp. 415-419 ◽

Cited By ~ 6

Author(s):

V. M. Harik ◽

J. R. Klinger ◽

T. A. Bogetti

Keyword(s):

Composite Laminates ◽

Stress Ratio ◽

Polymer Matrix Composites ◽

Low Cycle Fatigue ◽

Strain Rates ◽

Matrix Composites ◽

Cycle Fatigue ◽

Degradation Rates ◽

Stress Ratios

Low cycle fatigue (LCF) of unidirectional glass/epoxy composite laminates is investigated. LCF conditions involve high loads that may reach up to 90 percent of the material ultimate strength. LCF has unique features that require some modifications to the existing fatigue models and engineering S-N curves. LCF characterization of polymer matrix composites (PMCs) is carried out to determine unique characteristics of the S-N curves corresponding to distinct loading conditions (e.g., stress ratios). LCF behavior of the PMCs studied is characterized by finite strains (1–3 percent), finite strain rates (0.05–10 s−1), and high property degradation rates, which are higher than those seen during high cycle fatigue of the glass/epoxy laminates. [S0094-4289(00)02504-4]

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SENSITIVITY OF THE FLOW STRESS OF NYLON 6 AND NYLON 66 TO STRAIN-RATE

International Journal of Modern Physics B ◽

10.1142/s021797920804661x ◽

2008 ◽

Vol 22 (09n11) ◽

pp. 1249-1254 ◽

Cited By ~ 12

Author(s):

ISSAM BENACEUR ◽

RAMZI OTHMAN ◽

PIERRICK GUEGAN ◽

ABDERRAZEK DHIEB ◽

FAKHREDDINE DAMEK

Keyword(s):

Flow Stress ◽

Strain Rate ◽

Polymer Matrix Composites ◽

Nylon 6 ◽

Strain Rates ◽

Matrix Composites ◽

Nylon 66 ◽

Mechanics Of Materials ◽

Study Results ◽

Wide Range

The sensitivity of the flow stress of polymers to strain-rate is one of the major concerns in mechanics of materials since polymers and polymer matrix composites are widely used in many engineering applications. In this paper, we present tests on Nylon 6 and Nylon 66 on wide range of strain-rates (0.001-5000 s −1). Specifically, we used INSTRON machine for low strain-rates. The high strain-rate measurements were inferred from the Hopkinson bar tests. Only the compressive behaviour was investigated. To eliminate any interference with temperature and humidity effects, test samples were conditioned at 20°C and 50% of hygrometry. Moreover, the effects of the specimen geometry were considered. The current study results are also compared to values found in literature.

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Damage by Improvised Incendiary Devices on Carbon Fiber-Reinforced Polymer Matrix Composites

Journal of Composites Science ◽

10.3390/jcs5030072 ◽

2021 ◽

Vol 5 (3) ◽

pp. 72

Author(s):

Sebastian Eibl

Keyword(s):

Polymer Matrix ◽

Large Scale ◽

Polymer Matrix Composites ◽

Sandwich Structures ◽

Laboratory Scale ◽

Electrical Heating ◽

Lightning Strike ◽

Protective Effects ◽

Matrix Composites ◽

Fire Tests

This study focuses on short-term thermal degradation of polymer matrix composites by one-sided impact of improvised incendiary devices (IID). Specimens of two commercial composites HexPly® 8552/IM7 and M18-1/G939 with various thicknesses (1–8 mm) are systematically investigated as well as sandwich structures thereof, applying various amounts of fire accelerant predominantly in laboratory scale fire tests. Results of preceding large-scale fire tests with IIDs justify the chosen conditions for the laboratory-scale fire tests. The aim is to correlate the amount of fire accelerant with heat damage and residual mechanical strength. Thermal damage is characterized visually and by ultrasonic testing, infrared spectroscopy, and residual interlaminar shear strength. Matrix degradation and combustion only contribute to the overall amount of released heat by the fire accelerant for thin and especially vertically aligned panels as tested by a cone calorimeter (without electrical heating), but not for horizontally orientated and thicker panels. Degradation processes are discussed in detail. Protective effects are observed for typical coatings, a copper mesh applied for protection against lightning strike, combinations thereof as well as an intumescent coating. Especially sandwich structures are prone to severe damage by assaults with IID, such as Molotov cocktails.

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