RESIDUAL PLASTIC STRAIN STATE AND DELAMINATION PATTERN OF COMPOSITE LAMINATES WITH AUTOMATED INDUCED-GAP SUBJECTED TO HEMI-SPHERICAL IMPACT LOADING

2021 ◽  
Author(s):  
MOHAMMADHOSSEIN GHAYOUR ◽  
MEHDI HOJJATI ◽  
RAJAMOHAN GANESAN
Keyword(s):  
Plastic Strain ◽  
Impact Loading ◽  
Residual Strain ◽  
Composite Structures ◽  
Strain State ◽  
Composite Plates ◽  
Structural Level ◽  
Manufacturing Defects ◽  
Initiation And Propagation ◽  
The Impact

Automated manufacturing defects are types of composite structure defects that occur during fiber deposition by advanced robots. The induced gap is the most probable type of defect in the Automated Fiber Placement (AFP) technique. This defect can affect the mechanical performance of the composite structures at both material level by inducing the material inhomogeneity and the structural level by introducing the consolidation effect in the structure during the curing process. The current study investigates the effect of induced-gaps on the damage assessment of thin composite plates under Low-Velocity Impact (LVI) loading. The paper focuses on the delamination initiation and propagation and the residual plastic strain state of the impacted plates. The primary application of this study is to understand the interaction of induced gaps on the delamination pattern of composite samples subjected to LVI. For this purpose, a series of LVI tests are performed. Ultrasonic C-scan analysis and microscopic observation are implied to evaluate the internal damage due to impact loading. Finite Element (FE) analyses are then performed to evaluate the residual strain of the composite plates under Impact Energy (IE) loading less than 15 J. Then, the residual plastic strain in the impact zone is evaluated using a meso-macro method, and the effect of the local plasticity that occurs in the gap zones on the delamination initiation and propagation is studied. Results show that the stress relaxation due to the resin plasticity at the gap areas can affect the delamination pattern of the impacted composite plates. It is also shown that the residual strain of the impacted plates at the gap areas are new sources of the damages that need to be considered in the LVI analysis of the composite plates manufactured by the AFP technique.

Strength Loss in Composite Cylinders Under Impact

1988 ◽  
Vol 110 (2) ◽  
pp. 180-184 ◽  
Author(s):  
A. P. Christoforou ◽  
S. R. Swanson
Keyword(s):  
Composite Structures ◽  
Composite Plates ◽  
Strength Loss ◽  
Pressure Vessels ◽  
Fourier Series Expansion ◽  
Lateral Impact ◽  
Low Velocity ◽  
Expansion Procedure ◽  
The Impact ◽  
Composite Cylinders

The problem of strength loss in composite structures due to impact appears to be important due to the sensitivity of advanced composites to these loadings. Although a number of studies have been carried out on impact of flat composite plates, relatively little work has been done on tubular geometries such as pressure vessels despite the usage in applications. We have addressed the problem of calculating strength loss due to low velocity, lateral impact of composite cylinders. In our model we use an existing Fourier Series expansion procedure to calculate ply stresses and strains, compare these values with allowables to predict fiber breakage during the impact, and finally use fracture mechanics to predict the strength loss due to the impact. Although the model is quite simplified, the general trends of experiments appear to be represented.

scholarly journals Modeling Analysis of Guided Ultrasonic Waves in Composite Plates with Impact Damage

2018 ◽  
Vol 7 (4.26) ◽  
pp. 175
Author(s):  
Noorfaten Asyikin Ibrahim ◽  
Bibi Intan Suraya Murat
Keyword(s):  
Composite Structures ◽  
Impact Damage ◽  
Composite Plates ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Fe Model ◽  
Element Analysis ◽  
Damage Area ◽  
Guided Ultrasonic Waves ◽  
The Impact

This paper investigates the propagation of guided ultrasonic waves and the interaction with impact damage in composite plates using a full three-dimensional Finite Element analysis. Impact damage in the composite plate was modeled as rectangular- and T-shaped delaminations. In order to provide guidelines for extending the modeling of realistic multimode impact damage, the impact damage was modeled as a combination of the delamination and reduced materials properties. The information obtained from these methods was compared to the experimental results around the damage area for a validation. There was a reasonable similarity between the experimental and FE results. The FE simulations can effectively model the scattering characteristics of the A0 mode wave propagation in anisotropic composite plates. This suggests that the simplified and easy-to-implement FE model could be used to represent the complex impact damage in composite plates. This could be useful for the improvement of the FE modeling and performance of guided wave methods for the in-situ NDE of large composite structures. 

scholarly journals Guided Waves for Damage Detection in Complex Composite Structures: The Influence of Omega Stringer and Different Reference Damage Size

2020 ◽  
Vol 10 (9) ◽  
pp. 3068
Author(s):  
Jochen Moll ◽  
Christian Kexel ◽  
Jens Kathol ◽  
Claus-Peter Fritzen ◽  
Maria Moix-Bonet ◽  
...  
Keyword(s):  
Composite Structures ◽  
Guided Waves ◽  
Fiber Composite ◽  
Composite Plates ◽  
Guided Wave ◽  
Probability Of Detection ◽  
Carbon Fiber Composite ◽  
Technical Validation ◽  
Pod Analysis ◽  
The Impact

The third dataset dedicated to the Open Guided Waves platform aims at carbon fiber composite plates with an additional omega stringer at constant temperature conditions. The two structures used in this work are representative for real aircraft components. Comprehensive measurements were recorded in order to study (I) the impact of the omega stringer on guided wave propagation, and (II) elliptical reference damages of different sizes located at three separate positions on the structure. Measurements were recorded for narrowband excitation (5-cycle toneburst with varying carrier frequencies) and broadband excitation (using chirp waveforms). The paper presents the results of a technical validation including numerical modelling, and enables further research, for example related to probability of detection (POD) analysis.

scholarly journals A self-powered triboelectric velocity sensor for impact detection in composite structures

2018 ◽  
Vol 211 ◽  
pp. 21004 ◽  
Author(s):  
Cristobal Garcia ◽  
Irina Trendafilova
Keyword(s):  
Structural Health Monitoring ◽  
Wind Turbines ◽  
Health Monitoring ◽  
Composite Structures ◽  
Composite Plates ◽  
Health State ◽  
Impact Detection ◽  
Potential Applications ◽  
Self Powered ◽  
The Impact

Impacts and collisions are frequent in aircrafts, wind turbines, bridges and other composites structures. Some examples are the collisions between birds and aircrafts during take-off and landing or the damages caused in wind turbines due to the impact of hailstones. Hence, the detection and measurement of these impacts is the vital importance for monitoring the health state of composites structures as aircrafts or wind turbines. The main purpose of the paper is to demonstrate the sensitivity of a novel triboelectric sensor for impact detection in composite structures as aircrafts. For this study, composite plates adhered with the fabricated triboelectric sensor are subjected to various impact velocities using a dropweight machine. The sensor electrical responses due to the impacts are measured with the aim to evaluate the sensitivity of the developed triboelectric sensor to variations in the impact velocities. The results show that the sensor electric responses increase linearly with impact velocity in the range between 1.3 and 2.4 m/s. This paper is the first attempt to demonstrate the potential applications of triboelectric sensors to measure the velocity of the impacts in composite structures, which play an important role for structural health monitoring in aircrafts, bridges and other composite structures.

A strain amplitude-based algorithm for impact localization on composite laminates

2011 ◽  
Vol 22 (17) ◽  
pp. 2061-2067 ◽  
Author(s):  
Cristobal Hiche ◽  
Clyde K. Coelho ◽  
Aditi Chattopadhyay
Keyword(s):  
Strain Amplitude ◽  
Composite Laminates ◽  
Composite Structures ◽  
Composite Plates ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Sensor Orientation ◽  
Fbg Sensors ◽  
The Impact ◽  
Impact Localization

Automated detection of damage due to low energy impacts in composite structures is very important for aerospace structural health monitoring applications. Low-velocity impact creates subsurface damage that can significantly reduce the stiffness of a component, yet show barely visible damage. This article proposes a novel methodology for impact localization based on the maximum strain amplitude measured by fiber Bragg grating (FBG) sensors during an impact event. The approach correlates the strain amplitude of each sensor pair to find the location of highest strain corresponding to the impact location. This approach requires minimal knowledge of the structure and fewer number of sensors as opposed to current localization methods. Both simulation and experimental data are used as proof of concept. Since FBG sensors measure strain in only one direction, the effect of sensor orientation on the performance of the algorithm is also studied. The algorithm is tested on graphite/epoxy composite plates and shows good localization results in all impact cases considered.

Composite material components damaged by impact loading: a methodology for the assessment of their residual elastic properties

2018 ◽  
Vol 1 (87) ◽  
pp. 18-24
Author(s):  
G. Belingardi ◽  
M.P. Cavatorta ◽  
D.S. Paolino
Keyword(s):  
Composite Material ◽  
Elastic Properties ◽  
Impact Loading ◽  
Composite Laminate ◽  
Impact Load ◽  
Damage Index ◽  
Composite Plates ◽  
Main Concern ◽  
Repeated Impact ◽  
The Impact

Purpose: Detection and evaluation of damage due to impact or fatigue loading in components made by composite materials is one of the main concern for automotive engineers. We focus on damage due to impact loading on long fibre, plastic matrix composite, as they represent one of the most interesting development solution for automotive components toward lightweight structure that in turn means reduction of fuel consumption and of Green House Gas emissions. Design/methodology/approach: An innovative simplified methodology is proposed, based on the impact and repeated impact behaviour of composite material, for the evaluation of the induced damage and of material residual elastic properties. The investigated composite laminate is made of eight twill-wave carbon fabrics impregnated with epoxy resin. The methodology consists of two phases: at first the identification of the impact response. Composite plates have been impacted at different energy levels and residual elastic properties measured through standard tensile tests. The relationship between impact energy and residual elastic properties is obtained. Then the exploration impact load is identified, large enough to give a well-defined picture of the suffered damage but soft enough to do not induce further damage in the composite laminate. Findings: This exploration impact test and the Damage Index (DI) value, as interpretation key, leads to a prediction of the local residual elastic properties in the damaged area. The proposed methodology has been validated on plate specimens. A strict correlation is found between the predicted and the actual residual elastic properties of the damaged composite plate. Practical implications: Subsequently it has been applied to a composite beam, with a omega shape transverse section, that can be considered as a demonstrator for a typical beam used in the car body frame. Originality/value: A selection on the following alternatives will be possible: a – don’t care the damage is not affecting the structure performance; b – repair is needed but will be sufficient; c – substitute the damaged component as soon as possible.

Impact Response of Fiber Composite Structures

1991 ◽  
Vol 44 (11S) ◽  
pp. S256-S263 ◽  
Author(s):  
Stephen R. Swanson
Keyword(s):  
Program Analysis ◽  
Impact Loading ◽  
Composite Structures ◽  
Analytical Study ◽  
Fiber Composite ◽  
Structural Response ◽  
Composite Plates ◽  
Surface Strain ◽  
Transverse Impact ◽  
Good Agreement

The problem of impact loading of fiber composite structures is important because of the possibility of accidental damage occuring during service. The present paper is a review of a combined experimental and analytical study of transverse impact loading of carbon/epoxy composite plates and cylinders. Scaling of response with structure size was investigated as part of the program. Analysis procedures for dynamic response were developed, using Ritz techniques for plates and Fourier series expansions combined with Laplace transforms for the cylinders. The experimental results showed good correlation with scaling rules developed for structural response. Good agreement was also obtained between experiment and analysis for surface strain response in both the plates and the cylinders. Scaling of damage is seen to be more complicated, with measured delamination sizes exhibiting a dependence on absolute specimen size as would be predicted by fracture mechanics.

Detection of Impact Damage in Composite Plates Using Surface Contact Method

2006 ◽  
Vol 326-328 ◽  
pp. 1693-1696
Author(s):  
Heoung Jae Chun ◽  
Dang Won Kim ◽  
Joon Hyung Byun
Keyword(s):  
Composite Structures ◽  
Lamb Waves ◽  
Impact Damage ◽  
Incident Angle ◽  
Composite Plates ◽  
Wave Form ◽  
Contact Method ◽  
Internal Damage ◽  
Fundamental Causes ◽  
The Impact

It is a well known fact that the fundamental causes of most failures in composite structures are in the forms of incipient damages such as delaminations and cracks which usually remain undetected until they grow to levels large enough to cause failure. In this study, unidirectional carbon/epoxy composite plates with known defects are investigated. The known defects are generated by impacting the composite specimens simulating external collision. A pair of transmitter and receiver was used for generation of Lamb waves and reception of signals. The received signals were monitored by scanning the receiver toward internal defect or by scanning both transmitter and receiver with confined distance over the surface of the composite plates which have known defects lie beneath them. The proper selection of incident angle and frequency are also considered. The characteristics of received signals such as amplitude, energy and wave form are analyzed. The acquired information is used to locate and to measure the size of the impact damage. The suggested method is very effective if the internal damage is presented closed to surface of the plate where the conventional pulse-echo method has problems. The proposed technique can be used widely for the real time and online monitoring of composite structures.

Effect of long-term moisture exposure on impact response of glass-reinforced vinylester

2021 ◽  
pp. 147509022199616
Author(s):  
Fatemeh Alizadeh ◽  
Navid Kharghani ◽  
Carlos Guedes Soares
Keyword(s):  
Water Uptake ◽  
Failure Modes ◽  
Sea Water ◽  
Composite Plates ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Water Type ◽  
Interfacial Damage ◽  
Impact Properties ◽  
The Impact

Glass/Vinylester composite laminates are comprehensively characterised to assess its impact response behaviour under moisture exposure in marine structures. An instrumented drop weight impact machine is utilised to determine the impact responses of dry and immersed specimens in normal, salted and sea water. The specimens, which had three different thicknesses, were subjected to water exposure for a very long period of over 20 months before tested in a low-velocity impact experiment. Water uptake was measured primarily to study the degradation profiles of GRP laminates after being permeated by water. Matrix dissolution and interfacial damage observed on the laminates after prolonged moisture exposure while the absorption behaviour was found typically non-Fickian. The weight of the composite plates firstly increased because of water diffusion up to month 15 and then decreased due to matrix degradation. The specimens with 3, 6 and 9 mm thickness exhibited maximum water absorption corresponding to 2.6%, 0.7% and 0.5% weight gain, respectively. In general, the results indicated that water uptake and impact properties were affected by thickness and less by water type. Impact properties of prolonged immersed specimens reduced remarkably, and intense failure modes detected almost in all cases. The least sensitive to impact damage were wet specimens with 9 mm thickness as they indicated similar maximum load and absorbed energy for different impact energies.

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