Delamination-Crater Interaction in Damage of Glass/Epoxy Composite Plates Subjected to Impact Fatigue

The use of composite materials is increasing although their behavior under impact fatigue loading remains rather unknown. This study is to assess the evolution of damage, especially delamination and crater, in a composite Glass/Epoxy woven fabric, using repeated impact tests at low energy levels (<10J). Both types of damage that arise and grow within the material cannot be independent from each other. Our objective in this work is to establish the interaction between two damages (delamination and crater) on laminate damage, and understand the contribution of each of them in the different phases through which passes the composite before perforation. To do this, impact fatigue tests are carried out on composite plates and measures of the crater size (diameter and depth) and the size of the delaminated area (diagonals from a diamond shape) are collected for different numbers of impacts and impact energies. A question worth asking; can we foster one of these damages over the other? especially when we are interesting to the “structure applications”, where one "prefers" perforation to delamination (while completing correctly the function's intended to the structure), or “shielding applications”, where one "prefers" the delamination to perforation. Although the range of impact velocities is not the same, it is still interesting to consider the synergy between these two damages at low impact velocities, always in the case of “structure applications” and “shielding applications”.

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Rupture by impact-induced fatigue of a copper foil strip embedded in a multifunctional composite material

Journal of Composite Materials ◽

10.1177/0021998321994327 ◽

2021 ◽

pp. 002199832199432

Author(s):

Yacine Ouroua ◽

Said Abdi ◽

Imene Bachirbey

Keyword(s):

Composite Material ◽

Mechanical Characteristics ◽

Glass Fibers ◽

Energy Levels ◽

Fatigue Tests ◽

Repeated Impact ◽

Aeronautical Industry ◽

Repeated Impacts ◽

Cracking Mode ◽

The Impact

Multifunctional composite materials are highly sought-after by the aerospace and aeronautical industry but their performance depends on their ability to sustain various forms of damages, in particular damages due to repeated impacts. In this work we studied the mechanical behavior of a layered glass-epoxy composite with copper inserts subjected to fatigue under repeated impacts with different energy levels. Damage evolution as a function of impact energy was carefully monitored in order to determine the effect of the copper inserts on mechanical characteristics of the multifunctional composite, such as endurance and life. Results of repeated impact tests show that electric current interruption in the copper inserts occurs prior to the total perforation of the composite material, and after about 75% of the total number of impacts to failure. This is the case for the three energy levels considered in this study, [Formula: see text] = 2, 3 and 4 Joules. The epoxy resin was dissolved chemically in order to preserve the mechanical structure of the damaged copper inserts and the composite fibers for further inspection and analysis. Scanning electron microscopy (SEM) of the fractured copper inserts revealed interesting information on the nature of the damage, including information on plastic deformation, strain hardening, cracking mode, temperature increase during the impacts, and most importantly the glass fibers and their roles during the impact-fatigue tests.

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Fatigue Damage Evaluation in CFRP Woven Fabric Composites Through Dynamic Modulus Measurements

Recent Advances in Nondestructive Evaluation Techniques for Material Science and Industries ◽

10.1115/pvp2004-2843 ◽

2004 ◽

Author(s):

Hideaki Kasano ◽

Osamu Hasegawa ◽

Chiaki Miyasaka

Keyword(s):

Fatigue Damage ◽

Material Properties ◽

Elastic Moduli ◽

Fatigue Loading ◽

Damage Function ◽

Fatigue Tests ◽

Woven Fabric ◽

Damage Development ◽

Dynamic Elastic Moduli ◽

Number Of Cycles

Advanced fiber reinforced composite materials offer substantial advantages over metallic materials for the structural applications subjected to fatigue loading. With the increasing use of these composites, it is required to understand their mechanical response to cyclic loading [1–4]. Our major concern in this work is to macroscopically evaluate the damage development in composites during fatigue loading. For this purpose, we examine what effect the fatigue damage may have on the material properties and how they can be related mathematically to each other. In general, as the damage initiates in composite materials and grows during cyclic loading, material properties such as modulus, residual strength and strain would vary and, in many cases, they may be significantly reduced because of the progressive accumulation of cracks. Therefore, the damage can be characterized by the change in material properties, which is expected to be available for non-destructive evaluation of the fatigue damage development in composites. Here, the tensiontension fatigue tests are firstly conducted on the plain woven fabric carbon fiber composites for different loading levels. In the fatigue tests, the dynamic elastic moduli are measured on real-time, which will decrease with an increasing number of cycles due to the degradation of stiffness. Then, the damage fimction presenting the damage development during fatigue loading is determined from the dynamic elastic moduli thus obtained, from which the damage function is formulated in terms of a number of cycles and an applied loading level. Finally, the damage function is shown to be applied for predicting the remaining fifetime of the CFRP composites subjected to two-stress level fatigue loading.

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The flexural behaviors of the impacted composite single-lap adhesive joints

Science and Engineering of Composite Materials ◽

10.1515/secm-2013-0308 ◽

2015 ◽

Vol 22 (5) ◽

Cited By ~ 1

Author(s):

Emin Ergun ◽

Hasan Çallioğlu

Keyword(s):

Experimental Study ◽

Impact Energy ◽

Energy Levels ◽

Composite Plates ◽

Lap Joints ◽

Adhesive Joints ◽

Single Lap Joints ◽

Impact Tests ◽

Impact Energies ◽

The Impact

AbstractThis experimental study deals with the flexural behaviors of composite single-lap adhesive joints after impact tests. Increasing impact energies are applied at the center of the composite plates having three different overlap lengths. It is shown that the overlap lengths and impact energy levels affect considerably the impact responses of the composite single-lap joints. It is also shown that the bending stiffness of the composite increases with increasing overlap length. For this reason, after the impact tests, how these effects influence the flexural behaviors of the impacted composite lap joints was also investigated. The flexural loads of the impacted and non-impacted composite single-lap joints were determined and compared with each other. It is shown that the residual flexural loads after impact increase with increasing overlap lengths but decrease with increasing impact energy.

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Thickness effect on repeated impact response of woven fabric composite plates

Composites Part B Engineering ◽

10.1016/j.compositesb.2013.01.019 ◽

2013 ◽

Vol 49 ◽

pp. 80-85 ◽

Cited By ~ 34

Author(s):

Cesim Atas ◽

Bulent Murat Icten ◽

Mümin Küçük

Keyword(s):

Composite Plates ◽

Impact Response ◽

Woven Fabric ◽

Thickness Effect ◽

Repeated Impact ◽

Fabric Composite

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Models for Estimating the Durability of Repeated Impacts

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.205 ◽

2007 ◽

Vol 348-349 ◽

pp. 205-208 ◽

Cited By ~ 1

Author(s):

Ion Dumitru ◽

Liviu Marsavina ◽

Nicolae Faur ◽

I. Hajdu

Keyword(s):

Strain Rate ◽

19Th Century ◽

Material Properties ◽

Cyclic Load ◽

Impact Test ◽

Fatigue Tests ◽

Impact Fatigue ◽

Repeated Impact ◽

Repeated Impacts

Many components from industry are subjected to repeated impacts, or in some cases these impacts can appear as additional loads. Repeated impacts define a fatigue phenomenon known under the name of Impact Fatigue. Because the strain rate changes the material characteristics it is to expect that the material properties at impact fatigue to be different in regard to those obtained at non-impact fatigue. First studies at repeated impacts were made at the middle of 19th Century, but the progress in this field is not as fast as non-impact fatigue, due to experimental difficulties and the lake of standards for impact fatigue tests. This paper presents a classification of repeated impact tests, and starting from this a series of parameters used for durability estimation will be analyzed. The high number of parameters used by different authors creates difficulties in comparison the different laboratories results. The importance of the shape and dimensions of specimens, and the stiffness of bearing are highlighted. In order to avoid these influences the authors proposed an experimental technique, based on testing of Charpy specimens, in similar conditions as single impact test. The paper presents a series of results obtained for additional impacts overlapped to a cyclic load.

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Residual properties of composite plates subjected to impact fatigue

Journal of Composite Materials ◽

10.1177/0021998318791324 ◽

2018 ◽

Vol 53 (6) ◽

pp. 799-817 ◽

Cited By ~ 1

Author(s):

Said Mouhoubi ◽

Krimo Azouaoui

Keyword(s):

Energy Level ◽

Residual Strength ◽

Damage Model ◽

Composite Plates ◽

Fatigue Tests ◽

Multiple Impacts ◽

Impact Fatigue ◽

Residual Properties ◽

Post Impact ◽

Major Factors

This work deals with post-impact residual mechanical behavior of composite plates made with glass fiber cloth and two different thermosetting resins (epoxy and polyester). It is well known that damages induced by multiple impacts greatly reduce the residual properties. How are the residual strength or stiffness affected by the impacts? How does impact energy and number of impacts contribute to the degradation of mechanical properties? What kind of supports induces more damages and consequently a larger reduction in residual properties? These are some questions that we attempt to clarify in this paper. To investigate and assess the effect of the energy level and number of impacts on the total induced damage and residual properties, impact fatigue tests were carried out at selected energy range of: 3 J, 4 J, 5 J, and 6 J. Then, coupons containing the damaged area are cut out, in order to estimate the tensile, compressive, and shear residual properties, particularly residual strength. The energy level and number of impacts are major factors influencing the loss of stiffness and strength. However, stiffness is more affected than strength by the repeated impacts. A clear decrease of compressive residual strength with the number of impacts for the two fixture conditions (clamped on two opposite sides and a circular clamp) is demonstrated. The drop in the case of the circular clamping is more visible, confirming a greater extent of damages. A three-parameter damage model is proposed and applied, with some conclusions are withdrawn in this investigation.

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An Assesment of the Impacted Composite Single-Lap Adhesive Joints

Journal of Mechanics ◽

10.1017/jmech.2015.9 ◽

2015 ◽

Vol 31 (4) ◽

pp. 433-439

Author(s):

H. Çallioğlu ◽

E. Ergun

Keyword(s):

Experimental Study ◽

Impact Energy ◽

Energy Levels ◽

Composite Plates ◽

Lap Joints ◽

Adhesive Joints ◽

Single Lap Joints ◽

Impact Energies ◽

The Impact ◽

Energy Profiling

AbstractThe aim of this experimental study is to investigate impact behaviors of the composite single-lap adhesive joints. The increasing impact energies, which are ranged from approximately 5 J to 30 J, are performed at the center of the composite plates having three different overlap lengths. It is shown that the overlap lengths and impact energy levels affect considerably the impact responses of the composite single lap joints. It is also shown that the bending stiffness of the composite increases by increase in the overlap length. An energy profiling method (EPM) is used to identify the penetration and perforation thresholds of composite lap joints. The damaged composite plates are visually inspected.

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Study on Damage Modes of a Sandwich Panel Impacted Repeatedly

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.980.147 ◽

2014 ◽

Vol 980 ◽

pp. 147-151

Author(s):

Krimo Azouaoui ◽

Said Mouhoubi

Keyword(s):

Sandwich Panel ◽

Energy Levels ◽

Testing Machine ◽

Fatigue Loading ◽

Impact Fatigue ◽

Damage Area ◽

Energy Impact ◽

Thickness Skin ◽

Different Diameters ◽

Fixture System

This paper describes an experimental investigation for determining the damage modes under low energy impact-fatigue of sandwich panels consisting of aluminum skins supported by honeycomb core made of aluminum. Square samples of 125mm by 125mm sides and 10mm thickness (skin of 0.6mm and 8.8mm of core) were subjected to impact fatigue loading using a testing machine at four different energy levels (2J, 3J, 5J and 7J). The square plates are clamped in a fixture system over a 100mm diameter hole. Three different diameters of impactor head (15mm, 25mm and 35mm) are used to study their influence on life duration of the sandwich plates. Results showed that damage area at impacted face and propagation of multi-cracks at rear face are greatly affected by energy level and impactor diameter.

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A Study of Nozzles in Pressure Vessels under Pressure Fatigue Loading

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1967_182_050_02 ◽

1967 ◽

Vol 182 (1) ◽

pp. 657-684 ◽

Cited By ~ 7

Author(s):

J. Spence ◽

W. B. Carlson

Keyword(s):

Fatigue Life ◽

Mild Steel ◽

Pressure Vessel ◽

Special Interest ◽

Maximum Stress ◽

Fatigue Loading ◽

Fatigue Tests ◽

Pressure Vessels ◽

Full Size

Nozzles in cylindrical vessels have been of special interest to designers for some time and have offered a field of activity for many research workers. This paper presents some static and fatigue tests on five designs of full size pressure vessel nozzles manufactured in two materials. Supporting and other published work is reviewed showing that on the basis of the same maximum stress mild steel vessels give the same fatigue life as low alloy vessels. When compared on the basis of current codes it is shown that mild steel vessels may have five to ten times the fatigue life of low alloy vessels unless special precautions are taken.

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