R. Zitoune - Profile on Academia.edu (original) (raw)

Papers by R. Zitoune

Composites Part A: Applied Science and Manufacturing, 2020

Conventional machining of carbon fiber reinforced plastic composites (CFRPs) generates minute chi... more Conventional machining of carbon fiber reinforced plastic composites (CFRPs) generates minute chips that get suspended in air causing a hazard compromising operator safety. This study investigates the influence of cutting parameters (feed speed, cutting speed, radial depth of cut, tool geometry and tool wear) during trimming of CFRP on the form and quantity of harmful particles dispersed. Also, performance of two classical PCD tool geometries (two straight flutes, two helix flutes) have been compared with newly designed (in collaboration with ASAHI Company) four serrated straight flutes for the purpose of dust emission reduction. The quantification of the number of harmful particles was estimated using laser spectroscopic dust monitor. The results reveal that, trimming with a combination of higher feed speed and lower cutting speed can reduce the dispersion of harmful particles. Further, the four serrated straight flutes recorded the least number of harmful particles compared to the conventional tools.

Comparison of composite specimen fracture with drilled and moulded holes

Repairing composites

Advances in Composites Manufacturing and Process Design, 2015

ABSTRACT

Role of the surface quality on the mechanical behavior of CFRP bolted composite joints

International Journal of Fatigue, 2015

Abstract In this research paper, the influence of two drilling processes on the mechanical behavi... more Abstract In this research paper, the influence of two drilling processes on the mechanical behavior of bolted composite joints was investigated. Two stacking sequences were studied namely, [±45°] 2S and [90/+45/0/−45] S . The composite specimens were drilled using conventional machining (CM) and abrasive water-jet machining (AWJM). Fatigue tests combined with infrared thermography (IR) were used to determine the high cycle fatigue strength and monitor damage accumulation and heat dissipation. Fatigue test results at 65% of the ultimate tensile strength showed that the damage for [±45°] 2S and [90/+45/0/−45] S bolted joints drilled with CM were 65% and 54% respectively. However, when the AWJM was used, the damage accumulated was 25% more compared to CM. This difference was confirmed by IR results which showed that [±45°] 2S bolted joints drilled with CM dissipate 23% more heat than those drilled with AWJM. The current study demonstrated that AWJM extends the high cycle fatigue strength and the fatigue life of bolted composite joints.

Compressive behaviour of concrete elements confined with GFRP-prefabricated bonded shells

European Journal of Environmental and Civil Engineering, 2014

In this paper, a new technique is proposed to confine concrete columns using GFRP-prefabricated b... more In this paper, a new technique is proposed to confine concrete columns using GFRP-prefabricated bonded shells and a shrinkage-compensating cement mortar. The confinement is performed with three identical shells, each of which contains two stepped lap joints at their ends. The main advantage of this technique is that the shells can be directly assembled on site by structural bonding to cover any column shape. The gap between the shells and the column is filled with shrinkage-compensating cement mortar. To evaluate the efficiency of this technique, several concrete specimens were confined, instrumented and tested under monotonic compression. To simulate the actual strengthening conditions, the load was directly applied on the concrete cross-section. The results show clearly the benefits of an efficient confinement in terms of a noticeable increase in the axial strength and ductility where the stress–strain curves are characterised by a third softening phase and the failure mode which spread over the whole length of the shells.

Influence of Tool Geometry and Machining Parameters on the Surface Quality and the Effect of Surface Quality on Compressive Strength of Carbon Fibre Reinforced Plastic

Materials Science Forum, 2013

In this chapter the influence of tool geometry and cutting conditions on cutting forces, surface ... more In this chapter the influence of tool geometry and cutting conditions on cutting forces, surface defects and the percetage of dust generated durring trimming and reaching the pulmonary alveoli is investigated. The surface defects were analysed using a scanning electron microscope and diferent surface roughness measurement devices. It was observed that these leters were highly depend on the cutting condition and the tool geometry, and more important that the effect of cutting parameters can be completely diferent from a tool to an other or even when considering different ranges of cutting parameters (standard cutting speed and high cutting speed). The compressive strenght after machining is also investigated. It is observed that whatever tool geometry, cutting conditions, surface roughnesses (defects) are, the response still the same for all the composite samples except for those machined at cutting temperatures higher than the glass fiber transition.

Influence of the damage generated by abrasive water jet texturing on the tensile static and fatigue behaviour of 3D woven composite in the context of repair

Composites Part A: Applied Science and Manufacturing, 2021

Abstract Abrasive water jet (AWJ) process has been certified in some aerospace companies for repa... more Abstract Abrasive water jet (AWJ) process has been certified in some aerospace companies for repair applications. However, there is no information in the literature on the influence of the induced damage on the mechanical behaviour of complex materials such as 3D woven CFRP composite. To fill this gap, three texturing levels have been produced and quantified using both surface roughness (Ra) and “crater volume” (Cv) criteria. The specimens have been subjected to tensile static and tension-tension fatigue tests. Contrarily to Ra measurements, a linear correlation was highlighted between the increase in Cv and the degradation of the specimens’ mechanical performances (ultimate tensile stress and fatigue limit). The damage scenario of the textured specimens has been identified via acoustic emission activity, thermal maps and X-ray tomography pictures. Wider cracks and a more intense acoustic activity leading to a greater rise in temperature have been observed when Cv increases (worse quality). However, the small alterations in mechanical properties consecutive to AWJ texturing prove that this technique can be used for surface preparation of 3D woven CFRP parts prior to bounding without damaging them. Moreover, an innovative method, based on the damage accumulation, has been proposed and accurately estimates the endurance limit of the specimens.

Composite Structures, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Wear, 2013

This article presents an experimental analysis of drilling using carbide drills on carbon fiber r... more This article presents an experimental analysis of drilling using carbide drills on carbon fiber reinforced plastic (CFRP) laminates specially made with copper mesh on one side and woven carbon fabric on the other side using carbide drills. The objective of this study was to improve the machining performance during drilling of sandwiched composite using various dimensions of double cone drill. The drill design in terms of its tribological characteristics (i.e. friction, wear) are analyzed including cutting force, life, chip form and hole quality. Results have shown that double cone drills generated less thrust force compared to standard twist drills. No delamination was found in the holes at high feed rates (above 0.1 mm/rev). This could be attributed to the presence of thermoplastic nodules between the layers of the CFRP laminate and the presence of woven fabric ply at the bottom of the laminate. Furthermore a relationship between the feed per cutting edge and the thickness of the thermoplastic layer has been developed to promote the formation of continuous chips during drilling. Finally, SEM observations reveal several damage when standard twist drills were used and less damage was observed with double cone drills. These damaged areas were observed in the plies of fibers oriented at À 451 and 901 compared with peripheral cutting speed of the drill.

Multi-scale analysis of the damage and contamination in abrasive water jet drilling of GLARE fibre metal laminates

Journal of Manufacturing Processes

Controlled Depth Milling of Hybrid Aerospace Grade Materials Using Abrasive Water Jet – Critical Review and Analysis

Machining and Machinability of Fiber Reinforced Polymer Composites, 2020

Composite Structures, 2020

The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure... more The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure, traverse speed and scan step) on the cutting depth of 3D woven Carbon Fibres Reinforced Polymer (CFRP) composite. The original material linked to this non-conventional milling process has not been treated yet. The depths of cut were measured and characterized as a function of the machining parameters. Finally, two prediction models for the cutting depth are proposed and validated experimentally. An increase in cutting depth with the pressure and a decrease as the traverse speed and/or the scan step increase were observed. The first prediction model, based on the pocket depth measurements, has a mean error of 5%. However, the error increases (up to 23%) when the pocket becomes shallow (lesser than 1 mm). The second prediction model, based on the algebraic sum of elementary passes modelled with Gaussian bells, shows at first a mean error of 12%. A correction was performed depending on the erosion regime piloted by the depth of the elementary trench constitutive of the pocket. This enhancement, performed thanks to the primary jet diameters measurements with high speed camera, has improved the second model with a mean error of 5% (error < 16%).

Study of drilling of multi-material (CFRP/Al) using Taguchi and statistical techniques

ABSTRACT

In this work a multidirectional CFRP is trimmed at high speed using a burr tool made of tungsten ... more In this work a multidirectional CFRP is trimmed at high speed using a burr tool made of tungsten carbide. In order to analyze the influence of the machining parameters on the total cutting forces and quality of the machined surface, sharp and used tool are considered. Total cutting forces, surface roughness and damaged zones (observed via SEM images) are higher when considering a used tool. Total cutting forces and surface roughness are also mainly influenced by the cutting parameters. To estimate the effect of tool wear and cutting parameters on the total cutting force and surface roughness depth, a statistical method (ANOVA) has been used. The results show that machining parameters (feed speed and cutting speed) and cutting distance are the major factors, responsible for the variation of total cutting forces and machining surface quality.

Benefit from Embedded Sensors to Study Polymeric Composite Structures

Damage and Fracture Mechanics, 2009

The present paper deals with the use of optical fibers with Bragg gratings for the identification... more The present paper deals with the use of optical fibers with Bragg gratings for the identification of process-properties relations for composite structures. This study relates a 7 year-experience in the field of process and mechanical characterization of composite ...

Experimental Mechanics, 2014

This paper focuses on the mechanical behavior in quasi-static tests (compression and inter-lamina... more This paper focuses on the mechanical behavior in quasi-static tests (compression and inter-laminar shear) of two composite materials machined by different processes. First, the impact of the variation of average surface roughness (Ra) and the machining process is studied for both materials and for each stress. The results of compression and inter laminar shear tests show that the mechanical behavior is greatly affected by the surface roughness and the machining temperatures. Secondly the effect of machining processes is detailed. The experimental results show the major dependence of the mechanical behavior on the machining process. The results obtained on the two materials being different, this work sheds light on the influence of the composition of composite materials on the surface defects and the mechanical behavior of such materials.

Experimental and analytical study of the influence of HexFit® glass fibre composite manufacturing process on delamination during drilling

International Journal of Machining and Machinability of Materials, 2008

ABSTRACT

International Journal of Machining and Machinability of Materials, 2013

In this paper, high speed trimming of a multidirectional CFRP using unused and used burr tools is... more In this paper, high speed trimming of a multidirectional CFRP using unused and used burr tools is considered in order to investigate the influence of the machining parameters (e.g., feed speed, cutting speed and cutting distance) on the cutting forces, machining temperature, and the machined surface quality. To estimate the effect of the tools' wear and cutting parameters on the cutting forces and surface roughness, a statistical method (ANOVA) has been used. When considering an unused tool, the recorded temperatures were below the glass transition temperature of the composite material (Tg). In the case of used tools, these temperatures were mostly higher than the Tg. Furthermore, SEM observations of the machined surface showed damaged areas. These areas were wider when the cutting distance increased. Statistical analyses have shown that the machining parameters have a significant influence on the variation of the machined surface quality and the cutting forces.

Experimental Mechanics, 2009

This study concerns the central reinforced zone of a composite structural specimen. In order to e... more This study concerns the central reinforced zone of a composite structural specimen. In order to estimate the strain distribution during a series of three and four-point bending tests, several optical fiber Bragg grating sensors have been embedded in various levels of the ply stack. Simultaneously, surface strain field measurements by 3-D digital image correlation are undertaken. Both techniques show a general linear distribution of longitudinal strains through the thickness of the thick zone but values are slightly different. A numerical model is developed and a test-calculation dialogue is carried out. The complementary information given by the two optical techniques for in-core and surface measurements reveals the importance of considering structural and edge effects.

Composites Part B: Engineering, 2014

The main focus of this paper is to investigate the defects generated by different machining proce... more The main focus of this paper is to investigate the defects generated by different machining processes (namely burr tool machining, abrasive water jet machining 'AWJM' and abrasive diamond cutter 'ADS') and their impact on the mechanical behavior of CFRP in quasi-static (compression and inter-laminar shear) and tensile-tensile fatigue tests. The cutting conditions are selected so that different levels of degradation can be obtained. The machined surface is characterized using roughness measuring devices with and without contact and SEM observations. The results show that the defects generated during the trimming process with a cutting tool are fibers pull-out and resin degradation. These defects are mainly located in the layers with the fibers oriented at À45°and 90°. However, when using abrasive water jet and abrasive diamond processes, the defects generated have the form of streaks and are not dependent on the fiber orientation. Furthermore, the results of quasi-static tests performed on specimens machined by cutting tools show that AWJ specimens offer a better resistance in compression but the ADS samples offer higher inter-laminar-shear strengths. Moreover, the results of fatigue tests show that specimens machined with a burr tool offer higher endurance limit. Finally, it is concluded that the type and the mode of the mechanical loading (quasi-static fatigue) affect the mechanical response of CFRP and favor a given machining process.

Composites Part A: Applied Science and Manufacturing, 2020

Conventional machining of carbon fiber reinforced plastic composites (CFRPs) generates minute chi... more Conventional machining of carbon fiber reinforced plastic composites (CFRPs) generates minute chips that get suspended in air causing a hazard compromising operator safety. This study investigates the influence of cutting parameters (feed speed, cutting speed, radial depth of cut, tool geometry and tool wear) during trimming of CFRP on the form and quantity of harmful particles dispersed. Also, performance of two classical PCD tool geometries (two straight flutes, two helix flutes) have been compared with newly designed (in collaboration with ASAHI Company) four serrated straight flutes for the purpose of dust emission reduction. The quantification of the number of harmful particles was estimated using laser spectroscopic dust monitor. The results reveal that, trimming with a combination of higher feed speed and lower cutting speed can reduce the dispersion of harmful particles. Further, the four serrated straight flutes recorded the least number of harmful particles compared to the conventional tools.

Comparison of composite specimen fracture with drilled and moulded holes

Repairing composites

Advances in Composites Manufacturing and Process Design, 2015

ABSTRACT

Role of the surface quality on the mechanical behavior of CFRP bolted composite joints

International Journal of Fatigue, 2015

Abstract In this research paper, the influence of two drilling processes on the mechanical behavi... more Abstract In this research paper, the influence of two drilling processes on the mechanical behavior of bolted composite joints was investigated. Two stacking sequences were studied namely, [±45°] 2S and [90/+45/0/−45] S . The composite specimens were drilled using conventional machining (CM) and abrasive water-jet machining (AWJM). Fatigue tests combined with infrared thermography (IR) were used to determine the high cycle fatigue strength and monitor damage accumulation and heat dissipation. Fatigue test results at 65% of the ultimate tensile strength showed that the damage for [±45°] 2S and [90/+45/0/−45] S bolted joints drilled with CM were 65% and 54% respectively. However, when the AWJM was used, the damage accumulated was 25% more compared to CM. This difference was confirmed by IR results which showed that [±45°] 2S bolted joints drilled with CM dissipate 23% more heat than those drilled with AWJM. The current study demonstrated that AWJM extends the high cycle fatigue strength and the fatigue life of bolted composite joints.

Compressive behaviour of concrete elements confined with GFRP-prefabricated bonded shells

European Journal of Environmental and Civil Engineering, 2014

In this paper, a new technique is proposed to confine concrete columns using GFRP-prefabricated b... more In this paper, a new technique is proposed to confine concrete columns using GFRP-prefabricated bonded shells and a shrinkage-compensating cement mortar. The confinement is performed with three identical shells, each of which contains two stepped lap joints at their ends. The main advantage of this technique is that the shells can be directly assembled on site by structural bonding to cover any column shape. The gap between the shells and the column is filled with shrinkage-compensating cement mortar. To evaluate the efficiency of this technique, several concrete specimens were confined, instrumented and tested under monotonic compression. To simulate the actual strengthening conditions, the load was directly applied on the concrete cross-section. The results show clearly the benefits of an efficient confinement in terms of a noticeable increase in the axial strength and ductility where the stress–strain curves are characterised by a third softening phase and the failure mode which spread over the whole length of the shells.

Influence of Tool Geometry and Machining Parameters on the Surface Quality and the Effect of Surface Quality on Compressive Strength of Carbon Fibre Reinforced Plastic

Materials Science Forum, 2013

In this chapter the influence of tool geometry and cutting conditions on cutting forces, surface ... more In this chapter the influence of tool geometry and cutting conditions on cutting forces, surface defects and the percetage of dust generated durring trimming and reaching the pulmonary alveoli is investigated. The surface defects were analysed using a scanning electron microscope and diferent surface roughness measurement devices. It was observed that these leters were highly depend on the cutting condition and the tool geometry, and more important that the effect of cutting parameters can be completely diferent from a tool to an other or even when considering different ranges of cutting parameters (standard cutting speed and high cutting speed). The compressive strenght after machining is also investigated. It is observed that whatever tool geometry, cutting conditions, surface roughnesses (defects) are, the response still the same for all the composite samples except for those machined at cutting temperatures higher than the glass fiber transition.

Influence of the damage generated by abrasive water jet texturing on the tensile static and fatigue behaviour of 3D woven composite in the context of repair

Composites Part A: Applied Science and Manufacturing, 2021

Abstract Abrasive water jet (AWJ) process has been certified in some aerospace companies for repa... more Abstract Abrasive water jet (AWJ) process has been certified in some aerospace companies for repair applications. However, there is no information in the literature on the influence of the induced damage on the mechanical behaviour of complex materials such as 3D woven CFRP composite. To fill this gap, three texturing levels have been produced and quantified using both surface roughness (Ra) and “crater volume” (Cv) criteria. The specimens have been subjected to tensile static and tension-tension fatigue tests. Contrarily to Ra measurements, a linear correlation was highlighted between the increase in Cv and the degradation of the specimens’ mechanical performances (ultimate tensile stress and fatigue limit). The damage scenario of the textured specimens has been identified via acoustic emission activity, thermal maps and X-ray tomography pictures. Wider cracks and a more intense acoustic activity leading to a greater rise in temperature have been observed when Cv increases (worse quality). However, the small alterations in mechanical properties consecutive to AWJ texturing prove that this technique can be used for surface preparation of 3D woven CFRP parts prior to bounding without damaging them. Moreover, an innovative method, based on the damage accumulation, has been proposed and accurately estimates the endurance limit of the specimens.

Composite Structures, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Wear, 2013

This article presents an experimental analysis of drilling using carbide drills on carbon fiber r... more This article presents an experimental analysis of drilling using carbide drills on carbon fiber reinforced plastic (CFRP) laminates specially made with copper mesh on one side and woven carbon fabric on the other side using carbide drills. The objective of this study was to improve the machining performance during drilling of sandwiched composite using various dimensions of double cone drill. The drill design in terms of its tribological characteristics (i.e. friction, wear) are analyzed including cutting force, life, chip form and hole quality. Results have shown that double cone drills generated less thrust force compared to standard twist drills. No delamination was found in the holes at high feed rates (above 0.1 mm/rev). This could be attributed to the presence of thermoplastic nodules between the layers of the CFRP laminate and the presence of woven fabric ply at the bottom of the laminate. Furthermore a relationship between the feed per cutting edge and the thickness of the thermoplastic layer has been developed to promote the formation of continuous chips during drilling. Finally, SEM observations reveal several damage when standard twist drills were used and less damage was observed with double cone drills. These damaged areas were observed in the plies of fibers oriented at À 451 and 901 compared with peripheral cutting speed of the drill.

Multi-scale analysis of the damage and contamination in abrasive water jet drilling of GLARE fibre metal laminates

Journal of Manufacturing Processes

Controlled Depth Milling of Hybrid Aerospace Grade Materials Using Abrasive Water Jet – Critical Review and Analysis

Machining and Machinability of Fiber Reinforced Polymer Composites, 2020

Composite Structures, 2020

The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure... more The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure, traverse speed and scan step) on the cutting depth of 3D woven Carbon Fibres Reinforced Polymer (CFRP) composite. The original material linked to this non-conventional milling process has not been treated yet. The depths of cut were measured and characterized as a function of the machining parameters. Finally, two prediction models for the cutting depth are proposed and validated experimentally. An increase in cutting depth with the pressure and a decrease as the traverse speed and/or the scan step increase were observed. The first prediction model, based on the pocket depth measurements, has a mean error of 5%. However, the error increases (up to 23%) when the pocket becomes shallow (lesser than 1 mm). The second prediction model, based on the algebraic sum of elementary passes modelled with Gaussian bells, shows at first a mean error of 12%. A correction was performed depending on the erosion regime piloted by the depth of the elementary trench constitutive of the pocket. This enhancement, performed thanks to the primary jet diameters measurements with high speed camera, has improved the second model with a mean error of 5% (error < 16%).

Study of drilling of multi-material (CFRP/Al) using Taguchi and statistical techniques

ABSTRACT

In this work a multidirectional CFRP is trimmed at high speed using a burr tool made of tungsten ... more In this work a multidirectional CFRP is trimmed at high speed using a burr tool made of tungsten carbide. In order to analyze the influence of the machining parameters on the total cutting forces and quality of the machined surface, sharp and used tool are considered. Total cutting forces, surface roughness and damaged zones (observed via SEM images) are higher when considering a used tool. Total cutting forces and surface roughness are also mainly influenced by the cutting parameters. To estimate the effect of tool wear and cutting parameters on the total cutting force and surface roughness depth, a statistical method (ANOVA) has been used. The results show that machining parameters (feed speed and cutting speed) and cutting distance are the major factors, responsible for the variation of total cutting forces and machining surface quality.

Benefit from Embedded Sensors to Study Polymeric Composite Structures

Damage and Fracture Mechanics, 2009

The present paper deals with the use of optical fibers with Bragg gratings for the identification... more The present paper deals with the use of optical fibers with Bragg gratings for the identification of process-properties relations for composite structures. This study relates a 7 year-experience in the field of process and mechanical characterization of composite ...

Experimental Mechanics, 2014

This paper focuses on the mechanical behavior in quasi-static tests (compression and inter-lamina... more This paper focuses on the mechanical behavior in quasi-static tests (compression and inter-laminar shear) of two composite materials machined by different processes. First, the impact of the variation of average surface roughness (Ra) and the machining process is studied for both materials and for each stress. The results of compression and inter laminar shear tests show that the mechanical behavior is greatly affected by the surface roughness and the machining temperatures. Secondly the effect of machining processes is detailed. The experimental results show the major dependence of the mechanical behavior on the machining process. The results obtained on the two materials being different, this work sheds light on the influence of the composition of composite materials on the surface defects and the mechanical behavior of such materials.

Experimental and analytical study of the influence of HexFit® glass fibre composite manufacturing process on delamination during drilling

International Journal of Machining and Machinability of Materials, 2008

ABSTRACT

International Journal of Machining and Machinability of Materials, 2013

In this paper, high speed trimming of a multidirectional CFRP using unused and used burr tools is... more In this paper, high speed trimming of a multidirectional CFRP using unused and used burr tools is considered in order to investigate the influence of the machining parameters (e.g., feed speed, cutting speed and cutting distance) on the cutting forces, machining temperature, and the machined surface quality. To estimate the effect of the tools' wear and cutting parameters on the cutting forces and surface roughness, a statistical method (ANOVA) has been used. When considering an unused tool, the recorded temperatures were below the glass transition temperature of the composite material (Tg). In the case of used tools, these temperatures were mostly higher than the Tg. Furthermore, SEM observations of the machined surface showed damaged areas. These areas were wider when the cutting distance increased. Statistical analyses have shown that the machining parameters have a significant influence on the variation of the machined surface quality and the cutting forces.

Experimental Mechanics, 2009

This study concerns the central reinforced zone of a composite structural specimen. In order to e... more This study concerns the central reinforced zone of a composite structural specimen. In order to estimate the strain distribution during a series of three and four-point bending tests, several optical fiber Bragg grating sensors have been embedded in various levels of the ply stack. Simultaneously, surface strain field measurements by 3-D digital image correlation are undertaken. Both techniques show a general linear distribution of longitudinal strains through the thickness of the thick zone but values are slightly different. A numerical model is developed and a test-calculation dialogue is carried out. The complementary information given by the two optical techniques for in-core and surface measurements reveals the importance of considering structural and edge effects.

Composites Part B: Engineering, 2014

The main focus of this paper is to investigate the defects generated by different machining proce... more The main focus of this paper is to investigate the defects generated by different machining processes (namely burr tool machining, abrasive water jet machining 'AWJM' and abrasive diamond cutter 'ADS') and their impact on the mechanical behavior of CFRP in quasi-static (compression and inter-laminar shear) and tensile-tensile fatigue tests. The cutting conditions are selected so that different levels of degradation can be obtained. The machined surface is characterized using roughness measuring devices with and without contact and SEM observations. The results show that the defects generated during the trimming process with a cutting tool are fibers pull-out and resin degradation. These defects are mainly located in the layers with the fibers oriented at À45°and 90°. However, when using abrasive water jet and abrasive diamond processes, the defects generated have the form of streaks and are not dependent on the fiber orientation. Furthermore, the results of quasi-static tests performed on specimens machined by cutting tools show that AWJ specimens offer a better resistance in compression but the ADS samples offer higher inter-laminar-shear strengths. Moreover, the results of fatigue tests show that specimens machined with a burr tool offer higher endurance limit. Finally, it is concluded that the type and the mode of the mechanical loading (quasi-static fatigue) affect the mechanical response of CFRP and favor a given machining process.