CNRS Mechanics, Surfaces and Materials Processing Laboratory

Paris, France

CNRS Mechanics, Surfaces and Materials Processing Laboratory

Paris, France
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Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Mansori M.E.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Procedia Manufacturing | Year: 2016

Owing to their enhanced mechanical properties and improved structural functions, the use of hybrid CFRP/Ti stacks (a sandwich of one CFRP laminate and one Ti alloy) has experienced an increasing trend in modern aerospace industry. The emergence of such composite-to-metal alliances, however, poses a series of new challenges to the manufacturing sectors for high-quality finishing of the material-made components. The key machining problems usually arise from the disparate natures of the stacked constituents (CFRP laminate and Ti alloy) and their respective poor machinability. To study the fundamental cutting characteristics of the bi-material assembly, this paper presents an experimental study concerning the machinability evaluation of the hybrid CFRP/Ti stacks. An orthogonal cutting configuration (OCC) derived from the real manufacturing operation was adopted to finalize the CFRP/Ti cutting comprehension by using the polycrystalline diamond (PCD) tipped tools. The cutting trials were performed under the reasonable cutting sequence strategy of CFRP → Ti as pointed out by most experimental studies. The key cutting responses including cutting forces, machined surface quality and tool wear mechanisms were precisely addressed versus the utilized cutting conditions. The experimental results highlight that a parametric combination of high cutting speeds and low feed rates often facilitates the reduction of cutting forces and induced damage extents. The basic damage modes promoted on the machined CFRP/Ti surfaces are observed to be fiber pullout, resin loss, surface cavity, deformation of feed marks and re-deposited materials. Moreover, the key wear mechanisms governing the PCD tool cutting are confirmed to be crater wear and flank wear, while the tool failure mode is edge chipping. To ensure the excellent machined surface quality, a stringent control of tool wear should be implemented when cutting hybrid CFRP/Ti stacks. © 2016 The Authors


Sanitas A.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Coniglio N.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Bedel M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
International Journal of Advanced Manufacturing Technology | Year: 2017

The sand mold 3D printing technologies enable the manufacturing of molds with great dimensional accuracy. However, the roughness of as-cast components is higher when cast in a 3D printed mold rather than in a traditional sand mold. Coating the inner cavity is an efficient solution but can be costly and, in the narrowest cavities, not achievable. Finding a procedure to reduce the as-cast roughness without coating would ease the casting procedures. In the present work, surface analysis of ZE41 magnesium alloy is presented after being cast in 3D printed furan sand molds without coating using the low-pressure casting process. The molten metal temperature was measured during casting at different positions along the cast cavity. The as-cast surface roughness was correlated to the molten metal temperature and solid fraction at the time of contact against the sand mold surface. © 2017 Springer-Verlag London


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Xu J.,Shanghai JiaoTong University | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
AIP Conference Proceedings | Year: 2016

This paper studied the machinability of hybrid CFRP/Ti stack via the numerical approach. To this aim, an original FE model consisting of three fundamental physical constituents, i.e., CFRP phase, interface and Ti phase, was established in the Abaqus Explicit/code to construct the machining behavior of the composite-to-metal alliance. The CFRP phase was modeled as an equivalent homogeneous material (EHM) by considering its anisotropic behavior relative to the fiber orientation (θ) while the Ti alloy phase was assumed to exhibit isotropic and elastic-plastic behavior. The "interface" linking the "CFRP-to-Ti" contact boundary was physically modeled as an intermediate transition region through the concept of cohesive zone (CZ). Different constitutive laws and damage criteria were implemented to simulate the chip separation process of the bi-material system. The key cutting responses including specific cutting energy consumption, induced subsurface damage, and interface delamination were precisely addressed via the comprehensive FE analyses, and several key conclusions were drawn from this study. © 2016 Author(s).


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Xu J.,Shanghai JiaoTong University | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
AIP Conference Proceedings | Year: 2016

Hybrid CFRP/Ti stack has been widely used in the modern aerospace industry owing to its superior mechanical/physical properties and excellent structural functions. Several applications require mechanical machining of these hybrid composite stacks in order to achieve dimensional accuracy and assembly performance. However, machining of such composite-to-metal alliance is usually an extremely challenging task in the manufacturing sectors due to the disparate natures of each stacked constituent and their respective poor machinability. Special issues may arise from the high force/heat generation, severe subsurface damage and rapid tool wear. To study the fundamental mechanisms controlling the bi-material machining, this paper presented an experimental study on orthogonal cutting of hybrid CFRP/Ti stack by using superior polycrystalline diamond (PCD) tipped tools. The utilized cutting parameters for hybrid CFRP/Ti machining were rigorously adopted through a compromise selection due to the disparate machinability behaviors of the CFRP laminate and Ti alloy. The key cutting responses in terms of cutting force generation, machined surface quality and tool wear mechanism were precisely addressed. The experimental results highlighted the involved five stages of CFRP/Ti cutting and the predominant crater wear and edge fracture failure governing the PCD cutting process. © 2016 Author(s).


Xu J.,Shanghai JiaoTong University | Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Wear | Year: 2017

CFRP/Ti stacks have become a viable alternative to conventional composite laminates and metal alloys in various aerospace applications because of their enhanced mechanical properties and improved structural functions. Machining these multilayer stacks with acceptable quality still remains a great challenge for the modern manufacturing sectors due to the ineffective management of the tool wear performance resulting from the varying properties of the stacked constituents. This paper describes, on a fundamental basis, the wear characteristics of polycrystalline diamond (PCD) tipped tools during the orthogonal cutting of CFRP/Ti stacks. Two cutting sequence strategies, i.e., cutting from CFRP to Ti and cutting from Ti to CFRP, were implemented throughout the cutting tests. The experimental results confirm the predominance of the cutting sequence strategy in affecting the CFRP/Ti chip separation and the machined surface quality. The chip adhesion is a most influential factor leading to the disparate influences of the two cutting sequence strategies on the CFRP/Ti cutting responses. The PCD tool suffers severe crater wear due to the Ti phase cutting, while it undergoes minor flank wear owing to its superior wear resistance against abrasive carbon fibers. The wear signatures on the tool-chip contact zone via the scanning electron microscope (SEM) observation reveal that the Ti phase cutting dominates the formation of the tool crater wear land. The edge chipping occurs mainly due to the sudden force variation in the CFRP/Ti interface machining and the inherent brittleness of the PCD material. The fiber orientation seems to have a great impact on the wear behavior of utilized PCD tools by altering the tool-chip contact length. © 2016 Elsevier B.V.


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Xu J.,Shanghai JiaoTong University | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Composite Structures | Year: 2016

Mechanical drilling has been frequently used for hole making of hybrid CFRP/Ti stacks in order to ensure excellent fastening assembly. Owing to their inhomogeneous behavior and poor machinability, drilling CFRP/Ti stacks in one-shot time has brought great challenges to the modern manufacturing community. Compared to the previous studies on drilling CFRP/Ti, this paper aims to highlight the following aspects: (i) the features of tool-work interaction and machinability classification in the bi-material drilling, (ii) the influences of different cutting sequences on CFRP/Ti drilling responses, and (iii) the effects of different tool geometries/materials on CFRP/Ti drilling performance. The experimental results have shown that the drill geometrical features, which ensure the cutting contacts of the stack combination, have a more significant effect on CFRP/Ti drilling output than tool material composition. The Ti → CFRP drilling strategy promotes higher quality of the machined hole surfaces (e.g., more consistent hole diameters and much better surface finish) with lower Ti burr extents, while the CFRP → Ti drilling strategy reduces only the induced delamination. The experiments discussed in this paper allow besides several recommendations for the cutting sequence selection and drill geometrical design when drilling hybrid CFRP/Ti stacks. © 2016 Elsevier Ltd


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Mkaddem A.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Composite Structures | Year: 2016

Hybrid composite stack, especially FRP/Ti assembly, is considered as an innovative structural configuration for manufacturing the key load-bearing components favoring energy saving in the aerospace industry. Several applications require mechanical drilling for finishing hybrid composite structures. The drilling operation of hybrid FRP/Ti composite, however, represents the most challenging task in modern manufacturing sectors due to the disparate natures of each constituent involved and the complexity to control tool-material interfaces during one single cutting shot. Special issues may arise from the severe subsurface damage, excessive interface consumption, rapid tool wear, etc. In this paper, a rigorous review concerning the state-of-the-art results and advances on drilling solutions of hybrid FRP/Ti composite was presented by referring to the wide comparisons among literature analyses. The multiple aspects of cutting responses and physical phenomena generated when drilling these materials were precisely addressed. A special focus was made on the material removal modes and tool wear mechanisms dominating the bi-material interface consumption (BIC) with respect of investigating strategies used. The key conclusions from the literature review were drawn to point out the potential solutions and limitations to be necessarily overcome for reaching both (i) enhanced control of drilling operation, and (ii) better finish quality of FRP/Ti parts. © 2015 Elsevier Ltd.


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Materials | Year: 2016

In hybrid carbon fiber reinforced polymer (CFRP)/Ti machining, the bi-material interface is the weakest region vulnerable to severe damage formation when the tool cutting from one phase to another phase and vice versa. The interface delamination as well as the composite-phase damage is the most serious failure dominating the bi-material machining. In this paper, an original finite element (FE) model was developed to inspect the key mechanisms governing the induced damage formation when cutting this multi-phase material. The hybrid composite model was constructed by establishing three disparate physical constituents, i.e., the Ti phase, the interface, and the CFRP phase. Different constitutive laws and damage criteria were implemented to build up the entire cutting behavior of the bi-material system. The developed orthogonal cutting (OC) model aims to characterize the dynamic mechanisms of interface delamination formation and the affected interface zone (AIZ). Special focus was made on the quantitative analyses of the parametric effects on the interface delamination and composite-phase damage. The numerical results highlighted the pivotal role of AIZ in affecting the formation of interface delamination, and the significant impacts of feed rate and cutting speed on delamination extent and fiber/matrix failure. © 2015 by the authors.


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | Voisin J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
Procedia CIRP | Year: 2016

Compared to the great interest of experimental studies on hybrid CFRP/Ti drilling, this paper provided a new contribution to study the hybrid composite machinability via the numerical approach. To this aim, the complex drilling operation was abstracted into the orthogonal cutting configuration (OCC) by considering the involved cutting sequence from one phase machining to another phase machining. The numerical model was established by incorporating four fundamental physical constituents (i.e., Ti layer, interface, CFRP layer and tool part) to simulate the hybrid cutting operation. Different constitutive laws and damage criteria were implemented to construct the anisotropic machinability of the stacked composite. The induced cutting responses including specific cutting energy (u) and induced damage formation, were precisely addressed versus the input variables. The numerical studies highlighted that the anisotropic machinability of the CFRP/Ti stack could be reflected in a "pigeon" like u polar map versus fiber orientation (θ). For minimizing the severe induced damage extent, high cutting speed, as well as low feed rate, should be adopted when machining this multi-phase material. © 2016 The Authors.


Xu J.,CNRS Mechanics, Surfaces and Materials Processing Laboratory | El Mansori M.,CNRS Mechanics, Surfaces and Materials Processing Laboratory
International Journal of Precision Engineering and Manufacturing | Year: 2016

Stacked composite CFRP/Ti is identified as an innovative structural configuration for manufacturing the key aircraft components favoring energy saving in the modern aerospace industry. Machining of this composite-to-metal alliance exhibits the most challenging task in manufacturing community due to the disparate natures of each phase involved and their respective poor machinability. Since the experimental studies are highly cost and time consuming, the numerical approach should be a capable alternative to overcoming the several technical limitations involved. In this research, an original FE model was developed to simulate the complete chip formation process when orthogonal cutting (OC) of hybrid CFRP/Ti stacks. Different constitutive models and failure criteria were implemented into the Abaqus/Explicit code to construct the entire machining behavior of the stacked composite material. The stack model was built to replicate accurately the key physical phenomena activated in the hybrid cutting operation. Special concentration was made on the comparative studies of the effects of different cutting-sequence strategies on the machining responses induced by CFRP/Ti cutting. The numerical results highlighted the significant role of cutting-sequence strategy in affecting the final machined surface morphology and subsurface damage extent, and hence emphasized the importance of selecting reasonable cutting-sequence strategy for hybrid CFRP/Ti machining. © 2016, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

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