Effects of tool geometry and process parameters on delamination in CFRP drilling: An overview

Fiber reinforced polymers (FRPs) show advantageous physical-mechanical, thermal, and dielectric characteristics, making them promising candidates for weight reduction in structural applications. However, machinability is often difficult because of the specificity of their structure. This paper highlights the latest advances in CFRP drilling. Key papers are analyzed with respect to workpiece materials, geometrical tool features, and input variables (such as variation in process parameters). The influence of tool geometry and process parameters on workpiece delamination and hole quality/integrity represents the primary focus of this review. In addition, some new data are presented and discussed

diamond drilling of carbon fiber reinforced polymers influence of tool grit size and process parameters on workpiece delamination

Abstract The physical and mechanical properties of advanced composite materials promote their application in structural components for the aerospace and automotive sectors. However, limitations in their machinability are due to anisotropy/inhomogeneity, poor plastic deformation, and abrasive behavior. For CFRP drilling, the process efficiency is heavily influenced by cutting conditions and tool geometry. This paper reports the outcomes of experimental diamond drilling tests. A 4-mm thick carbon-epoxy composite laminate was machined. The plate was made of ten layers, in which the carbon fibers were intertwined at 90°. 6-mm diameter core drills were used. Core drills were characterized by an electroplated bond type and an AC32-H diamond grain type. Four different tool grit size ranges were tested: (1) 63/53 μm, (2) 125/106 μm, (3) 212/180 μm, and (4) 212/180 plus 63/53 μm. The results are reported in terms of workpiece delamination, thrust force, torque, and chip morphology. Overall, the results allow identifying the cutting conditions for the minimum drilling-induced delamination while retaining a satisfactory process productivity

Investigation of micro-blasting process on surface treatment of bio-implants

This project develops the capabilities of micro-abrasive jet machining (MAJM) for tailoring of surface integrity aspects responsible for osseointegration, adhesion strength, and lubrication of artificial articular joints (AAJs). The thesis starts with a literature review outlining six aspects of MAJM process, which must be addressed to enable surface functionalization of AAJs. In the second chapter, the project develops an analytical-numerical model of particle velocity field generated by micro-nozzle. The investigation highlights the effect of process parameters on the magnitude of particle velocity and the nature of its change. In the third chapter, an analytical solution is developed to describe the temperature rise during the impact of a single particle. Further, several numerical models and measurements are addressed for elaborating the steady-state thermal field during MAJM. The fourth chapter delivers a modified Hill’s ratio predicting lateral crack nucleation druing impact-induced fracturing and erosion rate of brittle materials. The following four chapters are application-focused. Fifth chapter is on the development of the bone/implant interfacial area. Six shape parameters of eight abrasive fractions and nine roughness parameters of Co-Cr-Mo surface eroded under sixteen blasting conditions are analysed. The fifth chapter improves adhesion strength and scratch-resistance of antibacterial coatings. The investigation contributes an extensive characterization of Ti-6Al-4V surface topography, microstructure, chemistry and wettability generated by milling, polishing, acid-etching and MAJM. The sixth and seventh chapters address the issue of poor tribological performance of AAJs, developing MAJM direct writing and a novel Tribo-blast surface texturing technique. This project delivers tools for managing particle velocity, jet kinetic energy, machining temperature, single crater size, surface roughness and erosion rate in MAJM. The bone/implant interfacial area, the scratch resistance of antibacterial coatings, and bearing index of the articular surface, all can be increased by a factor of two. The femoral head of a hip joint can be covered by micro-channels within a few minutes using only one nozzle and one gram of abrasives without the patterning masks or precision CNC actuators. Overall, the productivity and cost-effectiveness, makes MAJM a strong candidate for industrial implementation in the manufacturing chain of life-long AAJs

The new designs of diamond drill bits for composite polymers tooling

The author explores the drilling operation of some new engineering materials such as carbon fiber reinforced plastics (CFRP) and other polymers that have an anisotropic structure, high-strength and elastic properties combined with low heat endurance. Such combination of properties makes impossible the simple transfer of the existing technologies for classic materials working to considered new class. At the same time, the existing tools cannot assure the specified quality of tooled products at the current productivity and tool life. Aim: The aim of this research is to increase the process efficiency of diamond drilling in composite polymers by developing the new designs of diamond drill bits. Materials and Methods: One of the most promising directions to solve this problem is the diamond coated abrasive type tool. This paper addresses and classifies the existing types of diamond drill bits according to their application and operation. The literature data analysis of known disadvantages during drilling operation, the quality of surface and joining face was performed. Results: The experimental researches of the author prove the negative meaning of the already known but kept out fact – the drill core blocking. The most important factors and structural features affecting the CFRP drilling process are revealed. The accounting of these factors allowed creating the set of unique designs of diamond drill bits for different purposes. The presented patented models has different allowance distribution schemes and cutting forces, thus satisfy the mechanical requirements of quality, productivity, tool life and hole geometry in the tooling of the specified material class

Особливості механічної обробки полімерних композиційних матеріалів

The specific features of the polymeric composite materials processing are pointed. The results of the previous experiment from diamond and blade drilling are given. The development prospective ways of the diamond processing of the polymer composite materials are identified.Указаны особенности обработки полимерных композиционных материалов. Приведены результаты предварительного эксперимента по алмазному и лезвийному сверлению. Выделены перспективные пути развития алмазной обработки полимерных композиционных материалов.Указані особливості обробки полімерних композиційних матеріалів. Наведені результати попереднього експерименту з алмазного та лезвійного свердлення. Визначені перспективні шляхи розвитку алмазної обробки полімерних композиційних матеріалів

Diamond drilling of Carbon Fiber Reinforced Polymers: Influence of tool grit size and process parameters on workpiece delamination

The physical and mechanical properties of advanced composite materials promote their application in structural components for the aerospace and automotive sectors. However, limitations in their machinability are due to anisotropy/inhomogeneity, poor plastic deformation, and abrasive behavior. For CFRP drilling, the process efficiency is heavily influenced by cutting conditions and tool geometry. This paper reports the outcomes of experimental diamond drilling tests. A 4-mm thick carbon-epoxy composite laminate was machined. The plate was made of ten layers, in which the carbon fibers were intertwined at 90°. 6-mm diameter core drills were used. Core drills were characterized by an electroplated bond type and an AC32-H diamond grain type. Four different tool grit size ranges were tested: (1) 63/53 μm, (2) 125/106 μm, (3) 212/180 μm, and (4) 212/180 plus 63/53 μm. The results are reported in terms of workpiece delamination, thrust force, torque, and chip morphology. Overall, the results allow identifying the cutting conditions for the minimum drilling-induced delamination while retaining a satisfactory process productivity

Characterizing ABS–copper chemistry-dependent adhesion: From the atomic to macro level

The electroplating of copper layers on acrylonitrile–butadiene–styrene (ABS) polymer surfaces is a common need in industrial applications. The development of new eco-friendly techniques to promote ABS–copper adhesion is crucial due to the harsh and expensive chemicals used in the existing processes. The initial path involves establishing a better understanding on chemistry-dependent ABS–copper adhesion mechanisms. By formulating the material with more functional groups, the adhesion between ABS and the coated copper layer was characterized through a multiscale approach. At the atomic scale, we performed ab initio density functional theory simulations to obtain the variations in the adsorption energy. At the nano and micro scales, we adopted atomic force microscopy to measure the adhesion forces on the bulk polymer surfaces. At the macro scale, we compared these adhesion results with both 90-degree peeling tests and finite element model analyses. This study presents the first comprehensive approach for bridging information gaps across the scales (from nano to macro) with computational and experimental data, facilitating the design of formulated ABS additives

Unlocking multiscale metallic metamaterials via lithography additive manufacturing

Metamaterials possess properties not found in nature and are expected to revolutionise the design of structural components. However large-scale production of metallic metamaterials remains locked due to the compromise between print size and resolution in existing metal 3D printing methods. We unlock the possibility of 3D printing of stainless steel metamaterials across scales using lithography metal manufacturing, a vat photopolymerisation technology that uses digital light processing (DLP) on metal-filled resin to 3D print a green body for further debinding and sintering in a furnace. Here in, were explore the effects of energy dose on overpolymerisation, minimal feature size, and print resolution as well as the effects of sintering temperature on microstructure, shape stability, and mechanical properties of 3D printed metamaterials. It has become possible to 3D print steel metamaterials with a twist and auxetic metamaterials with micro-scaled structures on a decimetre scale. Our benchmarking experiments demonstrate that lithography metal manufacturing competes with laser powder bed fusion regarding print accuracy, surface roughness, and design freedom and provides a viable solution for translating metallic metamaterials from laboratories to markets.</p