Grinding performance and workpiece integrity when superabrasive edge routing carbon fibre reinforced plastic (CFRP) composites

Data is presented for wheel wear, cutting forces and workpiece integrity when high speed routing 10 mm thick CFRP laminates using single layer electroplated diamond and CBN grinding points as opposed to standard end milling tools. A 60,000 rpm retrofit spindle was utilised to accommodate the 10 mm diameter wheels having grit sizes of 76, 151 and 252 μm employed under either roughing or finishing parameters. Wear of CBN points exhibited a near two-fold increase over diamond with a similar ratio for cutting forces. Despite use of flood cooling, point geometry when roughing compromised life and integrity due to excessive clogging.     

Induced drilling strains in glass fibre reinforced epoxy composites

Residual strains induced by drilling of glass-fibre reinforced polymers (GFRPs) were determined using a hybrid experimental–numerical methodology. Experimentally, a set of GFRP specimens were drilled under well-defined tensile (calibration) stresses, using an especially designed tensile test device. To remove the effect of the initial residual stresses, this methodology considers differential stress values instead of absolute ones. Numerically, the experimental procedure was simulated using the finite element method. The induced drilling strains were determined by comparing the experimental measured strains with those calculated numerically. Clear differences between the selected drilling operations could be observed and evaluated.     

Size effects in micro drilling of carbon fiber reinforced plastic composite

The contribution presents investigations regarding the size effects on cutting forces in micro drilling of carbon fiber reinforced plastic composite. Generally, size effect is described as non-linear increase of specific cutting force with decreasing chip thickness. Specific cutting forces are determined by dividing cutting force components by chip area. In a mathematical model, specific cutting force is expressed as a function of the ratio of undeformed chip thickness to cutting edge radius. The coefficients of the model are determined by regression analysis using experimental results. Non-linear increase of specific cutting force is observed when the ratio decreases, especially when the ratio is less than unity.     

Processing and properties of copper-coated carbon fibre reinforced aluminium alloy composites

Aluminium alloy matrix composites with carbon fibre reinforcement were prepared by stir casting method. In order to avoid any interfacial reactions in the carbon fibre reinforced composites, the carbon fibres were coated with copper. The fibres were coated by electroless coating method and then characterized. Composites containing different amounts of carbon fibres were prepared by stir casting and then subjected to age-hardening treatment. Fibre distribution was fairly uniform in the composites containing up to 4 wt% carbon fibres. Tensile strength of the composites was found to be increasing up to 4 wt% carbon fibre.     

B4C增强铝基复合材料钻削温度的非接触测量和多目标分析（英文）

采用光学高温计对在不同钻削条件下的B4C金属基复合材料的钻削温度进行非接触测量。研究了颗粒含量、切削速度、进给速率和刀具材料对最高钻削温度的影响。基于最高切削温度和刀具磨损对钻削参数进行优化。结果表明:对最高切削温度影响最大的因素主要为颗粒含量、进给速率以及切削速率与颗粒含量间的相互作用。切削速率与切削材料对最高切削温度的影响相对较小。当颗粒含量较小,切削速度较低,进给速率较高,利用硬质合金刀具时,切削温度较低。采用优化后的钻削参数可以获得较低的切削温度和较小的刀具磨损。     

Laser direct joining of carbon fibre reinforced plastic to stainless steel

Abstract

This study was performed to evaluate the characteristics and strengths of dissimilar joints between carbon fibre reinforced plastics (CFRP) and stainless steel using high brightness continuous wave disc laser. Tensile shear tests demonstrated that strong CFRP steel joint with ～4800 N could be produced. The joints were tightly bonded on atomic or molecular sized level through Cr–Fe oxide film on the metal surface, and small fragments of type 304 steel were detected on the fractured CFRP. Many bubbles of submillimetre size were formed all over the plastic melted zone in the CFRP. The gas compositions inside the bubbles were H₂ and hydrocarbon series as pyrolysis gases of the CFRP as well as N₂ in air. These results suggest strong chemical and physical bonding of the CFRP on the oxide film of the type 304 plate. Consequently, it was confirmed that a strong joint could be produced between CFRP and type 304 stainless steel with a laser beam.     

针刺整体毡C/C复合材料整体喉衬烧蚀分析

采用针刺整体毡炭／炭（C／C）复合材料整体喉衬进行小型固体火箭发动机地面点火实验，结合扫描电镜（SEM）及能谱分析（EDS），分别对烧蚀后整体喉衬收敛部位、喉径部位和扩张部位的烧蚀形貌进行分析。结果表明：在较高压强（12～14MPa）条件下，针刺整体毡C／C复合材料整体喉衬烧蚀均匀，烧蚀型面光滑、烧蚀率低，但因轴向纤维少及轴向强度较低，接近喉径部位的收敛部位和喉径部位易产生分层；不同部位的烧蚀形貌不同，是由于整体喷管中的燃气温度、组分浓度和速度所致。     

硬质合金高温性能对碳纤维复合材料切削加工的影响研究

制备了主元素一致的两种WC-Co基细晶粒硬质合金材料,材料A添加有微量TaC（NbC）,材料B未添加微量元素。采用高温维氏硬度计对两种硬质合金材料进行高温硬度测试,并用这两种材料制成的菱齿立铣刀对碳纤维复合材料进行铣削加工。结果表明:硬质合金菱齿立铣刀铣削碳纤维复合材料时,磨粒磨损是刀具磨损的主要原因;硬质合金材料A的高温硬度高于材料B;在相同的使用条件下,材料A的耐磨性能比材料B好,制成的刀具使用寿命更长,更适合碳纤维复合材料的切削加工。      

Resistance welding of carbon fibre reinforced polyetheretherketone composites using metal mesh and PEI film

Weldability of polyetheretherketone( PEEK) with polyetherimide( PEI) is tested. And carbon fiber reinforced PEEK laminates are resistance welded using stainless steel mesh heating element. The effects of the welding time and welding pressure on the lap shear strength of joints are investigated. Results show that PEEK can heal with PEI well in welding condition and the lap shear strength of PEEK/CF(carbon fibre) joint increases linearly with welding time, but reaches a maximum value when welding pressure ranging from 0.3 MPa to 0.5 MPa with constant welding time. The fracture characteristics of surface are analyzed by SEM techniques, and four types of fracture modes of lap shear joints are suggested.     

Dissimilar materials joining of metal/carbon fibre reinforced plastic by resistance spot welding

ABSTRACT

Dissimilar materials joining of metal to carbon fibre reinforced plastic (CFRP), which consisted of PA6, modified polypropylene (PP) or polyphenylene sulphide (PPS) as matrix polymer with short carbon fibre, was performed using series resistance spot welding (series-RSW). The metal plate was placed on CFRP plate as the lap joint, and electrodes of series-RSW were pressed only on the metal plate side. The metal around the electrode was heated by electrical resistance heating, and the thermoplastic near the interface was slightly melted by the heat conduction from heated metal. The objectives of this research are to confirm the possibility of direct joining of CFRP and metal, and to investigate the effects of the heat input during series-RSW, silane-coupling treatment and chemical structure of matrix plastics on the joint properties.

The direct joint formations of SUS304 to CFRP (PA6) and CFRP (PP) were accomplished, and CFRP (PPS) was not. The joining area, which corresponding to the melted area of CFRP, enlarged with increasing the welding current and welding time, therefore, the tensile shear fracture load also increased. The silane-coupling treatment for metal surface was highly effective to increase the joining strength. The maximum tensile shear strength of about 13 MPa was obtained for SUS304/CFRP (PA6) joint.     

Effects of high speed in the drilling of glass fibre reinforced plastic: Evaluation of the delamination factor

High speed machining (HSM) is an outstanding technology capable of improving productivity and lowering production costs in manufacturing companies. Drilling is probably the machining process most widely applied to composite materials; nevertheless, the damage induced by this operation may reduce drastically the component performance. This work employs HSM to realize high performance drilling of glass fibre reinforced plastics (GFRP) with reduced damage. In order to establish the damage level, digital analysis is used to assess delamination. A comparison between the conventional (F_d) and adjusted (F_da) delamination factor is presented. The experimental results indicate that the use of HSM is suitable for drilling GFRP ensuring low damage levels.     

Evaluation of drilling parameters on thrust force in drilling carbon fiber reinforced plastic (CFRP) composite laminates using compound core-special drills

Drilling is the mostly used secondary machining of the fiber reinforced composite laminates, while the delamination occurs frequently at the drill exit in the workpiece. In the industrial experiences, core drill shows better drilling quality than twist drill. However, chip removal is a troublesome problem when using the core drill. Conventional compound core-special drills (core-special drills and step-core-special drills) are designed to avoid the chip removal clog in drilling. But the cutting velocity ratio (relative motion) between outer drill and inner drill is null for conventional compound core-special drills. The current study develops a new device and to solve the problems of relative motion and chip removal between the outer and inner drills in drilling CFRP composite laminates. In addition, this study investigates the influence of drilling parameters (cutting velocity ratio, feed rate, stretch, inner drill type and inner drill diameter) on thrust force of compound core-special drills. An innovative device can be consulted in application of compound core-special drill in different industries in the future.     

钎焊金刚石磨粒钻钻削C/SiC陶瓷基复合材料孔时切屑对钻削过程的影响

钎焊金刚石磨粒钻适合钻削碳纤维增强碳化硅陶瓷基复合材料孔,但大量切屑会对孔的钻削过程产生不利影响。为此,针对切屑排出过程,分析切屑形貌,研究钻削时切屑对轴向钻削力、孔加工质量、钻头磨损的影响。结果表明：切屑对轴向钻削力有影响,尤其钻削深孔时影响显著。切屑对孔进口的加工质量几乎没有影响,只表现为孔进口处的轻微崩边;切屑对孔出口的加工质量影响显著,可引起严重的纤维断裂、撕裂缺陷以及基体的大区域脱落。同时,切屑加剧钻头磨损,使钻头不仅出现崩刃、微裂纹等轻微磨损,而且还产生基体剥落、金刚石剥落等严重磨损行为。     

Cu含量对Mullite／Al—Cu复合材料时效硬化行为的影响

用挤压铸造方法制备了Mullite/Al-Cu复合材料,用硬度测试仪、差示扫描量热仪（DSC）和透射电镜（TEM）等设备研究了铝基复合材料及其基体合金中Cu含量变化对时效硬化行为的影响,同时还研究了增强纤维对时效相的板出序列、析出相和位错结构的影响。结果表明,无论是在复合材料中还是在基体合金中,随着Al-Cui合金中Cu含量的增加,时效硬化过程均有不同程度的加速;Mullite纤维的引入提高了Al-Cu合金的时效硬度,明显加速了Al-Cu合金的时效硬化过程,对GP区的形成有抑制作用,但不影响基体沉淀相的析出顺序。     

Thermal conductivity and mechanical properties of pitch-based carbon fibre reinforced aluminium composites fabricated by squeeze casting

Pure aluminium and high-silicon aluminium alloy were reinforced with the discontinuous pitch-based carbon fibres by squeeze casting, then the thermal conductivity and the mechanical properties of the composites were investigated. Optical microscopy revealed that the fibres were in a random planar arrangement, and the transmission electron microscopy revealed that there is no interfacial reaction between the matrices and the fibres. The random planar arrangement of the fibres leads to the anisotropy of the composite. The fibre-reinforcement increased the thermal conductivity in the parallel direction for both pure aluminium and its alloy matrices, while the thermal conductivity decreased in the vertical direction. The increase in the elastic modulus by the reinforcement was not observed for both matrices. The proof stress of the pure aluminium increased by the reinforcement especially in the parallel direction, while that of the high-silicon alloy decreased by the reinforcement.     

Drill geometry and operating effects when cutting small diameter holes in CFRP

The paper details experimental results when drilling small holes (1.5 mm diameter cemented carbide drills with varying end point and helix geometry) in thin quasi-isotropic, unbacked carbon fibre reinforced plastic (CFRP) laminate (typical cutting time 0.4 s/hole). The study utilised an L12 Taguchi fractional factorial orthogonal array with analysis of variance (ANOVA) employed to evaluate the effect of drill geometry and drilling conditions on tool life and hole quality. Main effects plots and percentage contribution ratios (PCR) are detailed in respect of response variables and process control factors. More conventionally, tool wear and cutting force data are plotted/tabulated, together with micrographs of hole entry/exit condition and internal hole damage. Drill geometry and feed rate in general had the most effect on measured outputs. Thrust force was typically below 100 N at test cessation; however, drill wear progression effectively doubled the magnitude of force from test outset. Entry and exit delamination factors (F_d) of 1.3 were achieved while the maximum number of drilled holes for a tool life criterion VB_Bmax of ≤100 μm was 2900 holes using a stepped, uncoated drill with a feed rate of 0.2 mm/rev.     

Characterization and optimization of vibration-assisted drilling of fibre reinforced epoxy laminates

Vibration-assisted drilling (VAD) can reduce thermal and mechanical defects associated with drilling of composites. Machinability maps are presented to establish the effect of the process parameters (speed, feed, frequency, and amplitude) in the low frequency–high amplitude regime (<200 Hz, <0.6 mm) on the hole quality attributes. The optimized VAD conditions can reduce the cutting temperature by 50% and the axial force by 40% and produce delamination-free holes, without affecting productivity. It is demonstrated that the intermittent cutting in VAD redistributes the cutting energy over the engagement cycles. This enhances the tool cooling and substantially reduces the axial force component.     

石英纤维增强陶瓷基复合材料制孔工艺研究

本试验针对目前硬质合金刀具加工石英纤维增强陶瓷基复合材料时存在的刀具磨损严重、加工质量差、效率低下等问题,对比了硬质合金刀具钻孔、PCD刀具钻孔和电镀金刚石套料钻螺旋铣磨制孔的效果,分析了切削力对制孔质量的影响。研究结果表明:纬纱纤维对X向和Y向切削力的影响明显大于经纱纤维,垂直于纬纱纤维方向的切削力较小,平行于纬纱纤维方向的切削力较大;PCD刀具钻孔质量相对较好,刀具磨损不明显,适用于石英纤维增强陶瓷基复合材料的制孔加工。      

聚氯乙烯包覆处理竹纤维对其增强摩擦材料摩擦学性能的影响

采用聚氯乙烯(PVC)包覆法处理竹原纤维,并将其应用于增强树脂基摩擦材料。通过定速摩擦试验、表面形貌观察及能谱分析、热失重分析等方法探讨PVC包覆处理竹纤维对其增强摩擦材料摩擦学性能的影响。结果表明,竹纤维经过PVC包覆处理后,能显著提高摩擦材料的整体摩擦学性能,尤其是中高温的摩擦因数。PVC溶液质量浓度为20 g/L,处理时间为20 min,材料具有良好的综合摩擦磨损性能。PVC包覆处理后竹纤维表面可形成一层均匀的PVC复合界面膜,使复合材料中竹纤维和树脂基体的界面黏结性能得到改善,令竹纤维在较高温度下仍然能对基体起到增强作用,提高了材料的摩擦磨损性能。     

The dependency of material properties and process conditions on the cutting temperatures when drilling polymers

Construction parts consisting of modern polymer materials still need to be machined. Thereby special attention has to be paid to the machining quality. The machining quality implies dimensional accuracy as well as a defect-free peripheral zone. Machining defects often occur as a consequence of excessive mechanical loads, which are often caused by unfavorable process conditions. Besides mechanical loads, the thermal influence on the composite material, which is induced by the cutting process itself, has to be considered as crucial. According to the thermo physical material properties of polymer materials the boundary conditions differ from the machining of metals. Especially the drilling of polymer composites is introduced in this article and moreover the influences of the material properties and the process conditions on the process temperatures are presented. The investigations presented in this paper are funded by the “Deutsche Forschungsgemeinschaft (DFG)”