Sequential Laser–Mechanical Drilling of Thick Carbon Fibre Reinforced Polymer Composites (CFRP) for Industrial Applications

From MDPI via Jisc Publications RouterHistory: accepted 2021-03-31, pub-electronic 2021-06-29Publication status: PublishedCarbon fibre reinforced polymer composites (CFRPs) can be costly to manufacture, but they are typically used anywhere a high strength-to-weight ratio and a high steadiness (rigidity) are needed in many industrial applications, particularly in aerospace. Drilling composites with a laser tends to be a feasible method since one of the composite phases is often in the form of a polymer, and polymers in general have a very high absorption coefficient for infrared radiation. The feasibility of sequential laser–mechanical drilling for a thick CFRP is discussed in this article. A 1 kW fibre laser was chosen as a pre-drilling instrument (or initial stage), and mechanical drilling was the final step. The sequential drilling method dropped the overall thrust and torque by an average of 61%, which greatly increased the productivity and reduced the mechanical stress on the cutting tool while also increasing the lifespan of the bit. The sequential drilling (i.e., laser 8 mm and mechanical 8 mm) for both drill bits (i.e., 2- and 3-flute uncoated tungsten carbide) and the laser pre-drilling techniques has demonstrated the highest delamination factor (SFDSR) ratios. A new laser–mechanical sequence drilling technique is thus established, assessed, and tested when thick CFRP composites are drilled

Drilling strategy for thick carbon fiber reinforced polymer composites (CFRP): a preliminary assessment

Carbon fiber reinforced polymer or CFRP composites are the epitome of high-performance materials in lightweight design. However, their machinability can be problematic due to non-homogenous and anisotropic material properties. This preliminary assessment emphasizes drilling strategy by using mechanical drilling and laser machining on 25.4 mm thick CFRP, which has not been investigated so far. In mechanical drilling, three drilling strategies were applied with the same parameters in order to assess the feasibility of drilling thick CFRP. The laser machining experiments were conducted to identify the potential of fiber laser machines to cut thick CFRP due to their superior laser beam quality. The results showed that choosing the appropriate drilling strategy in mechanical drilling is essential for reducing damage when drilling thick CFRP. Significant damage occurred in all experiments. The results are useful to define the relationships between machining parameters related to mechanical/laser drilling and hole/cut quality

Study on dimensional stability of particleboard made using glutardialdehyde modified corn starch as the binder at various relative humidity

The objective of the study was to evaluate the dimensional stability of experimental particleboard panels made from rubberwood (Hevea brasiliensis) using modified starch as binder. Panels were manufactured using 15% corn starch modified with glutardialdehyde and 13% modified starch with 2% Urea Formaldehyde resin as improvement. The particleboards were tested for their dimensional stability towards moisture. Results found that the 2% replacement of modified starch with urea formaldehyde resin showed a little increased in dimensional stability compared to using glutardialdehyde modified corn starch only as the binder. Therefore, this study indicated that combination of modified corn starch and urea formaldehyde resin can have a potential to be used as an improved binder to produce particleboard panels with accepted properties

Modeling physical interaction and understanding peer group learning dynamics: Graph analytics approach perspective

Physical interaction in peer learning has been proven to improve students’ learning processes, which is pertinent in facilitating a fulfilling learning experience in learning theory. However,observation and interviews are often used to investigate peer group learning dynamics from a qualitative perspective. Hence, more data-driven analysis needs to be performed to investigate the physicalinteraction in peer learning. This paper complements existing works by proposing a frameworkfor exploring students’ physical interaction in peer learning based on the graph analytics modeling approach focusing on both centrality and community detection, as well as visualization of the grap model for more than 50 students taking part in group discussions. The experiment was conducted during a mathematics tutorial class. The physical interactions among students were captured through an online Google form and represented in a graph model. Once the model and graph visualization were developed, findings from centrality analysis and community detection were conducted to identify peer leaders who can facilitate and teach their peers. Based on the results, it was found that five groups were formed during the physical interaction throughout the peer learning process, with at least one student showing the potential to become a peer leader in each group. This paper also highlights the potential of the graph analytics approach to explore peer learning group dynamics and interaction patterns among students to maximize their teaching and learning experience

Mechanical and laser drilling of thick carbon fibre reinforced polymer composites (CFRP)

Carbon fibre reinforced polymer, or CFRP composite materials, play an increasingly important role in modern manufacturing. They are widely used in aerospace, and their use is currently Spreading to other industries where high strength-to-weight ratios are required. However, machining of composites is still a challenging task and often hampered by poor quality. Despite the extensive research that was conducted on the machining of composite materials over the last few years, mechanical drilling still suffers from delamination, fibre pull-out and poor surtace finish, whereas laser cutting produces microstructured defects and a taper problem. This thesis reports on the drilling of CFRP composites by demonstrating the possibility of drilling small diameter holes (i.e. 8mm) into 25.4mm thick carbon fibre reinforced polymer composites (CFRPs) using mechanical drilling and laser drilling as stand-alone processes and as a sequential combination. The research involved four main phases of experimental testing. The first part of Phase 1 involved preliminary experiments of drilling thick CFRP to identify the most suitable drilling strategy. Three mechanical drilling strategies conducted in the same parameter by using a 2-flute uncoated WC twist drill that was assessed with respect to feasibility of drilling thick CFRP. The results showed that the single-step strategy was the most feasible strategy to drill thick CFRP compared to 2- and 4-peck drilling strategies. The second part of Phase I concerned the influence of speed-feed co nations on hole quality by utilising three twist drills with different materials and geometries in both an uncoated and coated condition. The results indicated that a significant increase in peel-up delamination was found with increasing feed rate. In contrast, using a constant feed rate but increasing the spindle speed seemed to reduce peel-up delamination. Furthermore, the hole entry for 2-flute uncoated WC drill bits was an uncommon study finding because most of the previous researchers experienced more damages at the hole exit and their investigation focused on the hole exit only. Currently, implementation of laser technology in cutting and drilling composites is becoming popular as an altenative solution. Various experiments were conducted with the goal of identifying the effects of machining parameters on key output measures (i.e. heat affected zone(HAZ), hole depth and other damages) in drilling of 25.4 mm thick CFRP by using a fibre laser. Phase 2 involved a number of machining parameters selected to identify the potential of a fibre laser in drilling thick CFRP composites (i.e. laser power, scanning speed, focal point plane position (FPP), assisted-gas type and gas pressure). The results proved that a fibre laser could penetrate thick CFRP to a 22mm depth only. Moreover, the spiral trepanning strategy was able to penetrate 80% out of the total thickness of the CFRP in continuous wave (CW) mode, whereas the modulated laser beam (i.e. laser pulse mode) can penetrate 67% only. This result was a major recorded breakthrough because previous research attempts cut up to Smm only. Laser power proved to be the most influential factor for hole depth in laser drilling of thick CFRP when the spiral trepanning strategy was applied. Machining rials were conducted in Phase 3 by using a 16kW fibre laser in modulated pulsed laser mode. In this phase, laser power of more than 1kW was attempted to cut the whole thickness of CFRP composites in CW mode, but it was unsuccessful. However, a new parameter was discovered (i.e. the cooling time between passes in modulated pulsed mode), which proved a considerable reduction of HAZ when the higher cooling time was imposed. Finally, phase 4 involved the experiments of sequential laser-mechanical drilling. A 1kW fibre laser was selected as a pre-drilling or initial step and followed by mechanical drilling as the final step. The sequential drilling method successfully reduced thrust force and torque for mechanical drilling by an overall average of 61%, resulting in high productivity and decreasing the thermal and mechanical stresses in the cutting tool and, in turn, promoting higher tool life. The highest delamination factor (Fa) ratio was experienced by the sequential laser 8mm - mechanical 8mm for both tools (i.e. 2- and 3-flute uncoated tungsten carbide) and laser pre-drilling strategies (i.e. single- and double-side). Thus, a novel laser-mechanical sequential drilling technique was developed, evaluated and tested in the drilling of thick CFRP composites; this is the first time ever in drilling thick CFRP (i.e. 25.4mm)

Sequential Laser–Mechanical Drilling of Thick Carbon Fibre Reinforced Polymer Composites (CFRP) for Industrial Applications

Carbon fibre reinforced polymer composites (CFRPs) can be costly to manufacture, but they are typically used anywhere a high strength-to-weight ratio and a high steadiness (rigidity) are needed in many industrial applications, particularly in aerospace. Drilling composites with a laser tends to be a feasible method since one of the composite phases is often in the form of a polymer, and polymers in general have a very high absorption coefficient for infrared radiation. The feasibility of sequential laser–mechanical drilling for a thick CFRP is discussed in this article. A 1 kW fibre laser was chosen as a pre-drilling instrument (or initial stage), and mechanical drilling was the final step. The sequential drilling method dropped the overall thrust and torque by an average of 61%, which greatly increased the productivity and reduced the mechanical stress on the cutting tool while also increasing the lifespan of the bit. The sequential drilling (i.e., laser 8 mm and mechanical 8 mm) for both drill bits (i.e., 2- and 3-flute uncoated tungsten carbide) and the laser pre-drilling techniques has demonstrated the highest delamination factor (SFDSR) ratios. A new laser–mechanical sequence drilling technique is thus established, assessed, and tested when thick CFRP composites are drilled

Development of Laser Drilling Strategy for Thick Carbon Fibre Reinforced Polymer Composites (CFRP)

Composites from carbon fibre reinforced polymers (CFRPs) play a significant role in modern manufacturing. They are typically used in aerospace and other industries that require high strength-to-weight ratios. Composite machining, however, remains a challenging job and sometimes is hampered by poor efficiency. Despite considerable research being conducted over the past few years on the machining of composite materials, the material nevertheless suffers from delamination, fibre loss, and imperfect finishing of the fuselage. Laser technology is becoming increasingly popular as an alternative approach to cutting and drilling composites. Experiments have been conducted with a CFRP thickness of 25.4 mm using fibre laser to test the effect of the machining parameters on the primary performance measurements. In this study, different machining criteria are used to assess the fibre laser ability of thick CFRP composites for drilling operation. The experimental findings revealed that a fibre laser is capable of penetrating a thick CFRP to a depth of 22 mm by using a novel drilling procedure

Sequential Laser - Mechanical Drilling of Thick Carbon Fibre Reinforced Polymer Composites (CFRP) for Industrial Applications

Carbon fibre reinforced polymer composites (CFRPs) can be costly to manufacture, but they are typically used anywhere a high strength-to-weight ratio and a high steadiness (rigidity) are needed in many industrial applications, particularly in aerospace. Drilling composites with a laser tends to be a feasible method since one of the composite phases is often in the form of a polymer, and polymers in general have a very high absorption coefficient for infrared radiation. The feasibility of sequential laser–mechanical drilling for a thick CFRP is discussed in this article. A 1 kW fibre laser was chosen as a pre-drilling instrument (or initial stage), and mechanical drilling was the final step. The sequential drilling method dropped the overall thrust and torque by an average of 61%, which greatly increased the productivity and reduced the mechanical stress on the cutting tool while also increasing the lifespan of the bit. The sequential drilling (i.e., laser 8 mm and mechanical 8 mm) for both drill bits (i.e., 2- and 3-flute uncoated tungsten carbide) and the laser pre-drilling techniques has demonstrated the highest delamination factor (S(FDSR)) ratios. A new laser–mechanical sequence drilling technique is thus established, assessed, and tested when thick CFRP composites are drilled