Kwang-Woon Jung

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.

Laser direct joining of carbon fiber reinforced plastic to aluminum alloy

Laser direct joining of carbon fiber reinforced plastic (CFRP) to aluminum alloy was performed using a high quality continuous wave diode laser with a line-shaped beam. The tensile shear test results demonstrated that a strong lap joint with about 3000 N could be produced between CFRP (of 3 mm thickness and 20 mm width) and aluminum alloy (of 2 mm thickness and 30 mm width). The joints fractured along the joint interface or in the melted zone of CFRP. It was observed from the cross sections of the joints that many bubbles of submillimeter size were irregularly formed in the wide and shallow melted zone of the CFRP. Moreover, melted polyamide plastic was tightly bonded on atomic or molecular sized level through nanometer thick aluminum oxide film (κ-Al2O3) existing on aluminum alloy surface, suggesting high possibility of chemical or physical bonding between CFRP and metal. Consequently, it was confirmed that a strong lap joint of CFRP to aluminum alloy could be produced by direct irradiation of a laser beam.

Ultra-high speed disk laser cutting of carbon fiber reinforced plastics

Laser cutting of carbon fiber reinforced plastics (CFRPs) has been known to be difficult due to the thermal damage to CFRP material. Therefore, with the objectives of evaluating the cutting possibility for long- or short-fiber pellet CFRP sheets of 3 mm in thickness and obtaining narrower heat affected zone (HAZ) for better cut quality, ultra-high speed cutting was conducted by using a continuous-wave high brightness disk laser. The increase in the laser power rendered the cutting time shorter and the kerf depth deeper for CFRP full cut. It was revealed that CFRP cut with narrow HAZ of less than 50 μm could be produced under the conditions of the laser powers of 2–5 kW, the cutting speed of 5 m/s, the time interval between repeated runs of 1 s, and the defocused distance of 0 mm. It was also confirmed that short fiber pellet CFRP was more easily cut and suffered less thermal damage in comparison with long fiber one. Furthermore, it was demonstrated that the tensile strength of fully laser-cut CFRP was alm...

High power laser cutting of CFRP, and laser direct joining of CFRP to metal

CFRP possesses an extremely high specific strength, and thus the development of cutting and joining technology of CFRP is expected for the increase in applications in various industrial fields. To obtain fine cut quality in CFRP, high-quality disk lasers are applied to various types and kinds of CFRP. It was understood that fine cut quality could be produced in some CFRP with a small focused laser beam at an extremely fast speed. Joints between Type 304 plate (of 3 mm thickness and 30 mm width) and CFRP sheet (of 2 mm thickness and 20 mm width) were produced with a disc laser. The joint possessed a high shear tensile load of about 4800 N, and the fracture occurred in the CFRP near the lap joint.CFRP possesses an extremely high specific strength, and thus the development of cutting and joining technology of CFRP is expected for the increase in applications in various industrial fields. To obtain fine cut quality in CFRP, high-quality disk lasers are applied to various types and kinds of CFRP. It was understood that fine cut quality could be produced in some CFRP with a small focused laser beam at an extremely fast speed. Joints between Type 304 plate (of 3 mm thickness and 30 mm width) and CFRP sheet (of 2 mm thickness and 20 mm width) were produced with a disc laser. The joint possessed a high shear tensile load of about 4800 N, and the fracture occurred in the CFRP near the lap joint.

Ultra-high speed disk laser cutting of CFRP and laser direct joining of pitch type CFRP to stainless steel

Recently, CFRP with high strength-to-weight ratio has been attractively noted, and simultaneously the technology development of cutting and dissimilar materials joining for CFRP is required for the applications as one of light-weight structural materials in various industrial fields such as automotives and aircrafts. In order to accomplish CFRP cutting with narrow HAZ, ultra-high speed disk laser cutting using laser scanner head was conducted for two kinds of PITCH type CFRP sheets (including 15% or 30 % carbon fiber). It was confirmed that CFRP with 15% carbon fiber was difficult to cut and had the wide HAZ, but CFRP with 30% carbon fiber was fully cut and had narrow HAZ. Through laser cutting experiments for only CFRP with 30% carbon fiber, it was demonstrated that CFRP full cut without strength reduction could be produced by ultra-high speed laser cutting. On the other hand, in the case of laser direct joining of CFRP to metal, it was revealed that the high strength joints between CFRP sheet (PC matrix with 30% carbon fiber) and SUS304 stainless steel plate could be rapidly produced by a laser, and main fracture occurred in the CFRP near the joint interface.Recently, CFRP with high strength-to-weight ratio has been attractively noted, and simultaneously the technology development of cutting and dissimilar materials joining for CFRP is required for the applications as one of light-weight structural materials in various industrial fields such as automotives and aircrafts. In order to accomplish CFRP cutting with narrow HAZ, ultra-high speed disk laser cutting using laser scanner head was conducted for two kinds of PITCH type CFRP sheets (including 15% or 30 % carbon fiber). It was confirmed that CFRP with 15% carbon fiber was difficult to cut and had the wide HAZ, but CFRP with 30% carbon fiber was fully cut and had narrow HAZ. Through laser cutting experiments for only CFRP with 30% carbon fiber, it was demonstrated that CFRP full cut without strength reduction could be produced by ultra-high speed laser cutting. On the other hand, in the case of laser direct joining of CFRP to metal, it was revealed that the high strength joints between CFRP sheet (PC matrix...