A study of laser surface treatment in bonded repair of composite aircraft structures

Developments in Laminate Modification of Adhesively Bonded Composite Joints

The use of carbon fibre reinforced polymer (CFRP) materials is increasing in many different industries, such as those operating in the aviation, marine, and automotive sectors. In these applications, composite parts are often joined with other composite or metallic parts, where adhesive bonding plays a key role. Unlike conventional joining methods, adhesive bonding does not add weight or require the drilling of holes, both of which are major sources of stress concentration. The performance of a composite joint is dependent on multiple factors and can be improved by modifying the adhesive layer or the composite layup of the adherend. Moreover, joint geometry, surface preparation, and the manufacturing methods used for production are also important factors. The present work reviews recent developments on the design and manufacture of adhesively bonded joints with composite substrates, with particular interest in adherend modification techniques. The effects of stacking sequence, use of thin-plies, composite metal laminates and its specific surface preparations, and the use of toughened surface layers in the composite adherends are described for adhesively bonded CFRP structures.

Enhanced Surface Properties of Carbon Fiber Reinforced Plastic by Epoxy Modified Primer with Plasma for Automotive Applications

Carbon fiber reinforced plastic (CFRP) is currently used as a lightweight material in various parts of automobiles. However, fiber reinforced plastic (FRP) material may be damaged at the time of joining via mechanical bonding; therefore, adhesion is important. When bonding is conducted without surface CFRP treatment, interfacial destruction occurs during which the adhesive falls off along with the CFRP. Mechanical strength and fracture shape were investigated depending on the surface treatment (pristine, plasma treatment times, and plasma treatment times plus epoxy modified primer coating). The plasma treatment effect was verified using the contact angle and X-ray photoelectron spectroscopy. The wettability of the epoxy modified primer (EMP) coating was confirmed through surface morphology analysis, followed by observation of mechanical properties and fracture shape. Based on test data collected from 10 instances of plasma treatment, the EMP coating showed 115% higher strength than that of pristine CFRP. The adhesive failure shape also changed from interfacial failure to mixed-mode failure. Thus, applying an EMP coating during the automotive parts stage enhances the effect of CFRP surface treatment.