Investigation of UV exposure in adhesively bonded single lap joints

Abstract

BackgroundIn recent decades adhesively bonded joints gained attention in many industries such as automotive, aeronautics and offshore, increasing structural mechanical repair services and thus promoting technological advances. It is a trend to nowadays replace welded and bolted joint for adhesively bonded joint. Advantages over welded and bolted joints are don't need a fire exposure, fast manufacturing, fatigue and corrosion resistance. Although the geometry of bonded joint is complex considering particularities at the end of joint, adhesive joint promotes a decrease of stress concentration [1,2].A relation between adherend and adhesive material and consequently the load transfer of joint is intrinsically related to surface state. The correct preparation requires total removal of contaminants (remaining corrosion layers, dirt, lubricating and bio-organisms) is needed [3]. A strong adhesion depends on bonding surface treatment in order to improve a joint strength, although bond strength doesn't increase with increase of roughening [4]. The surface roughness modifications in the bonded area of the joint promote an expressive effect in the bonded structures [5,6].The main techniques for surface modification are sandblasting, grinding and chemical cleaning that makes a generation of specific surface topographies at bonding area. The advantages of bonding area preparation are a great mechanical coupling of the adhesive AbstractAdhesively bonded joints are being widely used in the fabrication process of aircraft and automobile structures. Surface roughness is an important parameter of product quality that strongly affects the performance of mechanical parts, as wel as production costs. This parameter highly influences the mechanical properties overall of such structures. The effects of UV radiation on the single lap joints manufactured with different types of surface preparation and temperature were examined before and after UV exposure. Sandblasting, sanding and chemical cleaning were used as surface preparation and two test temperatures were used for investigation, 25 and 115 °C. The results of those tests showed that surface preparation highly influences shear strength, but does not affect the stiffness of the tested joints. Temperature also influences the shear strength and stiffness. UV radiation contributes to increase shear strength and do not degrade the tested single lap joints.

Development and characterization of a polypropylene matrix composite and aluminum hybrid material

“…Eventually, the LFT and the TTRs separated completely and there was a sudden load drop finally to nearly 0 N. From the load–displacement curve, there was no sudden load drop at the peak load as is normally seen in adhesively bonded specimens. 2,34,35 The SEM micrographs in Figure 7 showed the inclined TTRs from original upward orientation due to the pullout. The angle was measured to be approximately 12°.…”

A review of the relationship between design factors and environmental agents regarding adhesive bonded joints

“…Since knowledge of Tg is very important to determine the operating temperature of the adhesive, Carbas et al [79], Carbas et al [102], Zhang, Adams and Da Silva [103], and Chandrathilaka and Fawzia Gamage [64] studied the effects of different curing and post-curing processes on the Tg. Environmental factors, such as operating temperature and UV radiation, can favor curing and improve mechanical properties or reduce performance of joints in service [49,101]. As reported by Viana et al [101], at the beginning of exposure to ultraviolet rays, there may be an improvement in the properties of the adhesive joint in relation to the postcuring effects.…”

“…The influence of the geometric configuration has been observed, such as the thickness of the adhesive layer and overlap length, along with processing factors on the behavior of joints, such as surface preparation and curing time and temperature. Furthermore, changes in the behavior of the adhesive bonded joints in harsh environments have also been identified in studies aimed at assessing the degradation of joints [47,[49][50][51][52]. Humidity, immersion in water, high or low temperature, UV radiation, sea water and corrosion are examples of environmental factors that can decrease the performance of joints in the field.…”

“…The environmental conditions to which joints will be subjected when in service can modify their mechanical properties. Therefore, many studies have analyzed the influence of environmental phenomena on adhesive bonded joints [21,22,38,49,98,100]. Among these factors are operating temperature, which can be high or low [52,65,107], humidity and immersion in water [19,47,80,107], saltwater mist or spray [50,108,109], corrosion [51] and UV exposure [20,49].…”

“…Therefore, many studies have analyzed the influence of environmental phenomena on adhesive bonded joints [21,22,38,49,98,100]. Among these factors are operating temperature, which can be high or low [52,65,107], humidity and immersion in water [19,47,80,107], saltwater mist or spray [50,108,109], corrosion [51] and UV exposure [20,49]. Moreover, the simultaneous or cyclic combination of these factors can intensify the changes caused in the joints.…”