Лако-красочные материалы — производство

Composite materials as well as adhesively bonded joints are not exempt from some problems even though they have great advantages and applicability. Defects related to composite bonded joints can be classified into two main streams — manufacturing defects and in service defects.

The source of manufacturing defects in a bonded composite joint can be due to defects during manufacturing the composites and during manufacturing the joint while bonding. The main composite manufacturing defects are delamination, resin starved areas, resin rich areas, blisters, air bubbles, voids, wrinkles, thermal decomposition [8]. On the other hand, while manufacturing adhesively bonded joints, most defects are to be found either at the interface between the adhesive and the adherent or within the adhesive (Figure 2) which can lead to poor durability of the joint.

Surface preparation is also very important for long term durability of bonded joints. Lack of proper surface preparation of substrates prior to adhesive bonding can attribute to surface contamination which leads to adhesive failure.

Apart from the manufacturing flaws, there are a number of in-service causes that can cause failure to bonded composite structures, such as environmental degradation, impact damage, fatigue, and cracks from local overloading from high static loads. Moreover, improper joint selection and design in bonded joints can result in a number of failure modes, including shear or peel failure in the adhesive; shear or peel in composite surface plies. The failure also depends on the joint configuration [9].

Furthermore, the mechanisms of load transfer from one adherend to another through adhesive layer, flaw initiating, spreading over the composite volume and leading to the ultimate failure can be very complicated, as shown in Figure 2, where a typical crack propagation in a composite bonded joint is shown, ultimately ending into delamination of the composite substrates. Therefore, clear description for the damage evolution and fracture behavior in composites remains a challenge work at present days. Hence, the structural health monitoring of adhesively bonded composite joints remains critically important for maintaining safe, damage tolerant design philosophy.