In-service damage

Environmental factors such as severe hailstorms and human errors such as impact by aircraft service equipment also cause in-service damage to bonded assemblies. Bonded honeycomb sandwich assemblies are particularly prone to such damage because of their customary use as lightly loaded fairings and flight control surfaces and subsequent thin facesheets and relative fragility. 

Despite an increase in life cycle, strength, and stiffness, composite materials may be subject to manufacturing or in-service damage that may cause a reduction in static strength and weaken structural integrity. The more likely events of occurrence of some of the most widely spread flaws, and their effect on the structural integrity of composites, are described next. 

Such tests can identify incorrect component dimensions, lack of adhesive, lack of filleting, edge voids and porosity at the manufacturing level, throughout the cross section of a laminate after the part has been cured [29]. Other in-service damages detectable include paint failure, lighting strikes, and peeled surfaces. 

The main characteristic of in-service damage is that it occurs during service in a random manner. A list of sources of in-service damage threats is given below ... 

Liao M., B.Y. R.G. (2012). Probabilistic risk analysis for aircraft structures with limited in-service damages. 28TH International Congress of The Aeronautical Sciences. 

Cooling water pipes are essential for the operation of power stations and must not cease to function. Pipelines for fire fighting are also important for safety reasons. Such steel pipelines are usually well coated. At areas of unavoidable damage to the pipe coating, there is an increased danger due to cell formation between steel and concrete where local corrosion rates of >1 mm a are to be expected [4], Damage to pipelines for fire fighting has frequently been observed after only a few years in service. 

Rejuvenation of Used Turbine Biades Nature of Service Damage in Turbine Biades... 

It would appear obvious for startup, and in some cases full-time operation. that a suction strainer or filter is mandatory. The reason for ilic strainer is to keep Junk and pipe scale out of the compressor. Fines from pipe scale and rust will make short work of the internal bore of a cylinder and are not all that good for the balance of the components. In some severe ca.ses, cylinders have been badly damaged in a matter of a few weeks. The strainer should be removable in service for cleaning, particularly when it is intended for permanent installation. Under all circumstances, provision must be made to monitor the condition of the strainer. Much frustration has been expended because a compressor overheated or lost capacity and no one knew if the strainer had fouled or blinded. 

Occasional in-service delaminations occurred at the aft tip of the wedge. Because there was no metal-to-metal closeout bond at the aft tip, any slight incidental damage could easily crack the bond slightly and allow moisture to enter the core. Eventually, freeze-thaw damage and delamination would occur. 

It is also important to assure that corrosion, erosion, or other damage has not affected the system to the point that it can no longer safely contain the design pressure. Maintaining mechanical integrity once the system has been placed in service is discussed later in this chapter. 

Continuous plating of wire and strip is, unlike the preceding techniques, a prefabrication process. The production of tinplate is the largest scale continuous operation, but any electrodeposit may be applied this way. Subsequent fabrication processes arc likely to damage the coating, so that pre-coating is best reserved for ductile coatings which are anodic to the substrate in service, as is the case for tin. 

The coating is applied to protect the steel from corrosion due to the acid or alkaline condition of the soil surrounding the pipe in service. Usually, the process requires three layers. First, an epoxy powder is applied to achieve adhesion to the pretreated metal and therefore resistance to cathodic disbondment. Second, a tie layer of polyolefin copolymer is applied and third a thick layer of polyethylene is cascaded, which in effect protects the epoxy from physical damage. 

Ways to Lessen Risk of Explosive Decompression (ED) Damage for Sealing Elastomers in Service... 

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