Composite repair

Baker, A.A., Bonded Composite Repair of Metallic Aircraft Components — Overview of Australian Activities, AGARD (Advisory Group for Aerospace Research and Development) Conference of Composite Repair of Military Aircraft Structures, 3-5 October 1994, Seville. 

Electron beam processed adhesives and their use in composite repair... 

Although the acrylate adhesives are readily available and studies have shown that they can produce reasonable bonding properties, they have the disadvantages of having high shrinkage, high fluid absorption, and low service temperatures. Acrylate adhesive applications would be limited. The development of EB-curable epoxy adhesives would have applications in the aerospace and automotive industry and potential wider uses. The most immediate application for these resin systems is composite repair of commercial and military aircraft. 

Table 3 lists the selected properties [16] that we have measured for several commercially available acrylate resins manufactured by the Sartomer Company and the Rohm and Haas Company. The resins were cured in an AECL Gammacell Model 240. The temperature rise was measured for an 8-g sample using Acsion s (formerly AECL Radiation Applications Branch) Gamma Calorimetry method [17]. All of this information is being used to evaluate the applicability of EB-cured acrylate adhesives for repairing composite structures. Combinations of these adhesives can be used to create electron-curable adhesives suitable for composite repair. 

The final section in this volume deals with applications of adhesion science. The applications described include methods by which durable adhesive bonds can be manufactured by the use of appropriate surface preparation (Davis and Venables) to unique methods for composite repair (Lopata et al.) Adhesive applications find their way into the generation of wood products (Dunky and Pizzi) and also find their way into the construction of commercial and military aircraft (Pate). The chapter by Spotnitz et al. shows that adhesion science finds its way into the life sciences in their discussion of tissue adhesives. 

For the high-performance or sandwich composites, repairs, when they are possible, are always much more delicate. However, race boats are currently repaired after damage. 

Table 11.1 Example of a UV Curable Formulation for Composite Repair. ..242...

Soutis C, Dm J-B. Design, analysis and structural health monitoring of bonded composite repair and substructure. In Boiler C, Chang F-K, Fujino Y, editors. Encyclopaedia of structural health monitoring. J. Wiley Sons Ltd. 2009, ISBN 978-0-470-05822-0. pp. 1923-40. 

Mansberger LL. General aviation composite repair. Arlington The University of Texas 2009. mansbergeraircraft.com. 

Baker A. Bonded composite repair of fatigue-cracked primary aircraft structure. Tenth Int Conf Compos Struct 1999 47(1—4) 431—43. 

Wood K. In-situ composite repair builds on basics. Higb-Performance Composites 10/20/ 2008. 

The assembly of composite structural elements into a complete integrated structure will often involve bonding processes. These may be co-bonds or secondary bonds. In co-bonds, a cured composite is assembled with a film adhesive to an uncured laminate layup. The assembly is cured in an oven or autoclave. Secondary bonds are bonds between two cured laminates. The adhesive may be film or paste, and the cure may be in an oven or at room temperature. Composite repair following a damage event usually involves a co-bond by scarfing out the damage area, laying... 

Takeda S, Yamamoto T, Okabe Y, Takeda N. Debonding monitoring of composite repair patches using embedded smaU-diameter FBG sensors. Smart Mater Struct 2007 16(3) 763-70. http //dx.doi.Org/10.1088/0964-1726/16/3/025. 

Koh YL, Chiu WK, Rajic N, Galea SC. Detection of disbond growth in a cyclically loaded bonded composite repair patch using surface-mounted piezoceramic elements. Struct Healih Monit Int J 2003 2(4) 327-39. 

The problem with scarf repairs is that they need extensive facilities and often require the structure to be sent to a major repair depot. To overcome this requirement, a new simplified repair methodology is currently under development. This methodology mimics that used in the composite repair of cracked metallic structures in that it only uses an external patch, or doubler, and is aptly illustrated in the work of Paul and Jones [1], Jones et al. [2] and Chalkley and Chester [5]. 

This repair technique was further illustrated using a damaged F/A-18 horizontal stabilator (Jones et al. [2]). The work was performed as part of the Composite Repair Engineering Development Program (CREDP) which is a joint program between the Canadian Forces, the Royal Australian Air Force and the United States Navy. The stabilator described in the report was initially classed as unserviceable and irreparable due to two fragment strikes from a tracer rocket. 

R Jones, L Molent, J Paul, T Saunders and W K Chiu, Development of a composite repair and the associated inspection intervals for the FlllC stiffener runout region , FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframes Durability and Damage Tolerance, May 1994, pp 339-350. 

Backman BE (2005) Composite stmctures, design, safety and innovation. Elsevier, Amsterdam Baker A et al (eds) (2002) Advances in the bonded composite repair of metallic aircraft structure. Elsevier, Amsterdam... 

J. Custddio, Performance and durability of composite repair and reinforcement systems for timber structures, PhD Thesis, Department of Mechanical Engineering, School of Technology, Oxford Brookes University, Oxford (2009). 

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