Composite bolted joints

Design and failure analysis of composite bolted joints for aerospace composites... 

This chapter presents both experimaital and finite element approaches that are commonly used to assist in the design and failure analysis of composite bolted joints. The work presented mostly stems from the authors work in the field over the past decade. Results from both local (i.e. detailed) finite element and global (Le. efficient) closed form and finite element approaches are presented, and expmmental results from the open literature are used to both calibrate and validate the modelling procedures. The primary variable under consideration is bolt-hole clearance, which is chosen as it induces significant three-dimensional stresses into the joint, and significandy alters the bolt-load distribution in multi-bolt joints, and so provides a rigorous test case for analysis. 

Figure 113 Failure modes in composite bolted joints (a) bearing failure, (b) net-tension failure, (c) shear-out failure, (d) cleavage failure, (e) fastener puU-through, (f) bolt failure.

A future trend in composite bolted joint design is the use of more advanced continuum damage mechanics approaches to model joint failure, so that non-linear shear behaviour and gradual stiffness degradation can be implemented. An important element of joint failure is delamination, and many efforts are being undertaken to implement delamination in finite element models. However, for bolted joints analysis this poses many problems due to the large number of delamination interfaces in thick laminates. 

Excellent websites for composites in general are the JEC website (www. jeccomposites.com) and the Net-Composites website (www.netcomposites.com). Two good bolting websites are due to Bolt Science (www.boltscience.com) and Nord-lock (www.nord-lock.com). Dedicated composite bolted joints websites are less common, but the EU Framework five Project BOJCAS (Bolted Joint in Composite Aircraft Structures) [19] produced a website which can be found at the following URL (http //www.smr.ch/bojcas/). The author s personal website (www.fem-ireland.ie) provides a list of many journal papers on the subject. 

Many industries, including automotive, aerospace, civil, raU, marine, high-speed machinery, process plant industries and high-end sports equipment, are currently concerned with composite bolted joints. The aerospace sector is now heavily implementing carbon fibre into wing and fuselage structures and companies such as Airbus and... 

The international journal Composite Structures provides a wealth on papers on composite bolted joints. Other journals such as Composites Science and Technology, Composites, Part A B and the Journal of Composite Materials all have excellent papers on composite bolted joints in their archives. The recently published book Composite Joints and Connections Principles, Modelling and Testing [59] is a dedicated text on composite joints and connections and is highly recommended as an introduction to the subject. 

Smith PA, Ashby MF, Pascoe KJ. Modehng clamp-up effects in composite bolted joints. J Compos Mater 1987 21 878-97. 

McCarthy MA, Lawlor VP, Stanley WF, McCarthy CT. Bolt-hole clearance effects and strength criteria in single-bolt, single-lap, composite bolted joints. Compos Sci Technol 2002 62(10-11) 1415-31. 

McCarthy MA, McCarthy CT, Lawlor VP, Stanley WF. Three-dimensional finite element analysis of single-bolt, single-lap composite bolted joints part I — model development and vahdation. Compos Struct 2005 71(2) 140—58. 

Tong L. Bearing failure of composite bolted joints with non-uniform bolt to washer clearance. Compos Part A 2000 31 609-15. 

Herringtion PD, Sabbaghian M. Effect of radial clearance between bolt and washer on the bearing strength of composite bolted joints. J ComposMater 1992 26(12) 1826—43. 

Lawlor VP. An experimental study of the effects of variable bolt-hole clearance on the mechanical behaviour of composite bolted joints, Ph.D. thesis. Ireland University of Limerick 2004. 

Gray PJ, McCarthy CT. An analytical model for the prediction of through-thickness stiffness in tension-loaded composite bolted joints. Compos Struct 2012 94(8) 2450—9. Lapczyk I, Hurtado JA. Progressive damage modeUing in fibre-reinforced materials. Compos Part A-Applied Sci Manuf 2007 28 2333-41. 

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