Hart-Smith

John Hart-Smith, Douglas Aircraft Company, Long Beach, Caiifomia, personal communication. 

Types of Bonded Joints and Their Failures (After Hart-Smith [7-9])... 

Bolted, bon and bonded-bolted joints have barely been introduced. Further befTavioral and design information is available in the book Joining Fibre-Reinforced Plastics edited by F. L. Mathews [7-11], which has chapters written by various authors including two chapters on design by L. J. Hart-Smith. 

L. J. Hart-Smith, Design of Adhesively Bonded Joints, in Joining Fibre-Reinforced Plastics, F. L. Mathews (Editor), Elsevier Applied Science, London and New York, 1987, pp. 271-311. 

Hart-Smith LJ. A re-examination of the analysis of in-plane matrix failures in fibrous composite laminates. Compos Sci Technol 1996 56 107-21. 

Hart-Smith LJ. The role of biaxial stresses in discriminating between meaningful and iUusaty composite failure theories. Compos Stmct 1993 25 3-20. 

Hart-Smith LJ. An inherent fallacy in composite interaction failure criteria. Composites 1993 24 523-4. 

Hart-Smith LJ. Mechanical-fastened joints for advanced composites — Phenomenological considerations and simple analysis. New York Plenum Press 1978. pp. 543—574. 

Hart-Smith LJ. Bolted joints in graphite-epoxy composites 1976. NASA Contractor Report, NASA CR-1444899. 

Nelson WD, Bunin BL, Hart-Smith LJ. Critical joints in large composite aircraft structure. NASA CR-3710 1983. 

McCarthy MA, Lawlor VP, Stanley WF. An experimental study of bolt-hole clearance effects in single-lap, multi-bolt composite joints. J Compos Mater 2005 39(9) 799—825. Hart-Smith LJ. Design and empirical analysis of bolted or riveted joints. In Joining fibre reinforced plastics. Elsevier Science 1987. pp. 227—69. 

Hart-Smith LJ. Design methodology for bonded-bolted composite ioints 1982. AFWAL-TR-81-3154. 

Hart-Smith U. Effects of flaws and porosity on strength of adhesive-bonded joints. Douglas Aircraft Co 1981. report DP 7388. 

According to Hart-Smith, a multihole joint is not necessarily much better than a single hole joint and several bolts would be needed to get a 25% improvement in strength [46]. 

L J Hart-Smith, Mechanically fastened joints for advanced composites -phenomenological considerations and simple analysis , Douglas Paper 1978 6748 1-32. 

The methods developed over the last decade or so to predict failure employ in-bondline non-linear adhesive characterisation. This in turn requires some fairly sophisticated experimental techniques, carefully conducted for a range of test conditions and environments. Hart-Smith concluded that a precise representation of the adhesive stress-strain characteristic is not important. He maintains that the... 

Hart-Smith, L.J. Developments in Adhesives - 2 (Ed. Kinloch, A.J.), Applied Science Publishers, London, 1981, Chapter 1. 

B. Bingol, G. Hart-Smith, C. Barner-Kowollik and G. Wegner, Macromolecules, 2008, 41, 1634-1639. 

P(l) The Hart-Smith failure criterion should be used for design. Design strengths shall be determined by experimental testing or taken from manufacturers data, and divided by the appropriate partial safety factor. 

P(l) The Hart-Smith failure envelope for a single ply shall be constructed as shown in Figures 4.13 (a)-(d) in the EUROCOMP Handbook. 

If the Hart-Smith failure envelope is being used, the failure criterion can be evaluated... 

Whenever possible it is recommended that the Hart-Smith method be employed. It is, however, recognised that in certain instances there may be no experimental strength data available and hence conservative methods for calculating strengths of materials, for use with the Tsai Wu technique, are included. 

When using the Hart-Smith approach, the laminate failure envelope is constructed by superimposing the failure envelopes of its constitutive laminae or alternatively by using failure data measured at the laminate level to construct a failure envelope in the same manner as for a single ply. 

The Hart Smith criterion proposes that the strength of laminates be characterised by generalizing the maximum-shear-stress criterion for ductile isotropic metals. 

Figure 4.13 Construction of Hart-Smith failure envelope.

Figure 4.14 Construction of the Hart-Smith failure envelope for a 07907-457+45° Laminate.

The choice of failure criterion for design will be governed by the amount of measured data available to the designer. If measured data are available, the designer should use the Hart Smith failure criterion. 

Edge distance A minimum value of the e/w ratio is required to develop full net-section strength of the joint. Hart-Smith (reference 5.9) presents results showing that the... 

Figure 5.33 Design of a double-lap joint according to Hart-Smith (reference 5.26).

Hart-Smith (references 5.25, 5.26, 5.30 and 5.31) has conducted extensive studies of bonded joints using the elastic—plastic model for the adhesive. He has covered the analysis of lap, strap, scarf and step-lap joints. He has modified the load eccentricity induced peel stress approach by using a modified bending stiffness. He has studied the effects of non-uniform adhesive thickness, adhesive non-uniform moisture absorbtion and defects in the bondline. He has also included thermal stresses in his models. 

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