JOINING OF COMPOSITE STRUCTURES 297 Table 9.2 Computer Programs Developed by Dr John Hart-Smith for Stress Analysis of Bonded Joints Joint to be analyzed Program Joint to be analyzed Program Single-lap joint: A4EA Double-lap joint:Elastic A4EB Joint strengths and efficiencies adherend and elastic/plastic in non-dimensional form. adhesive. Deals only with identical Can deal with unbalanced adherends.Three failure cases joints and allows for thermal are considered:a)adherend mismatch between adherends. bending,b)adhesive shear, Provides ratio of maximum to and c)adhesive peel. average shear strength and non-dimensionalized joint strength. Scarf Joint: A4EE Step-lap joint: A4EG Elastic adherend and elastic/ Elastic adherend and elastic/ plastic adhesive. plastic adhesive. Provides a)shear stress Provides a)shear stress distribution along the joint b) distribution along the joint, displacement of inner and b)displacement of inner and outer adherends,and c) outer adherends,and c) potential joint strength. potential joint strength. Step-lap joint: A4EI Elastic adherend and elastic/ plastic adhesive. Similar to A4EG but more comprehensive;allows for variations in adhesive thickness and adhesive defects.Bond width can also be varied. complex for most analytical approaches.However,as discussed later,Hart-Smith shows that a simple elastic/ideally plastic formulation gives similar results to more realistic representations of adhesive behavior,providing the strain energy density in shear in the adhesive (area under the stress-strain curve)is comparable to that expected for the real curve. As a major part of these studies,software programs were developed for the analysis of double-overlap and the other types of joint discussed here;these are listed in Table 9.2.Similar programs are available through the Engineering Sciences Data Unit (ESDU)9 and proprietary programs have been developed by manufacturers. Inevitably,many of the complications in real joints are neglected or inadequately dealt with in these relatively simple studies.These include:Table 9.2 JOINING OF COMPOSITE STRUCTURES Computer Programs Developed by Dr John Hart-Smith for Stress Analysis of Bonded Joints 297 Joint to be analyzed Program Joint to be analyzed Program Single-lap joint: A4EA Double-lap joint: Elastic A4EB Joint strengths and efficiencies adherend and elastic/plastic in non-dimensional form. adhesive. Deals only with identical Can deal with unbalanced adherends. Three failure cases joints and allows for thermal are considered: a) adherend mismatch between adherends. bending, b) adhesive shear, Provides ratio of maximum to and c) adhesive peel. average shear strength and non-dimensionalized joint strength. A4EE Step-lap joint: A4EG Elastic adherend and elastic/ plastic adhesive. Provides a) shear stress distribution along the joint, b) displacement of inner and outer adherends, and c) potential joint strength. Scarf Joint: Elastic adherend and elastic/ plastic adhesive. Provides a) shear stress distribution along the joint b) displacement of inner and outer adherends, and c) potential joint strength. Step-lap joint: Elastic adherend and elastic/ plastic adhesive. Similar to A4EG but more comprehensive; allows for variations in adhesive thickness and adhesive defects. Bond width can also be varied. A4EI complex for most analytical approaches. However, as discussed later, Hart-Smith shows that a simple elastic/ideally plastic formulation gives similar results to more realistic representations of adhesive behavior, providing the strain energy density in shear in the adhesive (area under the stress-strain curve) is comparable to that expected for the real curve. As a major part of these studies, software programs were developed for the analysis of double-overlap and the other types of joint discussed here; these are listed in Table 9.2. Similar programs are available through the Engineering Sciences Data Unit (ESDU)9 and proprietary programs have been developed by manufacturers. Inevitably, many of the complications in real joints are neglected or inadequately dealt with in these relatively simple studies. These include: