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The evolution of residual stresses in thermoplastic bonding to metals

1997; Elsevier BV; Volume: 17; Issue: 4 Linguagem: Inglês

10.1016/s0143-7496(97)00030-4

1879-0127

Karthik Ramani, Wenping Zhao,

Polymer crystallization and properties

The ability to create strong joints between thermoplastics and metals offers many advantages. Differential properties between the polymer and metal generate residual stresses during cooling. In our study, both amorphous thermoplastic thin films and semi-crystalline thermoplastic thin films are joined to metal strips and the curvature is measured during controlled cooling. A series of five designed experiments uses a fast cooling (∼30°C/s) and slow cooling (∼4.5–10°C/min) to create different residual stresses. Experimental evidence shows that the residual stresses begin to develop at ∼190°C for amorphous Poly Ether Imide (PEI, Tg = 210°C), but at ∼255°C for semi-crystalline Poly Ether Ether Ketone (PEEK, Tg = 143°C). A mechanics based curvature model, combined with the elasticity and viscoelasticity of thermoplastics, successfully predicts the residual stress development. An elastic behavior is exhibited during the fast cooling (∼30°C/s), whereas a viscoelastic behavior occurs during slow cooling (∼4.5°C/min).