An extended cohesive damage model with a length scale in fracture analysis of adhesively bonded joints

•An extended cohesive damage model was developed.•Proposed adhesive or cohesive law firstly considered the length scale influence.•Different bounding qualities can be studied by the proposed model with a length scale.•Internal particles of heterogeneous adhesives can also be studied by the proposed model.•Damage laws with length scales were established for micro and macroFEA modelling.

This paper introduced an extended cohesive damage model (ECDM) in fracture analysis of adhesively bonded joints. A length scale of pore size at joints was introduced in the accumulation of damages in the proposed ECDM. This microdamage scale based model was used to build up an extended cohesive finite element modelling of adhesively bonded joints at a macrolevel. An adhesive damage law (ADL) was used to simulate debonding at interfaces. A cohesive damage law (CDL) was proposed to simulate internal cohesive cracks. These two microdamage laws firstly considered the length scale influence from the interfacial pores and internal particles. These ECDM models were used to deal with the stress discontinue problems at interfaces or internal materials. As an example, an adhesively bonded bone-cement joint was investigated in this paper. The failure mechanism of bone-cement joint under tension, with different bonding qualities, was studied using the developed ECDM models. This investigation indicated that the effect of bonding quality on the loading capacity of bone-cement joint can be studied properly by the ECDM with a length scale of interfacial pore size. This ECDM based damage modelling technique supplied an effective and efficient approach in cohesive and adhesive damage analysis.