Cohesive/Adhesive failure interaction in ductile adhesive joints Part I:A smeared-crack model for cohesive failure

AbstractThis paper proposes a new methodology for the finite element (FE) modelling of failure in adhesively bonded joint. Unlike current methods, cohesive and adhesive failures are treated separately. Initial results show the method׳s ability to give accurate prediction of failure of adhesive joints subjected to thickness-induced constraint and complex multi-axial loading using a single set of material parameters. The present paper (part I), focuses on the development of a smeared-crack model for cohesive failure. Model verification and validation are performed comparing the model predictions with experimental data from 3 point bending End Notched Flexure (3ENF) and Double Cantilever Beam (DCB) fracture tests conducted on adhesively bonded composite panels of different adhesive thicknesses

Cohesive/Adhesive failure interaction in ductile adhesive joints Part II:Quasi-static and fatigue analysis of double lap-joint specimens subjected to through-thickness compressive loading

AbstractThis paper proposes a new methodology for the finite element (FE) modelling of failure in adhesively bonded joints. Cohesive and adhesive failure are treated separately which allows accurate failure predictions for adhesive joints of different thicknesses using a single set of material parameters. In a companion paper (part I), a new smeared-crack model for adhesive joint cohesive failure was proposed and validated. The present contribution gives an in depth investigation into the interaction among plasticity, cohesive failure and adhesive failure, with application to structural joints. Quasi-static FE analyses of double lap-joint specimens with different thicknesses and under different levels of hydrostatic pressure were performed and compared to experimental results. In all the cases studied, the numerical analysis correctly predicts the driving mechanisms and the specimens’ final failure. Accurate fatigue life predictions are made with the addition of a Paris based damage law to the interface elements used to model the adhesive failure

An experimental investigation of the consolidation behaviour of uncured prepregs under processing conditions

This paper presents a methodology and research study that characterises toughened materials, as is needed for optimisation of composite manufacturing processes. The specific challenge is to cover all of the stages of advanced composite manufacturing: fibre deposition by automatic fibre placement machines, hot or room temperature debulking, and consolidation in an autoclave. In these processes the material experiences a wide range of processing parameters: pressure, load rate, temperatures, and boundary constraints. In these conditions, toughened prepregs exhibit complex rheological behaviour, with diverse flow and deformation mechanisms at various structural scales. Here a series of experimental results are presented in order to describe the temperature, viscosity, flow mechanisms, and scale-effects of simple uncured prepreg stacks. The driver for this study is to obtain a further understanding of flow mechanisms throughout the consolidation phase of composites manufacture since fibre path defects are most likely to occur during compaction, prior to vitrification. </jats:p

Adaptive Real-Time Characterisation of Composite Precursors in Manufacturing

Experimental data accompanying the paper of A.Koptelov et al on new testing framewor