Multistep Experimental Calibration of Mechanical Parameters for Modelling Multilayer Antishatter Safety Films in Structural Glass Protection

Glass material is largely used in buildings and facilities due to various motivations. Besides, glass still represents a vulnerable component for building occupants. Careful attention is required especially for glass elements that may be subjected to extreme design loads, such as impact, vibrations, etc. Among various approaches and techniques to prevent danger for people in case of glass breakage, multilayer antishatter safety films (ASFs) are commercially available for the retrofit of existing monolithic glass members. In the present research study, a multistep experimental program is presented to obtain the characterization of key input mechanical parameters that are required for the numerical analysis of glass elements protected by ASFs. Relevant characteristics are derived for the definition of an equivalent material and monolithic tape able to reproduce the ASF experimental outcomes. On the side of experiments, artificially aged specimens (healing process) are investigated. A major advantage is taken from small-scale peel and tensile tests on ASF samples, as well as Operational Modal Analysis (OMA) techniques for nondestructive vibration measurements on preliminary fractured specimens of ASF-bonded glass elements. Efficient Finite Element (FE) numerical models calibrated with the support of experimental data and Cohesive Zone Modelling (CZM) techniques are presented for discussion of comparative results, giving evidence of rather good estimates and possible extension of the multistep experimental procedure.

High-fidelity damage modelling of CFRP laminates for impact and crashworthiness applications – dynamic tube crushing simulations

Drop weight impact experiments were conducted on angle-ply carbon fibre reinforced polymer (CFRP) composite crush tubes. The dynamic response was modelled using explicit finite element methods and continuum damage mechanics and cohesive zone modelling in both Abaqus/Explicit and LS-DYNA. User-defined constitutive models for the intra-ply behaviour were used and a fibre-aligned meshing technique was implemented. The results of the experiments and simulations are compared to evaluate accuracy of the different modelling techniques, highlighting the advantages and drawbacks of each approach. Among these, the choice of meshing strategy is shown to be especially important in capturing the physical propagation of cracks and damage mechanisms in CFRP laminates.

Characterization and Numerical Modelling of Through-Thickness Metallic-Pin-Reinforced Fibre/Thermoplastic Composites under Bending Loading

Through-Thickness Reinforcement (TTR) technologies are well suited to improving the mechanical properties in the out-of-plane direction of fibre-reinforced composites. However, besides the enhancement of delamination resistance and thus the prevention of overall catastrophic failure, the presence of additional reinforcement elements in the composite structure affects also the mechanical properties in in-plane direction. In this work, the flexural behaviour of a glass-polypropylene (GF/PP) hybrid yarn-based composite with TTR in form of metallic pins has been investigated experimentally and numerically. The insertion of the metallic pins is realized via thermoactivated pinning technology (TAP). In four-point-bending tests, it is shown that the flexural stiffness and strength decreases with an increase of the overall pin density. Hereby, it is observed that the pins act as crack initiators. For numerical modelling on specimen level, a continuum damage mechanic (CDM) model is used to predict the nonlinear deformation response of the composite, as well as fibre fracture and matrix cracking. A debonding and slipping phenomena of the pin in the composite is modelled by a cohesive zone modelling approach for the interface between pin and composite.

A modified degradation technique for fatigue life assessment of adhesive materials subjected to cyclic shear loads

Understanding the fatigue response of adhesive joints under cyclic shear stress is important to avoid fatigue failure of the bonded structures. Recently, a cohesive zone modelling (CZM) technique was developed where the cohesive properties of the elements were degraded by a proposed empirical relation. However, based on this degradation approach, the fatigue life of the joints should be known before running the analysis. The aim of the current study is to improve the numerical method in which the fatigue life of the joints will be automatically estimated during the analysis. To achieve this, the concepts of fracture mechanics are considered by using the Paris’ law combined with the degradation model. A user material subroutine is developed to conduct the numerical calculations based on the concepts of CZM. End notched flexure (ENF) tests were carried out to evaluate the numerical data. Based on the results, it was found that the modified approach, in which the total fatigue life is obtained automatically, can be employed for fatigue life assessment of adhesive joints subjected to cyclic shear stresses.