Simulation of Delamination Growth at CFRP-Tungsten Aerospace Laminates Using VCCT and CZM Modelling Techniques

J Jokinen,M Kanerva

doi:10.1007/s10443-018-9746-5

Abstract

Delamination analysis in advanced composites is required for the laminate design phase and also during the operation of composite aerospace structures to estimate the criticality of flaws and damage. The virtual crack closure technique (VCCT) and cohesive zone modelling (CZM) have been applied to delamination simulation as numerical tools of crack modelling. VCCT and CZM have their unique advantages and disadvantages per application. This study focuses on the application of VCCT to a brittle delamination in a hybrid tungsten–carbon-fibre reinforced composite (CFRP-W) and pursues to identify the challenges due to very high internal residual stresses and strain energy as well as unstable crack propagation. The CFRP-W composites have application areas in high-performance, light-weight radiation protection enclosures of satellite electronics and ultra-high frequency (e.g. 5G) systems. In our work, we present the effects of free-edge stress concentrations and interfacial separation prior to nodal release on a combined VCCT-CZM model and compare the results to pure VCCT and CZM models of the interfacial crack. Parameter notes are given based on the results to apply the combined method for delamination analyses with interfaces heavily loaded by internal residual strains.

Highlights

Carbon-fibre-reinforced plastics (CFRPs) have been used in structures and in electronics housings of satellites due to the weight efficiency achieved in extreme light-weightApplied Composite Materials (2019) 26:709–721 concepts [1, 2]
This study focused on the analysing of the application of pure Virtual Crack Closure Technique (VCCT), pure Cohesive Zone Modelling (CZM), and a combined VCCT-CZM crack model in the simulation of highly brittle and high-energy intensive mode II dominated fracture
Hybrid CFRP-W radiation shielding laminate was simulated in a cracked lap-shear (CLS) test setup

Summary

Introduction

Carbon-fibre-reinforced plastics (CFRPs) have been used in structures and in electronics housings of satellites due to the weight efficiency achieved in extreme light-weightApplied Composite Materials (2019) 26:709–721 concepts [1, 2]. In the case of electronic housings, the typical means to realize high enough protection against various radiation from the (space) environment, and to control the thermal and electrical conductance of the CFRP-based parts, is to laminate metal foils as part of the CFRP lamination These enclosures are not always primary load-carrying components, delamination of CFRP and metal foil would lead to significant deviation of the heat flux, radiation attenuation, and geometry. The main numerical methods for finite element delamination analyses are the Virtual Crack Closure Technique (VCCT) and Cohesive Zone Modelling (CZM) Both methods have their pros and cons in a practical design process since VCCT is primarily applied for structures with an initial flaw [6] and CZM requires fitting parameters other than pure fracture toughness and standardized fitting procedures do not exist. The scientific challenge is to understand the limits of brittle crack propagation for VCCT so that dynamic effects remain insignificant

Methods

Results

Discussion

Conclusion