21 st International Conference on Composite Materials Xi’an, 20-25 th August 2017 IMPACT BEHAVIOUR OF CARBON FIBRE REINFORCED POLY (METHYL METHACRYLATE) THERMOPLASTIC COMPOSITE Daiva Zeleniakiene 1 , Kristina Zukiene 2 and Paulius Griskevicius 3 1 Department of Mechanical Engineering, Kaunas University of Technology, Studentu st. 56, 51424 Kaunas, Lithuania, daiva.zeleniakiene@ktu.lt, http://ktu.edu 2 Department of Production Engineering, Kaunas University of Technology, Studentu st. 56, 51424 Kaunas, Lithuania, kristina.zukiene@ktu.lt, http://ktu.edu 3 Department of Mechanical Engineering, Kaunas University of Technology, Studentu st. 56, 51424 Kaunas, Lithuania, paulius.griskevicius@ktu.lt, http://ktu.edu Keywords: carbon fibre reinforced poly (methyl methacrylate) composite, impact behaviour, damage, failure criteria, finite element modelling ABSTRACT The aim of the present study was to investigate the low velocity impact behaviour and damage patterns of carbon fibre reinforced methyl methacrylate composites. The process of low-velocity impact damage in composite was simulated using the finite element method and experimentally verified. Orthotropic plane stress conditions of homogenized continuum lamina were used to model composite structure. The evolution of damage was simulated using the finite element code LS-DYNA by material models MAT58 based on Matzenmiller’s damage mechanics model with four Hashin’s failure criteria and MAT54 based on four failure criteria by Chang-Chang. Damage variables were determined performing calibration of numerical model according to the experimental results of three- point bending and impact tests. Detailed quantitative comparisons were carried out between delaminated areas simulated by the model and those characterized experimentally by ultrasonic C- Scan method. The results of the numerical analyses demonstrate good agreement with experimental data. 1 INTRODUCTION The low-velocity transverse impact could cause various damages, such as matrix cracks, delamination and fibre breakage [1]. Such damages influence on the significant reductions of strength and stiffness of the materials and are difficult characterized. The damage mechanism of laminated composites under impact loading can be defined as intralaminar damage such as fibre and (or) matrix debonding or fibre fracture, matrix cracking or plasticity; and interlaminar failure, which develops at the interface between adjacent plies in the form of debonding between layers, so called delamination [2]. Such type of damage is very difficult to predict and the number of various approaches based on failure criteria were proposed for fibre reinforced plastic composites [3-6]. Commercially available codes such as LS-DYNA, ABAQUS, and others, offer material models which utilize a different modelling strategy, include failure criterion, degradation scheme, material properties, and usually a set of model-specific input settings that are typically needed for the computation but do not have an immediate physical meaning [7]. The constitutive materials models can be divided in two main groups: progressive failure models (PFM) and continuum damage mechanics models (CDM). For composite materials the LS-DYNA offers both PFM (MAT22, MAT54 and MAT55) and CDM (MAT58 and MAT162) material models [8]. The authors of this paper are presented some studies for damage analysis of real structures and constructions made from sandwich composites, eg. plates, used in civil engineering or cylindrical structures used for pipes and tanks [9-11]. In this work, the well-known fracture criteria were used to simulate impact behaviour of fiber- reinforced thermoplastics composites (FRTC) using finite element code LS-DYNA.