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Effective Elastic Property of Randomly Damaged Composite Laminates

  • April 2017
  • Conference: Engineering Postgraduate Research Symposium
  • At: University of Aberdeen, Aberdeen, AB24 3UA, Scotland, UK
Authors:
Susmita Naskar at University of Southampton
Susmita Naskar
Srinivas Sriramula at University of Aberdeen
Srinivas Sriramula
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Effective Elastic Property of Randomly
Damaged Composite Laminates
S. Naskar*, S. Sriramula
School of Engineering, University of Aberdeen, Aberdeen, Scotland, UK , AB24 3UA
*Website: www.susmitanaskar.com; email : r01sn15@abdn.ac.uk
Introduction
The production of composite laminates is subjected to large
variability because of unavoidable fabricating imperfections,
operational factors, inaccurate experimental data etc. [1, 2]. In
the conventional deterministic analysis of structures, the
variations in the system parameters are neglected and mean
values of system parameters are used in the analysis with some
factor of safety. During operational period matrix cracking is one
of the predominant modes and early stage of damage in
composite laminates. To account for the effect of such damage,
normally effective elastic properties are calculated and thereby it
is used to calculate global structural response such as natural
frequencies, deflection etc. We have developed an analytical
framework to analyse the effect of spatially random matrix
cracking damage in composite laminates [1].
Conclusion
This investigation deals with developing an analytical framework for effective elastic properties of damaged composite laminates including the
effect of spatially varying material properties. Such effective elastic properties can be used in efficiently characterizing different global responses of
the structure (such as natural frequency, deflection etc.). Sensitivity analysis is carried out to quantify the relative importance of different input
parameters. Future research will be carried out to quantify the influence of such spatially varying damages and material property distribution in the
global dynamic responses of structure based on the proposed SRVE based approach.
References
[1] Naskar, S., Mukhopadhyay, T., Sriramula, S. & Adhikari, S. (2017). Stochastic natural frequency analysis of damaged thin-walled laminated composite beams with uncertainty
in micromechanical properties. Composite Structures,160 312 –334
[2] Dey S.,Naskar S., Mukhopadhyay T., Gohs U., Spickenheuer A., Bittrich L., Sriramula S., Adhikari S., Heinrich G. (2016) Uncertain natural frequency analysis of composite
plates including effect of noise –A polynomial neural network approach, Composite Structures,143 130–142
Key Idea
A novel concept of stochastic representative volume element
(SRVE) has been proposed to account for the spatially random
variation of material properties and crack density. In this
approach, each representative unit (structural elements) of the
structure are considered as stochastic, instead of considering
homogenized properties of a conventional representative volume
element throughout the entire domain. In traditional approach,
typically a single RVE is considered, wherein one RVE
represents the entire analysis domain. In the present approach
we ensure to account for all the information pertaining to
randomly varying matrix cracking damage and stochastic
material properties in the analysis.
Results and discussion
Results are presented for stochasticity in micro-mechanical and macro-
mechanical properties, separately. From the probability density function
plots, it can be noticed that response bound is more for micro-mechanical
analysis compared to macro-mechanical analysis while same degree of
stochasticity is considered in both the cases. This observation can be
explained by the cascading effect showing that consideration of
stochasticity in more elementary level of the multi-scale hierarchy
increases the response bound of output parameters at the global level.
Sensitivity of different micro and macro-mechanical properties are shown
above using the measure of relative coefficient of variation (RCOV). Such
analysis is crucial to determine the relative influence of different input
parameters to the output quantity of interest. The effective elastic property
of damaged composite laminate can be used to characterize different
global responses [1] of the structure as shown below.
... Following several decades of deterministic studies, the aspect of considering the effect of uncertainty in material and structural attributes have recently started receiving due attention from the scientific community. Both probabilistic (Sakata et al. (2008), Goyal and Kapania, (2008), Manan and Cooper (2009), Dey et al. (2016aDey et al. ( , 2016e, 2018bDey et al. ( , 2019, , 2017c, Naskar (2017)) as well as non-probabilistic , Pawar et al. (2012)) approaches have been investigated to analyse the influence of variability in the material and structural attributes of composite structures. Plenty of researches have been reported based on intrusive methods to quantify the uncertainty of composite structures (Lal and Singh (2010), Scarth and Adhikari (2017)), wherein the major drawback can be identified as the requirement of intensive analytical derivation and lack of the ability to obtain complete probabilistic description of the response quantities for systems with spatially varying attributes. ...
... A non-intrusive method based on Monte Carlo simulation, as adopted by many researchers (Dey et al. (2016a(Dey et al. ( , 2016g, 2015d), Mukhopadhyay and Fig. 1 (a) Typical distribution of a material property E 1 along a cross-sectional view (X-Z plane) of two laminae for a random realization in case of the layer-wise random variable approach (b) Typical distribution of a material property E 1 along a cross-sectional view (X-Z plane) of two laminae for a random realization in case of the random field approach Adhikari (2016c)), can obtain comprehensive probabilistic descriptions for the response quantities of composite structures. Besides consideration of random variability in material and structural attributes, recent studies related to uncertainty quantification of laminated composite structures include the effect of environmental (Dey et al. (2015a)), operational (Dey et al. (2015b)) and service life conditions (Naskar et al. (2017), Karsh et al. (2018a)) following the non-intrusive approach. A careful consideration of available scientific literature unveils that most of the studies conducted so far to quantify the effect of uncertainty in composite structures are based on a ply-level random variable based approach, where the spatial variation of stochastic parameters in the laminae is neglected. ...
... The entire lattice structure is assumed to be consisted of several RUCEs and the global SRVE based approach for analyzing spatially random two dimensional systems mechanical properties of the entire irregular lattice can be computed by assembling the RUCEs based on equilibrium and compatibility conditions. The concept of SRVE for analyzing one dimensional beam-like structures with random material properties and crack density is first adopted byNaskar et al. (2017). In this paper, we have generalized the concept for stochastic analysis of two-dimensional plate-like structures with randomly inhomogeneous form of uncertainty). ...
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