Session: 01-06-02: Impact, Fatigue, Damage and Fracture of Composite Structures

Paper Number: 105199

105199 - Low-Velocity Impact Analysis of Stiffened Composite Plates Using Higher-Order Layer-Wise Models 

Composite materials are increasingly used in fields where high mechanical strengths and low specific weights are required, such as the aerospace sector. Composites may require advanced modeling approaches due to some challenging features of this class of materials. For instance, the orthotropy of composite materials leads to low out-of-plane strength if compared with in-plane strength, making them vulnerable to impact phenomena [1]. During maintenance, landing, and take-off, foreign objects can hit parts of the aircraft at low velocity and cause damage inside the structure that is not visible or barely visible to the human eye [2]. The onset of damage inside the structure can significantly reduce its strength and stiffness capabilities and significantly threaten the whole aircraft's safety [3,4]. An impact can cause various damages, e.g., indentation, intralaminar, and interlaminar damage. In the case of reinforced structures, an impact phenomenon may cause a debonding between the panel and the reinforcement, severely limiting the strength contribution of the reinforcement to the structure [5]. Over the last decades, many authors have studied the behavior of stiffened panels subjected to impact, highlighting how the presence of the reinforcement and the point of impact strongly influence the dynamic and damage behavior of the structure [6-7]. Furthermore, another critical aspect to consider is the difference in elastic properties between two differently oriented plies and the discontinuity due to the presence of the reinforcements, generating a concentration of stresses inducing damage and debonding. The vast majority of the scientific community studies the behavior of reinforced structures using the finite element method based on the classical plate or shell models. However, this approach does not accurately evaluate transverse axial and shear stresses. Other authors obtained a good match between the experimental and numerical data by modeling the individual plies with three-dimensional elements and studying the effects of delamination using cohesive elements. This approach can provide good results but may require high computational costs. This work adopts higher-order structural theories based on the Carrera Unified Formulation [9] to provide an efficient and accurate mathematical model. The aim is the accurate description of the kinematic of the reinforced structure using beam and shell elements, thus, avoiding the more expensive 3D elements. The focus is on the evaluation of the 3D stress field and the evaluation of the damage onset via failure indexes. The results obtained with the proposed model are compared with commercial codes and literature data to highlight the soundness of the proposed solution and its numerical efficiency.

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[3]   TA Sebaey, EV González, CS Lopes, et al, Damage resistance and damage tolerance of dispersed CFRP laminates: design and optimization Compos Struct, 95 (1) (2013), pp. 569-576

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[5]   PL Vachon, V Brailovski, P Terriault, Prediction of the propagation of impact-induced delamination in carbon/epoxy laminates Compos Struct, 95 (1) (2013), pp. 227-235

[6]   A Faggiani, BG Falzon, Predicting low-velocity impact damage on a stiffened composite panel. Compos Part A: Appl Sci Manuf, 41 (6) (2010), pp. 737-749

[7]  W Sun, Z Guan, T Ouyang, et al, Effect of stiffener damage caused by low-velocity impact on compressive buckling and failure modes of T-stiffened composite panel Compos Struct, 184 (2018), pp. 198-210

[8]  C Mittelstedt, W Beker, Interlaminar stress concentrations in layered structures: Part I-a selective literature survey on the free-edge effect since 1967. J Comps Mater 2004; 38-(12) 1037-62

[9] MH Nagaraj, E Carrera, M. Petrolo, Progressive damage analysis of composite laminates subjected to low-velocity impact using 2D layer-wise structural models, Int. J. of Non-Linear Mech., 127, (2020)

Presenting Author: Marco Petrolo Politecnico Di Torino

Presenting Author Biography: Marco Petrolo is an Associate Professor and a member of the MUL2 Lab in the Department of Mechanical and Aerospace Engineering of Politecnico di Torino (www.mul2.com). His current research activity deals with the multiscale analysis of composites, micromechanics, and the development of higher-order structural theories. He is cooperating with various institutions, including the University of British Columbia, the University of Washington, Deakin University, and NASA. He is a member of Governing Board of the Italian Association of Aeronautics and Astronautics (AIDAA).

Authors:

Salvatore Saputo Politecnico di Torino
Manish Hassan Nagaraj University of Massachusetts Lowell
Alfonso Pagani Politecnico di Torino
Marco Petrolo Politecnico Di Torino
Erasmo Carrera Politecnico di Torino