Study on the effect of delamination defects on the mechanical properties of CFRP composites

Delamination in reinforced panels is one of the primary challenges facing the safety and reliability of aerospace structures. This article presents a sensitivity analysis of the fatigue behaviour during the compression of a composite aeronautical stiffened panel experiencing delamination. The main objective is to assess the impact of delamination size and depth on the lifecycle and structural integrity of the panel. Different dimensions and positions of delamination are considered to cover a comprehensive range of damage scenarios. The key feature of this sensitivity analysis is the adoption of a numerical procedure that is mesh- and load-step-independent, ensuring reliable results and providing valuable insight into the criticality of delamination and its impact on the fatigue behaviour during the compression of reinforced aeronautical panels. Sensitivity analyses are essential for enhancing the design process of aerospace structures, thereby contributing to the increased safety and reliability of structural components. In this regard, the use of robust and effective numerical procedures is of crucial significance. This may be seen as the real added value of this paper.

Section: Resultsmentioning

confidence: 99%

Influence of Delamination Size and Depth on the Compression Fatigue Behaviour of a Stiffened Aerospace Composite Panel

Russo,

Castaldo,

Palumbo

et al. 2023

“…The common defects of composites mainly include fiber wrinkles [7][8][9], delamination [10][11][12], resin-rich [13][14][15], and void. Void defects are cavities that form during the molding process of composites [16].…”

Section: Introductionmentioning

confidence: 99%

Effect of Resin-Missing Defects on Tensile Behavior of Carbon Fiber/Epoxy Composites

Li,

Zhu

2024

This study explores the impact of resin-missing defects on the mechanical properties of composite laminates through experimental and finite element methods. Specimens with varying defect contents (5.3%, 8.0%, 10.7%, 13.3%, and 16.7%) were prepared via Vacuum Assistant Resin Infusion process. Experimental tests were conducted with the assistance of Digital Image Correlation measurements to illustrate the impact of resin-missing defects on failure characteristics. The experimental results indicate that the existence of resin-missing defects altered the stress distribution, increased the local stress, and reduced the tensile strength of the composite laminate. The DIC results indicate that the presence of defects weakens the matrix, leading to premature damage and deterioration. Numerical modeling with a progressive damage analysis method was developed to simulate the failure process and the influence of the resin-missing defects. The simulation results agree well with the experimental results, and the maximum error was 3.06%. The failure modes obtained from finite elements are consistent with the experimental and DIC results. Furthermore, a study was conducted on how the location of resin-missing defects affects the mechanical properties of composite laminates. The findings suggest that defects situated at the edges or on the surface of the material have a more significant impact on the tensile strength.

“…Increased delamination leads to stress concentration which adversely modifies the failure phenomenon [ 10 ]. Recently, Li et al [ 11 ] have analyzed the effect of delamination on the compression properties of CFRPs by means of numerical simulation. They found that strength is remarkably affected by the delamination area but, if it is below a critical value or if delamination is placed in the middle of the hole, the compression properties are not affected.…”

Section: Introductionmentioning

confidence: 99%

Experimental Analysis and Application of a Multivariable Regression Technique to Define the Optimal Drilling Conditions for Carbon Fiber Reinforced Polymer (CFRP) Composites

Molina-Moya,

García-Martínez,

Miguel

et al. 2023

Carbon fiber reinforced polymers (CFRPs) are interesting materials due to their excellent properties, such as their high strength-to-weight ratio, low thermal expansion, and high fatigue resistance. However, to meet the requirements for their assembly, the drilling processes involved should be optimized. Defects such as delamination, dimensional errors and poor internal surface finish can lead to the premature failure of parts when bolt-joined or rivet-connected. In addition, the characteristic anisotropy and heterogeneity of these materials, and the issues related to the temperature reached during drilling, make it difficult to obtain optimal cutting parameters or to achieve high material removal rates. This research focuses on the optimization of the CFRPs drilling process by means of experimental analysis—varying the feed and spindle speed—for two different types of commercial drills—a twist tool and a dagger tool. An automatic image processing methodology was developed for the evaluation of the dimensional accuracy and delamination of the holes. The optimization was carried out using a multi-objective regression technique based on the dimensional deviations, delamination and surface finish. The areas with favorable machining conditions have been delimited for both tools and the results indicate that the twist tool allows one to achieve more productive cutting conditions than the dagger tool, when the combination of low feeds and high spindle speeds are the conditions to be avoided.