Progressive damage behavior of composite L‐stiffened structures with initial delamination defects under uniaxial compression: Experimental and numerical investigations

In the paper, a detailed experimental and numerical investigation of compression after impact (CAI) behavior of hygrothermal aged T300 985LV carbon/ epoxy composites is presented. Rectangular fabric laminates are damaged by low-velocity impact, and moisture absorption conditioning is carried out. The moisture absorption curves agree with Fick's law, with a moisture equilibrium rate of 0.84% at 1392 h. Then, CAI experiments are carried out on moisture saturated specimens at different temperatures. The effects of hygrothermal environments on CAI strength are obtained with an interpretation of corresponding mechanism. Furthermore, finite element analysis based on hygrothermal mechanics formulation and incremental Newton-Raphson mixed iteration equation is established. The numerical results are in good agreement with the experimental ones, with an accuracy of up to 92%, which demonstrates the effectiveness of the established numerical model. The results show that the CAI strength of 85 RH% hygroscopic saturated laminates is decreased by approximately 12% at 85 C and 17% at 128 C. Additionally, the allowable compression value of 3546 μϵ is obtained for T300 985LV composite laminates, which is useful for applications in civil aircraft design. K E Y W O R D Scompression after impact, finite element analysis, hygrothermal aged, impact damage, moisture absorption | INTRODUCTIONCarbon fiber reinforced plastic (CFRP) is widely used in aerospace, marine and other engineering industries. [1,2] Compared with conventional materials, CFRP is characterized by the advantages of high specific strength, high specific stiffness, and excellent fatigue characteristics. [3][4][5][6][7] The percentage of CFRP used in civil aircraft ranges from 25% for the A380 to 50% for the later B787, which indicates that the usage of composite is increasing in primary components for aircraft structures. [8] Since the environment that the composite structure is exposed to significantly affect its performance, it must be accounted for during design. The most important aspect of the CFRP is temperature and moisture (hygrothermal), [9][10][11][12] which are crucial for understanding these effects and considering them in composite design. In addition, the impact damage is another factor that significantly affects composite properties. The impacts (i.e., tool drop, runway gravel, and hail) cause through-thickness stress waves in

Section: Simulation Methodology and Modelmentioning

confidence: 99%

Experimental and numerical investigation on compression after impact behavior of hygrothermal aged CFRP laminates

Huang

Xie

et al. 2022

“…However, the manufacturing and use of CFRP components may result in certain defects, including delamination, fiber waviness, fiber breakage, and missing bundles. [1][2][3] To ensure the longevity of these components, various non-destructive testing (NDT) techniques have been developed, including ultrasonic testing, 4,5 eddy current testing (ECT), [6][7][8] pulsed eddy current (PEC) thermography, 9 infrared (IR) thermography, 9,10 x-ray tomography, 11 and microwave emission. 12 Among these methods, ECT is considered a vital NDT technique for CFRPs as it provides detailed information on the fiber distribution within the material.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, carbon fiber‐reinforced polymers (CFRPs) have gained popularity across the aerospace, automotive, and marine industries owing to their exceptional properties, such as low weight, high strength, and superior fatigue resistance compared to those of other materials. However, the manufacturing and use of CFRP components may result in certain defects, including delamination, fiber waviness, fiber breakage, and missing bundles 1–3 . To ensure the longevity of these components, various non‐destructive testing (NDT) techniques have been developed, including ultrasonic testing, 4,5 eddy current testing (ECT), 6–8 pulsed eddy current (PEC) thermography, 9 infrared (IR) thermography, 9,10 x‐ray tomography, 11 and microwave emission 12 .…”

Section: Introductionmentioning

confidence: 99%

A new probe‐based electromagnetic non‐destructive testing method for carbon fiber‐reinforced polymers utilizing eddy current loss measurements

Yang

Feng

2023

Eddy current testing (ECT) is a widely used technique for detecting defects in carbon fiber‐reinforced polymers (CFRPs) at high frequencies. However, designing high‐frequency systems can be challenging, and high noise levels can be problematic. To address these issues, non‐destructive testing (NDT) methods that can detect CFRP defects at lower frequencies must be explored. In this study, a novel NDT method for detecting defects in CFRP at low frequencies was proposed. This method is an alternative to pulsed eddy current thermography and can achieve similar detection and imaging results at low frequencies. Furthermore, the developed method has a simpler structure and is easier to implement. This method uses the eddy current loss to characterize the thermal power of the eddy current in CFRP. A new probe was used to detect the eddy current loss to inspect the CFRP. The effectiveness of the proposed method was experimentally verified using different types of CFRP samples based on the C‐scan technology. The scanned images demonstrate that the developed method can provide appropriate detection results up to a frequency of 750 kHz. Furthermore, rotation experiments were performed to detect the fiber direction; the proposed method successfully detected the fiber direction up to 750 kHz. Thus, the proposed method can improve the detection of defects and enhance the longevity of CFRP components. Future work will focus on enhancing the sensitivity of this method at even lower frequencies.

“…Carbon fiber reinforced polymer (CFRP) composites have been widely utilized in the field of the aviation industry as a consequence of their outstanding mechanical behaviors such as high strength/stiffness to weight ratio, high specific modulus and excellent fatigue resistance, and they are gradually replacing the conventional metallic materials like aluminum alloy to achieve the light-weight of the structure and enhance the maneuverability of the aircraft. [1][2][3][4][5] The composite stiffened panel, which is made up of the skin panel and the stiffener with a certain stacking sequence of the composite prepreg, [6,7] is one of the most common used structural components in the manufacturing process of the airplane, and it is going to sustain complicated loading conditions like axial compression during the process of the service, [8][9][10][11][12] which may directly trigger the emergence of the buckling. [13,14] However, these structural components are very vulnerable to the low velocity impact (LVI) loading while the airplane is flying.…”

Section: Introductionmentioning

confidence: 99%

A novel methodology to research the residual compressive mechanical properties of composite stiffened panel after low velocity impact based on quantification damage simulation

Xiao

et al. 2022

Self Cite

Composite stiffened panels have become one of the most usual components in the design process of the aircraft's structure due to their splendid mechanical properties in the last decades. The main purpose of this work is investigating and presenting a more precise method to forecast the residual compressive mechanical behavior of the composite stiffened panel. First of all, an axial compression after impact (CAI) test is performed to understand the failure mechanism of different type of L‐shaped stiffened carbon fiber reinforced polymer panels with barely visible impact damage, which is introduced by the low velocity impact test. Subsequently, a finite element model, which contains a quantification damage model, is established in ABAQUS software based on the CAI test results to predict the mechanical behavior of these composite stiffened panels during the CAI test process. Both of the experimental and predicted results demonstrate that the propagation of the delamination caused by LVI is going to exert a destructive influence on the total failure of the composite stiffened panel, and the prediction results of the residual compressive strength of these composite stiffened panels are well consistent to that measured in the CAI test.