The effect of alternating the sequence of variable‐energy repeated impact on the residual strength and damage evolution of composite laminates

In this paper, the repeated low velocity impact responses and compression‐after‐impact (CAI) behaviors of woven glass fiber‐reinforced composite laminates were studied at the same total impact energy. Three types of impact energies, 30, 40, and 60 J, were chosen for the repeated impact tests relative to the single 120 J impact event. The impact behaviors including impact contact force–displacement and energy–time curves during the impact testing were recorded. The variations of the impact mechanical characteristics such as peak impact force, maximum displacement, and energy absorption were evaluated. The methods of visual inspection and stereo microscope were applied to identify the damage morphology of the impacted laminates. The damage accumulation was evaluated employing the absorbed energy fraction and normalized maximum displacement. It was found that the influences of impact energy on the repeated impact mechanical response are more remarkable than that of the impact number, and the impact events with fewer impact numbers cause more damage to the laminates for the same accumulative impact energy. Furthermore, the load–displacement and the CAI strength versus impact number curves were compared for the CAI testing. The ultimate load and the resulted CAI strength decrease with the increase of impact number owing to the influence of damage accumulation in repeated impacts.Highlights Repeated impact responses were studied at the same total impact energy. The impact energy makes significant influence on the impact dynamic responses. The impact events with fewer impact numbers cause more damage to the composites. The CAI behavior was explored considering the effect of damage accumulation. The CAI strength of damaged laminates decreases with impact number increasing.

Section: Introductionmentioning

confidence: 99%

Experimental investigations on the repeated low velocity impact and compression‐after‐impact behaviors of woven glass fiber reinforced composite laminates

Li,

Yu,

Tao

et al. 2023

Impact damage assessment in laminated composites using acoustic emission and finite element methods

Saeedifar

2023

Self Cite

This study aims to quantify impact damage in laminated composites using acoustic emission (AE) and to verify the AE results with finite element (FE) method. Carbon fiber reinforced polymer (CFRP) composite specimens were subjected to quasi‐static out‐of‐plane indentation loading. A procedure, including feature extraction, feature selection, data dimensionality reduction, and data clustering using an evolutionary algorithm, that is, differential evolution (DE) optimization algorithm, was proposed to identify and quantify different damage mechanisms using AE. The AE results showed that the dominant damages were matrix cracking and delamination. For the quantitative evaluation of the AE results, the indentation test was simulated using the FE method. A FE model based on cohesive zone modeling and continuum damage mechanics was implemented to predict interlaminar and intralaminar damages. The quantity of the damaged elements associated with the matrix cracking and delamination was consistent with the AE results. This study showed the applicability of the AE for impact damage identification and quantification in composite structures.Highlights Indentation damage in CFRP is experimentally quantified using the AE method. The DE algorithm is used to cluster the AE data. CZM and CDM are used to numerically model the damage. The AE clustering results are compared with the numerical results.

Influence of lay‐up sequences on cylindrical parts drawability of CFRP laminates

Zhang,

Jia,

Xue

et al. 2024

Carbon Fiber Reinforced Polymers (CFRP) is one of the ideal materials in the field of automotive lightweight. As one of the traditional manufacturing processes of CFRP, autoclave process has long production time, high cost and complicated operation. To overcome these shortcomings, deep drawing can be used for CFRP forming. It has the advantages of stable product quality, good repeatability, low cost, simple operation and can produce parts with complex shapes. In this paper, the influence of lay‐up sequences on the drawability of cylindrical parts was studied by using self‐made deep drawing device. The results showed that among the four lay‐up sequences [0]°12, [0/90]°6, [0/90/45/‐45/90/0]°S and [15/30/……/180]°, the [15/30/……/180]° lay‐up parts had excellent deformation coordination ability due to less angular variation in the fiber direction, and the maximum depth of 21.99 mm could be obtained. Due to the influence of wrinkles, the thickness of [15/30/……/180]° parts increased at the die corner and side wall. The thickness decreased at the flange, punch corner and bottom due to the compressive pressure. In addition, [15/30/……/180]° lay‐up parts benefited from the high level of in‐plane isotropy of the helicoidal structure, it had the fewest forming defects. The resin poor areas and resin rich areas were less and no fiber cracks were found.Highlights Investigated the influence of lay‐up sequences on the drawability of CFRP. The forming depth of [15/30/……/180]° parts was 21.99 mm. [15/30/……/180]° lay‐up parts had the best drawability. No cracks were found on the [15/30/……/180]° part.