Effects of yarn defects and specimen size on impact compressive damages of 3-D angle interlock woven composites

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This paper aims to investigate the thermal ageing effect on the impact and post-impact behaviors of 2.5-D woven composites. A combined experimental and numerical study is carried out over a range of impact energies with the subsequent residual flexural tests on both aged (in the air for 32 days at 180℃) and pristine samples. Low-velocity impact tests are performed to assess the degradation of impact-resistant ability in terms of energy absorption mechanism and failure modes. Subsequently, three-point bending tests are conducted to determine the post-impact behaviors with respect to strain concentration, stress transfer and damage evolution process. The strain fields in the finite element model are compared with experimental results obtained by the DIC method. A larger strain concentration area could be found at higher energy levels and longer ageing time. Extended impact damage, such as fiber breakage and delamination, plays an important role in load transfer process in post-impact behavior, thus leading to the decrease of residual stress in aged samples.

Section: Introductionmentioning

confidence: 99%

Low-velocity impact and residual flexural behaviors of 2.5-D woven composite under accelerated thermal ageing: Experiment and numerical modelling

Cao

2019

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“…The compression strength was studied by using a kink band model that emphasized the matrix plasticity and fiber nonlinearity. Liu et al (2017) investigated the effects of yarn defects and specimen size on impact compressive damages of 3D woven composites. Dharan and Lin (2007) divided the matrix surrounding the fiber into a discrete interphase region adjacent to the fiber and matrix phase beyond the interphase based on an analytical model.…”

Section: Introductionmentioning

confidence: 99%

A progressive damage model for 3D woven composites under compression

Guo

Liu

et al. 2018

A progressive damage model is proposed to investigate the damage initiation and evolution of 3D woven composites under uniaxial compression at a micromechanical level. The typical compressive experiments were carried out. Based on the observations, the compression failure modes of 3D woven composites mainly include fiber kinking, transverse failure of fiber tow, matrix fracture, and interfacial debonding. The initial damage criteria are according to the physically based failure criteria for the fiber kinking, the Puck criteria for the transverse failure of fiber tow, and the maximum stress criterion for the matrix. The damage of fiber tow–matrix interfacial is simulated through cohesive contact. Particularly, the fiber’s initial misalignment angle is taken into account in the damage model. The simulated compression results agree well with the experimental ones. The compressive stress–strain response of the 3D woven composite is forecasted. The damage evolution of each constituent of the 3D woven composite is obtained. The results show that the influence of the fiber’s initial misalignment angle on the compression strength of the 3D woven composite needs to be considered.

“…A high-speed photography camera (i-speed 7 high-speed photography camera, supplied by iX Inc, UK) was used to record the CMOD as well as the crack initiation and propagation. The frame rate is 100,000 fps and the maximum resolution is 2048 × 1536 pixels (Liu et al., 2018).…”

Section: Methodsmentioning

confidence: 99%

Impact fracture behaviors of three-dimensional braided composite U-notch beam subjected to three-point bending

Shi

Liu

Siddique

et al. 2018

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Impact fracture behaviors of three-dimensional braided composites are critical to designing the braided composite parts. Here we report the impact fracture behaviors of three-dimensional braided composite U-notch beam tested on a modified split Hopkinson pressure bar. Crack mouth opening displacement, deformation process, and crack evolutions were recorded with high-speed photography camera. The digital image correlation method was used to calculate deformation contours of the braided composite. A microstructure model of the three-dimensional braided composite U-notch beam was established for analyzing damage evolution and fracture mechanisms. The histories of deformation, the load, and the crack mouth opening displacement were obtained from the impact fracture test and finite element analysis. It was found that the impact fracture resistance and morphologies were influenced by the braided structure and braided yarn orientations. The crack generated at the notch tip and then propagated along the braided angle direction rather than the perpendicular direction that often occurred for isotropic materials, such as the epoxy resin solid. The combinations of different braided angle and yarns are recommended for high impact fracture behavior design.