Impact resistance and damage tolerance are of great significance in the design of composite structures. This study researched the damage and failure mechanism of carbon fiber reinforced poly-ether-ether-ketone (CF/PEEK) composite laminates under the low-velocity impact (LVI) and compression after impact (CAI) loading conditions. The test included four impact energy levels (15, 30, 45, and 60 J) and compared the effect of two different stacking sequences ([0 /90 ] 8S and [0 /45 /90 /À45 ] 4S ) on performance. The results shown that the peak impact force of the two different stacking sequences increased from 7.8 kN/8.3 kN-11.4 kN/13.7 kN, and the CAI strength decreased from 370.5 MPa/419.3 MPa to 212.8 MPa/232.5 MPa, respectively. Nondestructive testing of low-velocity impact specimens by ultrasonic C-Scan was employed to investigate structural damage. Digital image correlation (DIC) was employed to perform full-field displacement measurements for the CAI experiment. The cross-section of typical specimen was observed using a scanning electron microscope (SEM) to determine the failure mode of the specimen. In addition, a 3D damage model based on continuum damage mechanics was established, with the consideration of the interlaminar delamination damage and intralaminar damage. Compared with the experimental results, the errors of the numerical simulation of the peak impact force, impact energy absorption, and CAI strength are 3.8%-14.8%, 3.7%-6.9%, and 2.2%-6.7%, respectively, which verifies the validity and rationality of the model. Furthermore, the numerical model and interpolation function were used to predict the ultimate residual strength.
Lightweight and high-strength sandwich structures with advanced materials are essential for the sustainable development of future industrial development. This paper focuses on investigating the fabrication technology and compression properties of the three-dimensional sandwich structure with lattice cores fabricated by using the continuous carbon fiber reinforced thermoplastic polyether ether ketone (CCF/PEEK). A novel fabrication technology for continuous carbon fiber reinforced thermoplastic polyether ether ketone lattice core is proposed utilizing the unique characteristic of repeated thermoforming of continuous carbon fiber reinforced thermoplastic polyether ether ketone. A mould was designed and then the continuous carbon fiber reinforced thermoplastic polyether ether ketone lattice cores were fabricated. Typical adhesive technology is selected to connect facesheets and lattice cores. The out-of-plane compression behaviors of continuous carbon fiber reinforced thermoplastic polyether ether ketone sandwich structures with lattice cores were investigated by experiment and simulation. Compared with the experimental results, the reliability and correctness of the simulation model were verified. By dint of the simulation model, the effect of stacking sequence of the lattice cores on the structural compression properties was investigated, and the correctness of lattice cores adopted [Formula: see text] stacking sequence in this paper was proved. The continuous carbon fiber reinforced thermoplastic polyether ether ketone lattice sandwich structures exhibit the competitive compression strength with other thermoplastic sandwich structures and surpasses some metal foams at a range of densities.
Purpose This paper aims to study the effect of elevated temperature on the compression behaviour of carbon fibre polyphenylene sulphide (CF/PPS) laminates notched and unnotched specimens made by film stacking method (FSM). Design/methodology/approach The surface of CF was coated with a silane coupling agent to form an effective transition layer with PPS, so as to enhance the interfacial interaction between CF and PPS. Considering the influence of fabrication pressure, forming temperature and cooling rate on the properties of laminates to obtain a reasonable preparation process. Conducting a compressive experiment of notched and unnotched specimens at different temperatures, which failure modes were examined by scanning electron microscope and stereo microscope. Findings The experimental observations highlight that with the increase of temperature, the transition failure mode from fibre broken to kink-band appeared in unnotched specimens, which were closely attributed to the matrix state. The notched specimens appeared more complex failure mode, which can be attributed to the joint effect of temperature and opening hole. Research implications A simple way of FSM for composite material laminates has been developed by using woven CF and PPS films. Originality/value The outcome of this study will help to understand the compression response mechanism of composite materials made by FSM at different temperature.
Unidirectional fiber‐reinforced composite laminates have limited resistance to out‐of‐plane impact and are prone to structural integrity damage during service due to low‐velocity impact (LVI). In this study, the hot‐press fusion method was employed to repair the impact‐damaged unidirectional carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) thermoplastic composites. No delamination or matrix cracking induced by impact was observed in the repaired specimens, as confirmed by ultrasonic scanning and digital microscope. In addition, the hot pressing treatment enables the fibers to be covered again by the resin matrix, which eliminates fiber pull‐out and fiber/matrix debonding. Afterward, typical responses of CF/PEEK composite laminates to re‐impact and post‐repair compression are presented in a comprehensive and detailed manner, and compared with the initial impact response and compression after impact (CAI) behavior. The effects of three impact energies and two stacking sequences are considered. The results indicate that quasi‐isotropic laminates are more susceptible to localized fracture damage upon re‐impact as the impact energy increases, due to initial fiber breakage, compared to orthotropic laminates. The hot‐press treatment enhances the compression residual strength of the specimen by 20%–30% compared to its state before repair. These studies offer technical insights into the application of the hot‐press fusion method to enhance the mechanical properties of composite laminates post impact damage.
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