Abstract
The effects of thermoplastic polyimide (PI) and polypropylene (PP) fibers and areal density of toughened layer on interlaminar fracture toughness and impact performance of carbon fiber/epoxy (CF/EP) laminated composites were studied. Mode I interlaminar fracture toughness (GIC) was analyzed via double cantilever beam (DCB) tests. When comparing for the toughener type, PI played a positive role in enhancing the mode-I fracture toughness, while PP was not effective due to the less fiber bridge formed during composite curing. The toughening effects of areal density of PI were further investigated by end notched flexure (ENF) testing and low velocity impact testing to better understand the toughening mechanisms. The results revealed that the toughening effect reached its best effectiveness when the areal density of toughened layer was 30 g/m2. Compared with the control group, GIC and GIIC of CF/EP laminated composite were increased by 98.49% and 84.07%, and Fmax and Ee were enhanced by 92.38% and 299.08% under low velocity impact. There is no obvious delamination phenomenon on the surface of laminates after low velocity impact, indicating the improved interlaminar and impact performance of laminated composite.
Highlights
Carbon fiber/epoxy (CF/EP) laminated composites with light weight, good tensile performance, low cost, and ease of operation are widely used in various fields, including the automotive, aerospace, and petrochemical industries [1,2,3,4]
The results showed that the GII of the investigated composite was enhanced by 1.5 times with short Kevlar reinforcement
The interlaminar toughness GIC and GIIC of our laminated composite can be increased by 98.49% and 84.07%, respectively, by using the PI fiber nets as a toughening layer
Summary
Carbon fiber/epoxy (CF/EP) laminated composites with light weight, good tensile performance, low cost, and ease of operation are widely used in various fields, including the automotive, aerospace, and petrochemical industries [1,2,3,4]. Poor interlaminar strength is an inherent drawback of any laminated composite due to its low delamination resistance and damage tolerance, under impact loading; this condition significantly reduces the load bearing capacity of laminated composites [5,6,7,8]. Improving the interlaminar fracture toughness of carbon fiber composite laminates has elicited the attention of researchers. Thermoplastic materials can be used as a toughener for epoxy resin to improve the mechanical properties, such as tensile strength and modulus, of thermosetting materials [9,10]. The use of thermoplastic materials as a toughener for thermosetting resins has elicited considerable attention.
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