Abstract
As a graphite derivative, graphite fluoride (GrF) has a remarkable fracture toughness improvement effect on epoxy materials. The fracture toughness variation of the epoxy could exert an influence on the low velocity impact resistance of the corresponding carbon fiber reinforced polymer (CFRP) composite. Therefore, the dependence of the low velocity impact resistance of the incorporated CFRP on the GrF content is worth analyzing. Here, different contents of GrF were applied to incorporate CFRP laminates and planned to find the optimal GrF content, in turn leading to the best impact resistance. Using a drop-weight impact test, the load vs. time curves and load vs. displacement curves were obtained. The incipient damage loads and maximum loads of various GrF contents of the samples were compared carefully. The absorbed energies during the impact process were calculated. The trend of absorbed energy decreased up to the 1 wt% sample, then increased significantly with the rise of GrF content. This deflection behavior can be explained by the combination of crack pinning, crack deflection and crack propagation, due to the rise in GrF content. Through the ultrasonic C-scan evaluation, the delamination areas of different GrF content of samples were measured. The trend of delamination area variation was accordant with the trend of absorbed energy variation. This presents a demonstration of the correlation between the absorbed energy and the damage level. The SEM images of the fracture surfaces were analyzed for the deflection behavior of the fracture toughness with various GrF contents. The plot of residual compression strength versus GrF content further indicated the 1 wt% was the optimal content at which the incorporated GrF endowed the most impact-resistant property to the CFRP laminates.
Highlights
As one of the most extensively used fiber-reinforced composite materials, carbon fiber reinforced polymer (CFRP) shows tremendous potential to replace traditional metal materials in aviation, and naval and automotive fields, due to its lighter weight, higher specific strength and better corrosion resistance
To more carefully confirm which content allowed for the best impact resistance improvement effect, we adopted only one impact energy level to test the composite laminates, so as to focus on the analysis of impact process data and post-impacted results in more detail
The composite laminates were manufactured from plain-woven carbon fiber and graphite fluoride filled epoxy resin
Summary
As one of the most extensively used fiber-reinforced composite materials, carbon fiber reinforced polymer (CFRP) shows tremendous potential to replace traditional metal materials in aviation, and naval and automotive fields, due to its lighter weight, higher specific strength and better corrosion resistance. The impact on CFRPs causes barely visible impact damage (BVID), and produces internal damage under the surface [6]—which is harder to inspect The latter will degrade the residual mechanical property of materials and lead to a sudden failure without warning when the materials are in service. To more carefully confirm which content allowed for the best impact resistance improvement effect, we adopted only one impact energy level to test the composite laminates, so as to focus on the analysis of impact process data and post-impacted results in more detail. The compression after impact test was carried out to evaluate the damage tolerance of the composite laminates, to establish the correlation between the residual compression strength and the variation of GrF content
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