Papers by Keyword: Mode I Interlaminar Fracture Toughness

Abstract: In this study, the effects of water absorption and freezing on flexural property and mode I interlaminar fracture toughness of Carbon Fiber Reinforced Plastics (CFRP) were investigated. Plain woven carbon fiber was used as reinforcement. Epoxy resin was used as matrix. Water absorption test was conducted at 90°C for 24, 100, 250 and 500 hrs. After water absorption, the specimens were kept under-15°C for 24 hrs. Static three point flexural and Double Cantilever Beam (DCB) tests were conducted after water absorption and freezing. As a result, flexural strength and mode I interlaminar fracture toughness of CFRP after water absorption and freezing decreased with an increase of immersion time. Flexural modulus of CFRP did not change after water absorption and freezing. And flexural strength and mode I interlaminar fracture toughness of frozen CFRP after water absorption were lower than those of water absorbed CFRP. From the observation using scanning electron microscope, it is understood that the water absorption and freezing affects the interfacial adhesion between fiber and matrix.

Abstract: Carbon fiber reinforced polymer matrix composites have been widely used in many fields. It is necessary to test the performance of interlaminar fracture toughness of composites and provide useful information for product development and material selection. In this paper polymer matrix films embedding with carbon fiber reinforced composite laminates curing at high temperature were used to study the performance of model I inter-laminar fracture toughness. Mode I interlaminar fracture toughness of composites reinforced by carbon fiber was measured according to ASTM D5528 standard. Three groups of samples cut into double cantilever beam (DCB) specimens were measured to compare their performance. The results showed that there was no fiber-bridging in multidirectional composite laminations. The delamination for all specimens extended slowly and stably. All of three groups of carbon fiber composites had strong model I interlaminar fracture toughness and high delamination tolerances. The sensitive to delamination is different because of different composition of these three carbon fiber reinforced composites.

Abstract: In this study, effect of Carbon Milled Fiber (CMF) addition on interlaminar fracture toughness of carbon fiber reinforced plastics (CFRP) was investigated. Plain woven carbon fiber was used as reinforcement. Epoxy resin was used as matrix. The addition amounts of CMF are 0.5wt%, 0.8wt%, 1.0wt% and 1.2wt% for the epoxy resin. Mode I and mode II interlaminar fracture toughness tests were conducted based on JIS K 7086. As a result, mode I and mode II interlaminar fracture toughness increased with an increase of addictive amount of CMF. But excess addition was not effective. Pull out of CMF in matrix was found after mode I and mode II interlaminar fracture toughness tests. The mode I and mode II interlaminar fracture toughness of CMF added CFRP can be improved by fiber bridging of CMF.