Provided is a liquid crystal polyester fiber in which gas generation from the liquid crystal polyester fiber can be suppressed when being heated. The liquid crystal polyester fiber has a total amount of carboxy end groups (total CEG amount) of 5.0 mEq/kg or less and a tenacity of 18 cN/dtex or higher. For example, the liquid crystal polyester fiber may have an initial elastic modulus variation of 3.0% or less. The liquid crystal polyester fiber may contain carboxy end groups as carboxyphenyl terminus at a CEG amount of 4.0 mEq/kg or less.

A method of producing a partially separated fiber bundle wherein, while a fiber bundle includes a plurality of single fibers travels along a lengthwise direction of the fiber bundle, a separator provided with a plurality of projected parts is penetrated into the fiber bundle to create a separation-processed part, and entangled parts, where the single fibers are interlaced, are formed at contact parts with the projected parts in at least one separation-processed part, thereafter the separator is removed from the fiber bundle, and after passing through an entanglement accumulation part including the entangled parts, the separator is penetrated again into the fiber bundle, characterized in that a separation processing time t1 during being penetrated with the separator and a time t2 from being removed with the separator to being penetrated again into the fiber bundle satisfy Equation (1): 0.03≤t2/(t1+t2)≤0.5.

A method of producing a partially separated fiber bundle wherein, while a fiber bundle includes a plurality of single fibers travels along a lengthwise direction of the fiber bundle, a separator provided with a plurality of projected parts is penetrated into the fiber bundle to create a separation-processed part, and entangled parts, where the single fibers are interlaced, are formed at contact parts with the projected parts in at least one separation-processed part, thereafter the separator is removed from the fiber bundle, and after passing through an entanglement accumulation part including the entangled parts, the separator is penetrated again into the fiber bundle, characterized in that a separation processing time t1 during being penetrated with the separator and a time t2 from being removed with the separator to being penetrated again into the fiber bundle satisfy Equation (1): 0.03≤t2/(t1+t2)≤0.5.

Provided is an improvement in a method for manufacturing a slit carbon fiber bundle. The method for manufacturing a slit carbon fiber bundle of the present invention is a method including a step of forming a resin film on one surface of a flat carbon fiber bundle to obtain a single-sided coated carbon fiber bundle, and a step of partially slitting the single-sided coated carbon fiber bundle using a slitter roll to obtain a slit carbon fiber bundle, which has been split into sub-bundles, wherein in the step of slitting, the single-sided coated carbon fiber bundle contacts a circumferential surface of the slitter roll on a surface where the resin film has been formed.

Provided is an improvement in a method for manufacturing a slit carbon fiber bundle. The method for manufacturing a slit carbon fiber bundle of the present invention is a method including a step of forming a resin film on one surface of a flat carbon fiber bundle to obtain a single-sided coated carbon fiber bundle, and a step of partially slitting the single-sided coated carbon fiber bundle using a slitter roll to obtain a slit carbon fiber bundle, which has been split into sub-bundles, wherein in the step of slitting, the single-sided coated carbon fiber bundle contacts a circumferential surface of the slitter roll on a surface where the resin film has been formed.

Provided is a useful improvement in a manufacturing method of a CF-SMC using a partially split continuous carbon fiber bundle. The manufacturing method of an SMC of the present invention includes (i) a step of drawing out a continuous carbon fiber bundle (10) from a package, the continuous carbon fiber bundle (10) having a filament number of NK and partially split into n sub-bundles in advance, (ii) a step of chopping the continuous carbon fiber bundle (10) drawn out from the package with a rotary cutter (234) into chopped carbon fiber bundles (20), and (iii) a step of depositing the chopped carbon fiber bundles (20) on a carrier film (41) traveling below the rotary cutter (234) to form a carbon fiber mat (30). In the manufacturing method, due to a fragmentation processing, in which at least some of the chopped carbon fiber bundles before being deposited on the carrier film (41) are fragmented by being brought into contact with a rotating body, a distribution of the filament number of the chopped carbon fiber bundles in the carbon fiber mat (30) is made different from that when the fragmentation processing is not performed.

Disclosed is a fiber-reinforced composite and methods and apparatuses for making the same. Some fiber-reinforced composites include a matrix material including a thermoplastic material and a non-woven fibrous region having a plurality of continuous fibers dispersed in the matrix material, wherein the width and the length of the non-woven fibrous region are substantially equal to the width and the length, respectively, of the liber-reinforced composite, wherein the non-woven fibrous region has a mean relative area fiber coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20, and wherein each of the plurality of continuous fibers is substantially aligned with the length of the fiber-reinforced composite.

Disclosed is a fiber-reinforced composite and methods and apparatuses for making the same. Some fiber-reinforced composites include a matrix material including a thermoplastic material and a non-woven fibrous region having a plurality of continuous fibers dispersed in the matrix material, wherein the width and the length of the non-woven fibrous region are substantially equal to the width and the length, respectively, of the liber-reinforced composite, wherein the non-woven fibrous region has a mean relative area fiber coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20, and wherein each of the plurality of continuous fibers is substantially aligned with the length of the fiber-reinforced composite.

A method of manufacturing and a device for manufacturing a partial split-fiber fiber bundle and a partial split-fiber fiber bundle obtained are characterized by piercing a fiber splitting means provided with a plurality of protruding parts into a fiber bundle formed from a plurality of single fibers while making the fiber bundle travel along the longitudinal direction thereof and creating a split-fiber processed part, forming entangled parts where single fibers are interlaced at contact parts with the protruding parts in at least one split-fiber processed part, thereafter pulling the fiber splitting means out of the fiber bundle, and after passing through an entanglement accumulation part including the entangled parts, once again piercing the fiber splitting means into the fiber bundle.

A method of manufacturing and a device for manufacturing a partial split-fiber fiber bundle and a partial split-fiber fiber bundle obtained are characterized by piercing a fiber splitting means provided with a plurality of protruding parts into a fiber bundle formed from a plurality of single fibers while making the fiber bundle travel along the longitudinal direction thereof and creating a split-fiber processed part, forming entangled parts where single fibers are interlaced at contact parts with the protruding parts in at least one split-fiber processed part, thereafter pulling the fiber splitting means out of the fiber bundle, and after passing through an entanglement accumulation part including the entangled parts, once again piercing the fiber splitting means into the fiber bundle.