A racquet including a frame including a head portion, a handle portion, and a throat portion. The head portion is a tubular structure including inner and outer peripheral walls, each having inner and outer surfaces. The head portion of the racquet being formed of a fiber composite material. The fiber composite material includes a plurality of ply arrangements. Each includes a pair of plies defining first and second angles with respect to a composite axis. A section of the outer peripheral wall from the inner surface to the outer surface includes at least three ply arrangements overlaying each other, and the first and second angles of at least two of the at least three ply arrangements being at least 35 degrees. When the racquet is tested under a racquet torsional stability test, the racquet has an angular deflection of less than 5.5 degrees about a longitudinal axis.

In an aspect, there is a method of determining allowable defects for a composite component comprising identifying at least one wrinkle characteristic of a composite component wrinkle defect; making a first plurality of specimens each having a predetermined wrinkle defect representative of the composite component wrinkle defect; measuring each of the predetermined wrinkle defects in the first plurality of specimens for at least one performance metric to generate performance data; and generating an allowable wrinkle defect profile based on the performance data from the first plurality of specimens. In other aspects, there are methods of making a specimen with a predetermined wrinkle defect.

This patent studies a scale-span modeling method to simulate the structural mechanical responses and dynamic progressive failure behaviors of carbon fiber reinforced plastics (CFRPs) in drilling. Firstly, considering the different mechanical behaviors of fiber and matrix in micro state, a three-dimensional multi-scale dynamic progressive damage evolution model based on micro failure theory is proposed. Based on the degradation elastic parameters of microcomponent in typical volume element model, a new damage evolution model of fiber and resin matrix and an auxiliary deletion criterion of failure element are proposed. Secondly, the relationship between the macro stress and the micro stress of representative volume element in the composite model is established by using the stress amplification factor. Combined with the bilinear cohesion element model, the damage behavior of the composite in and between layers under the cutting action of dagger drill is simulated.

A racquet including a frame including a head portion, a handle portion, and a throat portion. The head portion forms a hoop that defines a string bed plane. The head portion of the racquet being formed of a fiber composite material. When the racquet is tested under a racquet forward/rearward bending test, the racquet has a forward/rearward deflection with respect to the longitudinal axis of at least 8.5 mm when measured in a direction that is perpendicular to the string bed plane and perpendicular to the longitudinal axis. When the racquet is tested under a racquet torsional stability test, the racquet has an angular deflection of less than 5.5 degrees about a longitudinal axis.

A racquet extending along a longitudinal axis and including a frame including a head portion, a handle portion, and a throat portion. The head portion forms a hoop that defines a string bed plane. At least the head portion and the throat portion of the frame are formed at least in part of a fiber composite material. When the racquet is tested under the racquet lateral bending test, the racquet has a lateral deflection of at least 6.0 mm when measured in a direction that is parallel to the string bed plane and perpendicular to the longitudinal axis.

Disclosed is a device for analyzing dynamic characteristics of a carbon composite material based on a test temperature, an orientation of a carbon material, and an external loading pattern applied thereto. The device includes a sensitivity analyzer configured to calculate a frequency response function of the carbon composite material based on a physical force signal and a vibration signal; and calculate a sensitivity of the carbon composite material to each of variations in the test temperature, an orientation of a carbon material contained in the carbon composite material, and the external loading pattern applied thereto, based on the calculated frequency response function.

The present invention is equipped with an AE sensor 12, a load test device 14, a storage device 22, a frequency center of gravity calculation unit 24 and a determination device 26. A loading pattern including, raising, retaining and unloading is repeatedly applied to a test subject 1 by the load test device 14, the maximum load is sequentially increased, and the AE waves 2 detected by the AE sensor 12 are stored with the load by the storage device 22. Next, the frequency center of gravity of the AE waves is obtained from the relationship between the frequency of the AE waves 2 and the intensity thereof by the frequency center of gravity calculation unit 24, and delamination preceding breakage is determined by the determination device 26 when the frequency center of gravity 5 is less than a prescribed first frequency.

In one version there is provided a test system including a layup tool having a layup surface, and two fairing bars attached to the layup surface. The test system includes the composite laminate having a plurality of stacked plies, and positioned between the two fairing bars. The test system includes fiber distortion initiator(s) positioned at one or more locations under, and adjacent to, one or more plies of the plurality of stacked plies. The test system includes two caul plates with a gap in between, and positioned over the composite laminate. When the test system undergoes a pressurized cure process with a vacuum compaction, a restricted outward expansion of the plurality of stacked plies by the fairing bars, and a pressure differential region formed by the one or more fiber distortion initiators at the one or more locations, create the controlled and repeatable out-of-plane fiber distortion in the composite laminate.

A racquet including a frame including a head portion, a handle portion, and a throat portion. The head portion is a tubular structure including inner and outer peripheral walls, each having inner and outer surfaces. The head portion of the racquet being formed of a fiber composite material. The fiber composite material includes a plurality of ply arrangements. Each includes a pair of plies defining first and second angles with respect to a composite axis. A section of the outer peripheral wall from the inner surface to the outer surface includes at least three ply arrangements overlaying each other, and the first and second angles of at least two of the at least three ply arrangements being at least 35 degrees. When the racquet is tested under a racquet torsional stability test, the racquet has an angular deflection of less than 5.5 degrees about a longitudinal axis.

A racquet extends along a longitudinal axis and is capable of being tested under a racquet lateral bending test and a racquet torsional stability test. The racquet lateral bending test includes mounting the racquet in a first orientation to a first test fixture at a first longitudinal location, attaching a clamp to the racquet at a second location, operably engaging a deflection indicator to the clamp, applying a first predetermined weight to the racquet at a third location, and removing the first weight to obtain a lateral deflection measurement of the racquet with respect to the longitudinal axis. The racquet torsional stability test includes mounting the racquet to second and third test fixtures at sixth and seventh locations of the racquet, respectively, placing a third predetermined weight on an arm extending from the second test fixture, removing the third predetermined weight to obtain an angular deflection about the axis. The racquet comprises a frame including head and handle portions and a throat portion positioned between the head and handle portions. The head portion forms a hoop that defines a string bed plane. When the racquet is tested under the racquet lateral bending test, the racquet has a lateral deflection of at least 6.0 mm when measured in a direction that is parallel to the plane and perpendicular to the axis. When the racquet is tested under the racquet torsional stability test, the racquet has an angular deflection of less than 5.0 degrees about the axis.