Journal of the Japan Society for Composite Materials

Research paper

Prediction about Temperature-Dependent Flexural Modulus of Discontinuous and Dispersed Carbon Fiber Mat Reinforced Thermoplastics

Wataru NAGATSUKA, Tsuyoshi MATSUO, Takashi MURAKAMI, Noriyuki HIRANO

2015 Volume 41 Issue 3 Pages 75-84
Published: 2015
Released on J-STAGE: June 03, 2016

DOIhttps://doi.org/10.6089/jscm.41.75

JOURNAL FREE ACCESS

Show abstractHide abstract

It is important to understand the contribution of out-of-plane properties in order to clarify the bending deformation of out-of-plane anisotropic material like the CFRTP (carbon fiber reinforced thermoplastics) in detail. The out-of-plane mechanical properties of CFRTP would be affected by matrix resin. So the analysis of the temperature-dependence of the matrix resin will be a very important. And a method for predicting the temperature-dependence of bending behavior is greatly helpful to the wide use of CFRTP. From this point of view, in this study, the theoretical model of temperature-dependent flexural elastic modulus of CFRTP focusing on viscoelastic properties of matrix resin was constructed and verified by use of polypropylene-based discontinuous CF mat reinforced thermoplastics (CMT) with in-plane isotropic. As a result, it was quantitatively clarified that the temperature-dependence of flexural modulus of CMT is due to viscoelastic property of matrix resin. And the contribution of out-of-plane shear modulus G_13c to flexural modulus was also clarified quantitatively. These results indicate that the temperature-dependence of flexural modulus of CMT was able to be predicted by Young′s modulus E_1c and out-of-plane shear modulus G_13c influenced from viscoelastic property of matrix resin, volume fraction of fiber and coefficient configuration of fiber reinforcement by using the ordinary measurement method.

View full abstract

Download PDF (1601K)
Impact Force Identification and Damage Monitoring of Sandwich Panels Using Radiated Sounds

Satoshi ATOBE, Masato MURAMOTO, Ning HU, Hisao FUKUNAGA

2015 Volume 41 Issue 3 Pages 85-93
Published: 2015
Released on J-STAGE: June 03, 2016

DOIhttps://doi.org/10.6089/jscm.41.85

JOURNAL FREE ACCESS

Show abstractHide abstract

This paper presents the identification of impact forces acting on sandwich panels, and also the detection of the impact-induced damage based on the identified impact force. In the present study, the impact location and the force history are identified using the radiated sound at impact which is measured with microphones. The impact location is identified using the differences in the arrival times of the sound wave at the microphones. The force history is determined from the measured sound pressure using the identification method based on experimental transfer matrices. Here, the experimental transfer matrix expresses the relationship between the applied impact force and the measured sound pressure, and it is constructed based on the measured data obtained by conducting preliminary impact tests. The damage occurrence is judged by examining the identified force history for the presence of sharp drops and small fluctuations due to damage propagation. The validity of the proposed method is verified experimentally with a sandwich panel composed of CFRP facesheets and an aramid honeycomb core by conducting impact tests using an impulse hammer. The results reveal that the location and force history of the applied impact can be identified accurately by using the radiated sound even when damages are induced within the structure. In addition, it is shown that the occurrence and location of the damage can be estimated in real time from the identified impact force.

View full abstract

Download PDF (1610K)
Probabilistic Evaluation of Interlaminar Tensile Strength of a Carbon Fiber Reinforced Composite Laminate Measured by 4-point Bending Test of L-shape Specimen

Hiroshi SUEMASU, Shintaro TAKIZAWA, Tetsuya MORIMOTO, Masahiro HOJO

2015 Volume 41 Issue 3 Pages 94-101
Published: 2015
Released on J-STAGE: June 03, 2016

DOIhttps://doi.org/10.6089/jscm.41.94

JOURNAL FREE ACCESS

Show abstractHide abstract

An interlaminar tensile strength of the CFRP laminates was measured following a test method (ASTM D 6415). L-shape specimens having three different corner curvatures were prepared and loaded by 4 point bending setup. The tested data were analyzed by supposing that the delamination started from a defect where the interfacial stress first exceeded its strength. The defect was assumed a spatial Poisson process. The expected number of the defects in a unit area which were weaker than an interlaminar tensile stress was assumed to follow a power form of the stress. By using the assumption, we were able to find two material properties under the condition that the failure might not occur at the highest stress interface. The probabilistic distributions of the strength based on the present assumption being expressed by maximum interlaminar tensile stress in the specimen and equivalent area calculated considering the nonuniform stress distribution became a Weibull distribution of the maximum interlaminar tensile stress. The experimental results were well agreed by the present probabilistic expression. The probabilistic expression of the interfacial strength is appropriate to assess the interfacial strength problem including volume effects and can be applied to the general interfacial failure problems with nonuniform arbitrary stress states.

View full abstract

Download PDF (2841K)

Register with J-STAGE for free!