Papers by Author: Isao Kimpara

Abstract: The effect of water absorption on the compressive strength after impact (CAI strength) and the post impact fatigue (PIF) properties of CFRP laminate were evaluated. Materials used were plain woven T300B-3K CFRP laminates and multi-axial knitted T700S-12K CFRP laminates molded by the vacuum assisted resin transfer molding (VARTM) method with vinylester as the matrix. Coupon specimens, which were applied the impact energy (1 J per unit thickness), were soaked in a water bath at 95oC for 120 hours up to the saturation water content of 0.6 wt%. CAI and PIF strengths of ‘Dry’ and ‘Wet’ specimens of plain woven CFRP showed almost same values. Thus, for T300B plain woven CFRP laminates, the effect of water absorption on PIF properties was small. On the other hand, multi-axial knitted CFRP laminates showed the large effect of water absorption, and Wet specimens showed lower PIF properties than Dry ones. However, net CAI and PIF strengths of multi-axial knitted CFRP were larger than that of plain woven CFRP.

Abstract: This paper presents the adaptation of the analytical method for transverse laminacracking in multidirectionally laminated composites to the finite element method. The damageinitiation and extension in a structure made of the laminated composite are evaluated by thedeveloped finite element method. The reduction in the stiffness of the laminated composite thatcaused by the crack growth is evaluated by the total force method. In the present analyses by thedeveloped method, the critical strain of the crack growth is the value of the strain which satisfiesboth energy criterion and stress criterion. To demonstrate the accuracy of the developed method,the analytical results of crack growth in CFRP quasi-isotropic laminate with a circular hole arecompared with experimental results.