Analysis of Residual Post-Impact Compressive Strength of Composite Laminates Under Hygrothermal Conditions

Abstract

This paper is a continuation study of the residual compressive strength of composite laminates after impact under hygrothermal conditions. Two carbon fibre/epoxy plywood specimens with different lay-ups ([45/-45/0/0/45/0/0/0/90/-45/0]s and [45/-45/0/90/0 /0/0/0/90/0/-45/45]s) were investigated, The materials were subjected to 500 h, 1000 h and 2000 h of service time in a climatic chamber at a temperature of 60 °C and 100% relative humidity, followed by low-velocity post-impact compression using an energy level of 15 J. Experimental and numerical simulations are used to study the residual compressive strength and damage extension of the material. Using the ultrasonic C-scan technique, the internal damage of the specimens was scanned, and the damage evolution in impact and compression tests was analysed. Damage evolution in impact and compression tests was investigated using ultrasonic C-scanning to scan the internal damage of the specimens. The strain change maps of the specimens during compression are studied using the Digital Imaging (DIC) technique. Vumat subroutine coded in Fortran and used in commercial software (ABAQUS) for numerical simulation. To study the effect of damage extension of materials on post-impact and post-impact compression for different hygrothermal times. It was found that the residual compressive strength depended on factors such as the material's hygrothermal time and the initial defects in the plywood; that the 90° and ± 45° fibre orientations played a positive role in the material's hygrothermal; that the hygrothermal made the material's damage more catastrophic; and that the buckling of hygrothermal specimens was not only at the impact position, but was also reflected at the edges. In CAI testing, it was found that the hygrothermally treated specimens were damaged similarly to the desiccation treated specimens, but that compression resulted in a flexural position affected by hygrothermal, which determined the material CAI strength.