THE EFFECTS OF STACKING SEQUENCE ON THE COMPRESSIVE PERFORMANCE OF COMPOSITES
Topic(s) : Special Sessions
Co-authors :
Yousef JOE RIFAI (UNITED KINGDOM), Laura Rhian PICKARD (UNITED KINGDOM), Giuliano ALLEGRI , Michael R. WISNOM (FRANCE)Abstract :
Fiber-reinforced composites demonstrate a lack of mechanical strength when subjected to compressive loading. Compressive performance of fiber-reinforced composites is difficult to measure due to challenges with the test methods. The primary reason for the lack of unidirectional compressive strength is the shear instability of the fibers [1]. Composite compressive strength can be improved using an optimized stacking sequence and improving laminate architecture.
In multidirectional laminates, the stacking sequence is an important factor that can be optimized to delay micro-buckling. Hoppel and Teresa show that angle-ply orientations influence the compressive strength of the laminate using [0_2/±θ] laminate with θ between 0° and 90° [2]. The claim is that the 30° angle plies provided the lowest compressive strength due to the high Poisson ratio. This indicates that an angle ply can affect the compressive performance of the adjacent ply.
Experimental investigation
A recent study at the University of Bristol presents a suitable compressive testing method for uni-directional fiber-reinforced composites using a sandwich structure in flexure [3]. This method shows reliable results with minimal variation. A four-point bend test according to ASTM D5467 standard was used to test a sandwich structure made from unidirectional carbon fiber IM7-8552 [4, 5]. The purpose is to measure the longitudinal compressive strains using the Vishay Precision strain gauges (C4A-06-125SL-35039P) in the middle of the gauge section of the top skin. The adapted test procedure prevents core shear or localized stress failure from occurring in the sample. Loading pads and a vertical crosshead displacement of 2 mm/min were used.
Cross-ply and quasi-isotropic arrangements with a range of stacking sequences were manufactured and tested. The aim is to analyze the compressive performance of each configuration and the effects of the stacking sequence and to identify factors for the optimum placement of highly loaded plies to be best supported in a laminate under compression. The experimentation on both configurations demonstrates how the stacking sequence can be used to support highly loaded plies thus enhancing the laminate’s compressive performance.
In multidirectional laminates, the stacking sequence is an important factor that can be optimized to delay micro-buckling. Hoppel and Teresa show that angle-ply orientations influence the compressive strength of the laminate using [0_2/±θ] laminate with θ between 0° and 90° [2]. The claim is that the 30° angle plies provided the lowest compressive strength due to the high Poisson ratio. This indicates that an angle ply can affect the compressive performance of the adjacent ply.
Experimental investigation
A recent study at the University of Bristol presents a suitable compressive testing method for uni-directional fiber-reinforced composites using a sandwich structure in flexure [3]. This method shows reliable results with minimal variation. A four-point bend test according to ASTM D5467 standard was used to test a sandwich structure made from unidirectional carbon fiber IM7-8552 [4, 5]. The purpose is to measure the longitudinal compressive strains using the Vishay Precision strain gauges (C4A-06-125SL-35039P) in the middle of the gauge section of the top skin. The adapted test procedure prevents core shear or localized stress failure from occurring in the sample. Loading pads and a vertical crosshead displacement of 2 mm/min were used.
Cross-ply and quasi-isotropic arrangements with a range of stacking sequences were manufactured and tested. The aim is to analyze the compressive performance of each configuration and the effects of the stacking sequence and to identify factors for the optimum placement of highly loaded plies to be best supported in a laminate under compression. The experimentation on both configurations demonstrates how the stacking sequence can be used to support highly loaded plies thus enhancing the laminate’s compressive performance.