IMP-11: Determination of Interlaminar Shear Strength of a Unidirectional Carbon/Epoxy Laminated Composite under Impact Loading(IMP-II: IMPACT BEHAVIOR OF MATERIALS AND STRUCTURES)

2005 ◽  
Vol 2005 (0) ◽  
pp. 33-34 ◽  
Author(s):  
T. YOKOYAMA ◽  
K. NAKAI
Keyword(s):  
Shear Strength ◽  
Impact Loading ◽  
Laminated Composite ◽  
Interlaminar Shear Strength ◽  
Impact Behavior ◽  
Interlaminar Shear

Thermal cycle effects on laminated composite plates containing voids

2018 ◽  
Vol 53 (4) ◽  
pp. 489-501 ◽  
Author(s):  
Shambhu K Gupta ◽  
Mehdi Hojjati
Keyword(s):  
Shear Strength ◽  
Thermal Cycle ◽  
Composite Structures ◽  
Laminated Composite ◽  
Composite Plates ◽  
Interlaminar Shear Strength ◽  
Void Content ◽  
Manufacturing Method ◽  
Polished Cross Section ◽  
Interlaminar Shear

Composite structures are often cured in an autoclave to acquire the required space grade quality. Now the industry is focusing on the out of autoclave manufacturing method which leads to more voids inside laminate with respect to those manufactured in the autoclave. In the present work, the influence of voids on microcrack formation under thermal cycling and environmental conditions was analyzed. Thermal cycle experiments were performed using liquid nitrogen and oven, followed by microscopic observation of the polished cross-section of the 90° layered plies. Cracks were monitored, counted, and measured with respect to void and void free areas. Void content was characterized using microscopic and ImageJ software was used. It was observed that the microcracks will be formed both around the voids and in void free areas. As the number of thermal cycle increases, the number of microcrack around the voids increases much faster than compared to the void free areas. Also it was observed that most of microcracks were propagated in the transverse direction. Interlaminar shear strength was measured. Results indicate that interlaminar shear strength reduces as the number of cycle rises due to the increase in the microcrack density. Finite element method was used to simulate the process. The micro, meso, and macro model were created with respect to original samples voids and positions to calculate the stress distribution and its concentration. Good agreement between experiment and simulation was observed.

Intralaminar Reinforcement for Biomimetic Toughening of Bismaleimide Composites Using Nanostructured Materials

Materials ◽  
2005 ◽  
Author(s):  
Thomas Tiano ◽  
Margaret Roylance ◽  
Benjamin Harrison ◽  
Richard Czerw
Keyword(s):  
Shear Strength ◽  
Carbon Fiber ◽  
Laminated Composite ◽  
High Strength ◽  
Interlaminar Shear Strength ◽  
Aircraft Wings ◽  
Trailing Edges ◽  
Interlaminar Shear ◽  
Strength And Stiffness ◽  
Walled Carbon Nanotubes

Many conventional composite materials are composed of multiple layers of continuous fiber reinforced resin produced by lamination of b-staged prepreg and subsequent cure. These materials exhibit very high strength and stiffness in the plane, dominated by the properties of the fibers. The Achilles heel of such composites is the interlaminar strength, which is dependent on the strength of the unreinforced resin, often leading to failure by delamination under load. Current methods for increasing the interlaminar shear strength of composites consist of inserting translaminar reinforcement fibers through the entire thickness of a laminated composite, such as z-pin technology developed by Foster-Miller [1]. While effective, this technique adds several processing steps, including ultrasonic insertion of the z-pins into the laminate, subsequently causing a significant cost increase to laminated composites. Described in this paper is a process utilizing single-walled carbon nanotubes (SWNTs) and vapor grown carbon nanofibers as reinforcing elements promoting interlaminar shear strength and toughness in carbon fiber/bismaleimide (BMI) resin composites. The resulting composites mimic the natural reinforcing mechanism utilized in insect cuticles. Three different methods of increasing the affinity of these carbon nanofillers for the BMI matrix were explored. The mechanical properties of these composites were assessed using end notch flexure testing. The results indicated that including nanofiller at the laminae interface could increase the interlaminar shear strength of carbon fiber/BMI composites by up to 58%. SEM micrographs revealed that the nanofiller successfully bridged the laminae of the composite, thus biomimicking the insect cuticle. Composite fabrication techniques developed on this program would have a wide variety of applications in space and aerospace structures including leading and trailing edges of aircraft wings.

The Edge Shear Test - An Alternative Testing Method for the Determination of the Interlaminar Shear Strength in Composite Materials

2015 ◽  
Vol 825-826 ◽  
pp. 806-813 ◽  
Author(s):  
Kay André Weidenmann ◽  
Lisa Baumgärtner ◽  
Benedikt Haspel
Keyword(s):  
Shear Strength ◽  
Composite Materials ◽  
Shear Test ◽  
Shear Failure ◽  
Interlaminar Shear Strength ◽  
Shear Load ◽  
Testing Method ◽  
Shear Loads ◽  
Interlaminar Shear

The interlaminar shear strength is a characteristic value describing the mechanical behavior of composite materials such as laminates. Several methods for the determination of the interlaminar shear strength are described in open literature by several authors. Among these methods, the ILSS test (DIN EN ISO 14130) measuring the apparent interlaminar shear strength by using a modified bending test is the state of the art technique, as both the necessary testing equipment and the sample geometry are quite common. However, the ILSS tests implements shear loads indirectly by bending often leading to sample failure which is then not solely initiated by shear loads. Particularly for ductile matrices or those showing pronounced elastic behavior under bending, no interlaminar shear failure can be implemented and the interlaminar shear strength can not been determined or – if the user is not sensitized to the identification of non-shear failure behavior – the determined value is not correct.Up to now, alternative methods for determining the interlaminar shear strength implementing a shear load directly to the sample are quite elaborate regarding the test equipment to be used or the specimen preparation and geometry. In this contribution the authors present a novel test setup for an edge shear test which allows both a direct shear load and at the same time a reduced complexity of the specimen geometry which is comparable to those used in the ILSS test. The authors present results based on this novel testing method in comparison to conventional ILSS tests.

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