Adhesive Bonding of Composite Joints

Polymer matrix composites have shown improved properties over traditional materials especially when considering weight normalized properties such as specific strength and stiffness. While this has been known for some time, the implementation of composites as structural materials still have complications due to limitations in bonding and fastening complex geometries.  Currently, composite panels bonding is completed primarily through the drilling of holes in critical locations within the panel and securing with the use of fasteners such as rivets and bolts. The mechanical fasteners link multiple panels together and also provide an added level of protection by mechanically limiting propagation of failure originating near the bond but in the panel itself. While this process is effective there is a significant weight cost, and the manufacturing of the necessary hole geometries has significant implications for overall performance, resulting in elevated stress concentration levels and delamination in the composite panel. Mechanical fasteners have consistently lead to significant over-design and a loss in overall efficiency gained from the improved specific strength.

Characterization of Particle Dispersion in Nanocomposites

Imaging is completed using a JEOL dual beam focused ion beam. The electron gun is mounted vertically and has high resolution capabilities. The liquid gallium ion gun is mounted at a 52° angle to the electron gun. A microtome is used to plane the sample which is then mounted on a 45° SEM stub and coated with a Au for electrical conductivity. The high contrast of the images obtained by differences in atomic number between constituents. Charging of the polymer matrix is also avoided by the alternating passes of the negatively charged electron beam and the positively charged ion beam.

 

3D Reconstruction
Slice and view images reconstructed from approximately 100 square slices are shown in the bottom right corner. A 3D surface image of the dispersion of zinca particles is shown below. The primary images are approximately 5 square microns and the slices are 30 nm thick

 

 

Download our MATLAB Code for Dispersion Quantification

In situ Testing of Nano-Structured Materials

Description
In situ load frame for simultaneous loading and imaging of samples within the FIB chamber.

Capabilities
High resolution strain measurement
Programmable load or displacement control
Very low strain rates are achievable

Testing modes
Tension, Compression, Fatigue, Bending, Fracture,
Compact tension

 

Stage Specifications

Load Capacity: 4500N

Load Cell Acuracy: 0.2% Max Load

Maximum Stain Travel: 30mm

Linear Scale Accuracy: 20 nm resolution

 

Micro-Milling of Test Samples Using A Focused Ion Beam

The focused ion beam and omniprobe micro-manipulator can be used to micro-mill test samples and manipulate them for investigation of fracture mechanisms in nano-structured materials. Three sequential images of micro cantilevers are shown for a filled and unfilled polymer system. The reinforced polymer system shows increased tortuosity of the crack path and microcracking and crack pinning are present in the system.