Abstract
Hybrid Polymeric Composites (HPC) structural materials pose a challenge of developing microcracks and delaminations under impact and dynamic loads. This paper presents the development and testing of an Intelligent Hybrid Polymeric Composite (IHPC) beam embedded with Ni-Ti Shape Memory Alloy (SMA) with crack growth retarding ability. Upon heating to austenite finish temperature (Af), Ni-Ti SMA wire contracts as a result of detwinned martensite-austenite phase transformation. The contraction of the SMA was utilized to stiffen and retard crack growth in the IHPC beam, hence resulting to an increase of mode I fracture stress intensity factor (KIC). The SMA wire specimens were aged at 250°C, then prestrained at 3% in order to stabilize austenite start (As) and austenite finish (Af)transformation temperatures. The values of As and Af for Ni-Ti SMA were determined. The IHPC and Polymeric Virgin (PV) notched beams were fabricated from epoxy resin. A four point bending test was performed on the beams to determine the effect of actuated Ni-Ti SMA on mode I fracture stress intensity factor KIC. The test was done at two temperatures, at T1 (below As) and at T2 (Af). Results showed that actuation of the Ni-Ti SMA increased the value of KIC for IHPC beams at T2 by 189% over the value of KIC for PV beams at T1. Actuation of the Ni-Ti SMA increased the value of KIC for IHPC beams at T2 by 41% over the value of KIC for IHPC beams at T1. Results showed that at T1 the loaded PV and IHPC beams fractured with unsteady crack propagation, while at T2 the loaded IHPC beams fractured with steady crack propagation. An increased value of KIC and steady crack propagation at T2 indicated that the SMA improved the crack retarding ability of the HPC beam. Key words: Intelligent hybrid polymeric composite, shape memory alloy, stress intensity factor, crack growth, crack retardation.
Highlights
Hybrid polymeric composites (HPC) are materials that result from a combination of either polymer and polymer or polymer and non polymer chemically distinct materials with a distinct interface separating the components
This paper presents the development and testing of an Intelligent Hybrid Polymeric Composite (IHPC) beam embedded with Ni-Ti Shape Memory Alloy (SMA) with crack growth retarding ability
When the IHPC beams were loaded at a temperature T2, the beams fractured at a force of 268 N with a corresponding critical stress intensity factor of 12.17 MN/m3/2
Summary
Hybrid polymeric composites (HPC) are materials that result from a combination of either polymer and polymer or polymer and non polymer chemically distinct materials with a distinct interface separating the components. The HPC material possesses desirable properties that cannot be achieved by any of the individual components of the composite (Trask and Bond, 2006; Collister, 2003). Hybrid polymeric composites being characterized by high corrosion resistance, high strength to weight ratio and relatively poor thermal and electrical conductance are widely used for the design of aerospace, automobile and civil engineering structures (Auricchio et al, 2003). One of the major challenges posed by HPC material structures is their brittle nature, when subjected to impact and dynamic loads, these materials undergo micro cracking and delaminations. Some cracks formed in the composite parts and structures can be inspected
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